This article provides a step-by-step tutorial for a fluid dynamic simulation of a non-return valve.
Valves under particular flow conditions can be simulated to obtain key performance quantities such as pressure drop through the system. Additionally, velocity and pressure results can be inspected in detail to identify regions of extreme pressure and flow inefficiencies. This tutorial acts as a guide for valve analysis best practices and can be used as a template for your future projects.
We are following the typical SimScale workflow:
Preparing the CAD model for the simulation.
Setting up the simulation.
Creating the mesh.
Run the simulation and analyze the results.
1. Prepare the CAD Model and Select the Analysis Type
First of all, click the button below. It will copy the tutorial project containing the geometry into your own workbench.
The following picture demonstrates what should be visible after importing the tutorial project.
You will notice that we are only modeling one half of the valve geometry. Having utilized the fact that the valve is symmetrical is a great way to save on both mesh size and simulation run time.
1.1 Create an Open Inner Region
Before we can begin a simulation, notice that we must first create the fluid volume. This has been done on the project you have imported from the link above. It is obtained by performing a geometry operation called Open inner region.
For the operation:
Select the surfaces surrounding the inlet and outlet openings as boundary faces.
Select any internal face as the seed face.
Once the operation is complete you will be left with the internal fluid volume.
1.2 Create a Simulation
Hitting the ‘Create Simulation’ button leads to the following options:
In this simulation, we calculate the flow of water through a valve. As long as the speed of the fluid is subsonic (Mach Number below 0.3), we select the incompressible analysis and create the simulation.
2. Assign Materials and Boundary Conditions
2.1 Define a Material
To apply the material to the geometry, press the ‘+ button‘ and the menu showed above lists the available materials. For this simulation, we will select ‘Water‘ and press ‘Apply‘ to confirm the material.
2.2 Assign Boundary Conditions
In the next step, boundary conditions need to be assigned. For this setup, flow and geometric boundary conditions are required.
In order to have an overview, the following picture shows the boundary conditions applied for this simulation:
a. Flow Conditions
Starting with the flow conditions, one needs to assign a Pressure inlet condition to the inlet as shown below:
After hitting the ‘+ button’ next to boundary conditions there will pop up a drop-down menu where one can choose between different boundary conditions.
Assign a Pressure inlet condition with total gauge pressure of 3e+5 \(Pa\):
Assign a Pressure outlet condition of mean value 0 gauge pressure to the outlet. This sets the outlet to atmospheric pressure allowing flow to exit freely.
b. Geometry Conditions
Assign Symmetry conditions to all the surfaces that lie directly on the plane of symmetry.
Don’t worry about the Simulation control settings, since their default values are optimized according to the chosen analysis type, hence valid for the majority of simulations. If you are a simulation expert however, you can have a look at them and change the settings as you like.
You can use Result control to observe the convergence behavior of certain items of interest. In this simulation it is not required.
To get the mesh, we recommend using the standard algorithm, which is a good choice in general because it is quite automated and delivers good results for most geometries.
Did you know?
Often, large changes in the mesh’s cell sizes are only spotted in a few regions.
Increasing the global mesh refinements rises the cells drastically.
When using the standard mesher, SimScale offers the option of physics based meshing. This algorithm detects regions which require a finer resolution based on the boundary conditions set.
You can also do this manually, by using one of the local refinement options, foremost being feature, surface and region refinements.
The resulting mesh will have about 226.6k nodes and look like this:
4. Start the Simulation
Now you can ‘start’ the simulation, and after few minutes you can have a look at the results.
Once your simulation is complete you can use the online post-processor to visualize the results. To get to grips with the post-processor please refer to the following documentation.
When analyzing valves, it is interesting to calculate the pressure drop and observe the velocity behavior through the system and whether any backflow occurs.
a. Pressure Drop
The pressure drop can be computed by using the Cutting plane filter and the bulk calculator to compute the average pressure upstream and downstream of the valve. Follow the steps below to calculate the pressure drop:
Make sure that there are no predefined filters and that you are at the last time step.
Select the ‘Cutting Plane’ filter in the Filters panel.
Change the orientation of the cutting plane in the y-direction by changing the Orientation to ‘Y’.
Place the cutting plane upstream of the valve with the Position: -0.213, -0.05, -0.032. The cutting plane will be similar to the figure below:
You can then use the bulk calculator to get the average pressure on the cutting plane. The average pressure upstream of the pipe is 2.558e+5 \(Pa\).
You can follow the same steps above to obtain the pressure downstream of the valve. However, the Orientation of the cutting plane will be in the ‘X’ normal direction with the Position: -0.3, -0.022, -0.032). Both cutting planes can be seen in the figure below:
From the figure above, the average pressure downstream of the valve is 455.7 \(Pa\). The pressure drop is calculated by subtracting the upstream pressure with the downstream pressure, which is 2.553e+5 \(Pa\).
Find more ways to calculate the pressure drop here.
Backflow is another phenomenon that is important when evaluating a valve. This is done by slicing the valve in the x-axis.
Choose the ‘Cutting Plane’ filter in the Filters panel.
The next step is to change the orientation of the cutting plane to the ‘X’ axis.
Next, change the Position of the cutting plane to the following coordinates: 0.02, -0.022, -0.032.
After that, slide the slider beside Vectors, this is to visualize the velocity vectors and change the Scale factor to ‘0.02’ and the Grid spacing to ‘7.5e-3’.
Finally, slide the slider beside Project vectors onto plane to project the velocity vectors onto the cutting plane. The cutting plane will be similar to the figure below:
We can see from the figure above that there is backflow occurring near the entrance of the valve and there are swirls inside of the pipe. This is critical to the valve performance as it hinders the flow patterns at critical locations affecting the desired pressure drop.
Analyze your results with the SimScale post-processor. Have a look at our post-processing guide to learn how to use the post-processor.
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