Welcome to the GELATO Manuals and Examples Page!
Introduction
GELATO(Universal Tracer Tracker) is a tool to track and visualize the trajectory of various materials specified by the user using the calculation result of various flow calculation solvers implemented in iRIC. The target transported substance is not only completely following the flow, but also the substance itself has a cruising ability, a typical example is a fish, by specifying its ability and characteristics to express its movement.
The GELATO determines the concentration (density) of the tracer particles at a given location in the fluid and it has the ability to clone or amalgamate itself as needed. This usually allows the tracer to be visualized the image in the detached area where particles cannot easily invade, or in the area where particles have accumulated and become extremely difficult to see.
In addition, GELATO can also display weighted particle concentrations that take into account splitting and binding. It is possible to analyze the concentration by a substantial Lagrangian method.
Note that the GELATO can extract the turbulence below the grid scale modeled in the solvers by introducing a random walk model. This allows to examine more realistic particle tracking and concentration diffusion fields.
Basically, there are three types of tracers to be tracked in GELATO.
Normal tracer (tracks only the position of particles)
Special tracer (also records and displays the position of its trajectory)
Fish tracer (a fish tracer that propels itself)
In addition to these, rod-like shape tracers such as driftwood tracers and can be tracked with their own movement and rotation
Driftwood tracer, NaysDw2 (2D driftwood tracking solver), which is a separate solver from GELATO.
The computation of GELATO is performed by the following procedure.
Computation of flows with flow calculation solvers (Nays2dh, Nays2dFlood, Nays2d+, etc.)
Saving of flow calculation results (CGNS file)
Starting GELATO
Setting tracer input and tracking conditions
Tracer tracking calculation using the above CGNS file.
Visualization of the calculation results
Overview
In this section, we describe the basics of the GELATO model.
How to describe the locations of tracers
The positions of the tracers used in the GELATO are represented using normalized coordinates in the downstream and transverse directions. For example, when boundary-fitted coordinates are used for rivers, as shown in Figure 1 , Non-dimensional coordinates of \(\xi\) in the downstream direction, and \(\eta\) in the transverse direction show the location of the tracers using values between 0 to 1.
:Non-dimensional description of tracers’ position
Random walk model considering the effect of turbulence
According to Callies (2011), and McDonald and Nelson (2020), the target tracer’s position vector \(\boldsymbol{r}\) is expressed by the following equation
\[\boldsymbol{r}(t+\Delta t) = \boldsymbol{r}(t)+ \boldsymbol{U} \Delta t + \boldsymbol{U}_p \Delta t + \boldsymbol{L}\sqrt{2K\Delta t}\]
Where \(\boldsymbol{U}\) is the velocity vector of the flow, \(\boldsymbol{U}_p\) is velocity vector of a tracer (the tracer’s own propulsive velocity vector), \(\boldsymbol{L}\) is a Gaussian vector whose values are such that it has mean 0 and standard deviation 1, \(\Delta t\) is the computation time step, and \(K\) is the turbulent diffusion coefficient.
Applying the Box-Muller transformation (Box and Muller, 1958) for \(\boldsymbol{L}\) , the following equations are obtained for the two-dimensional case.
where \(U_1\) and \(U_2\) are mutually independent 0 to 1 normal random numbers. This is the so-called Random Walk model, When these are applied for tracer tracking. \(K\) can be given as a linear function of \(\nu_t\) as,
In the GELATO model, \(a\) and \(b\) in the above equation are given as parameters. As for \(\nu_t\) , it is automatically loaded from the result of the flow calculation.
Tracer cloning
The tracer supplied from upstream is transported downstream by the flow, but depending on the flow conditions, the tracers may not be got into areas particularly, in the place where the flow is stagnant, the separation zone, and the one of the paths where the flow is divided, etc, even if a large amount of tracer is supplied from upstream, it may not easily to reach the target region. In general, there is an upper limit to the number of feeds from the upstream, and it is not infinite, so some ingenuity is required. In the GELATO, a new tracer can be added to a cell with a small number of tracers (or no tracers), to control the tracer concentration while tracking the flow even in areas where there is not enough tracer. For example,
When the number of tracers in a cell reaches one, split it into two
But the weight is set to 1/2, and it is stored
Cloning can be repeated as many times as necessary, but it can be terminated at a given generation.
Optionally, a single tracer can be generated for cells with zero tracers.
In this case the tracer The weights are assumed to be zero, but visualization is possible, so it is effective as a tracer for flow visualization.
Figure 2 shows the schematics of the tracer division.
: Division of the tracer (image of cloning)
When defined as the first tracer submitted is the first generation, the one generated by the first split is the second generation, and the next one is the third generation… The wight is 1/2 at the second generation, the weight is 1/2 in the third generation, and the weight is 1/4 in the fourth generation. In the \(n\) generation, considering it is experienced \(2^{n-1}\) times cloning, it’s weight becomes \(W={1}/{2^{n-1}\) . Using this, we can count the total number of weighted tracers in each cell to obtain concentration can be calculated. Thus, for example, in the 10th generation when \(n=10\) , weight is \(W=\cfrac{1}{2^9}=0.000195\), and in the 20th generations when \(n=20\), the weight becomes \(W=\cfrac{1}{2^{19}}=0.00000195\) .
Calculation results of two-dimensional flows used in GELATO
Since the GELATO tracks tracers in a two-dimensional “flow” in a Lagrangian manner, the results of the “flow” calculation have to be prepared in advance( Figure 3 ). By default, the GELATO read the flow information stored in the CGNS files with 2-dimensional structured grid format. At present, flow solvers which satisfy this condition in iRIC (as of April 1, 2021), are Nays2dH, Nays2dFlood, Nays2d+, and FastMech. For more information about the flow calculation models available in iRIC, please visit the iRIC website (https://i-ric.org/) for more details.
: Calculation Procedure by GELATO
The CGNS file that contains the calculation results of the flow used in GELATO is Specify from [Calculation conditions], [Settings], and [CGNS file to load flow calculation results] of the bar. (Figure 4)
: Specify the CGNS file which contains the calculation result of the flow
Computational grids used in GELATO
In most cases, the computational grid is imported from the GNS files which contains the computational flow results. As shown in Figure 5 , from the “Object Browser” in the “Pre-Preprocessing Window”, Right-click [Grid(No data)], select [Import], and select a CGNS file which contains the grid information as Figure 6 . In most cases in iRIC, the file name is [Case1.cgn].
: Importing computational grid.
: Select a CGNS file
When you try to read the grid data from CGNS file produced by other than GELATO, Figure 7 is displayed. This means that the current project(GELATO project) is different from the flow calculation project. This is a warning that you are trying to import grids from a wrong project, but you can just click “OK”, and the grid information is imported and the result is displayed as Figure 8 .
: Warning message
: Grid import completed
After this, the following procedure is used to calculate the tracer and display the result by GELATO. Examples are given in the next section.
Set computational condition
Calculation execution
Visualization of the solution
Examples
In this section, we show an actual example of calculation by GELATO.
[Example 1] Tracer transport in a straight channel
Flow calculation by Nays2DH
Select a solver
In the [iRIC start page] , select [Create New Project], and when the [Select Solver] screen appears, choose [Nays2DH iRIC 4.x 1.0 64bit] and click [OK] button.
: Select Solver
A windows with “Untitled - iRIC 4.x.x.xxxx [Nays2DH]” appears as Figure 10.
: Untitled
Grid Generation
From the main menu of the screen, Figure 10, choose [Grid]->[Select Algorithm to Create Grid] as Figure 11.
: Select Algorithm to Create Grid
In the [Select Grid Creating Algorithm] window, select [Simple Straight and Meandering Channel Creator] and click [OK] (Figure 12).
: Select Grid Creating Algorithm
In the window of Figure 13 , click “Channel Shape” and set [Select Channel Shape of the Main Part] as [straight channel], and other values as shown in Figure 13, then click [Create Grid].
:Setting Channel Shape
When the confirmation window appears as Figure 14, click [Yes] to generate the grid, then the computational grid is generated as Figure 15 .
:Confirmation of mapping
:Grid Generation Compete
Setting of calculation conditions for flow by Nays2DH
The next step is to set the calculation conditions. From the menu bar, select [Calculation Conditions]->[Settings], then the [Calculation condition setting window] as Figure 16 appears.
:Calculation Condition Window
As Figure 17, in the [Group] of the [Boundary Condition], click [Edit] at the [Time series of discharge at upstream and water level at downstream]. Then the [Time series of discharge at upstream and water level at downstream] appears as Figure 18 .
: Boundary Condition
: Time series of discharge at upstream settings
In Figure 18, input [Time] and [Discharge] values, and click [OK] when you finish, and close this window.
:Time parameters
Select [Time] and set parameters as Figure 19 and click [Save and Close].
Flow calculation run by Nays2DH
:Window when the solver is running
From the main menu, when you select [Simulation]->[Run], you will get the message like “We recommend you to save the project before running solver. Do you want to save?” Select [Yes] and save the project with an appropriate name. At this time, do not save the project as an ipro file, but save it as a project. A window as Figure 20 is shown during the computation, and Figure 21 appears when the computation is finished. Then press [OK], and the computation is completed.
:Computation completed
Important Whenever you finished the computation, select [File]->[Save] from the menu bar to save the results as Figure 22 . This result is important for later analysis by GELATO.
:Saving computational results
Visualization of the calculated results
After the calculation, select [Calculation Result] -> [Open New 2D Post-processing Window] to open the visualization window.
: 2D Post-processing Window
Velocity Vectors
In the [Object Browser], put check marks in the boxes by [Arrow] and [Velocity], click Focus on [Arrow] and click the right mouse button [Properties]. Vector setting” window as Figure 24 appears. Set the values in the red line and click [OK]. Figure 25 is the depth-averaged velocity vector. Here, the velocity distribution is uniform under the constant flow condition.
: Vector Settings
: Depth averaged velocity vectors
Display Particle Movement
Uncheck “Vectors” in the Object Browser, and put check marks in “Particles” and “Velocity” ( Figure 26 )
: Particles(1)
Right click [Particle] and select [Properties] as Figure 27 .
: Particles(2)
Set parameters for particle injection as shown in red box in Figure 28 .
: Set particle parameters
As shown in Figure 29 , set time bar back to zero, and select [Animation]->[Start/Stop Animation] rom the main menu bar. Then the particle animation starts.
: Start Particle Animation
: Particle animation by NAys2DH
As can be seen in Figure 30, since the sub-grid scale turbulence is not included in the output velocity from the solver. It only shows very simple steady and uniform movement.
Tracer Tracking by GELATO
Starting GELATO
From the iRIC startup screen, select [New Project], and in the solver selection screen appears. Select “GELATO” and click “OK” ( Figure 31 ).
: Selecting GELATO and Starting
A window with [Untitled -iRIC 3.0.xxxx] [GELATO] appears, and the GELATO session is started. (Figure 32 )
: Opening GELATO
At this stage, the [Grid] in the [Object Browser] shows [No data] as shown in Figure 32 , we will first import the grid data created in Grid Generation session.
: Grid data import
Right click [Grid(No Data)] and select [Import] as (Figure 33 ).
: Select CGNS file contains grid data
As shown in Figure 34, select [Case1.cgn] which contains the grid data used in the previous section of [Computational Results of NAys2DH], and click [Open].
: Warning Message
A warning message is coming out as Figure 35 , Just click [Yes] without worry, and the grid import is completed as Figure 36 .
: Grid import completed
Single Tracer Tracking(Without Turbulent Diffusivity)
Condition Settings
Choose [Calculation Condition]->[Setting] as Figure 37
: Calculation Condition Settings(0)
Set parameters as follows.
[Flow information file name] is Locat of the CGNS file to read the calculation result of the flow field. Here, the CGNS file produced by the Nays2DH computation.( Flow calculation run by Nays2DH ).
: Basic Settings
: Primary Tracers Supplying Condition
: Secondary Tracers Supplying Condition
: Time Settings for Normal Tracers
: Diffusion Condition
Launch GELATO
From the main menu bar, select [Simulation]->[Run], then you are asked [Do you want to save?] as Figure 43. When you click [Yes] and save project, the computation starts as Figure 44.
: Do you want to save?
: Launch GELATO
When the computation finishes, Figure 45 appears, and click [OK] for confirmation.
: Computation finished
Visualization of Computational Results
From the main menu, select [Calculation Result]->[Open ne 2D Post-processing Window], then [2D Post Processing Window] appears as Figure 46.
: 2D Post Processing Window
From the main menu, select [Animation]->[Start/Stop] as Figure 47, animation starts ( Figure 49 ).
: Visualization of computational results
Right-click [Primary Nomal Tracers] and [Secondary Nomal Tracers] in the [Object Browser] and click [propertie]. Then [Particles Scalar Setting] that appears,and you can set the primary and secondary have different colors by setting like Figure 48.
: Setting particles colors
: Tracer movement(No diffusivity)
It is obviously very simple because it doesn’t including any turbulent effect (Figure 49).
Single Tracer Tracking(With Turbulent Diffusivity)
Setting Computational Condition
Change the calculation conditions to take into account for the effect of turbulent diffusion. From the main menu, select [Calculation Conditions] → [Setting], and show the Figure 42. Set [Diffusion Condition]->[Diffusivity Correction]->[Yes], set the parameter [A Value] to [1], and then click “Save and Close”.
: Calculation Condition (Diffusion Condition)
Launch GELATO and the Results Visualization
Computation can be conducted through the same procedure as previous example, the animation becomes as Figure 51.
: Tracer Movement(With Turbulent Diffusivity A=1)
When the value of A is set as [10], the results become as Figure 52, the effect of the turbulent becomes stronger.
: Tracer Movement(With Turbulent Diffusivity A=10)
[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 53, and the experimental condition and plane and cross sectional view pictures are shown in Figure 54.
: Experimental Video
: 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 iRIC3x 1.0 64bit] in the Figure 55.
: Solver Selection
A window titled as「Untitled- iRIC 3.x.xxxx [Nays2DH iRIC4X 1.0 64bit]」appears.
: Launch Nays2DH
Grid Creation
Select from the main menu [Grid]->[Select Algorithm]. Then a window appears as Figure 57, select [2d arc grid generator (Compound Channel)] and click [OK].
: 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 58 , Figure 59 , Figure 60 , and Figure 61 , respectively.
: Grid Creating Condition(1)
: Grid Creating Condition(2)
: Grid Creating Condition(3)
: 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 61. After clicking [Create Grid] button, you will be asked [Do you want to map?], then answer [Yes], and the computational grid is created. ( Figure 62 )
: Confirmation of mapping.
Put check marks in [Grid], [Cell Attributes] and [Fixed or Moveable bed] in the object browser, Figure 63 appears with the fixed bed part in red and the moveable bed part shown in blue.
: 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 64, 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].
: 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 65.
: 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 66 , Figure 67 , Figure 68 , and Figure 69, respectively.
: Calculation Condition(Solver TYpe)
: Calculation Condition(Boundary Condition)
: Calculation Condition(Tme)
: Calculation Condition(Bed Material)
In addition, in the [Boundary Condition] setting of Figure 67, 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 70, and press [OK].
: 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 71)
: Save Project
From the main menu, select [Simulation]->[Run], then a window asking [Do you want to save?] appears as Figure 72. Then press [Yes], save as a project, and the computation starts running as Figure 73.
: 「Do you want to save?」
: 「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 74.
: 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 75.
: 「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 76, and set parameters as marked with red squares in the Figure 76.
: [Arrow Settings]
Put the [Time Scale Bar] back to zero, select [Animation]->[Srart/Stop] to start animation as Figure 77.
: [Launch Animation]
As shown in Figure 78, it is shown that the bed elevation change reached an equilibrium.
: 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 79, select [File]->[Export]->[Calculation Result].
: Exporting Computational Results(1)
When the [Export Calculation Result] setting window (Figure 80) is appeared, choose [Format] as [Topography Files(*.tpo)].
: Exporting Computational Results(2)
The output folder can be any name, and uncheck the checkbox at [All timesteps], and set [Start] and [End] as 10,800. Then click [OK] to complete the export of the calculation Results Figure 81.
: Exporting Computational Results(3)
The exported calculation results are stored in the specified folder. As shown in Figure 82, 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.
: 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 83, and press [OK].
: 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 84 is coming out, press [Yes], and complete importing grid (Figure 85).
: [Warning]
: [Grid import complete]
Import Bed Elevation
From the main menu, select [Import]->[Geographic Data]->[Elevation](Figure 86).
: Import Elevation
In the import file selection window, Figure 87, assign the file [Results_1_Elevation(m).tpo], which was exported from Nays2dH calculated results in the previous section.
: Select bed elevation file to import
Figure 88 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 89).
: Import Bed Elevation (Setting Thinning)
: 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 90.
: 「Execute Mapping」
As Figure 91, you will be asked which [Geographic Data] to be mapped. Put check mark in the box of [Elevation(m)], and press [OK].
: Selection of the Mapping Item
When the mapping is completed, press [OK] as Figure 92.
: 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 93, Figure 94, Figure 95, Figure 96, and Figure 97, respectively.
: Discharge and downstream water surface elevation
: Time and bed erosion parameters
: Boundary Condition
: Other computational parameters
: 3D Velocity Profile
In addition, while in the settings of the [Discharge and downstream water surface elevation], Figure 93, press [Edit] and set discharge data in in the [Time series of discharge and downstream stare] setting window as Figure 98.
: 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].
: 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 100).
: 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 101).
: Select and Launch GELATO
Import Grid
Right click [Grid(No Data)] and select [Import] as Figure 102.
: [Import Grid(1)]
From the [Select Import File] window as Figure 103, choose [Case1.cgn] in the folder [Nays2d+Flow] which is produced by the [Nays2d+] calculation in the previous section.
: [Import Grid(2)]
Press [Yes] button when warning message is coming out as Figure 104, and the grid import is completed as Figure 105.
: [Warning Message]
: [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 in the [Groups] of [Basic Settings], [Normal Tracers Supplying Condition] and [Diffusion Condition], as Figure 106, Figure 107, and Figure 108, respectively. In this section, we first perform tracer tracking without considering the effect of sub-grid turbulence.
: Basic Settings
: Primary Tracers Supplying Condition
:Time Settings for Normal Tracers
: Diffusion Condition
In addition.Figure 100 The [CGNS file to read the flow calculation results] in the [CGNS file to read the flow calculation results] is the same as the one in the previous section [Flow calculation with Nays2d+]. Select [Case1.cgn] in the [Nays2d+Flow] project folder where you saved the results of ( Figure 103)
In addition, the [Flow information input file] in Figure 106, is the same file with the [Case1.cgn] which was produced by the flow simulation of [Nays2d+] in the previous section (Figure 110).
: Assign CGNS file to read flow simulation results
Run GELATO
From the main menu, select [Simulation]]->[Run], then you will be asked to save project as usual, save project as recommended. ( Figure 111).
: Saving GELATO Project(1)
In the Figure 112, either [Save as file (*.ipro)] or [Save as Project] will do, but in this example, the file is saved as [GELATO1].
: Saving GELATO Project(2)
When the computation starts, Figure 113 appears, and when the computation finishes, Figure 114 appears. Press [OK] to finish computation.
: Execution of GELATO(1)
: 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 115)
: [2D Post Processing Window]
Since the orientation of the Figure 115 is the opposite to the experimental image shown at the beginning of this chapter Figure 53, press the 90° rotation mark twice to rotate 180° (Figure 116).
: 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 117), display [Time Setting] and set the font size appropriately large (Figure 118).
: Time Setting(1)
: Time Setting(2)
As shown in Figure 119, put time bar back to 0, and from the main menu, select [Animation]->[Start/Stop], then the animation starts( Figure 120).
: Starting Animation
: 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 121, set in the [Group]->[Diffusion Condition], [Diffusivity Correction]->[Yes] and set the value [A=10] of the [Diffusivity Parameter]
: Random Walk Parameter Setting (A=1)
: 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 123, Figure 124 and Figure 125.
: Animation of the Tracer Motion (A=5)
: Animation of the Tracer Motion (A=10)
: Animation of the Tracer Motion (A=50)
When we compared with the experimental results of the Figure 53, it seem that the case with A=10, Figure 124, 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 126. Select [Diffusion Condition] and set [A=10] and press[OK] as Figure 127. Then execute the GELATO solver by choosing [Simulation]->[Run], and show the results (Figure 128).
: Setting the Tracer Cloning(1)
: Setting the Tracer Cloning(2)
: Animation of Tracer Cloning (Maximum Generation 20, A=10)
The spread range of the tracers in Figure 53 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 129.
: Color-coded View of the Clone Generations
When this is animated, it becomes as Figure 130.
: 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 129, 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.
Uncheck the check box at [Scalar] in the object browser (Figure 131).
: Uncheck the check box by [Scalar]
2. Put check mark at [Scalar(Cell Center)] and [Weighted numbers of tracers] in the Object Browser (Figure 132).
: Put check mark at [Weighted numbers of tracers]
Right click [Weighted numbers of tracers] and press [Property]
: [Weighted numbers of tracers]->[Property]
In the [Scalar Setting] window, setting as shown Figure 131.
: Scalar Settings
5. As shown in Figure 135, put time bar back to 0, and from the main menu, select [Animation]->[Start/Stop], then the animation starts( Figure 136).
: Starting Animation
: 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 53.
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 137 and Figure 138, respectively, and press [OK].
: Calculation Condition Setting(1)
: 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]->[Srat/Stop], and the animation with evenly distributed tracers in the whole channel is visualized.
: 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.
: Setting Condition or Fish(1)
: Setting Condition for Fish(2)
: Setting Condition of Fish(3)
: Setting Condition of Fish(4)
: 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 145, and select [Animation]->[Start/Stop]. Then Figure 146 is played.
: Choosing Fish Animation
: Swimming Fish Animation
Driftwood Tracking by NaysDW2 and Visualization
In this section, driftwood tracking simulation by NaysDW2 (Nays Driftwood 3D) 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 147, and press [OK].
: Selecting [NaysDw2] (Simple 2D Driftwood Tracker)
Import Computational Grid
As shown in Figure 148, from the [Object Browser], right click [Grid(No data)], and press [Import]
: [Import Grid(1)]
When the file selection window appears, select [Case1.cgn] in the [Nays2d+Flow] folder in which the computational results of the [Nays2d+] stored. (Figure 149)
: [Import Grid(2)]
Neglect the waring message as Figure 104, press [Yes], and the grid importing is completed (Figure 151).
: [Warning Message]
: [Grid Import complete]
Setting Condition
From the main menu, select [Calculation Condition]->[Setting],and set the calculation condition as follows.
In the [Calculation Condition] window, press file selection bar as Figure 152.
: Select CGNS File to Read(1)
In the [Select File] window, Figure 153, select [Case1.cgn] which contains the calculation results of the [Nays2d+] in the previous section.
: Select CGNS File
Set other parameters in [Basic Setting] as Figure 154.
: Other settings in [Basic Setting]
Set parameters in [Driftwood Feeding Condition] as Figure 155.
: [Driftwood Feeding Condition]
Set [DEM Coefficients] parameters as Figure 156, and press [OK].
: [DEM Coefficients]
Run Driftwood Simulation
From the main menu, select [Simulation]->[Run] as Figure 157.
: [Simulation]->[Run]
When you are asked [Do you want to save?] as Figure 158, press [Yes] and save the project.
: [Do you want to save ?]
As Figure 159, 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].
: [How to save project]
When the calculation starts, Figure 160 is displayed, and Figure 161 is appear when the calculation ends. Then click [OK] to finish calculation.
: Solver Running
: Calculation finished
Visualization of driftwood motion
From the main menu, select [Calculation Result]->[Open New 2D Post-processing Window] as Figure 162.
: Open New 2D Post-processing Window
In the [Object Browser] of Figure 163, put check marks in the boxes at [iRICZone], [Scalar(node)] and [res_Velocity(magnitude)], right click [res_Velocity(magnitude)] and choose [Property].
: Scalar Setting(1)
Set the parameters for [Scalar Settings] as Figure 164, and press [OK].
: Scalar Setting(2)
Set the time bar back to zero, and select [Animation]->[Start/Stop] from the main menu bar as Figure 165, and start animation as Figure 166
: Start Animation
: Driftwood Tracking Animation
[Example 3] Tracer Tracking Simulation in Real River
In this section, we perform s simulation of tracking floats for the discharge measurements in a real river. Floats are injected from a bridge and velocities are calculated by measuring the flow time between two sections ste up with 100m interval in which the upper section is located 130m downstream of the bridge. Using a discharge of 384m \(^3\)/s, flow calculation is conducted using Nays2d+, and the paths of the floats are simulated by GELATO.
Flow Calculation by Nays2d+
Selection of Solver
From the start window of the iRIC, launch [Nays2d+] as Figure 167.
: Solver Selection
Import Geometric Data and Making Computational Grid
Importing River Bed Elevation Data
From the main menu, select [Import]->[Geographic Data]->[Bed Elevation(m)] as Figure 168, and read “tikei.tpo (Point Claud Data)” as shown in Figure 169.
: Import River Bed Data File
: Selecting a tpo file
While reading the data, you need to set filtering value as Figure 170. In this example, choose [1] just for without filtering.
: Input Filtering Value
The geometric data (ground elevation data) is shown as Figure 171.
: Geometric Data
Setup Background image
From the main menu, select [File]->[Property], and press [Edit] button at [Coordinate System:] information as Figure 172.
: Project Property
in the [Select Coordinate System] window, type “Japan” at [Search:] box, and select [EPSG ….. Japan …. IV] from the list below the [Search:] box, and press [OK] as Figure 173. Then close the [Project Property] window by pressing [Close].
: Select Coordinate System
In the [Object Browser], put check marks at [Background Images (Internet)] ->[国土地理院(標準地図)] as Figure 174.
:Select Background Image
Grid Creation
From the main menu, select [Grid]->[Select Algorithm to Create Grid], and select [Create grid from polygonal line and width] in the next window (Figure 175)
: Select Grid Creating Algorithm
Assign channel center points from the upstream side to down stream side as Figure 176. 上流側から下流へ向けて中心位置を選択する.
: Assign Center Points
In the [Grid Creation] window, Figure 177, input values as Ni=200, Nj=60 and W=120, then the grid size becomes about 3.2mx2m as Figure 178.
: Grid Creation
: Created Grid Shape
Setup for Bridge Piers
From the [Object Browser] in the left side of the window, hide the [Point Cloud Data 1] by removing the check mark. Right click [Obstacles], select [Add]->[Polygons], and make polygons by clicking the outer edge of the piers, and assign them as [Obstacle] (Figure 179) Surround all the cells in one polygon and assign it as [Normal Cell]. Note that the [Normal Cell] polygon has to be located at lower layer than the [Obstacle] polygons (Figure 180).
:Obstacle Cells for Bridge Piers
:Normal Cells for All the Area
Set Manning’s Roughness Coefficient
[マニングの粗度係数]よりポリゴンから全格子囲みn=0.030を入力する.
In the [Object Browser] under the group of [Geographic Data], right click [Manning’s roughness coefficient] and select [Add]->[Polygons], and make a polygon covering all the grid domain, and input n=0.030 (Figure 181).
:Set Manning’s Roughness Coefficient
Attributes Mapping
From the main menu, select [Grid]->[Attributes Mapping]->[Execute] (Figure 182).
:Select Attributes Mapping
Put check marks at [Elevation(m)], [Obstacle] and [Maninng’s roughness coefficient] in the [Attribute Mapping] window as Figure 183, and press [OK] to execute mapping.
:Choose Mapping Items and Execute Mapping
Set Calculation Condition
From the main menu, select [calculation Condition]->[Setting], and input parameters in the [Calculation Condition] window as the following figures of Figure 184, Figure 185, Figure 186, Figure 187, Figure 188 and Figure 189. When you finished to input parameters, press [Save and Close].
:Discharge and downstream water surface elevation settings
:Time series of discharge and downstream stage
:Time and bed erosion parameters
:Boundary Condition
:Other computational condition
:3D Velocity Profile
Execute a Solver
Save the project with some name, and run the solver by [Simulation]->[Run]. When the simulation finished, save the results and close the project.
Tracking Virtual Tracers by GELATO
Select a Solver
In the [Select Solver] window, which appears when you select [Create New Project] in the startup window of the iRIC, select [GELATO] and press [OK] as Figure 190.
:Select GELATO Solve
Import Grid Data
Right click [Grid(No Data)] in the [Object Browser] and select [Import] as Figure 191.
:Select GELATO
Choose [Case1.cgn] which contains the calculation results of [Nays2d+] saved in the previous section (Figure 192)
: Select a File to Import
Confirmation of Geographic Data
Set coordinate system by selecting [File]->[Property] from the main menu as Figure 193.
:Select Property
In the [Project Property] window, press [Edit] located at the [Coordinate System:] lin (Figure 194)
:Project Property
Type “Japan” in the box next to [Search:], select a line with [ EPSG:…Japan….CS VI], and press [OK] as Figure 195.
:Select Coordinate System
Select [Background Images(Internet)]->[国土地理院(標準地図)] from the Object Browser as Figure 196.
:Background Image
Tracer Tracking by GELATO
Calculation Condition
From the main menu, select [Calculation Condition]->[Setting], and set the [Calculation Condition] as Figure 197, Figure 198, Figure 199 and Figure 200. In which the CGNS file to read in the Figure 198 is usually the same file imported for calculation grid in Figure 192.
:[Basic Settings]
:Set the CGNS file to read the flow field information
:Set special tracer information for path tracking
:Diffusion Condition
Execute Calculation
From the main menu, save thr project by selecting [File]->[Save Project as], and execute GELATO by selecting [Simulation]->[Run].
Visualization of the Calculation Results
From the main menu, select [Calculation Result]->[Open new 2D Post-Processing Window]. Put check marks in [Background Images(Internet)] and [GSI(Ortho Images)(Japan only)] in the Object Browser, as Figure 201.
:Show Background Image
Right click the [Trajectory] at the [Polygon] in the Object Browser, and select [Property] as Figure 202.
:Property of the Polygon
In the [Polygon Setting] window, set [Line Width] as [3] as Figure 203.
:Polygon Setting
From the Object Browser, put check marks at [Scalar(node)] and [Velocity] and right click [Velocity] and press [Property]. In the [Scalar Setting] window, as shown Figure 204, uncheck [Automatic], set [Max:] and [Min:] vales, and uncheck [Fill lower area].
:Scalar Setting
After above settings the calculation results of the tracers injected from the Bridge can be visualized as follows.
:Tracer Tracking Paths
: Tracer Tracking Animation
References