[Example 2] Suspended Material Transport in a Simple Bed Flume

In this section, we perform the following computations using a simple curved flume with straight inlet out let parts. The Cross section of the flume is composed with a compound channel in which both the low water channel and the flood plane with moveable bed. Then flood plane is located only left side of the low water channel. The experiment was carried out by CTI Engineering Co. Ltd. on behalf of Civil Engineering Research Institute of Cold Region . A movie taken from a drone during the experiment is shown in Figure 54, and the experimental condition and plane and cross sectional view pictures are shown in Figure 55.

Figure 54 : Experimental Video

Figure 55 : Flume Shape

The computational exercises in this section is conducted as the following procedure.

• Flow and bed deformation by Nays2DH until the bed reaches an equilibrium state

• Quasi 3-dimensional flow field by Nays2d+

• Tracer tracking by GELATO. Check the effect of turbulent diffusivity by changing parameter

Calculation of Flow and bed deformation by Nasy2DH

Select a Solver

From the iRIC startup screen, click [Create New Project], and select [Nays2DH iRIC4x 1.0 64bit] in the Figure 56.

Figure 56 : Solver Selection

A window titled as”Untitled- iRIC 4.x.xxxx [Nays2DH iRIC4X 1.0 64bit]”appears.

Figure 57 : Launch Nays2DH

Grid Creation

Select from the main menu [Grid]->[Select Algorithm]. Then a window appears as Figure 58, select [2d arc grid generator (Compound Channel)] and click [OK].

Figure 58 : Select Algorithm to Create Computational Grid

In the [Groups] of the [Grid Creation] window, set parameters of, [Channel shape], [Cross section], [Additional Channel] and [Roughness and fixed/moveable bed] as, Figure 59 , Figure 60 , Figure 61 , and Figure 62 , respectively.

Figure 59 : Grid Creating Condition(1)

Figure 60 : Grid Creating Condition(2)

Figure 61 : Grid Creating Condition(3)

Figure 62 : Grid creating Condition(4)

When you finished all the settings of the grid creating condition, click [Create Grid] in the above grid creating condition windows, e.g. Figure 62. After clicking [Create Grid] button, you will be asked [Do you want to map?], then answer [Yes], and the computational grid is created. ( Figure 63 )

Figure 63 : Confirmation of mapping.

Put check marks in [Grid], [Cell Attributes] and [Fixed or Moveable bed] in the object browser, Figure 64 appears with the fixed bed part in red and the moveable bed part shown in blue.

Figure 64 : Grid Shape with Fixed and Moveable bed Colored

The red part of the fixed bed along the boundary between the low water channel and the flood plane is assumed to be a revetment, in this grid creating tool, however, since the revetment in the actual experiment is only the bend part plus short length of upstream and downstream. So, as shown in Figure 65, focus [Fixed or Moveable bed], and right-click on a straight section of the revetment part (in this case, the red section upstream of grid number 101) and change the attribute to [Moveable bed], and press [OK].

Figure 65 : Change attribute from fixed bed to moveable bed

Since the downstream end is the fixed bed, set the attribute of the downstream end cells into [Fixed Bed], by expanding and rotating, as demonstrated in Figure 66.

Figure 66 : Change downstream end cell attribute to fixed bed

Setting Computational Condition

Show the [Calculation Condition] window by selecting [Calculation Condition]->[Setting], and in the [Group] of [Solver Type], [Boundary Condition], [Time] and [Bed Material] , set the parameters, as Figure 67 , Figure 68 , Figure 69 , and Figure 70, respectively.

Figure 67 : Calculation Condition(Solver TYpe)

Figure 68 : Calculation Condition(Boundary Condition)

Figure 69 : Calculation Condition(Tme)

Figure 70 : Calculation Condition(Bed Material)

In addition, in the [Boundary Condition] setting of Figure 68, press [Edit] of [Time series of discharge at upstream end ……], and set [Time] and [Discharge] hydrograph data in the [Time series of discharge at upstream end ……] window as Figure 71, and press [OK].

Figure 71 : Setting Discharge Hydrograph

When you finished the settings of all the computational condition parameters, press [OK] in the [Calculation Condition] window.

Run Nays2DH

Before executing the Nays2DH, select [File]->[Save as Project] and save the project. Here we save the project as a name of [Nays2DH_flow_bed] (Figure 72)

Figure 72 : Save Project

From the main menu, when you select [Simulation]->[Run], you will get the message like Figure 73 . Then press [OK], save as a project, and the computation starts running as Figure 74.

Figure 73 : “warning”

Figure 74 : “Nays2DH is running”

When the computation finished, save the results by selecting [Calculation Result]->[Save], from the main menu.

Display the Calculation Results

Open a [Post Processing Window] by selecting [Calculation Result]->[Open new 2D Post-Processing Window] as Figure 75.

Figure 75 : Open Post Processing Window

In the object browser of the [Post Processing Window], put check marks in [iRICZone], [Scalar(node)] and [ElevationChange(m)], right click [ElevationChange(m)] to show [Property] and press it, open [Scalar Settings], and set parameters as Figure 76.

Figure 76 : “Scalar Setting”

In the object browser, put check marks in [Arrow] and [Velocity(m)], right click [Arrow], show [Property] and press it, open [Arrow Setting Window] as Figure 77, and set parameters as marked with red squares in the Figure 77.

Figure 77 : [Arrow Settings]

Put the [Time Scale Bar] back to zero, select [Animation]->[Start/Stop] to start animation as Figure 78.

Figure 78 : [Launch Animation]

As shown in Figure 79, it is shown that the bed elevation change reached an equilibrium.

Figure 79 : Animation of velocity vectors and bed elevation changes

Export the Computational Results

In order to use the calculated bed elevation as an boundary conditions for the quasi-3D flow calculation by Nays2d+ in the next section, we export the calculated results to a text file. As shown in Figure 80, select [File]->[Export]->[Calculation Result].

Figure 80 : Exporting Computational Results(1)

When the [Export Calculation Result] setting window (Figure 81) is appeared, choose [Format] as [Topography Files(*.tpo)].

Figure 81 : Exporting Computational Results(2)

The output folder can be any name, and uncheck the checkbox at [All time steps], and set [Start] and [End] as 10,800. Then click [OK] to complete the export of the calculation Results Figure 82.

Figure 82 : Exporting Computational Results(3)

The exported calculation results are stored in the specified folder. As shown in Figure 83, many files contain different values as water depth, velocity, sediment transport rate, riverbed elevations, and so on, however, since only the riverbed elevation is used for the flow calculations in the next section, all files except [Result_1_Elevation(m).tpo] can be deleted.

Figure 83 : Exporting Computational Results(4)

Quasi-3D Flow Calculation by Nays2d+

Selecting a Solver

From the iRIC startup screen, click [Create New Project], and select [Nays2d+] in the Figure 84, and press [OK].

Figure 84 : Solver selection of Nays2d+

Importing Computational Grid, Channel Bed Elevation and Mapping

Importing Grid

From the main menu, select [Import]->[Grid], and choose [Case1.cgn] in the folder of [Nays2DH_floe_bed] which was created in the previous section. While importing, a warning as Figure 85 is coming out, press [Yes], and complete importing grid (Figure 86).

Figure 85 : [Warning]

Figure 86 : [Grid import complete]

Import Bed Elevation

From the main menu, select [Import]->[Geographic Data]->[Elevation](Figure 87).

Figure 87 : Import Elevation

In the import file selection window, Figure 88, assign the file [Results_1_Elevation(m).tpo], which was exported from Nays2DH calculated results in the previous section.

Figure 88 : Select bed elevation file to import

Figure 89 appears, but if there is no particular need to thin out the data, you can leave it as it is, and press [OK] to complete the import the [Bed Elevation] (Figure 90).

Figure 89 : Import Bed Elevation (Setting Thinning)

Figure 90 : Bed Elevation Data Import Completed

Execute Mapping

The imported bed elevation data is mapped onto the imported computational grid. Select [Grid]->[Attribute Mapping]->[Execute] as Figure 91.

Figure 91 : “Execute Mapping”

As Figure 92, you will be asked which [Geographic Data] to be mapped. Put check mark in the box of [Elevation(m)], and press [OK].

Figure 92 : Selection of the Mapping Item

When the mapping is completed, press [OK] as Figure 93.

Figure 93 : Mapping Completed

Setting Calculation Condition for Nays2d+

In the window of [Calculation Condition] which appears when you select [Calculation Condition]->[Setting], set parameters in the [Groups] of [Discharge and downstream water surface elevation], [Time and bed erosion parameters], [Boundary Condition], [Other computational parameters] and [3D Velocity Profile] as, Figure 94, Figure 95, Figure 96, Figure 97, and Figure 98, respectively.

Figure 94 : Discharge and downstream water surface elevation

Figure 95 : Time and bed erosion parameters

Figure 96 : Boundary Condition

Figure 97 : Other computational parameters

Figure 98 : 3D Velocity Profile

In addition, while in the settings of the [Discharge and downstream water surface elevation], Figure 94, press [Edit] and set discharge data in in the [Time series of discharge and downstream stare] setting window as Figure 99.

Figure 99 : Setting the time series of discharge Data

When you finish setting all the calculation condition, press [OK] in the [Calculation Condition] window.

Execute Nays2d+

We will skip the explanation of how to executing Nays2d+ because it is exactly same as other solvers. However, it is recommended that you save the project before running the calculation. In this case, we save the file to a project named [Nays2d+Flow].

Figure 100 : Save project(Nays2d+Flow)

The results are saved in a CGNS file named [Case1.cgn], which will be used for the tracer tracking computation of GELATO as input data. Be sure to save the result using [Calculation Result]->[Save] even when the calculation is finished. (Figure 101).

Figure 101 : Save the Results of the Computation (Don’t Forget!)

Tracer Tracking by GELATO

Select a Solver

From the iRIC startup screen, select [New Project], and in the solver selection screen appears. Select “GELATO” and click “OK” (Figure 102).

Figure 102 : Select and Launch GELATO

Import Grid

Right click [Grid(No Data)] and select [Import] as Figure 103.

Figure 103 : [Import Grid(1)]

From the [Select Import File] window as Figure 104, choose [Case1.cgn] in the folder [Nays2d+Flow] which is produced by the [Nays2d+] calculation in the previous section.

Figure 104 : [Import Grid(2)]

Press [Yes] button when warning message is coming out as Figure 105, and the grid import is completed as Figure 106.

Figure 105 : [Warning Message]

Figure 106 : [Grid Import Completed]

Tracer Tracking Simulation by GELATO

Setting Simulation Condition

From the main menu bar, when you select [Calculation condition]->[Setting]. [Calculation Condition] window appears, and in this window, set parameters as Figure 107, Figure 108, Figure 109, and Figure 110, respectively. In this section, we first perform tracer tracking without considering the effect of sub-grid turbulence.

Figure 107 : Basic Settings

Figure 108 : Primary Tracers Supplying Condition

Figure 109 :Time Settings for Normal Tracers

Figure 110 : Diffusion Condition

In addition, the [Flow information input file] in Figure 107, is the same file with the [Case1.cgn] which was produced by the flow simulation of [Nays2d+] in the previous section (Figure 111).

Figure 111 : Assign CGNS file to read flow simulation results

Run GELATO

From the main menu, select [Simulation]]->[Run], then you are asked as will be asked as Figure 112 . so, click [OK] and save project.

Figure 112 : Saving GELATO Project(1)

In the Figure 113, either [Save as file (*.ipro)] or [Save as Project] will do.

In this example, save as [GELATO_A=0].

Figure 113 : Saving GELATO Project(2)

When the computation starts, Figure 114 appears, and when the computation finishes, Figure 115 appears. Press [OK] to finish computation.

Figure 114 : Execution of GELATO(1)

Figure 115 : Execution of GELATO(2)

Showing the Results of GELATO

From the main menu, select [Calculation Result]->[Open new 2D Post Processing Window], and the calculation results are shown (Figure 116)

Figure 116 : [2D Post Processing Window]

Since the orientation of the Figure 116 is the opposite to the experimental image shown at the beginning of this chapter Figure 54, press the 90° rotation mark twice to rotate 180° (Figure 117).

Figure 117 : 2D Post Processing Window 180° rotate

Since the [Time] display is so small that it’s hard to see, select [Time]->[Properties] in the object browser (Figure 118), display [Time Setting] and set the font size appropriately large (Figure 119).

Figure 118 : Time Setting(1)

Figure 119 : Time Setting(2)

As shown in Figure 120, put time bar back to 0, and from the main menu, select [Animation]->[Start/Stop], then the animation starts( Figure 121).

Figure 120 : Starting Animation

Figure 121 : Tracer Animation (Turbulent Diffusivity A=0)

There is almost no diffusion and the tracers are just flowing straightly.

Comparison of the Turbulent Diffusivity

Select [Calculation Condition]->[Setting] and open [Calculation Condition] window. As shown in Figure 122, set in the [Group]->[Diffusion Condition], [Diffusivity Correction]->[Yes] and set the value [A=10] of the [Diffusivity Parameter]

Figure 122 : Random Walk Parameter Setting (A=1)

Figure 123 : Animation of the Tracer Motion (A=1)

In the same manner, if we do the simulation with [A=5], [A=10] and [A=50], the results becomes as Figure 124, Figure 125 and Figure 126.

Figure 124 : Animation of the Tracer Motion (A=5)

Figure 125 : Animation of the Tracer Motion (A=10)

Figure 126 : Animation of the Tracer Motion (A=50)

When we compared with the experimental results of the Figure 54, it seem that the case with A=10, Figure 125, is the closest to the experiment.

Cloning of the Tracers

In the main menu, select [Calculation Condition]->[Setting] to show [Calculation Condition]. In the [Calculation Condition] window, select [Tracer Cloning and Amalgamation], set parameters as Figure 127.

Select [Diffusion Condition] and set [A=10] and press[OK] as Figure 128. Then execute the GELATO solver by choosing [Simulation]->[Run], and show the results (Figure 129).

Figure 127 : Setting the Tracer Cloning(1)

Figure 128 : Setting the Tracer Cloning(2)

Figure 129 : Animation of Tracer Cloning (Maximum Generation 20, A=10)

The spread range of the tracers in Figure 54 is close to the diffusion range of the green dye in the experimental movie. The number of tracers appears to be enormous, but if you put check marks in [Particles]->[Scalars]->[Generations] in the object browser, generations of the tracers are displayed as Figure 130.

Figure 130 : Color-coded View of the Clone Generations

When this is animated, it becomes as Figure 131.

Figure 131 : Tracers Clone Animation(Maximum 20 Generations, A=10, Color-coded View)

As described in Overview , the substantial weight in the 10th generation is W=0.00195, and in the 20th generation is W=0.00000195.

Therefore, Figure 130, the concentrations of the tracers of green, yellow, red, etc. are logarithmically lower than that of the central blue tracers.

To see the real concentration, the substantial concentration in each cell is visualized by the following procedure.

1. Uncheck the check box at [Scalar] in the object browser (Figure 132).

Figure 132 : Uncheck the check box by [Scalar]

2. Put check mark at [Scalar(Cell Center)] and [Weighted numbers of tracers] in the Object Browser (Figure 133).

Figure 133 : Put check mark at [Weighted numbers of tracers]

3. Right click [Weighted numbers of tracers] and press [Property]

Figure 134 : [Weighted numbers of tracers]->[Property]

4. In the [Scalar Setting] window, setting as shown Figure 132.

Figure 135 : Scalar Settings

5. As shown in Figure 136, put time bar back to 0, and from the main menu, select [Animation]->[Start/Stop], then the animation starts( Figure 137).

Figure 136 : Starting Animation

Figure 137 : Animation of the tracer concentration considering the weight

The diffusion situation is similar to that of the green dye in the experimental movie of Figure 54.

Flow Visualization using Tracer Cloning

Flow visualization using tracer cloning is shown in this section. In the main menu, click [Calculation Condition], and set parameters in the [Group] of [Normal Tracers Supplying Condition] and [Tracer Cloning and Amalgamation] as Figure 138 and Figure 139, respectively, and press [OK].

Figure 138 : Calculation Condition Setting(1)

Figure 139 : Calculation Condition Setting(2)

Then after running the GELATO solver. in the [Object Browser], remove check mark from [Weighted numbers of tracers], put check marks in boxes at [Particles], [Scalar] and remove the check mark form the [Generation].

From the main menu, select [Animation]->[Start/Stop], and the animation with evenly distributed tracers in the whole channel is visualized.

Figure 140 : Flow Visualization with Virtual tracers

Swimming Fish Simulation

Set the following parameters in the [Computation of Fish Motion] in the [Calculation Condition] window menu followed by selecting [Calculation Condition]->[Setting] in the main menu.

Figure 141 : Setting Condition or Fish(1)

Figure 142 : Setting Condition for Fish(2)

Figure 143 : Setting Condition of Fish(3)

Figure 144 : Setting Condition of Fish(4)

Figure 145 : Setting Condition of Fish(5)

After setting these parameters, run the solver by [Simulation]->[Run]. Once close the existing [2D Post-processing 2D window], open a new [2D Post-processing 2D window], put check mark on [Polygon]->[Fish]->[Type] as Figure 146, and select [Animation]->[Start/Stop]. Then Figure 147 is played.

Figure 146 : Choosing Fish Animation

Figure 147 : Swimming Fish Animation

Driftwood Tracking by NaysDW2 and Visualization

In this section, driftwood tracking simulation by NaysDW2 (Nays Driftwood 2D) is shown.

Select a Solver

From the iRIC startup screen, click [Create New Project], and select [NaysDw2(Simple 2D Driftwood Tracker)] as shown in Figure 148, and press [OK].

Figure 148 : Selecting [NaysDw2] (Simple 2D Driftwood Tracker)

Select the flow calculation project

As shown in Figure 149, click […] and select CGNS files that calculated Nays2D+ project in “ Quasi-3D Flow Calculation by Nays2d+ “

Figure 149 : [Select CGNS(1)]

Figure 150 : [Select CGNS(2)]

When you select a CGNS file, the specifications of the selected project will be displayed, such as Figure 151 . Then, go ahead and click [OK].

Figure 151 : [Select CGNS(3)]

So, you will be asked whether to import the grid, so click [Yes] ( Figure 152 ).

Figure 152 : [Select CGNS(4)]

Then A warning, as shown in Figure 153 , will then appear, but simply ignore it and click [Yes] again.

This will complete the grid import process, as shown in Figure 154 .

Figure 153 : [Warning Message]

Figure 154 : [Grid Import complete]

Setting Condition

From the main menu, select [Calculation Condition]->[Setting],and set the calculation condition as follows.

Set other parameters as Figure 155 ~ Figure 158

Figure 155 : Other settings in [Basic Setting]

Figure 156 : Other settings in [Driftwood feeding condition]

Figure 157 : [Driftwood Feeding Condition]

Figure 158 : [DEM Coefficients]

Run Driftwood Simulation

From the main menu, select [Simulation]->[Run] as Figure 159.

Figure 159 : [Simulation]->[Run]

When you are asked as Figure 160, press [Yes] and save the project.

Figure 160 : warning

As Figure 161, when you are asked [How to save the project], in this example, select [Save as project], and press [OK]. Choose an empty folder to save project, and press [Select Folder].

Figure 161 : [How to save project]

When the calculation starts, Figure 162 is displayed, and Figure 163 is appear when the calculation ends. Then click [OK] to finish calculation.

Figure 162 : Solver Running

Figure 163 : Calculation finished

Visualization of driftwood motion

From the main menu, select [Calculation Result]->[Open New 2D Post-processing Window] as Figure 164.

Figure 164 : Open New 2D Post-processing Window

In the [Object Browser] of Figure 165, put check marks in the boxes at [iRICZone], [Scalar] and [Velocity(magnitude)], right click [Velocity(magnitude)] and choose [Property].

Figure 165 : Scalar Setting(1)

Set the parameters for [Scalar Settings] as Figure 166, and press [OK].

Figure 166 : Scalar Setting(2)

Set the time bar back to zero, and select [Animation]->[Start/Stop] from the main menu bar as Figure 167, and start animation as Figure 168

Figure 167 : Start Animation

Figure 168 : Driftwood Tracking Animation