User Manual - Institut für Strömungsmechanik und Umweltphysik im
Contents
1. 2204200420rsenseensennensnnnsneennennn 6 Stream function SOMOS se usa 7 Irregular waves through wave spectra uuesssessssssssensneessnensnnnnnnnnnnnnnennnnennnennnsnnnsnennnnn nen 8 Local Fourier approximation for irregular waves esssesssesssessnsensnensnnensnnnnnnnnnneennnen nenn 9 Mass Transport aueh 10 SIE IE ee ee er ee re ers 10 Load Calculation seien 10 Morison equalion usa ee 10 Coefficients in Morison equation een 11 Adapted Morison equation for inclined tubes sesseesnennennnennnnnn nennen 11 Recommended Readins nennen een 11 WaveLoads in MS DOS Environment ivccurecasetaysenesuastenrennsvnsevainen vuuesieansnaintotaatsxaetuauncaes 12 Graphical User Interface sie 12 put Pile Goss cuts carci cibvessenedeeniccs ac etevap E EN E E E eee 15 Input file for wave parameters eek 15 Input file for discretised Spec iin ans dataccnpaheaunieviendade etacevtabeeubiaas 19 Input file for structure parameters naar 20 O tp t Files een 23 Model Q output Dies need 23 Airy theory output Ples een 23 Stokes 2 order output files nennen 23 Stokes 3 order output files sacseccsissssscosscssscdsnvsscdssacssuvssvesvecsvassnestavustecsvonssesdsavsnsessvdusciacaes 24 Stokes 5 order output Hiles naeh 24 Lagrangian approach by Woltering output files eee cecceeeceeeeeeeeeeeeceseceeeeeeeeeeaeees 25 Stream function by Dean Dalrymple output files 0 eee ee cccseeeteceeeeeeeeeeseeenseeneneeees 25 Stream functio2. 0 Ox 02 For solving the preceding differential equations following boundary conditions are used 1 bottom boundary condition 2 0 on z d d water depth Z 2 kinematic free surface boundary condition Ob On ODO Oz Ot Ox amp on z 7 x t 7 surface elevation User Manual WaveLoads 4 45 www gigawind de 4 p Institut f r Str mungsmechanik Ei Gigawind und Elektronisches Rechnen im Bauwesen de B Universit t Hannover F Universit t Hannover 3 dynamic free surface boundary condition Py O 0x 0OD 0z P OD i p 2 Ot 4 for regular waves periodic lateral boundary condition D x z t B x L z t x z t T Assumptions for solving are that the flow is irrotational and the water is inviscid gz B on z n x t Airy s or linear wave theory Airy s wave theory describes the propagation of a sine wave For calculating the kinematics a solution for the velocity potential is found As is apparent in the name linear wave theory only linear terms are considered Amplitudes are assumed to be small The dynamic boundary condition on the surface is thus simplified to oD i SE gz B on z 0 small amplitude Thus the solution for a simple sine wave is obtained H 27 27 t cos kx at k n x t 5 cos at oO 7 z u a Sl MG cos kx at w sa Aa sin kx at 2 sinh kd 2 sinh kd Ou z H re CSG z sao Ow 2 H o ARNA z ri ot 2 sinh kd ot 2 sin
3. 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover IF I Universit t Hannover WaveLoads A computer program to calculate wave loading on vertical and inclined tubes User Manual Version 1 01 August 2005 K Mittendorf and B Nguyen M Bl mel Partners of GIGAWIND research project Fluid Mechanics Institute Coordination Steel Construction Institute Prof Dr Ing W Zielke Prof Dr Ing P Schaumann Curt Risch Institute Institute for Foundation and Soil Mechanics Rock Mechanics Dipl Ing W Gerasch and Tunnel Construction Essen Prof Dr Ing W Richwien Dipl Ing Fluid Mechanics Institute University of Hannover Germany code developing Dr rer nat Fluid Mechanics Institute University of Hannover Germany code developing Dipl Ing Fluid Mechanics Institute University of Hannover Germany extending of manual User Manual WaveLoads 1 45 www gigawind de E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Universitat Hannover Table of contents SUC TOT cx asvisa E EET 3 Available Wave Theonies nenne 4 Governing differential equations and boundary conditions ueessennsennseneneesnennnnen 4 Airy sor linear wave THEOL Y ays seines 3 Stokes 2 3 and 3 order ect 5 Lagrangian wave in the formulation by Woltering
4. SEEGANG HS SEEGANG TP Institut f r Str mungsmechanik und Elektronisches Rechnen im Bauwesen E B Universit t Hannover name of gauging station kind of measurement e g buoy date of measurement YYYYMMDD time of measurement hhmm 1 non directional spectrum 0 directional spectrum JONSWAP SEEGANG SPECTRUM MODE 0 based on a cosine power model 1 directional spectrum JONSWAP SEEGANG SPECTRUM MODE 0 based on Banner s hyperbolic type model if SEEGANG_ DIRECTION MODEL 1 the peak wind direction angle has to be defined in radian 1 n if SEEGANG DIRECTION MODEL 0 the spreading angle theta in radian has to be defined 1 1 if SEEGANG_SPECTRUM MODE 2 the significant wave height has to be defined if SEEGANG_SPECTRUM MODE 2 the the peak period has to be defined A simple wave input file for regular waves could look like this WAVELOADS STEERING FILE MODEL 13 5 STOKES FITH ORDER THEORY if DURATION gt 30 simulating 30 seconds TIMESTEP paf time step is 0 1 second WATERDEPTH 30 0 water depth 30 m WAVEHEIGHT 12 0 wave height 12 m User Manual WaveLoads 18 45 www gigawind de Universitat Hannover l Universitat Hannover WAVEPERIOD 13 0 wave period 13 s alternative WAVELENGTH 200 switched off EULERCURRENT N without Euler current CURRENTVELOCITY 0 01 will be ignored because EULERCURRENT is sw
5. 1996 Wiegel R L Oceanographic Engineering Prentice Hall Englewood Cliffs 1964 Special waves Sobey R J A local Fourier approximation method for irregular wave kinematics Applied Ocean Research Vol 14 pp 93 105 1992 Woltering S Eine LAGRANGEsche Betrachtungsweise des Seeganges Dissertation Franzius Institut Universit t Hannover 1996 Loads Abdelradi M E The curve fitting of Sarpkaya s results for inertia draft and lift coefficients Dep of Naval Architecture University of Glasgow 1983 Sarpkaya T Mechanics of wave forces on offshore structures Van Nostrand Reinholdt Comp Inc 1981 User Manual WaveLoads 11 45 www gigawind de Institut f r Str mungsmechanik PP und Elektronisches Rechnen im Bauwesen 4 IS E B Universit t Hannover Gigawind WaveLoads in MS DOS Environment For all applications WaveLoads can be started in the MS DOS environment WaveLoads consists of a single executable file Further you need two ASCII files one file describing the wave condition and a second one for the structure information When using the discretised spectrum an additional file containing the spectrum is required To start the program type WaveLoads name of wave parameter file name of structure parameter file and press return compare with Figure 1 The calculation will start immediately and the results will be written in several ASCII files D WAUES gt D WAUES gt DE NWAUES gt waves waves dat s
6. Fy 0 0000 kN CRNA REl Min Fy 0 0000 kN 0a Integrated Morison Force FZ kN Of lt 3 lt a ___Max Fz 0 0000 kN Calculate Graphic Wave Parameter File _Maria wL_VD40504 BIN wellemt dat Stucutre Parameter File _Maria v L_V040504 BIN struktmt dat Figure 3 Graphical output of results m cowe eee lei x Figure 4 Graphic for complex structure in GUI User Manual WaveLoads 14 45 www gigawind de Universitat Hannover f Gi A Institut f r Str mungsmechanik igawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Input Files Every line beginning with is a comment und will be ignored The parameters which can be defined by a user always start with a special keyword followed by and the value which is to be given in SI units m kg s Note When a spectrum is defined by parameters the frequency is given as the angular frequency 2nf If the spectrum is defined through a file containing the discretised spectrum this spectrum uses fas frequency Input file for wave parameters Here is a list with all possible keywords MODEL following wave theories can be chosen 0 Calculation and comparison of boundary conditions errors for the wave models Airy Stokes 1 5 Stokes First Order Theory Airy Stokes Second Order Theory Stokes Third Order Theory Lagrangian formulation by Woltering Stokes Fifth Order Theory Str
7. and kx are solved numerically Mass transport Mass transport takes into consideration that a mean flux exists in wave direction It is a non periodic drift in the direction of wave propagation in the formulation of velocities in the theories of higher order It influences the wave s length and the velocity in the wave propagation direction Two approaches for calculating the mass transport are implemented e Stokes mass transport due to Stokes drift velocity or mass transport velocity e Eulerian mass transport which is due to asymmetry of velocities at a fixed point Stretching For Airy s theory the wave kinematics calculation is only valid up to mean water level To remedy this either the values are extrapolated or the results are stretched or compressed to the actual water level with Wheeler s stretching function This transforms the term k d n in some hyperbolic trigonometric functions to kd For example in the calculation of the velocity in wave direction the term cosh k d 7 sinh kd becomes cosh kd sinh kd Load Calculation Morison equation WaveLoads calculates the loads due to wave impact on defined structures with diameters considerably smaller than the wave length For that the well known Morison equation is used aD Ov dF c 9 e Diy 4 ot 2 In WaveLoads p is assumed to be 1025 kg m Lift forces due to wave impact are not considered User Manual WaveLoads 10 45 www gigawin
8. in x direction in z direction velocity m s 0 5 10 15 20 25 30 time s Figure 13 Particle velocities at the surface User Manual WaveLoads 33 45 www gigawind de E 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover LF Universit t Hannover EB Example 2 Morison forces on a monopile Fenton stream function The parameters MODEL 7 Fenton Stream Function Model Wave height 6 9 m DURATION 220 Water depth 22 0 m TIMESTEP 0 10 Wave period 14 0 s WATERDEPTH 0 HEIGHT 90 EPERIOD 0 Pile diameter 0 8m oa oe 7 Pile length 27 0 m RANSPORT Drag coefficient 0 7 PORTMODEL Inertia coefficient 2 0 ECHINGSMODE Number of Nodes 271 en n NCT X EANDAMP ING ENTONSTEP Euler current 0 0 m s DE Wave theory Fenton stream function MORE Zee n 4 DI B The calculated surface elevation elevation m 0 2 4 6 8 10 12 14 16 18 20 22 time s Figure 14 Surface elevation Fenton stream function User Manual WaveLoads 34 45 www gigawind de Universitat Hannover IF Universitat Hannover VE t A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B total force kN EEEE eee ees See ee eee re foi ie eee ae eee ere ee eee eee 0 2 4 6 8 0 1 14 16 18 2 2 time s Figure 15
9. r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover LFI Calculated wave characteristics Wave parameters Lagrangian model Wave height m 7 000000 Wave period s 12 000000 Water depth m 22 000000 Wave length m Fenton Approach 160 072201 Wave length m Iteration IWB 161 003994 Wave amplitude m 3 500000 angular frequency Hz 0 523599 frequency 1 s 0 083333 Wave number 0 039025 W_Group velocity m s 13 339350 L d 13 416999 Wave characteristics w_height g w_period 2 0 004955 steepness 0 043477 H d 0 318182 H L 0 043477 d L 0 136643 Eulerian current 0 020000 gravity 9 810000 density 1 025000 Stretchingsmode wave nodes in x direction wave nodes in z direction time nodes per wave period Number of time steps User Manual WaveLoads 38 45 www gigawind de elevation m E A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universit t Hannover m U Universit t Hannover LFI Example 4 Morison forces on an inclined tube Stokes 3 order The parameters Wave height 12 0m Water depth 30 0 m Wave period 13 0s Euler current 0 00 m s Pile diameter 0 91 m Pile length 46 1 m Drag coefficient 0 7 Inertia coefficient 2 1 Number of Nodes 51 m J il Wave theory Stokes 3 NSUBSTRUCT SUBSTRUCTINDE XU YU p l w Ooo
10. Total Morison force Fenton stream function In Figure 15 the total Morison force is shown its maximum is 47 2 KN at 13 5 s User Manual WaveLoads 35 45 www gigawind de Universitat Hannover LF Universitat Hannover Ei 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Example 3 Moment on monopile Lagrangian wave The parameters Wave height 7 0m Water depth 22 0 m Wave period 12 0s Euler current 0 02 m s Stokes mass transport Pile diameter 0 9m Pile length 29 0 m Drag coefficient 0 7 Inertia coefficient 2 0 Number of Nodes 291 Wave theory Lagrangian wave The resulting surface elevation surface elevation m t s Figure 16 surface elevation Lagrangian wave User Manual WaveLoads 36 45 www gigawind de t A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover IF Universit t Hannover E B velocity m s in x direction in z direction time s Figure 17 surface velocities In Figure 17 the velocities on the surface are shown The curve for the moment at the sea bottom due to the Morison loads is plotted in Figure 18 Moment at sea bottom kNm oO loa m amp O 1000 1500 2000 0 t s Figure 18 Moment at sea bottom due to Morison loads User Manual WaveLoads 37 45 www gigawind de Universitat Hannover E A 3 Institut f
11. author in WaveLoads the ones by Wiegel are used for 2 4 and 3 order for 5 order the ones after Fenton are used Mean water level is lifted by Ah from still water level For 2 order theory the lift in mean water level in the formulation after Wiegel is mH 3 1 coth kd 4L 2 sinh kd This term differs from that of the commonly used one by the expression in the brackets For higher order theories the wave frequency will become dependent on the amplitude Stokes wave theories are valid for d L lt 0 125 Ah Lagrangian wave in the formulation by Woltering In contrary to the prior ones this formulation uses the Lagrangian approach Thus the water particles are traced over time through space The surface elevation is viewed as the result of the upper particles movement along their orbits The Lagrangian surface contains harmonic components of higher frequency The equations for the orbits are taken from the Eulerian approaches of Stokes theory The time derivatives of the orbit equations give the wave kinematics The coordinates of the surface particles orbit origin Xo Zo the vertical correction lift Ah and the belonging wave kinematics are calculated iteratively The first calculation yields wave induced mass transport of the same amount as Stokes 2 order drift velocity in common formulation causes For compensation the mean water level is lifted by Ah This is gained from the demand of equal areas under cr
12. coefficient 2 0 Number of Nodes 271 ELEMENT UMBMOMTREF OMTREF INDEX N I NSUBSTRUCT 1 Wave height 4 0m SUBSTRUCTINDEX 0 Water depth 17 0m XU 7 0 Wave period 9 05 u 0 0 Euler current 0 0 m s 4 i r 3 0 0 Pile diameter 0 8 m 17 0 Pile length 23 1 m 0 4 Pile angle 18 5 0 7 2 0 0 1 0 Ox De Ta Mom OS ea Oe he ee Oo ei Ses Wave theory Sobey stream function ra Calculated wave characteristics Wave Length m 101 937140 C_Phase 11 326349 Wave Number k 0 061638 The resulting surface elevation 2 5 oO a evelation m an o 2 4 6 8 10 12 14 16 18 20 22 time s Figure 22 Surface elevation Sobey stream function User Manual WaveLoads 41 45 www gigawind de t A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover IP Universitat Hannover EB Force in x direction Force in z direction 20 16 Rees ened kennen RN hese poe UNE bernunen F AR Ve eee Integrated Force kN 0 2 4 6 8 10 12 14 16 18 20 22 time s Figure 23 total Morison force Sobey stream function The maximum force in x direction is 17 2 kN at 8 6 s the maximum in y direction is 4 9 kN at 2 4 s User Manual WaveLoads 42 45 www gigawind de Universitat Hannover E 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover LFI Example 6 Composi
13. input file EHEIGHT ERIOD ERCURRENT CURRENTVELOCITY MASSTRANSPORT TRANSPORTMODEL User Manual WaveLoads 31 45 www gigawind de E 3 A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover IF Universit t Hannover EB The structure input file NSUBSTRUCT BSTRUCTINDE 000000 000000 000000 000000 000000 000000 ah N HE K dR ODS EON FE OK FE OS FE HE oO 4 g un 000000 x 700000 Ss 000000 EMENT UMBMOMTREF a6 Soe SS EEE O H EF INDEX 000000 000000 000000 The results The integrated maximum force is 2787 KN at 12 8 s Integrated Force kN 2500 2000 1500 1000 1000 F 1500 2000 2500 i an User Manual WaveLoads 32 45 www gigawind de i i 0 5 10 15 20 25 time s Figure 11 Total Morison force t a Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover IF I Universit t Hannover In Figure 12 the calculated water surface elevation over time is shown elevation m 0 5 10 15 20 25 3 time s Figure 12 Calculated water surface elevation with Stokes 5 theory The next image Figure 13 shows the particle velocity in x and z direction at the surface
14. 5 1 0 140 2 95000 38 1 0 150 3 69400 41 1 0 160 4 37200 44 1 0 170 1 92300 45 1 0 180 0 73890 48 1 0 190 0 51770 55 1 0 200 0 55240 54 1 User Manual WaveLoads 19 45 www gigawind de F t 3 Institut f r Str mungsmechanik Sigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover F Universit t Hannover 0 210 0 89860 56 1 0 220 0 75430 57 1 0 230 0 47660 60 1 0 240 0 30280 01 1 0 250 0 31520 03 1 0 260 0 26500 04 1 0 270 0 16110 07 1 0 280 0 14690 10 1 0 290 0 17340 08 1 0 300 0 11790 12 1 0 310 0 11710 15 1 0 320 0 12920 18 1 0 330 0 11000 21 1 0 340 0 06794 22 1 0 350 0 06085 29 1 Input file for structure parameters In this file the number of circular structure components and their location will be defined The user has to enter the inertia and drag coefficients as well as the diameter The coordinate system is a right handed system Z Figure 5 WAVELOADS uses a right handed coordinate system The x axis is the wave propagation direction The origin in z direction is located on the mean water level Up is positive and down is negative on the scale so the sea bottom is at the negative water depth To define a structure the ending points of its components are specified as well as their diameter and the Morison coefficients to be used for each part Additionally the number of elements or nodes for the calculating is given As loads
15. Oo Fr ON OCG oO CO Oo oC Oo oC e ew E U UMBMOMTRI OMTREF INDE K NE N M X X Z M M M l w be 5 10 15 20 25 time s Figure 20 Calculated Surface Stokes 3 wave theory User Manual WaveLoads 39 45 www gigawind de Universitat Hannover IE 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover LHI Calculated wave characteristics Calculated Wave Parameter Wave height m 12 0000 Wave Period s 13 0000 Water Depth m 30 0000 Wave length m Fenton Approach 198 1978 Wave amplitude m 5 8404 1 s 0 4833 f Hz 0 0769 k 0 0317 c m s 15 2460 L d 6 6066 H g T 0 0072 steepness 0 1851 H d 0 4000 H L 0 0605 d L 0 1514 The calculated forces are shown in Figure 21 As the tube is merely slightly inclined the main force is in x direction Its maximum is 135 3 KN at 12 6 s Force in x direction Force in y direction Force in z direction Integrated Force kN 50 100 o 5 10 15 20 25 time s Figure 21 Total forces on inclined member User Manual WaveLoads 40 45 www gigawind de Universitat Hannover Ei 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover LFI Example 5 Morison forces on an inclined tube Sobey stream function The parameters Drag coefficient 0 7 Inertia
16. RANSPORTMODEL If mass transport is activated you can chose between two ways for the series expansion of high order WaveLoads of the non periodic component no mass transport 1 Stokes transport model Euler transport model STRECHINGSMODE Method for finding the wave kinematics above mean water level 0 Extrapolation of Airy results from mean water level 1 Wheeler s stretching method Only necessary for Stream Function Theories N_ ORDER Order of the Fourier series maximum order is 15 MPUNCT Number of segments on wave profile must be odd default 121 for Fenton it must be larger than 100 for others a value of about 20 suffices KMAX The upper limit for the number of iterations DEANDAMPING Damping coefficient for the iteration default 0 3 If stream function theory by Fenton is chosen FENTONSTEP Subdividing the vertical direction in N zones for calculation default N 10 Only necessary for Wave Spectrum Approach SEEGANG 3D OBERFLAECH 1 a file with a time dependent 3D surface profile will be generated for Tecplot file name Seegang_3DXYZOberflaech plt User Manual WaveLoads 16 45 www gigawind de E Gigawind Universit t Hannover 1I SEEGANG DURATION SEEGANG_ TIMESTEP SEEGANG TIEFE X_SEASTREAM Y SEASTREAM SEEGANG SPECTRUM MODE SEEGANG SPECTRUM DATAFILE SEEGANG N OMEGA SEEGANG SUPERPOS MODE Institut f r Str mungsmechanik und Elektronisches Rechnen im Bauwesen E B Universit t Hannover 0 no water s
17. The wave parameter input file MODEL LABEL 22 03 95 18UhrNSB SEEGANG_3D_OBERFLAECH SEEGANG_DURATION SEEGANG_TIMESTEP SEEGANG TIEFE X_SEASTREAM Y_SEASTREAM SEEGANG_SPECTRUM_MODE SEEGANG_SPECTRUM_DATAFILE EL1995 8PC SEEGANG_N_OMEGA SEEGANG_SUPERPOS_MODE SEEGANG_OMEGA_MIN SEEGANG_OMEGA_MAX end of the Waves Input User Manual WaveLoads 44 45 www gigawind de FE 3 A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover IF Universit t Hannover Ee m water surface 0 100 200 300 400 500 i In 6 100 200 300 400 500 Tel Figure 28 Generated Load Series Figure 28 shows the resulting loads in x direction using the available methods for superposition of waves User Manual WaveLoads 45 45 www gigawind de
18. am function are 1 Bottom boundary condition no flow through sea floor Y x d 0 atz d 2 kinematic free surface boundary condition Y x n 0 atz n Q net flow between sea surface and seabed 3 dynamic free surface boundary condition 2 2 1 gn B atz n B Bernoulli constant 2 ox Oz The first formulation was by Dean It is a symmetric stream function theory which is nonlinear and similar to Stokes higher order theories due to using same assumptions Consequently some of its limitations are also inherent in this theory L N Y x z ra gt C sinh nk d z cos kx n l The coefficients C are found through a best fit to the dynamic free surface boundary condition in the least square sense Another formulation of this problem is the one by Fenton It is similar to Dean s stream function theory but has a broader range of applicability Another advantage is that this theory requires less complicated calculations Fenton s stream function is valid in deep and shallow water depths efficient in calculation of numerical coefficient and uses kH 2 in the perturbation instead of ka as in Stokes theories sinh jk d 2 os jkx cosh jkd Bu 1 2 N Y x z Uld z z YC j l Sobey s formulation gives better results for waves near breaking than the other approaches The iteration also aims to fulfil the surface boundary conditions g sinh jk d z Y x Z dr DC eae User Manua
19. are calculated for the defined structures the number of nodes influences the calculated integral forces and moments It is necessary to define at least one reference point for which the moment will be calculated The list of all available keywords and their meanings NSUBSTRUCT defines the number of structure components SUBSTRUCTINDEX index of a substructure always starting with 0 so the first index of the first member is 0 User Manual WaveLoads 20 45 www gigawind de Universitat Hannover A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l XU x coordinate of the upper endpoint of the current member YU y coordinate of the upper endpoint of the current member ZU z coordinate of the upper endpoint of the current member XL x coordinate of the lower endpoint of the current member YL y coordinate of the lower endpoint of the current member ZL z coordinate of the lower endpoint of the current member RADIUS radius of the circular member in meter CD drag coefficient default 0 7 CM inertia coefficient default 2 0 NELEMENT number of elements in which the structure is divided NNODES instead of NELEMENT Number of nodes in which the structure is divided NNODES NELEMENT 1 According to the number of members this block must be repeated NUMBMOMTREF Number of reference points for calculating the moment limited to max 5 points MOMTREFINDEX Index of a referenc
20. awind Universitat Hannover l Institut f r Str mungsmechanik und Elektronisches Rechnen im Bauwesen E B Universit t Hannover 6 zstokes2_structmoment plt The calculated moments at a chosen point s Stokes 3 order output files stokes3_par dat dstokes3_moris fem parameters for Stokes wave File prepared for processing with ANSYS dstokes3_integralkraft plt This file contains a time series of the integrated dstokes3_substr plt dstokes3_surface plt Morison forces in kN in all possible directions All calculated parameters over structure in Tecplot style The calculated surface depending on time dstokes3_structmoment plt The calculated moments at a chosen point s dstokes3_fskindynbe plt Stokes 5 order output files l 8 9 10 stokes5_structmoment plt wellenpar dat stokes5_moris fem stokes5_integralkraft plt stokes5_accexz plt stokes5_substr plt stokes5_surface plt stokes5_oberfl plt stokes5_xvelo plt stokes5_zvelo plt 11 stokes5_fskindybe plt All calculated parameters on surface over time ASCII FILE containing general information about the calculated wave File prepared for processing with ANSYS This file contains a time series of the integrated Morison forces in kN in all possible directions A time series of the acceleration in x and z direction Tecplot style All calculated parameters over structure in Tecplot style The calculated surface depending o
21. d de E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Universitat Hannover Coefficients in Morison equation In the Morison equation the parameters cy and c are used They are dependent upon the state of flow and the structure These dependencies are expressed by the Reynolds number Re by the Keulegan Carpenter number KC and the structure s roughness k D Extensive experiments have been done by Turgut Sarpakya to obtain values for ca and Cm His results are often used and have been curve fitted for usage in numerical computations Adapted Morison equation for inclined tubes For inclined tubes an adapted Morison equation is used The unit vector in axial direction being e e e e sin pcos 9 sin pcos J cos o the velocity terms can be written as follows v u e eut ev ew v v e e u e v e w v w e eu e v e w This leads to the absolute value for the velocity lvy Ju w e u e w The terms for acceleration are formed analogously For calculating the wave forces in the respective direction following expressions are used fe CnP c SD v f Cup 2 C Ds v re Diy v Recommended Reading General Dean R G Dalrymple R A Water Wave mechanics for engineers and scientist World Scientific Singapore 1984 Massel S R Ocean surface waves their physics and prediction World Scientific Singapore
22. e point always starting with 0 XM x coordinate of the node for moment calculation YM y coordinate of the node for moment calculation ZM z coordinate of the node for moment calculation According to the number of nodes for moment calculation this block must be repeated A structure input file describing two members could look like this NSUBSTRUCT 2 SUBSTRUCTINDEX 0 XU 0 0 YU 0 0 User Manual WaveLoads 21 45 www gigawind de 4 a Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover I FI Universit t Hannover ZU gt 20 0 E XL pg B YE 0 0 E ZL 30 0 E RADIUS 0 455 E CD 07 E CM gt 24 E NELEMENT lt 350 E SUBSTRUCTINDEX 1 RADIUS 0 455 H CD 0 700 H CM 2 0000 H NELEMENT 40 NUMBMOMTREF 2 Number of reference points on the structure where the moments of Morison forces must be calculated H Coordinates of the first point index from 0 up to NUMBMOMTREF 1 MOMTREFINDEX 0 it XM Oe m YM 2080 m ZM 30 0 m it Coordinates of the second point index from 0 up to NUMBMOMTREF 1 MOMTREFINDEX 1 a XM 0 0 m YM 0 0 m ZM 10 0 User Manual WaveLoads 22 45 www gigawind de Gi ind Institut f r Str mungsmechanik mein und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Universitat Hannover m End of t
23. eam function Theory in Formulation by Sobey Stream function Theory in Formulation by Fenton Stream function Theory in Formulation by Dalrymple Wave Spectra Approach OMmANANIDMNBWN Ke LABEL here a name for the problem can be defined DURATION defines the simulation time in seconds only for regular wave models TIMESTEP defines the time step WATERDEPTH the fixed water depth in meters WAVEHEIGT wave height in meters WAVEPERIOD wave period in seconds only if WAVELENGTH is not active you can decide whether you want to describe the wave by period or by wavelength WAVELENGTH wave length in meter only if WAVEPERIOD is not active you can decide whether you want to describe the wave by period or by wavelength User Manual WaveLoads 15 45 www gigawind de Universitat Hannover E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l EULERCURRENT The calculation can be performed with or without a constant basic current component Y for YES calculation with current N for NO calculation without current CURRENTVELOCITY Basic current velocity in meter second value gt 1 in direction of wave propagation value lt 1 opposed to wave propagation if calculation shall be performed with constant current MASSTRANSPORT Calculations can be performed with or without mass transport Y for YES calculation with mass transport N for NO calculation without mass transport T
24. est and trough 2 wer AL L The formulation for the orbits for 1 order theory uses the orbits of Airy s theory ER H cosh 2z z d L sinf 2a 3 u 2 sinh 27d L L T 2 _ H Sea Es d L aa 2a Xo 3 R aH sa 2r z d 2 sinh 2 zd L 4L xo x coordinate of orbit origin Zo z coordinate of orbit origin The orbit s time Fa give the velocities ge Zo cer 2 dt sinh kd a kU sin xk o Saad a dt sinh kd U current In WaveLoads Lagrangian waves of the first order have been implemented User Manual WaveLoads 6 45 www gigawind de Universitat Hannover l Universitat Hannover E A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Stream function solutions The stream function theory was first introduced by Dean These approaches solve the problem for the stream function and derive the wave kinematics from it There exist several formulations for the stream function the ones by Dean Fenton and Sobey are included in WaveLoads All ofthem use a Fourier series for calculating the stream function and require that the boundary condition is satisfied at the surface It is a numeric solution of the problem Differences between the three approaches are apparent for steep waves the results for gentle slopes are close There are no assumptions used only the number of elements in the Fourier series influences the quality The boundary conditions for the stre
25. h kh d water depth H wave height n surface elevation angular frequency z coordinate from MWL upward k wave number Stokes 2 3 and 5 order theory The Stokes waves are extensions to Airy s theory still assuming small amplitudes They give amore realistic surface with higher narrower crests and lower broader troughs For their development the velocity potential is written as an expansion O 7 with e ka which is assumed to be small Therefore terms of higher order of are neglected The order of the theory is the number of terms considered For the 1 order a 0 5H and the equations become the same as in Airy s theory The expressions for 2 etc remain the same for each extension The changes are for which is still dependent on the wave height but with increasingly complicated expressions The solutions which are obtained through successive approximation become more complicated for each expansion Here the surface elevation for Stokes 2 order theory is given 2 2 coth kd cos 2 kx at 4L 2sinh kd n x t Z cos kr ot User Manual WaveLoads 5 45 www gigawind de E a A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universit t Hannover l Universitat Hannover EB For higher order waves this expression is extended by more cosine terms and altered by other coefficients The coefficients differ by
26. hanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Universit t Hannover Available Wave Theories This section gives a short overview of the wave theories available in WaveLoads The intention is to give the user an idea of what is behind the offered possibilities For more detailed and comprehensive information other sources should additionally be consulted A short list of recommended reading is added For calculation of regular waves eight theories have been implemented four analytical solutions and four iterative approaches For irregular waves wave spectra approaches are available using superposed linear waves The inclusion of non linear irregular waves through the Local Fourier Approximation is currently under progress Mostly 2D waves are calculated Additionally a 3D spectral approach is included Governing differential equations and boundary conditions Some general equations have to be fulfilled by the solutions for the wave kinematics They include the mass conservation law and constraints at the bottom and the free surface ao Ao Laplace s equation 0 h x r 6 velocity potential x wave propagation direction z upward direction origin in MWL The velocity potential yields the velocities as oD oP ee v Ox Oz The relation between the velocity potential and the stream function being ob _ av ob oY ax az Oz Ox follows the Laplace equation for Y Or OV
27. he input block Output Files In the file _integralkraft plt the integrated force is saved specified for substructures for all models except model 0 Model 0 output files 1 Allwaves_Fskindynbc plt file including water surface profiles orbital velocities orbital accelerations and kinematic and dynamic free surface boundary condition errors for the Airy and Stokes wave theories Airy theory output files 1 wellenpar dat ASCII FILE containing general information about the calculated wave 1 w_moris fem File prepared for processing with ANSYS 2 w_integralkraft plt This file contains a time series of the integrated Morison forces in kN in all possible directions 3 w_fskindynbc plt All calculated parameters in Tecplot style for surface 4 w_morissubstr plt All calculated parameters over structure in Tecplot style 5 w_surface plt The calculated surface depending on time 6 w_structmoment plt The calculated moments at a chosen point s Stokes 2 order output files 1 zstokes2_moris fem File prepared for processing with ANSYS 2 zstokes2_integralkraft plt This file contains a time series of the integrated Morison forces in kN in all possible directions 3 zstokes2_substr plt All calculated parameters over structure in Tecplot style 4 zstokes2_surface plt The calculated surface depending on time 5 zstokes2_param plt All calculated parameters in Tecplot style User Manual WaveLoads 23 45 www gigawind de f Gig
28. irtschaft und Technologie The research group GIGAWIND at Hannover University deals with environmental and structural design aspects of offshore wind energy converters OWEC One aim of this research is to develop and improve methods and tools for the design and construction of offshore wind energy turbines in order to optimize their design and to reduce construction and operating costs To reach this aim there is aneed for having a reliable tool for calculating wave loading on OWEC support structures Therefore the software WAVELOADS which includes both regular and irregular wave loading was developed The Fluid Mechanic Institute limits the user support for WAVELOADS However questions remarks bug reports suggestions etc that may contribute to the continued development of WAVELOADS are always welcome and we will try to respond as soon as possible Please send your bug reports to mdorf hydromech uni hannover de or nba hydromech uni hannover de A current version of WAVELOADS will be available through the GIGA WIND web site www gigawind de once the user has signed a licence agreement WaveLoads is copyrighted by the Fluid Mechanics Institute ISEB Copyright holders will not be liable for any direct indirect special or consequential damages arising out of any use of the software or documentation A re distribution of the software is not allowed User Manual WaveLoads 3 45 www gigawind de f A 3 Institut f r Str mungsmec
29. itched off MASSTRANSPORT N without mass transport TRANSPORTMODEL 0 no mass transport THE END t 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Input file for discretised spectrum The input file for a discretised spectrum is structured as follows Information about where and when the spectrum was measured is specified in the first line The second line contains the peak frequency the energy of the peak frequency its direction and spread the significant wave height height of long waves T gt 10s mean period zero crossing period wave length and the number of values Significant among those are the peak frequency and its energy as the first two values and the last value the number of following value groups The following value groups are written in the order frequency energy main direction spread The latter two are only of significance if directional sea state is considered Note Be careful to have the same amount of letters and digits as in the example The first frequency in the discretised file must be larger than zero All frequencies are in Hz and the angles are in HELWR 199503221800 0 160 4 37200 44 1 1 81 6 25 5 60 5 40 6 08 33 0 030 0 03322 80 10 0 040 0 01275 12 12 0 050 0 01438 65 15 0 060 0 00987 18 18 0 070 0 01442 70 20 0 080 0 02476 22 22 0 090 0 05182 25 25 0 100 0 08146 28 1 0 110 0 24910 30 1 0 120 0 25330 33 1 0 130 0 62340 3
30. iversit t Hannover Universitat Hannover obeys 8 Airy 4 Fenton eta m T s Figure 7 Surface elevation for Airy s theory and stream function solutions after Fenton and Sobey 8000 7000 6000 5000 4000 3000 2000 1000 0 1000 Stokes 2 Stokes 5 n ASSES 2000 3000 4000 5000 30 T s Figure 8 Accumulated force for Airy Stokes 2 Stokes 3 and Stokes 4 order theories User Manual WaveLoads 29 45 www gigawind de t 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universitat Hannover IF Universitat Hannover 5000 Sobeys N f Fenton 4000 3000 2000 3000 Airy Ss 1000 2000 3000 4000 T s Figure 9 Accumulated force for Airy s theory and stream function solutions after Fenton and Sobey User Manual WaveLoads 30 45 www gigawind de Universitat Hannover E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover LFI Appendix Example 1 Morison forces on a monopile Stokes 5 order The parameters Wave height 10 0 m Water depth 34 0 m Wave period 15 0 s Euler current 0 01 m s Stokes Mass transport Pile diameter 6 0 m Pile length 54 0 m Drag coefficient 0 7 Inertia coefficient 2 0 Number of Nodes 501 Wave theory Stokes 5 order Figure 10 Node forces on a monopile The wave
31. l WaveLoads 7 45 www gigawind de t 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Universitat Hannover Irregular waves through wave spectra Common modelling of irregular waves consists of superposition of linear waves with differing amplitudes and frequencies WaveLoads supplies a tool for generating such waves out of wave spectra These are either parameterised JONSWAP spectra or discretised ones The JONSWAP spectrum is used in this form _ 0 oO ag 1 25 5 5 200 0 22 S Pa y e E ga 007d X 0 0081 u X wind fetch length u wind velocity p peak frequency y 3 3 for lt wp P p 0 07 for w gt ap P P2 0 09 The formulation for the JONSWAP spectrum using significant wave parameters H and T as given in Offshore Standard DNV OS J101 June 2004 has likewise been implemented This calculates the parameter y using the above mentioned values in the following way r 5 gt m 3 6 eon gt ee exp 5 75 1 15 3 65 5 r 1 e Ir Observe that the following expressions include some random values Therefore two calculations using the same parameters will not give the same time series The generated waves are linearly superposed by one of the following methods For all methods N n t gt A c0s t 9 p is uniformly distributed n l 1 constant frequency interval gives periodic waves A o Omna
32. le containing STREAM FUNCTION COEFFICIENTS dalrymple_structmoment plt The calculated moments at a chosen point s The calculated surface over time dalrymple_integralkraft plt This file contains a time series of the integrated dalrymple velo_acce plt wavepar dat Morison forces in kN in all possible directions Calculated velocities accelerations and water surface elevation in Tecplot style empty file Stream function by Fenton output files User Manual WaveLoads 25 45 www gigawind de E Gigawind Universit t Hannover l l 2 fenton_moris fem fenton _substr plt testfenton dat Institut f r Str mungsmechanik und Elektronisches Rechnen im Bauwesen E B Universit t Hannover File prepared for processing with ANSYS All calculated parameters over structure in Tecplot style Test file fenton_structmoment plt The calculated moments at a chosen point s fenton_integralkraft plt This file contains a time series of the integrated fenton_surface plt fenton_oberfl plt wavepar dat Fentontest dat Morison forces in kN in all possible directions Calculated water surface elevation in Tecplot style note time not in seconds but in time steps calculated water surface over space ASCII FILE containing general information about the calculated wave empty file Stream function by Sobey output files sobey_substr plt All calculated parameters over structure in Tecplot style sobey_s
33. n by Fenton output files as una 25 Stream function by Sobey output files 0 0 ee ec ccsecsteceeeeeeeeeeseeceeceeeeeeeenseeesaeeneeeees 26 Wave spectrum approach output Teen 21 Effects of Using different Wave Theo ee 28 PS ee seele 31 Example 1 Morison forces on a monopile Stokes 5 order 31 Example 2 Morison forces on a monopile Fenton stream function uneee 34 Example 3 Moment on monopile Lagrangian Wave ccssesseeeeeeeceeeceeeeneeeneeenees 36 Example 4 Morison forces on an inclined tube Stokes 3 order 39 Example 5 Morison forces on an inclined tube Sobey stream function 4 Example 6 Composite structure Dean Dalrymple stream function 43 Example 7 Wave spectrum approach method 0 cccccesccesseeeeceeeeeeeeceeeceeeeeeeenseeesaees 44 User Manual WaveLoads 2 45 www gigawind de Universitat Hannover E a A Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover l Introduction This software for calculating wave induced loading on hydrodynamically transparent structures has been developed by B Nguyen and K Mittendorf within the research project Structure Design and Environmental Aspects of Offshore Wind Energy Converters GIGAWIND This project is supported by the German Federal Ministry of Economics and Technology Bundesministerium f r W
34. n time The calculated surface depending on space The calculated horizontal velocities depending on time The calculated vertical velocities depending on time The calculated moments at a chosen point s All calculated parameters on surface over time User Manual WaveLoads 24 45 www gigawind de f Gigawind Universitat Hannover 1 12 stokes5_param dat Institut f r Str mungsmechanik und Elektronisches Rechnen im Bauwesen E B Universit t Hannover Parameters for Stokes wave Lagrangian approach by Woltering output files 8 9 wellenpar dat Oberflach fil Igr_moris fem Igr_integralkraft plt lgr_surface plt lgr_oberfl plt lgr_fskindynbe plt Igr_substr plt Igr_structmoment plt ASCII FILE containing general information about the calculated wave surface over time File prepared for processing with ANSYS This file contains a time series of the integrated Morison forces in kN in all possible directions The calculated surface depending on time The calculated surface depending on space All calculated parameters at surface in Tecplot style All calculated parameters over structure in Tecplot style The calculated moments at a chosen point s Stream function by Dean Dalrymple output files 8 dalrymple_moris fem dalrymple_substr plt dalrymple_surface plt File prepared for processing with ANSYS All calculated parameters over structure in Tecplot style dalrympletest dat Test fi
35. r calculating the random numbers is used Local Fourier approximation for irregular waves A new feature of WaveLoads is the Local Fourier Approximation for irregular waves which also works for regular waves This is presently not included in the distributed version Nevertheless a short description is included for future reference The local Fourier Approximation LFA was developed by Sobey The wave kinematics are predicted using a given surface time series at a fixed location The LFA is an extension of the Fourier model for regular waves finding the solution over a moving time window For each window the velocity potential is expressed as J P x z t ee sin j kx at ia cosh jkd a with Ug Euler current m s d water depth m User Manual WaveLoads 9 45 www gigawind de Universitat Hannover l Universitat Hannover J Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Aj Fourier coefficients k wave number 1 m angular wave frequency 1 s j order of For each window i the kinematic free surface boundary condition is formulated for each surface node fi k kx A gw D 2 pu Dw E i w Dt t Dt Dt and the dynamic free surface condition is formulated for each node as i i f k kx A P boul iw tn B 0 ot 2 with B Bernoulli constant These non linear implicit equations with the unknown a k A
36. t empty file User Manual WaveLoads 27 45 www gigawind de Universitat Hannover l Universitat Hannover f A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Effects of Using different Wave Theories In this section the different wave theories are applied to one exemplary wave on a monopile The following pictures show the calculated surface elevations and the accumulated forces The parameters Wave height 17 5 m Water depth 34 0 m Wave period 15 0 s Euler current 0 00 m s Stokes Mass transport Pile diameter 6 0 m Pile length 54 0 m Drag coefficient 0 7 Inertia coefficient 2 0 Number of Nodes 501 For this wave with an H d 0 5 the calculated surface elevations for the stream functions are practically identical see Figure 7 The results for Stokes fifth order are similar to these Stokes 2 order is apparently now longer valid as is visible in the trough region see Figure 6 Interesting in the calculation of accumulated force is the fact that the results for the stream function differ somewhat see Figure 9 even as the surface elevation is practically the same Stokes 5 Stokes 3 Stokes 2 Airy eta m T s Figure 6 Surface elevation for Airy Stokes 2 Stokes 3 and Stokes 4 order theories User Manual WaveLoads 28 45 www gigawind de f t 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Un
37. te structure Dean Dalrymple stream function Calculated Structure The parameters x Wave height 15 0m Water depth 30 0 m Wave period 16 0s Euler current 0 00 m s Pile diameter 0 91 m Pile length 0 20 0 m Pile length 1 50 0 m Pile length 2 70 71 m Pile length 3 70 71 m Drag coefficient 0 7 Inertia coefficient 2 0 Number of Nodes 31 Figure 24 Composite Structure Wave theory Dean Dalrymple stream function The resulting integrated forces in x direction for each structure member 250 200 150 100 50 TotalMorison x 0 5 10 15 T Figure 25 Integrated wave loads in x direction User Manual WaveLoads 43 45 www gigawind de E 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen Universitat Hannover rl Universit t Hannover Example 7 Wave spectrum approach method The parameters Monopile Pile diameter 0 91 m Pile length 40 0m Drag coefficient 0 7 Inertia coefficient 2 0 Number of Nodes 20 Water depth 30 0 m Input spectrum 22 03 1995 06 00 pm NSB Figure 27 shows the resulting time series of water surface elevation which are generating from a spectrum by using following methods Method 1 constant delta omega Method 2 irrational omega Method 3 Webster and Trudell EB 0 1 02 0 3 04 05 0 6 omega Figure 26 Input Spectrum The discretised spectrum is read from the file HEL1995 SPC
38. the structure see Figure 4 In general the GUI s features are the same as when working in the MS DOS environment One exception is that it is not possible for wave spectra to be calculated without use of User Manual WaveLoads 12 45 www gigawind de J 2 Institut f r Str mungsmechanik BE c igawind und Elektronisches Rechnen im Bauwesen EB Universit t Hannover LI l Universit t Hannover direction Using the directional information enhances calculating time considerably ca factor 50 Another limitation with using the GUI is that the maximum number of reference points for which the moment is calculated is three compared to five when working in the MS DOS environment E WaveLoads 1 0 Project Name Finding Optimal Model for Data Set Extrapolation on Wave Parameter File tempw Stucutre Parameter File temps Figure 2 Graphical User Interface User Manual WaveLoads 13 45 www gigawind de t s Institut f r Str mungsmechanik BEE cisawina und Elektronisches Rechnen im Bauwesen E B Universit t Hannover Universitat Hannover WaveLoads 1 0 101 x File work Info zs Imegular waves Structure Water Surface Integral Forces 1 Integral Forces 2 Integral Forces 3 Integrali 451 36 1 __ Integrated Morison Force FX kN ie Max Fx 49 9339 kN g 02 _Min Fx 40 2536 kN 9 8 __ Integrated Morison Force FY kN Oe z 3 0 7 ___Max
39. tructmoment plt The calculated moments at a chosen point s sobey_moris fem File prepared for processing with ANSYS sobey_integralkraft plt This file contains a time series of the integrated Morison forces in kN in all possible directions sobey_surface plt Calculated water surface elevation in Tecplot style sobey_info dat parameters of Sobey wave User Manual WaveLoads 26 45 www gigawind de E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universitat Hannover LF Universitat Hannover Wave spectrum approach output files When using the wave spectrum approach it depends on the kind of spectrum chosen which output files are written 1 seegang_integralkraft plt This file contains a time series of the integrated Morison forces in kN in all possible directions 2 seegang_moris fem File prepared for processing with ANSYS 3 seegang param dat File with all wavelets if discretised spectrum 4 seegang_structmoment plt The calculated moments at a chosen point s 5 seegang_substr plt All calculated parameters over structure in Tecplot style 6 seegang 2DXZoberfl plt 2D water surface elevation in Tecplot style 7 seegang dataspec plt Input spectrum in Tecplot style if discretised spectrum 8 seegang spectrum plt Spectrum of the calculated sea state in Tecplot style 9 optional Seegang 3DXYZOberflaech plt 3D time dependent water surface elevation in Tecplot style 10 surf da
40. truktur dat argc 3 argu 0 waves argv i waves dat argv 2 struktur dat wellendatei waves dat strukturdatei struktur MODEL 5 stw MODEL wert 5 5 DURAT I ON z 26 stw DURATION wert 26 26 666666 TIMESTEP s 8 18 stw TIMESTEP wert 6 16 A 38 8 wert 36 12 6 wert 12 13 8 wert 13 Y stw EULERCURRENT wert 7 CURRENTUELOCITY 01 wert 6 61 bd stw MASSTRANSPORT wert Y z TRANSPORTMODEL a I stw TRANSPORTMODEL wert 1 1 N_ORDER 5 stw N_ORDER wert 5 Figure 1 Starting a calculation with WaveLoads in a MS DOS environment Graphical User Interface For most applications the graphical user interface GUI can be used In this one can create input files or load existing input files and run the program When the calculation is concluded the resulting wave elevations integral forces and moments will be graphically shown Figure 3 shows the integrated force on the fourth member of a composed structure The integrated forces are shown for the specified substructures and moments are shown for the reference points Additionally all results will be written into output files as described in following sections Figure 2 shows the general layout of the GUI For using define the wave parameters and the structure then press the Calculate button To load existing input files or for saving use the menu File Load Wave Parameter and its equivalents The button Graphic gives a general view of
41. urface file will be generated duration for the sea state simulation in seconds defines the time step for the simulation the fixed water depth in meters current velocity in meter second in x direction current velocity in meter second in y direction 0 parameterised JONSWAP Spectrum using coefficients 1 discretised spectrum given by data file 2 parameterised JONSWAP Spectrum with H and T file name for a discretised spectrum if SEEGANG_ SPECTRUM MODE 1 number of grid points for dividing the wave spectrum 1 Mode 1 constant Aw 2 Mode 2 irrational 3 Mode 3 Webster amp Trudell for details look into section rregular waves through wave spectra SEEGANG OMEGA MIN SEEGANG OMEGA MAX lowest frequency min highest frequency Omax If no discretised spectrum file is defined you have to give all recommended parameters for a JONSWAP spectrum SEEGANG ALPHA SEEGANG BETAI SEEGANG_BETA2 SEEGANG GAMMA SEEGANG OMEGA M Phillips Alpha constant for high frequency tail relates respectively to the widths of the left side of the spectral peak relates respectively to the widths of the right side of the spectral peak peak enhancement factor peak frequency User Manual WaveLoads 17 45 www gigawind de Gigawind Universitat Hannover l SEEGANG STAT SEEGANG MART SEEGANG DATUM SEEGANG_UHRZEIT SEEGANG_ DIRECTION MODEL parameterised parameterised SEEGANG PEAK THETAO SEEGANG SPREAD
42. x Onin N A 285 a Aa 2 irrational frequency gives non periodic waves Aw nnt1 On I Nnnn A 25 a Aa 3 Webster amp Trudell gives non periodic waves A 42m N Ar 0 my S do n N A ZZ User Manual WaveLoads 8 45 www gigawind de E A 3 Institut f r Str mungsmechanik Gigawind und Elektronisches Rechnen im Bauwesen E B Universit t Hannover IF Universit t Hannover Ar is the area under the spectral function for the frequency interval Ao Aa is calculated through the condition that Ar is the same for all Ao Furthermore it is possible to give a directional wave spectrum This gives for each frequency i e wave component its main direction and spread in addition to its magnitude The spectral density is distributed over the direction by multiplying the non directional spectrum with the spread function D S 0 S D 0 S q is calculated according to the above described methods Two spread functions are implemented 1 Cosine model D 6 cos40 0 Z lt 0 lt mT 2 NIA O is the frequency direction Qo is the main peak frequency direction 2 Banner s hyperbolic model D T cosh 0 in which ae is the frequency is the frequency of the peak 1 24 lt 0 56 2 612 0 56 lt p lt 0 95 B 9 28 2 13 0 95 lt 2 lt 16 w F 10 0 440 8394exp 0 56 i gt gt 16 When using the non directional quasi 2D spectrum another method fo
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