|00:01||Hello and welcome to this tutorial on Setting up a test case in OpenFOAM.|
|00:07|| In this tutorial, we will learn to:
Set up a case in OpenFOAM
|00:13||Access the case files using terminal|
|00:17||Pre-process a case|
|00:20||Run a case, and Post-process a case|
|00:25|| This tutorial is recorded using,
Ubuntu Linux OS version 18.04
|00:34||OpenFOAM version 7|
|00:37||ParaView version 5.6.0, and gedit Text editor|
|00:45||You may use any other text editor of your choice.|
|00:50||As a prerequisite: You should be familiar with basic Linux commands.|
|00:58||If not, please go through the prerequisite Linux tutorials on this website.|
|01:04||In this tutorial, we will learn to set up the lid driven cavity case.|
|01:10||Lid driven cavity is one of the most widely used 2D test cases for the validation of a CFD code.|
|01:19||This is the diagram of Lid Driven Cavity Flow.|
|01:24||It consists of 3 fixed walls and a moving top wall.|
|01:30||Open a terminal by pressing the Ctrl, Alt and T keys together.|
|01:37||Here onwards please remember to press the Enter key after typing each command.|
|01:44||Now, let’s create a RUN directory.|
|01:48||To do so, type the command as shown.|
|01:52||Tutorial cases will later be copied into the RUN directory.|
|01:57||Go to the RUN directory using the cd command.|
|02:02||Now our present working directory is the RUN directory.|
|02:07||OpenFOAM installation comes with a set of test cases.|
|02:12||The TUTORIALS directory contains these test cases.|
|02:17||The Lid driven cavity case already exists inside the TUTORIALS directory.|
|02:23||We’ll now copy the Lid driven cavity case from the TUTORIALS directory into the RUN directory.|
|02:31||To do so, type the following command.|
|02:36||The mesh generator for OpenFOAM is a utility called blockMesh.|
|02:42||The input dictionary for blockMesh utility is blockMeshDict.|
|02:49||The blockMeshDict file is located in the system folder.|
|02:55||Open the blockMeshDict file in a text editor.|
|03:00||Now let’s look at the contents of the file.|
|03:04||The blockMeshDict contains details of the geometry like vertices, blocks, edges and boundaries.|
|03:17||Close the blockMeshDict file.|
|03:20||The 0 folder contains the initial and boundary conditions for the simulation.|
|03:27||Type the following command to move into the 0 folder inside the cavity case directory.|
|03:35||Type ls and press Enter to view the files in the 0 folder.|
|03:41||The 0 folder contains the kinematic pressure file p and the velocity file U.|
|03:49||Open the kinematic pressure file p in a text editor.|
|03:54||The p file contains the initial and boundary conditions of kinematic pressure.|
|04:01||The dimensions of kinematic pressure is meter squared per second squared.|
|04:07||The internalField defines the values in the interior of the domain.|
|04:13||The initial field is set as 0 kinematic pressure.|
|04:17||This field is uniform across the domain.|
|04:21||You can see that all walls are imposed with a zero gradient pressure boundary condition.|
|04:29||Let us close the p file.|
|04:32||Now open the velocity file U in a text editor.|
|04:37||The U file contains the initial and boundary conditions of velocity.|
|04:43||You can see that the moving wall is imposed with a velocity of 1 m/s in the x direction.|
|04:52||Also notice that the no-slip condition is imposed on the three fixed walls.|
|04:59||Now let us close the U file.|
|05:02|| We’ll go back to the cavity folder.
Type cd (space)(dot)(dot)
|05:10||Next, we will view the transport properties file which is in the constant folder.|
|05:17||The transportProperties file contains the details of kinematic viscosity.|
|05:24||The dimensions of kinematic viscosity is meter squared per second.|
|05:30||The kinematic viscosity is defined by: nu equals magnitude of U times d by Re|
|05:41||where velocity is 1 m per second|
|05:45||characteristic length is 0.1 meters|
|05:50||The Reynolds number (Re) for the flow is taken as 10.|
|05:55||The kinematic viscosity is therefore 0.01 meter squared per second|
|06:01||Now let me switch back to transportProperties file.|
|06:05||The value of kinematic viscosity is indicated in the transportProperties file.|
|06:11||Close the transportProperties file.|
|06:14||To move into the system folder, type the following command.|
|06:19||Type ls to view the contents of the system folder.|
|06:24|| The system folder contains the following files:
blockMeshDict, controlDict, fvSchemes and fvSolution.
|06:37||The fvSchemes dictionary contains the finite volume discretisation schemes.|
|06:44||The fvSolution dictionary contains the linear equation solvers and tolerances.|
|06:51||It contains other algorithm controls as well.|
|06:56||The controlDict dictionary contains the simulation control parameters.|
|07:02||The dictionary input includes the control of time and reading and writing of the solution data.|
|07:09||Let’s open the controlDict file in a text editor.|
|07:14||The start and stop times and the time step for the run must be set.|
|07:21||The start time is set at 0 seconds.|
|07:25||The time at which the simulation stops, is specified using the keyword stopAt.|
|07:32||Here, stopAt is specified using the keyword endTime.|
|07:38||The endTime is set at 0.5 seconds.|
|07:43||This means that simulation stops after 0.5 seconds.|
|07:49||The value of the keyword deltaT defines the time step for the simulation.|
|07:56||The time step for the current simulation is set as 0.005 seconds.|
|08:03||Temporal accuracy and numerical stability is essential while running the simulation.|
|08:10||To achieve this, a Courant number of less than 1 is required.|
|08:16||Keeping this in mind, the time step is set to 0.005 seconds.|
|08:22||Please refer to the additional reading material on this tutorial page for details.|
|08:28||It mentions the steps used to calculate the time-step.|
|08:33||icoFoam is the OpenFOAM solver used to simulate the lid driven cavity flow.|
|08:39||Close the controlDict file.|
|08:42||Go back to the cavity folder using cd command.|
|08:47||Type the command blockMesh and press Enter to mesh the geometry.|
|08:53||The command takes input from the blockMeshDict dictionary and creates the geometry and meshes it.|
|09:01||The meshing is now complete.|
|09:04||The lid driven cavity flow is an incompressible flow.|
|09:09||It is solved using the OpenFOAM solver icoFoam.|
|09:14||To start the simulation, type icoFoam in the terminal.|
|09:20||The iterations are now complete.|
|09:23|| Let us view the simulated results in ParaView.
So, type paraFoam in the terminal.
|09:32|| In the ParaView window, go to the Properties tab on the left.
Then click on the green coloured Apply button.
|09:41||Go to the Active Variable Controls at the top.|
|09:46||Click on the vtkBlockColors dropdown and select U.|
|09:52||Ensure that you click on the U option with a point icon and not the box icon, in the dropdown.|
|10:00||The box icon would display contours without any grading.|
|10:04||The velocity contour at the start of the simulation is now displayed in the layout.|
|10:11||Let us see how the velocity contours develop through the simulation.|
|10:16||To do so, go to the VCR Controls and click on the Play button.|
|10:23||The velocity contour at the end of the simulation is now displayed in the layout.|
|10:30||Close the ParaView window.|
|10:34||With this we have come to the end of the tutorial.|
|10:36||To summarise, in this tutorial we have learnt to:|
|10:42||Set up a case in OpenFOAM|
|10:45||Access the case files using terminal|
|10:49|| Pre-process a case
Run a case, and
|10:54||Post-process a case|
|10:57|| The video at the following link summarises the Spoken Tutorial project.
Please download and watch it.
|11:05|| We conduct workshops using Spoken Tutorials and give certificates.
Please contact us.
|11:13||Please post your timed queries in this forum.|
|11:17|| Do you have any general/technical questions?
Please visit the forum given in this link.
|11:24||The FOSSEE team coordinates solving feasible CFD problems of reasonable complexity using OpenFOAM.|
|11:31||We give honorarium and certificates to those who do this.|
|11:35||For more details, please visit these sites.|
|11:39|| The Spoken Tutorial project is supported by MHRD, Govt. of India.
The script for this tutorial is contributed by Ashley Melvin.
|11:49||And this is Swetha Sridhar from IIT Bombay signing off.
Thank you for joining.