Open Channel Flow - Universidade Federal do Paraná
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1. N gi a e KARLSRUHE 2 o Wildpark stadion Schlo Kaiserstra e Universitat 500 Karlsruhe a A ee CSN A OIN S N Europahalie AbschnittB AM L 20380 a e Figure 2 Alb near Karlsruhe Pad Open Channel Flow Project Water level calculation with HEC RAS Appendix 2 Details on the geometry of the stop log weir Thickness of the stop logs 0 10 m Height of the stop logs 0 15m Centerline location of the stop log weir is at km 5 600 Boundary of the outer weir fields 20 0 m and 30 0 m Upper edge of the closed outer weir fields 102 00 m b 10m b 10m b 10m Overfall height h Z 99 63 mNN 99 63 mNN Q 2m s Figure 3 geometric details of the weir W 99 33 mNN Figure 4 cross section view of the stop log weir and schematic definition of overfall height weir height and spillway approach height 12 sidi ad Open Channel Flow j UFPR Project Water level calculation with HEC RAS CM Appendix 3 Standard Weir Equation and Weir Coefficients S a SA wa SERTARE uE memo A EA HERE 9 TALL Ty YELLE 0 4 h 8 0 08 wW 0 04 0 w A Co 1 3 2 i V2 8 ho hy hy Co 0 407 0 053 lt 6 2 w for W Rehbock 3 2 w C 0 707 f a Z lt 0 06 3 for 0 Boss Figure 5 Standard weir equation and discharge coefficients for fully aerated sharp crested weirs h is used for the water2. Edit Geometric Data Cross Section Options Ineffective Flow Areas gt HEC RAS User s Manual S 6 16 Modify those areas after the first model run to check for model sensitivity related to that schematization 7 Iteratively calculate the overflow height at the weir for mean water flow MQ 2 m s using appendix 3 Choose the accuracy at which to abort the iteration and substantiate your decision 8 Create a discharge profile for the calculation with mean water flow MQ 2 m s Edit Steady Flow Data Rename this profile to MQ Options Edit Profile Names Enter the known control water surface elevation 99 72 m at river station km 5 595 as a boundary condition Define the condition of the weir gates left and right weir field closed central field opened as shown in appendix 2 under Edit Steady Flow Data Options Gate Openings HEC RAS Users s Manual S 7 1ff Calculate the water surface elevations Note You can change the boundary conditions with the button Reach Boundary Conditions in the Steady Flow Editor There you choose Set boundary for one profile at a time and then you can define the control water surface elevation with the button Known W S for your mean water discharge profile MQ 9 Undertake a sensitivity analysis changing uncertain model parameters e g ineffective areas weir equation boundary conditions and quantifying their influence on model results c
3. Open Channel Flow Course paper Water level calculation with HEC RAS a VA VA eer 1 am ESA Prof Dr Ing Tobias Bleninger Graduate Program for Water Resources and Environmental Engineering PPGERHA Universidade Federal do Paran UFPR Centro Polit cnico Bloco V Caixa Postal 19011 81531 990 Curitiba PR Brasil Tel 041 3361 3212 Cel 041 8497 5685 bleninger ufpr br www tobias bleninger info 21 junho 2015 rara iid OEN r Open Channel Flow 6 UFPR Project Water level calculation with HEC RAS Acknowledgements This work is based on the seminar paper developed by Markus Vaas and Nikolai Stache of the Institute for Hydromechanics of the Karlsruhe Institute of Technology www ifh kit edu Germany The author acknowledges their help and support and that they made the work available for teaching purposes at the UFPR Further information on the German project can be found under http www ifh kit edu english 418 php Introduction The Influence of river engineering activity on the water levels is estimated by using one dimensional simulation software This is done to enable planning and evaluation of river engineering measures regarding navigational issues or danger of flooding and erosion For the calculation of water surface elevations in open channels numerical models are increasingly employed using existing real world data These simulation models have to adequately account for the physical and geome
4. choose the correct profile MHQ for the display of the results 4 Save your new discharge profile and the weir gate positions again under the name a flow Edit Steady Flow Data File Save Flow Data The geometry remains unchanged a_geo_1 3 1 3 Water Surface Calculation for Highest Flood Water In case of a maximum floodwater discharge HHQ 100 m s all weir fields are opened completely Because of the higher water surface elevation downstream of the weir no free flow is possible and a backwater will occur For this case the control water surface elevation at the downstream channel end is defined as 104 49 m Calculate the water surface elevation for HHQ 100 m s Procedure 1 Insert a third discharge profile for HHQ 100 m s in the Steady Flow Data Editor Enter the new control water surface elevation as a boundary condition for the new profile 2 Adjust the weir gate openings for the profile HHQ Edit Steady Flow Data Options Gate Openings 3 Calculate the water surface elevations 4 Export a table of water surface elevations to your paper and also add a longitudinal plot of the water surface elevations Note choose the correct profile HHQ for the display of the results 5 Save your flow data again under the name a flow Edit Steady Flow Data File Save Flow Data 6 Compute additional parameters such as bed shear stress velocity profile surface velocity shear velocity
5. mean velocity profile and profile of turbulent fluctuations for the same cross sections for all three discharges and compare those with each other using tables and graphs rara iid gee Open Channel Flow P UFPR Project Water level calculation with HEC RAS a 1 4 Simulation of a Bridge at River Station km 8 0355 At river station km 8 0355 a bridge with four piers is planned The elevation of the bottom edge of the bridge is 104 90 m The planned location and the geometric properties of the bridge and of the piers can be taken from appendices 4 and 5 Implement the bridge into the existing dataset Check if in case of the maximum flood water HHQ 100 m s a minimum freeboard of freq 0 10 m under the bridge remains Procedure 1 Do an approximate manual calculation for the expected energy loss cause by the bridge piers using the table and graphs provided during the class or literature values 2 Insert the required cross profiles gt HEC RAS Users s Manual S 6 11ff The x y data of the additional cross profiles is given in appendix 4 3 Model the bridge HEC RAS Users s Manual S 6 31ff All required data is given in app 5 4 Define the ineffectice flow areas caused by the outer bridge piers and implement them for the cross profiles directly adjacent to the bridge Edit Geometric Data Cross Section Options Ineffective Flow Areas HEC RAS Hydraulic Reference Manual S 5 5ff 5 Calculate the water s
6. equations 5 6 7 Calculate compare and analyze characteristic parameters for each measurement and each measurement point mean standard deviation Calculate characteristic parameters for each profil vertical horizontal and visualize the profiles and values Add theoretically determined profiles to the plot and compare fit qualitatively and quantitatively including the measurements from the propeller and the confetti Calculate the total mean velocity and the total discharge and compare with theoretical values and the measured value Calculate the theoretical water level using Darcy Weissbach and Manning equation and compare with measured water levels ii ie it 2H D Open Channel Flow j UFPR Project Water level calculation with HEC RAS CM 4 Technical Report Write a technical report taking into account all results of parts 1 to 3 for submission to local authorities The report herefore should also contain information on e project region description of river and available data objectives of the study compilation description and discussion of available data description of governing equations and numerical scheme and software implementation description and analysis of simulation results statistical analysis of obtained results sensitivity analysis conclusions pm Open Channel Flow Project Water level calculation with HEC RAS Appendices Appendix 1 Map of the river Alb M 1 50 000 1km 2km
7. the affected river sections to prevent flooding Calculate the speed at which the wave travels down the river Save your flow data under the name b unstd flow Edit Unsteady Flow Data File Save Unsteady Flow Data as and your calculation plan under Run Unsteady Flow Analysis File Save Plan as with the name b 3 plan 3 Laboratory studies 3 1 Lab setup and measurements The laboratory setup and the applied measurement technique should be described analyzed and evaluated Lab procedure 1 2 3 4 Describe the laboratory setup geometries scales pictures Describe the measurement techniques Describe the measurement program coordinate system locations periods frequencies boundary conditions etc The following steps should be done for two different discharges and interchanging groups a Determine the total flow using the flow meter of the lab and approximate equations b Measure surface velocities using confetti and running a statistically representative number of tests c Measure velocities at different characteristical points at least 6 within the channel using the propeller flow meter d Measure at least three vertical velocity profiles close to the previous points and using at least 4 points for each profile using the ADV Office procedure The following steps should be done in the office analyzing the obtained data comparing characteristic parameters with theoretical
8. 1 90 112 50 Open Channel Flow UFPR Project Water level calculation with HEC RAS Appendix 7 Unsteady discharge On Feb 12 and 13 following flow rates were measured at km 20 454 13 02 time discharge hh mm _Q ms 0000 20 0100 0100 20 02 00 0200 20 03 00 0300 20 04 00 20 20 20 05 00 06 00 07 00 08 00 09 00 10 00 11 00 12 00 13 00 13 00 12 00 14 00 15 00 16 00 17 00 18 00 19 00 20 00 21 00 22 00 23 00 00 00 20 20 20 20 20 20 20 1 2 3 4 5 6 7 7 7 8 8 9 9 NINININI N N POPP PP NIN wo wo w Co CO CIO CO gt SLI KOLI KOLIKON O N A A W O
9. 103 43 102 09 29 0 102 10 37 2 103 45 102 11 29 0 102 13 41 2 105 43 103 33 31 9 103 33 103 43 37 2 103 43 103 45 37 2 103 45 Appendix 5 Geometric Details for the planned bridge Width of the bridge The centre of the Bridge is at equates to River Station of the bridge 105 43 41 2 Boundary of the outside piers at Station Symmetry axis of the inside piers at Station Width of the inside pillars Up to elevation 101 00 m Up to underside of the bridge shape of the piers 105 43 10 00 m Km 8 0355 3 50 and 33 50 m 13 50 and 23 50 m Thickness of the inside pillars 2m im Square profile with semi circular ends see HEC RAS Hydraulic Reference Manual Page 5 13 fm vere i iT ul Open Channel Flow i UFPR Project Water level calculation with HEC RAS 6 Hithenee nj 1067 10E 104 1CE 4 SHe J 4 ds 102 Edno 401 Bagmaes a Volaccs 10C T T T 1 10 O 10 20 40 50 Saton m Appendix 6 Measured water levels Measured water levels between river station km 17 550 and km 20 454 during mean water discharge MHQ 20 m s The sections between these cross profiles can be considered as areas of linear roughness grade Water surfaceManning s n elevation m sim 109 86 110 17 110 39 110 67 111 07 11
10. F file is submitted in the end Include a table of contents and appropriate labels for all tables and figures Also refer to the suggestions in these guides http people ufpr br tobias dhs orientacao htm e Use accuracy adequate for engineering work for your end results e Include the tabular results from HEC RAS in your paper where required or appropriate Within HEC RAS you can define your own tables and then export them to a word processing program to be modified or extended or re formatted All tables and figures have to be labeled and commented e All required results have to be included in the paper and all solutions must be complete and consistent e Please submit all your final HEC RAS files together with a printed and a digital version of your paper either on CD on a USB flash drive or as a ZIP file by email e Please share with us any comments or suggestions regarding this project paper You will help us and the students following you Please tell us the total time required to complete the assignment e f you have any problems or questions make use of the office hours or contact your supervisor by email any time e You are allowed to work in groups of 2 students handing over one result and receiving a joint grade However copying between distinct groups is not allowed and will cause grade 0 e All steps in the instruction below must be reported in the final report e All material must be in English The final presentation of the resu
11. at river station km 17 500 The reduction of the channel width induces an increase of the water surface level at the cross section km 17 550 of about 0 10 m during mean water discharge MHQ 20 m s Determine the backwater limit or stagnation point i e how far upstream the increase of the water level at km 17 550 has an effect on the water surface level Procedure 1 Check for criticality again as before 2 Insert a second profile in the Steady Flow Data Editor containing the modified control water surface elevation at km 17 550 as a boundary condition Name this profile MHQ constricted 3 Insert interpolated cross profiles with a maximum distance of 20 m in the channel reach between km 17 550 and km 19 000 HEC RAS Users s Manual S 6 102ff 4 Calculate and compare the water surface elevations before and after the building activity Show both water surface profiles in a comparison table Insert a column which displays the difference of the water surface elevations before and after the building activity Display the course of the water level before and after the building activity in a longitudinal profile plot Determine the location of the stagnation point and show it in an enlarged profile plot Explain the advantage of using interpolated cross sections in this case Save your flow data Edit Steady Flow Data File Save Flow Data under the name b flow Calculate the backwater curve manually or using an own cod
12. depth in these equations instead of y Open Channel Flow Project Water level calculation with HEC RAS Appendix 4 Table of the cross profiles for the planned installation of the bridge at km 8 0355 Profile 8 030 Profile 8 041 Profile 8 050 y x y x y 105 47 4 0 105 47 4 0 105 47 103 48 0 0 103 48 0 0 103 48 103 47 0 01 103 47 0 01 103 47 103 29 5 3 103 29 5 3 103 29 102 33 7 6 102 32 7 6 102 31 102 12 8 1 102 11 8 1 102 09 102 11 8 1 102 09 9 2 101 44 101 48 9 2 101 46 10 7 100 59 100 62 10 7 100 61 12 3 100 29 100 61 10 7 100 6 13 9 100 32 100 29 12 2 100 29 14 4 100 32 100 32 13 8 100 32 15 4 100 28 100 32 14 3 100 32 16 5 100 23 100 28 15 3 100 28 17 0 100 21 100 23 16 4 100 23 18 6 100 16 100 21 16 9 100 21 20 5 100 22 100 16 18 5 100 16 21 5 100 21 100 22 20 4 100 22 22 4 100 21 100 21 21 4 100 21 24 3 100 26 100 20 22 3 100 21 24 5 100 29 100 24 24 2 100 25 26 7 100 74 100 27 24 4 100 28 27 4 101 17 100 68 26 7 100 71 29 0 102 12 100 71 26 7 100 74 31 9 103 33 101 10 27 4 101 14 37 2
13. e by using the single step method and using a unique simplified profile and compare with the HEC RAS data and discuss the results a OND ne ee n ras Open Channel Flow Va UFPR Project Water level calculation with HEC RAS CM 2 3 Calculation of a Flood Wave Due to an intense rain event in the watershed a flood wave is passing through the Alb River Check if river reach B offers the necessary capacity to convey the temporarily increased discharge volume Note Reach B already carries the mean water flow MHQ 20 m s when the wave occurs Procedure 1 2 3 Da Enter the unsteady flow data Edit Unsteady Flow Data Use the discharge hydrograph of the flood water at km 20 454 from appendix 7 Run the simulation for the given time period Determine whether the flow remains within the maximum cross sectional area If not so identify the flooded sections and calculate the time period of flooding for one of these cross sections Add a table and cross sectional plot as well as a plot of the water level over time at that section Mark the water level at which the flooding occurs Note For the analysis of unsteady discharge HEC RAS needs the list of the cross sections where the unsteady water levels are calculated Unsteady flow analysis Options Stage and flow output locations By default only the results from upstream and downstream limits are shown Up to which height do sandbags have to be stacked at
14. lts should also be prepared and presented in English with a duration of approximately 15min Have fun with the HEC RAS project Project definition As the planning engineer you are tasked with supplying the required verifications for different river engineering measures to authorities The German river Alb is a medium sized river with a watershed of approximately 457 km and a running length of 56 km It originates in the northern Black Forest at a DE eae a height of about 750 m above sea level and enters the Rhine valley near Ettlingen Karlsruhe and joins the river Rhine at Rhine kilometer 367 5 s Figure 1 Figure 1 River Alb at Ettlingen It flows through For the planned construction of a bridge within reach A of the Alb River and for renaturation and other construction work within reach B of the river an assessment of the expected water levels and roughness distribution in this area is needed The problem is to be solved with the aid of numeric calculations The tasks are arranged chronologically This means that data results and calibrations should be carried over from preceding tasks if not stated otherwise tit fan iP em a Open Channel Flow j UFPR Project Water level calculation with HEC RAS CM 1 River Reach A Calculation of water surface elevations and simulation of a bridge in channel reach A considering variations in channel roughness A bridge is planned across the Alb River within reach A km 5 595
15. m freeboard fre 0 10 m at the bridge is still met for the maximum flood water HHQ 100 ms 3 Compare the results of 1 5 and 1 6 in a table and or graph 4 Interpret the differences between your results from 1 5 and 1 6 What does that mean for the excavation work in the main channel 5 Save your new geometric data under the name a 5 geo Edit Geometric Data File Save Geometric Data as iit R PI om nN Open Channel Flow G UFPR Project Water level calculation with HEC RAS 2 River Reach B Investigation of channel reach B between river stations km 17 550 and km 20 454 Note Please create a subdirectory part B in your working directory Copy the file aufg b prj there Use this directory for all files and data of part B 2 1 Calibration of the water surface level Because of renaturation measures along the river in reach B of the Alb River km 17 550 20 454 see appendix 1 the roughness changes in this area The energy loss calculated with the original roughness allocation no longer complies with the natural conditions and results in wrong water level calculations The roughness is to be calibrated with the aid of water level measurements which were obtained after the renaturation during mean water flow MHQ 20 m s Take the measured water levels from the cross profiles in appendix 6 The channel geometry after the renaturation is contained in the file aufg b prj Choose reasonable
16. n from measurements Procedure 1 Describe the project region using the provided data as well as information from a literature review Note Focus on technical information e g maps and satellite images and explore the provided data in detail to obtain for example the mean bed slope mean river width bed material etc 2 Check for criticality of the flow and determine the direction of the numerical calculation upstream or downstream Note Calculate an approximate normal depth using Manning s law Compare with the critical depth y Assume a wide rectangular channel 3 Calculate an approximate mean inclination of the water surface manually for the whole branch and all discharges as a first estimate and compare with HEC RAS results afterwards 4 In HEC RAS model the stop log weir as an inline structure using the information in appendix 2 Note First define the outer shape of the completely closed weir as a rigid structure Weir Embankment at the correct location using the geometry editor Edit Geometric Data Inline Structure Then add the three weir fields Gates to this structure Choose the right weir geometry weir crest shape HEC RAS User s Manual p 6 64ff 5 Describe the principle of ineffective areas its justification and its consequences for the solved equations using the HEC RAS manual or additional information 6 Define ineffective areas around the weir by adding them in the respective adjacent cross profiles
17. or composite channels 2 Change the roughness on the overbanks to a typical roughness coefficient for light brush and trees in summer HEC RAS Hydraulic Reference Manual S 3 14 3 Check the minimum freeboard under the bridge freq 0 10 m 4 Explain the result and make a statement regarding the importance of controlling growth on the overbanks 5 Compare the obtained results with your hand calculation for the expected water level increase 6 Save your new geometric data under the name a 5 geo Edit Geometric Data File Save Geometric Data as 1 6 Simulation of Increased Roughness in the Main Channel Several small floods in the area up to 1 km upstream of the stop log weir resulted in strong sediment transport To prevent overflow of the river during floods the channel bottom is to be excavated again Due to the irregularities introduced by the excavation work bottom roughness will increase in the main channel between km 5 595 und km 6 600 Check if the minimum free board freq 0 10 m at the bridge is still met Procedure 1 Change the roughness in the part of the main channel stated above to a typical value for a natural stream clean winding some pools and shoals HEC RAS Hydraulic Reference Manual S 3 14 fit ee erry Be RN i tat E a Vad c Open Channel Flow i UFPR Project Water level calculation with HEC RAS CM 2 Calculate the water surface elevations and check if the minimu
18. or supercritical flow the steps follow the flow direction At the respective starting locations the water surface elevations have to be known as boundary conditions A detailed discussion of the calculation of water surface elevations is provided in class or in the related literature on Free surface flows Open channel flow Fluvial Hydrauilcs or similar Within the context of the project numerical water surface calculations for two different reaches of the Alb River see appendix 1 are done using a one dimensional flow model The software package HEC RAS is used for modeling and calculation For help on using HEC RAS as well as documentation of the underlying mathematical model and equations employed the manuals HEC RAS User s Manual HEC RAS Applications Guide and HEC RAS Hydraulic Reference Manual can be downloaded The geometric data files containing the cross sections for both river reaches are also available at the course homepage http people ufpr br tobias dhs canais htm Sn TATA GEA MET E Sent pa pp pen Channel Flow UFPR Project Water level calculation with HEC RAS 6 Instructions and Notes e You can download HEC RAS and its manuals here http www hec usace army mil software hec ras e The project files and geometric data files here http people ufpr br tobias dhs canais htm e Any word processing software can be used to write the seminar paper e g Word OpenOffice Latex as long as a PD
19. roughness coefficients and explain your choice Procedure 1 Check for criticality again with an approximate calculation by hand and choose the correct direction for the calculations upstream or downstream 2 Calculate the water surface elevations for a sensibly chosen constant roughness coefficient HEC RAS Hydraulic Reference Manual S 3 14 The natural river bed of the Alb River is clean and without major anomalies in this area Take the control water surface elevations from appendix 5 Name the profile MHQ normal in the Steady Flow Data Editor 3 Vary the roughness coefficients step by step moving along the cross sections until the water level of the current channel reach agrees with the measured water levels 4 Document the roughness coefficients and the water levels of the individual cross profiles in a table and compare them to the original coefficients from 1 2 5 Interpret the new final new roughness coefficients that you just obtained Are they reasonable and how do they compare to the original values Display a longitudinal plot of the water surface profile in your paper Save your new geometric data Edit Geometric Data File Save Geometric Data as under the name b 1 geo and your flow data Edit Steady Flow Data File Save Flow Data as using the name b flow No 2 2 Backwater Curve Calculation Because of construction work a constriction of the channel is introduced in river reach B
20. s E Bda au Vaal tas Open Channel Flow UFPR Project Water level calculation with HEC RAS CM 10 Export a table of relevant model results e g water surface elevations depths widths velocities and several more to your paper and also add a longitudinal plot and some cross sectional plots of the water surface elevations HEC RAS User s Manual S 9 1ff S 9 13ff 11 Compare the calculated water level at the stop log weir with the water level obtained from your hand calculation in A 1 7 What could be the reason for a potential difference in the results 12 Compare the calculated parameters with your hand calculations from A 1 2 and A 1 3 13 Save your new geometric data Edit Geometric Data File Save Geometric Data as under the name a_geo_ 1 3 and your flow data Edit Steady Flow Data File Save Flow Data as using the name a flow 14 Compute additional parameters such as bed shear stress velocity profile surface velocity shear velocity mean velocity profile and profile of turbulent fluctuations for 3 arbitrary cross sections and compare those with each other using tables and graphs 1 2 Water Surface Calculation for Medium Flood Water In the next step calculate the water surface elevation for mean flood water flow MHQ 20 m s Vary the water depth by changing the weir height in the center field within the limits of the stop log weir so that both of these conditions are met To a
21. to km 8 744 at km 8 035 A numerical calculation of the water surface elevations must be done for different discharges The effects on the water levels of a change in roughness on the overbanks and in the main channel have to be investigated especially in the vicinity of the bridge The downstream water surface is controlled by a stop log weir at km 5 600 Itis a three field system with weir field widths of b 10 m see appendix 3 The geometric data of the channel is already known Use the supplied project file filename aufg a prj Also contained in the file are the roughness coefficients Manning s n Note Please create a subdirectory part A in your working directory Copy the file aufg a prj there Use this directory for all files of part A of this assignment 1 1 Water Surface Calculation for Mean Water A water surface calculation with a mean water flow MQ 2 m s in channel reach A of the Alb River km 5 595 8 744 is necessary to estimate mean water elevations and minimum flow velocities Only the centre field of the stop log weir is partially opened the outer fields are closed see appendix 2 You can assume the weir to be sharp crested and assume free flow downstream of the weir i e no backwater The weir crest of the center field is initially set to an elevation of 99 63 m for mean water flow The control water surface elevation 99 72 m at river station km 5 595 for mean water flow MQ 2 m s is know
22. tric complexity of the watershed and have to meet the demands of river engineering in terms of accuracy and economic efficiency For the calculation of water surface elevations in open channel flows one dimensional mathematical models are available Therein the following simplifying assumptions are made one dimensional approach mild slope of the river bed constant roughness and linear friction slope between adjacent cross profiles rigid boundaries no sediment transport The one dimensional approach is based on the energy loss in each calculation step The individual calculation steps are each tied to a cross profile along the river For the calculation of the energy loss HEC RAS uses Manning s law as a flow formula The roughness coefficients n Manning s n also known as Strickler coefficient kg m s 1 n used in this formula are taken as constant in the individual calculation steps From the real world geometric data of the individual cross profiles suitable x y datasets have to be derived for the numerical calculation of the water surface elevations This is done with the x axis being defined normal to the flow direction from an arbitrary base point and the y axis as the elevation of the cross profile point The distances between adjacent cross profiles have to be known too For subcritical flow the calculation of the water surface is done stepwise against the flow direction according to the control location concept Hence f
23. urface elevations with HEC RAS twice once with the energy equation Bernoulli and then with the momentum equation HEC RAS Users s Manual S 6 55ff und HEC RAS Hydraulic Reference Manual S 5 9ff Select one of the methods for your further calculations Explain your decision 6 Check if the minimum freeboard freq 0 10 m remains Note You can see all data relevant to the bridge in the special Bridge type table under View Detailed Output Tables Type Bridge 7 Export a table of water surface elevations to your paper and also add a longitudinal plot of the water surface elevations Also add an enlarged longitudinal plot for the area containing the bridge Note choose the correct profile HHQ for the display of the results Compare the obtained results with your hand calculation for the expected energy loss Save your new geometric data under the name a 4 geo Edit Geometric Data File Save Geometric Data as and your flow data Edit Steady Flow Data File Save Flow Data 00 1 5 Simulation of Increased Roughness on the Overbanks For ecological reasons the effect of uncontrolled vegetation growth on the overbanks on the water surface elevations near the bridge in the case of flood water flow is to be investigated Therefore an increased roughness on the overbanks has to be simulated Procedure 1 Do an approximate manual calculation for the water level increase using the equation f
24. void sediment transport during medium flood water maximum flow velocity must not exceed 0 75 m s anywhere in the river reach Note Velocities exceeding 0 75 m s will occur and are allowed in the immediate vicinity of the weir ll To avoid waterlogging of the soil near river station km 8 744 the water surface elevation must remain below 102 13 m The outer fields of the weir remain closed The control water surface elevation 100 60 m is known for mean flood water flow MHQ 20 m s at km 5 595 from measurements Procedure 1 Add a new discharge profile MHQ with mean flood water discharge MHQ 20 m s and the boundary conditions given above to your discharge data Note To insert a new discharge profile increase the number of profiles from 1 to 2 Enter Edit Number of Profiles in the Steady Flow Editor and name this new profile MHQ Under Reach boundary Conditions you can now enter the control water surface elevation for the new profile 2 Vary the weir height in the center weir field under Edit Steady Flow Data Options Gate Openings for your profile MHQ so that both conditions given above are met HEC RAS User s Manual S 9 13ff Also specify weir heights that have not worked and state which conditions were not met Observe that each stop log has a height of 15 cm see appendix 2 3 Export a table of water surface elevations to your paper and also add a longitudinal plot of the water surface elevations Note
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