Two-Dimensional Finite-Volume Hydrodynamic Model for River
Contents
1.2. yu pozenbs saou 60 0 322 ali E o1enbs 910070 pasenbs pouenbs 9 soyout o1enbs ES VIV Sou 1z9 0 S21j2tuO 1 wy uix sanau 191 soi nu spied 601 sanau S21 2UI 716 0 sp p y 123 BTE sapu soau 0 0 pay y ul sauoul 6 0 0 VST sayoul ul HIONGTT loqui amp g put oL Ag dnn UUM 1944 109045 OL Kg mouy uaa 1 5 SLINA IS OL SNOISSIHANOO FALVAIXOUdd V SYO LOVA NOISSHANOO ORLLAN NUACGOW IS SLINA 1 OL SNOISVIHMANOO ALVWIXOUddv TABLE OF CONTENTS Technical Report D ocumentation ii Modern Metric Conversion Factors eene iii iv OL FIOS donde nde disque V 1 Examples with Analytical Solutions sss 1 1 D Riemann Problem eene 1 B Involuntary Movement 9 C Gate Open Problem eene 13 Di SUMMA iste atl tbid as 15 2 Real Site Simulation 17 17 B Import Outline D Sla 18 C Coarse Gid e tp OU ddp SR CUR 19 Pee GTI eoe E 20 E Boundary Conditions 21
3. Hydrodynamics Model Tidal Flow No restrictions This document is Marsh available to the public through the National Technical Information Service Springfield Virginia 22161 19 Security Classif of this report 20 Security Classif of this page 21 No of Pages 22 Price Unclassified Unclassified Form DOT F 1700 7 8 72 Reproduction of completed page authorized juouroansuoJA JO 5 LUO VULIIUY I 10 oquiAs SI JS 2 2 ool 08 09 o ot 0 oz Ot ooz 081 01 08 or Or ut 986 z d 2118124191 4 2o SMPO 6 ZE a s 21niraduisi 1 98X9 UO LL V Cad AL 4 C 408 1 Jy 5193 L060 91 0002 suoi uous L 08 25 UNLV ad WL sudo spunod 1 41049 SE8z soouno zo L qi 000Z suoi 1045 TOUI swegegau qi spunod 055 5 33 20 23110 511219 3 tu Ur UMOS oq T 0001 uet 2216218 saum 0A ILON SSVW Qu paqno saaw S9L 0 spy oIqna P PA spied 214 8071 paqna so otu poqns sanaw 8200 193J aiqna W di 123 21 SIESE paqna sanaw Uu Sou suojjed 123 198 5101185 950 sont somni 1967 s uno piny 20 zo pini F EO O d 1 SNWIYIOA UA pasenbs s24jouio t 652 218165 UU asenbs 9350 porenbs uy vu SIPA coro 2428 ov ov 59128 52101291 vu yu porenbs saou 9 8 0 sp1e o1enbs 206 10 123J 21enbs POLO pazeubs
4. Project Options Figure 1 14 Project O ptions for G ate O pen Problem 6 Now savethe project as tutorial3 est 7 Right click and choose Select from the Context Menu Left click and hold the mouse button just outside the cell in row 1 and column 1 then drag the mouse cursor and enclose all the cells in column 1 through 20 in the select box vignette box Release the left mouse button and you will have the selected the cells Right dick and choose Edit Grid from the Context Menu Assign the selected cells a head of 10 meters and check the Head check box and then click OK This will assign a head value of 10 meters to all the cells upstream of the gate Follow the same procedure to select all the downstream cells and specify a head of 5 meters to those cells 8 Savethe Project O ptions and the project is ready to run 14 9 Run the project using the Modeling Options shown in Figure 1 15 For later validation let the calculation run for 7 1 seconds Again the results will be saved in tutorial3 r00 Modeling Options 125 2 f2 fa2 fo sss fs 22 2 Figure 1 15 Modeling O ptions for G ate O pen Problem shows the distribution of water surface elevation along a line TOW Tom upstream to downstream through the center of the gate at 7 1 seconds after the gate is opened In the figure a comparison is also made with the analytical solution for the same problem D Summary The above th
5. Performing Organization Code 7 Author s 8 Performing Organization Report No J D Lin W G Liao K J Qiu M W Lefor JHR 02 277 9 Performing Organization Name and Address 10 Work Unit No TRAIS University of Connecticut Connecticut Transportation Institute 12 Sponsoring Agency Name and Address 13 Type of Report and Period Covered Connecticut Department of Transportation Tutorial 280 West Street Rocky Hill CT 06067 0207 SPR 2214 15 Supplementary Notes Conducted in cooperation with the U S Department of Transportation Federal Highway Administration 16 Abstract The Tutorial is a companion document of Report JHR 02 275 entitled Two Dimensional Finite Volume Hydrodynamic Model for River Marsh Systems User s Manual which provides in detail the description of the model and its operational procedures An Intel Pentium at 200MHz or above running under Windows NT 4 0 or Windows 95 or 98 is required to run the model This document is prepared for users who would like to have a hands on experience of the model s operation before applying the model to simulate shallow water flow in a river marsh system Three examples with analytical solutions and a real site project are provided for practice The step by step instruction will guide a user from creating a project for simulation to presenting the results The model and all necessary data are provided in the disk included 17 Key Words 18 Distribution Statement
6. together with BC Type Repeat this procedure for all the boundary sections to complete the list in the box as shown in Figure 2 5 and click OK to save it 22 Boundary Sections LA la la la la st 2 Figure 2 5 Boundary Sections Edit D ialog The three boundary selections in this Tutorial problem should be highlighted in the Workspace as shown in Figure 2 6 through When you edit for a section it is highlighted Then when you edit the next section the new one is highlighted and the previous highlight is removed Several conditions must be met to successfully specify a boundary section 1 the section must consist of a single continuous line segment 2 sections must not overlap 3 each section must have its own section number and 4 each section may only have one boundary condition type The Boundary Sections edit dialog checks these conditions before accepting a boundary section into the model Section 1 in Figure 2 6 consists of all of the boundary walls in the lower half of the computational domain The boundary condition is Type 2 the no flow condition Section 2 in Figure 2 7 consists of all of the boundary lines in the upper half of the 23 computational domain The boundary condition is Type 1 observed water surface elevation vs time These values have to be specified at the selected locations see next section Section 3 in Figure 2 8 is the boundary of the central island in
7. 1 First save the boundary condition entries to a text file with the bdc extension using the format above In this example there are two files tutorial4_s1Lbdc and tutorial4 s13 Right click the associated node in the boundary section where you want to assign a given boundary condition to bring up the Context Menu and choose Edit Grid This will bring up the N ode edit dialog for that node If the node has no boundary condition already assigned to it it should appear as shown in Figure 2 9 If there is a boundary condition already attached it should look like Figure 2 10 Click the button labeled Observed Data to bring up a file Open dialog Browse to the boundary condition file and click Open The model will then retrieve the boundary condition from the file and attach it to the node If there is only one node in a boundary section with attached boundary condition the whole section will use the same boundary condition on all of its nodes If two or more nodes have attached boundary conditions the above procedure has to be repeated for each node Then the program will interpolate the boundary condition over the section nodes based on the locations of the nodes along the section line If no boundary conditions have been attached to any of the nodes in a section a value of zero will be assigned to it The 0 signifies no flow the second type boundary condition For the first type boundary condition head equals zero Thus you must g
8. F Initial 29 G Grid A CISC osse deridet Geben 30 H Simulation and Results sees 31 I CO MGIISIONS db Ed DEDERE 32 LIST OF FIGURES Figure 1 1 The FVHM Window eee 2 Figure 1 2 Project Options for 1 D Riemann Problem 3 Figure 1 3 Node Editing DJaloQp ascen ao ioa een a 4 Figure 1 4 First Gello niece reet deos 4 Figure 1 5 Cell Property Edit D ialog ses 5 Figure 1 6 Modeling O ptions D ialog ees 6 Figure 1 7 Velocity Field at 10 Seconds After Flow Starts 6 Figure 1 8 Comparison Between Simulated Results and the Afalytcal9olubioTk bit rp pn pa e PAR 0 Figure 1 9 Involuntary Movement Problem ss 9 Figure 1 10 Project Options for Involuntary Movement Problem 10 Figure 1 11 Linearly Interpolating the Values in End Cells 11 Figure 1 12 Assigning a Head Value to All Selected Cells 11 Figure 1 13 Gate O pen PrIODIGH sodio ttes 13 Figure 1 14 Project O ptions for G ate O pen Problem 14 Figure 1 15 Modeling Options for G ate O pen Problem 15 Figure 1 16 Comparison of Analytical and Calculated Results 16 Figure 2 1 Project Options for Westbrook 18 Figure 2 2 Outline Import for We
9. a one dimensional Riemann problem and the result will be compared with that of an analytical solution The second application is an open gate example which has been used in many other similar studies The result of the open gate simulation will be compared with results from other studies in the literature A 1 D Riemann Problem A one dimensional open channel flow formulated with shallow water approximations is generally known as a one dimensional Riemann Problem This example deals with opening of a gate or breaking of a dam in the middle of a straight rectangular open channel Initially the water surface forms a step at this location of the gate No flow or a vertical wall is considered as the boundary condition at both ends of the channel From the folder where you saved the files from the FVHM system diskettes you may start the model by double clicking the FVHM icon This will bring up the Main Window initially with an empty Workspace as shown in Figure 1 1 To solve the 1 D Riemann problem the channel can be represented by a grid of a single row of computational cells shown below Follow the procedure below to create a new tutorial project 1 Create a new project by using File New The new project is named Umie by default Y ou may proceed with the default If you want to name the project now click on the Workspace and then click File N ew again The Estu dialog appears click Yes to bring up the Save as dialog to save the
10. formed as many sided polygons which are not suitable for use in the model but this is an initial step in constructing a grid for a complex computational domain This coarse grid will be edited into a fine grid as shown in Figure 2 4 The procedure here is first to get into the create New Cell mode by right click in the Workspace to bring up the Context Menu and selecting New Cell Then click continuously to form each cells each of which outlines a section as shown in Figure 2 3 It is important to carefully select where you click to position node points which may or may not be outline points and also not to create cells that overlap each other Note also that the imported outline points in some cases may not be sufficient to define the topographic features of the site therefore the selection of cells should be guided by a topographic map 19 Figure 2 3 Coarse G rid for Westbrook Site D Fine Grid By splitting the walls and the cells you can arrive at a fine grid as shown in Figure 2 4 In this step bottom elevations and other cell attributes are assigned to each cell The attributes of a cell include center coordinates x y head bottom elevation and Manning s n To split a cell select the Edit Split cell menu and click the node of a cell where you want the split to start Then you may click inside each cell to make connecting new nodes and walls When you click another node of the same cell the cell will be split In other
11. solid wall the white space with an opening the colored portion is placed across the middle of the basin as shown in Figure 1 13 The opening is placed off center and extended to the bottom of the basin which will introduce asymmetry in flow Initially the gate in the opening is closed and a differential head exists between the upstream left and downstream right water levels At time zero the gate opens instantaneously and water in the upstream basin gushes through the Opening creating a supercritical flow downstream of the gate in the lower basin See Figure 1 13 Figure 1 13 Gate Open Example This exercise starts with the construction of the computational cells following the procedure outlined in the previous two examples 1 Open anew project 2 Specify the entries in the Project Options as shown in Figure 1 14 3 Create the first cell and specify the locations of its four nodes at 0 0 5 0 5 5 and 0 5 4 Using the cell just created use Copy and Paste to make up a 40 x 40 grid 13 5 The cell coordinates at the lower left corner are row 1 and column 1 of the grid Select the cells at column 199 rows 1 to 19 and 35 to 40 column 20 rows 1 to 19 and 35 to 40 and delete them To select cells right click and choose Select from the Context Menu Click and drag over the cells you want to select Clicking a cell again will deselect it To delete cells right click and choose Delete from the Context Menu
12. the marsh It has Type 2 the no flow boundary condition Figure 2 6 Boundary Section 1 Type 2 at Westbrook Site Boundary Conditions Each boundary section may have zero default one or more boundary conditions specified forit but the type of boundary condition must match that of the boundary section FVHM uses boundary condition files to associate boundary conditions with boundary sections A typical boundary condition file for a boundary section may look like the following 1100 1996 10 26 5 37 59 0 39 1996 1026 6 6 23 0 33 1996 10 26 6 34 47 0 15 1996 10 26 7 311 0 15 1996 10 26 7 31 35 0 53 24 1996 10 26 259 59 0 99 1996 10 26 8 28 23 1 48 1996 10 26 8 56 47 1 98 1996 10 26 9 25 11 2 46 1996 10 26 9 53 35 2 88 In the first row the first value 1 indicates the type of boundary condition in this case Type 1 or water surface elevation prescribed as a function of time The second value 10 indicates the number of entries The third value indicates the system units used 0 English 1 metric From the second row on entries in the columns from left to right are year month day of the month hour minute second and water surface elevation If there is more than one set of observed boundary conditions in a boundary section you will need more than one file i e one file for each set of data To associate a boundary condition with its associated node in the boundary section follow the procedure below
13. 5 Time date Interpolation of Staff 13 on 10 26 86 ta 10 27 96 Ba Staff Readings ft 26 265 27 27 5 28 2865 Time date o Observation Interpolation Figure 2 11 Boundary Conditions for Westbrook Site F Initial Condition The initial condition can be specified at each cell while you are generating the grid Another way to do this by giving an initial uniform value to all of the cells and let the simulation run through several tidal cycles and use the results as the initial condition In this example we gave an initial uniform value of 3 5 ft an average water elevation at 5 37 am on October 26 1996 to all the cells Figure 2 6 shows the overall picture after the initial value was assigned You can see that almost all of the region is dry except for a few wet blue spots in the channel indicating stagnant water Because we wanted an initial condition at the later of the two boundary conditions October 26 1996 at 5 37 59 am we started the calculation with a uniform initial value 29 and let it run from October 26 1996 at 5 37 59 am through four full tidal circles We know the water elevation at the downstream location should begin and end at 3 5 ft This is not realistic but is considered acceptable The final state of the region was saved into the project as the initial condition To save the result as the initial condition you can either choose File Save and overwrite the given uniform initial val
14. Node Data Attached X 201378 366 Y 327928498 i Es Remove Observation DK Cancel Figure 2 10 Node Edit D ialog with Boundary Condition Attached In this example two boundary conditions tutorial4_siLbdc and tutorial4 s13 bdc have been specified at two locations indicated by the two arrows in Figure 2 9 These data were collected in the field on O ctober 26 and 27 1996 The plot of observed data is shown in Figure 2 11 As you can see in two sinusoid curves were interpolated to fit the data The boundary conditions used in the calculation were taken from the fitted curves instead of from the actual data By sampling 100 points from each curve over time we derived two boundary condition files that contain four full tidal circles lasting for about two days At the upstream location to the right at Staff 11 data collection began on October 26 1996 at 5 20 59 am and ended on October 28 at 5 45 02 am At the downstream location at the top at Staff 13 data collection began on October 26 1996 at 5 37 59 am and ended on October 28 1996 at 4 58 05 am The data collected at the two locations show a time lag in the tidal peak from upstream to downstream Also notice that four full tidal circles from the fitted curve last for about 47 hours 40 minutes instead of 48 hours as expected 28 Interpolation of Staff 11 on 10 26 86 to 10 27 96 056 B RN Staff Readings ft 26 26 5 21 2T 28 28
15. TWO DIMENSIONAL FINITE VOLUME HYDRODYNAMIC MODEL FOR RIVER MARSH SYSTEMS TUTORIAL Version 1 0 June 2002 J D Lin W G Liao and K J Qiu Department of Civil and Environmental Engineering M W Lefor Department of G eology University of Connecticut JHR 02 277 Project 93 4 This research was sponsored by the Federal Highway Administration the Joint Highway Research Advisory Council JHRAC of the University of Connecticut and the Connecticut D epartment of Transportation and was carried out at the Connecticut Transportation Institute of the University of Connecticut This document is disseminated under the sponsorship of the Federal Highway Administration in the interest of information exchange The United States Government assumes no liability for its contents or use thereof The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein The contents do not necessarily reflect the official views or policies of the Federal Highway Administration the University of Connecticut or the Connecticut D epartment of Transportation This report does not constitute a standard specification or regulation Technical Report Documentation Page 1 Report No 2 Government Accession No 3 Recipient s Catalog No JHR 02 277 4 Title and Subtitle 5 Report Date Two Dimensional Finite Volume Hydrodynamic June 2002 Model for River Marsh Systems Tutorial Version 1 0 6
16. and check Right click the nghtmost cell in row 6 and specify a value of 1 9 for its bottom elevation as above Right click and choose Select from the Context Menu and then select row 6 in by dragging the mouse from left to right over the cells on row 6 Select Tools Linear Interpolate In the Select Property dialog check the Bottom box see Figure 1 11 and click OK Y ou should now see that the bottom elevation has been linearly interpolated over the entire row 10 Select Property LI Figure 1 11 Linearly Interpolating the Values in End Cells 7 Repeat the above procedure for row 7 Next you need to specify a uniform water elevation of 5 meters for the entire computational domain as follows 8 First right click the mouse to select the entire computational domain 9 Right click again and select Edit Grid to bring up the Cell Property Edit Dialog See Figure 1 12 10 Specify a head of 5 0 meters and check the check box for H ead Click OK to close the dialog Cell Property E dit Dialog I Figure 1 12 Assigning Head Value of 5 to All Selected Cells 11 Now save the project as tutorial2 est and the user is ready to run the simulation 11 Run the simulation for as long as you like there should be no involuntary water movement 12 C Gate Open Problem The computational domain of the Gate Open Example is a square basin of 200m x 200m with a level bottom A
17. d give them a head of 0 25 meters following the same procedure 11 To see a depiction of the water elevation on your screen click the Toolbar button _ Cell Property Edit Dialog Head Bottom D VelocityU D VelbctyV Manning s 0 Figure 1 5 Cell Property Edit D ialog 12 For the 1 D Riemann problem you do not have to specify any boundary conditions The default boundary condition is set for no flow on all sides which is just what is needed for this problem Please remember to save again 13 To start running the calculation click the Toolbar button The Modeling Options dialog will be brought up as shown in Figure 1 6 The dialog will show the current system time in your computer which will be used as the starting time Therefore the time values in the dialog shown on your computer will be different from the values shown in Figure 1 6 Add 10 seconds to the ending time to have the program run 10 seconds from the time the water starts to flow Also type in the other entries as shown in the dialog Click O K and let the program run Modeling Options 1999 Ja 118 ps fh 999 e fi f fo Figure 1 6 Modeling O ptions Dialog 14 The calculated result of the velocity field should look like that shown below in Figure 1 7 Show Velocity enabled Figure 1 7 Velocity Field 10 Seconds After Flow Starts The bar radiating out from the center of each cell represents t
18. e 010 1 21225e 010 2000 01 19 20 37 43 2 91066e 010 2 67368e 010 1 56611e 010 2000 01 19 20 37 44 3 39577e 010 3 06982e 010 1 90189e 010 2000 01 19 20 37 45 3 88088e 010 3 45807e 010 2 23672e 010 2000 01 19 20 37 46 4 36597e 010 3 84142e 010 2 57545e 010 2000 01 19 20 37 47 4 851e 010 4 22095e 010 2 91841e 010 To validate the results the water surface elevation has been compared with the analytical solution of the 1 D Riemann problem Tan 1992 It indicates good agreement as shown in the Figure 8 Time after dam break 10sec ha Do I Cn Vater surface elevation rn E i o 2D Model using Oscher Scheme Analytical Solution 0 Sa a Ba E aa ee 150 100 50 0 50 100 150 Distance from dam location m Figure 1 8 Comparison Between Simulated Results and the Analytical Solution Tan W Y 1992 Shallow Water Hydrodynamics Elsevier ceanography Series V ol 55 Elsevier Amsterdam B Involuntary Movement Problem Bottom slope inside the simulation region has an important effect on the flow pattern throughout the computational domain One problem associated with numerical models when dealing with bottom slope however is the involuntary movement problem In the case of a confined area flooded with water the water surface remains still even with bottom slope variations But because a numerical model introduces round off errors the simulated result might show an involuntary movem
19. e 09 NE Go NE pum in 0 0 0 10 15 10 15 10 15 Time Time Time QObservation Calculation x Small grids Figure 2 15 Comparison of Calculated and bserved Results at Westbrook Site I Conclusions In this example it has been shown that the real site simulation is much more complicated Y ou can rarely use copy and paste in constructing the computational grid because there are not many similar cells that you can copy from When constructing the computational grid you more likely will use the split cell split wall move node and interpolation tools You almost certainly will need a lot of grid adjustment There is also an important issue regarding grid generation i e detail vs efficiency An increase in the number of cells will result in more detailed results but also an increase in computation time A trade off has to be made in most cases bearing in mind the intent of the work and the accuracy required for the application of the final results You may run the model with a coarser grid when you are only interested in the general pattern of the flow field on the other hand an extremely detailed grid is needed when you are interested in the spatial distribution of tidal ranges and their effects on salt marsh vegetation for example In conjunction with other related documentation for FVHM we hope that this tutorial will provide you an overview and hands on experience by working through all the examples 32
20. ent of water over time if the bottom slope has not been treated properly This example deals with a rectangular basin that has a level bottom with an inclined trough running from one end to the other along the centerline of the basin The basin is filled with water The calculation starts with a level water surface and proceeds forward in time If involuntary movement is absent in the FVHM the water surface should remain level at all time The grid used for testing the bottom slope effect in the present model is shown in Figure 1 9 The entire computational domain represents 800x600 square meters and each cell represents an area of 50x50 square meters B 1 Figure 1 9 Involuntary Movement Problem To construct this grid follow the same procedure outlined earlier for the 1 D Riemann problem example For this problem your Project Options should look like those shown below in Figure 1 10 Project Options Figure 1 10 Project O ptions for Involuntary Movement Problem The procedure is as follows 1 2 Construct the first cell with its four nodes at 0 0 50 0 50 50 and 0 50 Use Copy and Paste to complete the rest of cells to cover the whole domain as shown in Figure 1 9 Right click the leftmost cell of row 6 and select Edit Grid from the Context Menu In the Cell property edit dialog specify a value of 0 4 for its bottom elevation
21. erial no 1 of the newly created cell to bring up the N ode editing dialog as shown in Figure 1 3 Serial 1 Data Attached 0000000 Y 0 000000 1 Observed Data Cancel Figure 1 3 Node Editing Dialog 6 Enter 0 forX and 0 for Y and then click the gt button Y ou should see that the first node moves to a new location 0 0 For the next node serial no 2 input 5 meters forX 0 for Y and then click the gt button For the third node serial no 4 input 5 for X 5 for Y and then click the gt button For the fourth node serial no 6 input 0 for X 5 for Y and then click the button This should bring you back to the first node serial no 1 and the cell should become a polygon in this case a perfect square displayed near the left lower comer of the Workspace Click OK to close the dialog M Figure 1 4 First Cell 7 Starting with this first cell you can now use Copy and Paste to create the rest of the cells for the 1 D Riemann problem Right click the Workspace and bring up the Context Menu Choose the Select menu item Left click inside the new cell to select it Bring up the Context Menu again and select Copy which will mark the selected cell for copying Bring up the Context Menu once more and select Paste Now when you move the mouse you should see an outline of the selected cell following the cursor Move this outline to the right side of the first cell and li
22. he magnitude bar length and direction of the velocity Using the Toolbar buttons other solutions such as velocity vectors Froude number etc may also be displayed in the grid If you now check the folder where you saved tutorialLest you will find that the calculation results of the 10 minute run have been saved as tutorial 1100 This file can not be viewed via the model because it is a binary file However after the simulation finishes you may export the result time history of the water surface elevations and velocity components at selected cells to a text file for post processing To do this first select the cells you want to export and then select Result Time History Export Y ou will be prompted to name this exported text file and the folder to save it in This file will have the extension tmh You may open this file for review now or later It consists of three sets of data Head U and V components of velocity in the selected cells over the run time The size of the file depends on the duration and the frequency of output that you have specified in the Modeling Options as shown in Figure 1 6 It is usually large In each set the heading of Head U or V is given in the position of first row and first column Following the heading serial numbers of the selected cells separated by spaces are listed in the first row From the second row on the first column is date and time and the rest are values for Head U or V in columns corres
23. ive a value to sections having the first type boundary condition to have meaningful results 25 TN E t a at FAA qi UIS t 94 Y MS An d lt a la Pen F m b Zu es a AN E a Ae a oth og CU ee Aes SS XN a 9 a mes ot Seri Y Pras ei lA Figure 2 7 Boundary Section 2 1 at Westbrook Site You must also consider the starting time differences among the boundary conditions The model uses the latest starting time found among all of the boundary conditions attached to the grid shown in the Modeling Options dialog as the starting time for a run The model also uses the earliest ending time found among all of the boundary conditions attached to the grid also shown in Modeling Option dialog as the simulation ending time 26 Figure 2 8 Boundary Section 3 Type 2 at Westbrook Site xi E Vata Attached 201975 811 227912253 lt E Observed data _ Figure 2 9 Node Edit Dialog without Boundary Condition A ttached After you have finished attaching a boundary condition the Node Edit Dialog will look like that shown in Figure 2 10 If you click the button labeled Remove 27 Observation you can remove the attached boundary condition from the node and its section Serial 42 Type
24. ne the two up Click the left mouse button and a new cell will be created to the right side of the first cell 8 Repeat the above Copy and Paste operation until 60 cells are lined up across the Workspace To do this more quickly select five cells after you create five then copy and paste five cells at a time In this case the total length of the 60 cells should be 300 meters because you specified the metric system in the Project Options dialog and the side of each cell is 5 meters long The grid now should look like the grid shown in Figure 1 7 in the Workspace 9 Now save your work by clicking the Save button saving the grid in the file tutorialLest This grid which can be used to solve the 1 D Riemann problem 10 Next you must specify the initial condition of the water surface across the 300 meter channel The bottom elevation of all cells is set at 0 meters by default as is the initial water surface elevation The gate open or dam break situation requires that an initial water surface drop be created as the initial condition in the middle of the channel Select the leftmost 30 cells and choose the Edit Grid menu item from the Context Menu The Cell Property Edit Dialog will be brought up See Figure 1 5 Assign head a value of 5 meters and check the checkbox to its right Click OK to close the dialog This procedure will assign the left 30 cells a water surface elevation of 5 meters above the bottom Select the rightmost 30 cells an
25. oss inaccuracies in the field data See the Final Report for JHRAC Project 93 04 The site was also chosen for calibration and validation of FVHM therefore field observed data from this site are available Outline and boundary condition data are included in the system diskette for you to use in this tutorial These data were tabulated as ASCII files output from AutoCAD The first type of data FVHM can use in initially defining a project is outline data Outline data are sets of point coordinates x 2 which provide the topography for the interior and the boundaries of the computational domain In this case the data consist of surveyed points on the marsh in the channels and its boundaries of the site in other cases the data may be derived from topographic maps or a combination of both Once imported into the model the outline data can be used to define the boundaries of the computational domain and in generating the grid for the site The second type of data is boundary condition data which provide the boundary conditions for driving the model through the calculation period It is also recommended that you try to compare your calculated results for tidal stage and or current with observed data as a way to learn how to generate an effective computational grid for further applications Project Options A new project is always created by first bringing up the Main Window and assigning a file name then saving it as a file here t
26. ponding to cell serial numbers A small sample of a result history file in ASCII format is shown below Head 9 159 225 2000 01 19 20 37 37 5 5 02 25 2000 01 19 20 37 38 5 4 9737 0 250067 2000 01 19 20 37 39 5 4 82315 0 26218 2000 01 19 20 37 40 5 4 57209 0 458918 2000 01 19 20 37 41 5 4 30033 0 868783 2000 01 19 20 37 42 5 4 05146 1 18513 2000 01 19 20 37 43 5 3 83808 1 33994 2000 01 19 20 37 44 5 3 6603 1 40224 2000 01 19 20 37 45 4 99996 3 51277 1 43056 2000 01 19 20 37 46 4 99975 3 38912 1 4501 2000 01 19 20 37 47 4 99895 3 28477 1 46904 U 9 159 225 2000 01 19 20 37 37 0 0 0 2000 01 19 20 37 38 4 16599 011 0 0367039 0 000421756 2000 01 19 20 37 39 6 44543 011 0 246589 0 0891948 2000 01 19 20 37 40 7 55947e 011 0 601752 1 77004 2000 01 19 20 37 41 4 57204 010 0 997408 4 24334 2000 01 19 20 37 42 1 55706 008 1 37218 5 51405 2000 01 19 20 37 43 2 97451 007 1 70425 6 04482 2000 01 19 20 37 44 3 90669e 006 1 9887 6 24917 2000 01 19 20 37 45 3 28045 005 2 23055 6 3188 2000 01 19 20 37 46 0 000174817 2 43801 6 32911 2000 01 19 20 37 47 0 000674845 2 61668 6 30906 9 159 225 2000 01 19 20 37 37 0 0 0 2000 01 19 20 37 38 4 8511e 011 4 83992e 011 2 42994e 012 2000 01 19 20 37 39 9 7022e 011 9 58086e 011 5 85129e 012 2000 01 19 20 37 40 1 45533e 010 1 41306e 010 3 23205e 011 2000 01 19 20 37 41 1 94044e 010 1 84817e 010 8 03447e 011 2000 01 19 20 37 42 2 42555e 010 2 26706
27. project with name you choose If there is a project already loaded and it has been modified you will be prompted to save the changes 2 Specify project options using the Project O ptions dialog brought up by clicking Project Options or pressing F8 The Project O ptions fora 1 D Riemann problem should appear and you will enter the items in the boxes as shown in Figure 1 2 Note that the display device size might be different depending on the computer you are using to run the model Click OK to close the dialog H Untitled Estu2D ele 8 a el Figure 1 1 The FVHM Main Window Project Options ie 4 Figure 1 2 Project Options for 1 D Riemann Problem 3 Right click the Workspace and bring up the Context Menu and select New Cell menu item You are now in the create new cell mode 4 Create a new cell by clicking the Workspace five times to form a closed loop This will define the corners nodes of the computational cell you are creating Make sure that you position the first and last clicks at the same location A new cell will be created at the last fifth click when you close the loop At this time it does not matter what the size and shape of the cell are because you will be able to edit it later using the Editing dialogs Now you have a cell in the Workspace The number shown in the cell is the cell serial number See Figure 1 4 5 Right click inside the first node s
28. ree examples although simple have demonstrated almost all of the basic features of FVHM If you have completed the exercises successfully you will have acquired the necessary rudimentary skill to use the FVHM For a complete and detailed explanation of all aspects of the model please refer to the User s Manual and continue on to next example one from a real world site 15 Longitudinal surface profile att 7 15 along center of the openning 10 Water surface elevation m 2D Model using Osher Scheme o Beam and vVarming 5 d 100 50 0 50 100 Distance from dam locationim Figure 1 16 Comparison of Analytical and Calculated Results 16 2 Real Site Simulation Building a modeling project for a real site simulation can be much more complicated than the examples given above The following example is based on a coastal river and marsh system consisting of a portion of a river tributary channels mosquito ditches and salt marsh in Westbrook Connecticut The site was first surveyed to the Connecticut Coordinate Grid System which included the x z coordinates of a section of the Menunketesuck River boundaries of the marsh locations and cross sections of channels surface of the marsh tide staffs etc Such a task can be simplified somewhat by the use of high definition GPS equipment and or a laser theodolite In all cases careful precautions must be taken when working on unstable substrates like marsh peat to avoid gr
29. ry condition no flow and it was not necessary to specify boundary sections and boundary conditions 21 Boundary Sections A boundary section is a continuous boundary line that has the same boundary condition type One project grid may have many boundary sections and the overall grid boundaries consists of all boundary sections combined The boundary sections for the fine grid in Figure 24 are shown in Figure 2 5 The Boundary Walls box on the left lists all of the boundary wall serial numbers in the first column boundary section number in the second and boundary condition type in the third A boundary wall attaches to only one cell whereas a non boundary wall attaches to two cells Use Edit Boundary Section to bring up the Boundary Sections dialog for specifying boundary sections The boundary wall serial numbers in the box are created when the grid is created Initially no boundary sections are specified The second column will be all 0 and the third column all 2 s no flow condition by default To edit the list select several walls from the left box and the corresponding walls on the boundary of the grid will be highlighted in the Workspace Check the consistency of the section before clicking the gt gt button in the middle to transfer them to the Section Walls box on the right Supply a Section number and check a boundary condition BC Type and dick the Set button A new boundary section will be specified in the boundary Walls box
30. stbrook 5 19 Figure 2 3 Coarse Grid for Westbrook Site sss 20 Figure 2 4 Fine Grid for Westbrook Site with Bottom Elevations 21 Figure 2 5 Boundary Sections Edit Dialog 23 Figure 2 6 Boundary Section 1 Type 2 at Westbrook Site 24 Figure 2 7 Boundary Section 2 1 at Westbrook Site 26 Figure 2 8 Boundary Section 2 at Westbrook Site 27 Figure 2 9 Node Edit Dialog without Boundary Condition Attached 27 Figure 2 10 Node Edit Dialog with Boundary Condition 28 Figure 2 11 Boundary Conditions for Westbrook Site 29 Figure 2 12 Initial Condition of Water Surface Elevation for Westbrook SIUC ais coni b epe eti 30 Figure 2 13 Cell Incompatible with Its Neighbors 31 Figure 2 14 Cell Compatible with Its Neighbors 31 Figure 2 15 Comparison of Calculated and O bserved Results at Westbrook SIUS aote teme tte 32 1 Examples with Analytical Solutions Two theoretical sample applications are explained here in detail in order to familiarize the user with the process of using this two dimensional finite volume hydrodynamic model FVHM for simulating shallow water flows over a river marsh system First the FVHM will be used to simulate
31. ue or File Save As anew project Figure 2 12 Initial Condition of Water Surface Elevation for Westbrook Site G Grid Adjustment One important step in achieving a high quality grid is to adjust the cells so that neighboring cell sizes are compatible By running a calculation in the Velocity Vector mode with Animation On you can very easily spot places in the grid where adjustments need to be made i e where the velocity vectors are pointing in all different directions The most likely place where this will occur is at channel junctions where one might create a cell like cell A in 30 Figure 2 13 Cell Incompatible with Its Neighbors Here cell A is not a compatibly sized cell Instead you should adjust the cell as shown in Figure 214 Figure 2 14 Cell Compatible with Its Neighbors H Simulation and Results After all the above preparation you now can start the real simulation and acquire some results For a project with a large number of cells it is better not to have Animation On while running the simulation In this way the model will run much faster The calculated results water surface elevation for this example is compared with the tidal staff readings taken in the field on October 26 1996 at three locations marked by amp in appears to be satisfactory as shown in Figure 2 15 31 Staff 12 on 10 26 96 Staff 15 on 10 26 96 Staff 10 on 10 26 96 2 g g g d T ae Ch Ch Ch a 5 2F m m m i i a 277 A
32. utoriald est Then bring up the Project Options dialog to type in your project entries and to check your options before you do anything else Figure 2 1 shows the entries in the Project O ptions for the Westbrook site 17 Project Options 36437567 Figure 2 1 Project O ptions for Westbrook Site B Import Outline Data The outline data file used in this model has the oln extension A sample section of an outline file for import to the project is given below 661904 154 1075664 550 2 160 662304 019 1073868 730 1 540 662757 129 1075789 082 1 660 663208 396 1075862 093 2 990 662528 066 1074158 698 2 930 in which the values for x 2 are separated by spaces After specifying the entries in Project Options choose File Import Outline and select the outline file to be imported into the project After importing the outline points should be visible in the Workspace as shown in Figure 2 2 The check box in 18 the Project O ptions dialog in Figure 2 1 labeled Contour must be checked in order to view the outline Figure 2 2 Outline Import for Westbrook Site You can use View Toggle Link to adjust links if necessary This will either draw or not draw lines between outline points C Coarse Grid Based on the outline points now in the Workspace you can start constructing a coarse grid by dividing the domain into large sections as cells as shown 2 3 the outline data are hidden Note that in this grid large cells are
33. words you create new nodes and walls connecting two nodes of the existing cell Selected cells may be removed or combined by simply clicking Delete or Merge Cells in the Context Menu or in the Edit menu on the Menu Bar Selected walls can be similarly edited The following tips may help you in these procedures 1 Assign cell attributes before you split a cell This will result in new cells having the same attribute values as the original cell 20 2 Select agroup of cells and assign attributes to all of them at the same time 3 Use Tools Linear Interpolate to automatically assign interpolated attribute values to selected cells 4 Move the mouse cursor to a cell and its attribute values will be displayed on the status bar The value of the attribute being displayed is determined by the selection of the current view icons on the toolbar such as water surface elevation velocity etc Y ket HRS EE ims s r Figure 2 4 Fine Grid for Westbrook Site with Bottom Elevations Shown E Boundary Conditions Boundary conditions of the boundaries enclosing the computational domain can be either fixed such as the no flow Type 2 condition for the upper landward banks of a marsh or variable such as tidal stages Type 1 or flow Type 3 at open boundary sections To apply boundary conditions you must first specify boundary sections The first three examples in this Tutorial used the default bounda
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