Week 4.2: Project - Transient simulation of flow over a throttle body

For this challenge, first it’s important to import the geometry, and for this we downloaded the model file and import it by dragging the file in the CONVERGE-STUDIO. After this go for the normal checks. which must be pointed in the direction of the flow. Then, a diagnosis is done to check for any kind of geometrical error. After verifying it, the case setup is set as per the given inputs and boundary conditions. In this case, all the basic parameters are selected with specific values, and all these values are setup together as input files for the model. At last, export the input files into the folder.

The simulation follows, that can be converged by using the Cygwin interface, which is required for giving the command to the software. In Cygwin, first we go to the directory where the input files are present and then command them for simulation. This simulation can be done automatically at the back end, and the output files are generated in the same folder as the results of the simulation.

Then those output files have to be exported in Paraview to see the results in the different interfaces and also in their plots in the Converge Studio. For importing the output files in Paraview, first we need to convert the data into a ".vtm file," which is done in the "post-Processing 3-D" option in Converge-Studio. Then all the 3D and 2-D analyses of the results are analysed separately. The rest of the plots can be seen in Converge-studio itself, specifically under the "line-plotting option."

By doing so, I was able to obtain all of the required results for this particular challenge and take screenshots of them. CFD analysis of this problem. The simulation is done steady state flow with fixed boundary embedding, and the results are attached in a word file. Kindly find it below. In the trasient phase we fix the throttle stationary.

Detailed explanations about the plots:

1. The cell count plot shows that as the mesh size decreases, the number of total cells counts increases, indicating that decreasing the mesh size increased the number of cells. We can also understand that by the same token, in the fixed volume, if the mesh size decreases, that means the per-mesh volume also reduces. So to equalise the sum-total volume of meshes with the total volume of the geometry, more cells are required, which increases the cell count.
2. The mass flow rate plots appear to be very unstable at first touch, but as the flow cycled on, convergence took effect. In this aprox. after the completion of 600 cycles the convergence came in the plot. After achieving the convergence shown in the graph, we observe that the mass of the flow that enters the geometry from the inlet per unit of time is equal to the mass of the flow that exits from the outlet. But due to the sign conventions, the input and output flows are represented, respectively, as positive and negative values for comparison.
3. The velocity plots also look unstable in the starting phase, but as the flow loops after a few circulations, the flow achieves its convergence as in the case of flow rate. If we analysis the velocity segment rather then the initial cycles then we get that inlet velocity of the air is little more then the outlet due to the presence of throttle in between the both open ends. Along with this as we look into the same from the Para-view interface it’s better to understand that the velocity of flow around the throttle is somewhat unstable and diverged from their flow pattern.As the throttle rotates the turbulence increases around the throttle area and the velocity respectively decreases at the outlet.
4. The pressure graphs look unstable in the starting phase also, but as the flow goes on, after some time, the flow achieves its convergence, as in the case of flow rate. In starting it goes up and then with the time overall graph goes down and converges at last. The initial unstable pressure plot is very similar to the velocity plot. The pressure at outlet and inlet varies due to different initial conditions that are given to both ends in the case setup for making fluid flow inside the channel. But there is a wide range of change is observed from the inlet to the outlet in the simulated results, in the direction of the flow, in the Para view file. As the mash size decreases, the local variation in the velocity flow becomes finer and clearer. Along with this the maximum pressure is observed around the throttle circumference at inlet side. That release the whole inlet pressure. Also, as the throttle rotates the turbulence increases around the throttle area and the pressure at that perticular area increases.

Thankyou

Animation link: https://www.youtube.com/watch?v=1iOL3hFqkEs

https://youtu.be/Ay2wxEJUb-I

Anubhav