Wierd looking velocity contour for DrivAer external airflow simulation

barry_1 · August 3, 2022, 06:18

Hi. I recently tried to do some velocity plots using a DrivAer car model on ANSYS Fluent. I have ended up with some really wierd "lightning-like" lines on my plots. I don't know why this is happening and want to know if I'm doing something wrong here. Could anyone point out what's going on?

Few details :
* K-omega SST turbulence model was used
* Inlet velocity was 40m/s and moving ground
* DrivAer model without wheels and smooth underbody was used
* Domain - 3L in front, 5L in the rear, 3H above and 3W for the side.

I have attached pictures for your reference.

velocity_plot.jpg

Thank you in advance

sbaffini · August 3, 2022, 12:22

I remember having similar issues (a decade ago), which are related to the parallel decomposition, but I honestly don't remember anymore when and why this happened, if it was my fault or Fluent fault, and if there was a fix about it.

If I had to point to something, it might be due to the node (as opposed to cell) visualization and the gradients probably not available yet, which probably happens when you first launch Fluent in parallel and go straight to the visualization without computing.

Try making a single iteration at least or switching to the cell visualization of the variables

August 3, 2022, 06:18	Wierd looking velocity contour for DrivAer external airflow simulation	#1
barry_1 New Member Barry Join Date: Mar 2022 Posts: 7 Rep Power: 4	Hi. I recently tried to do some velocity plots using a DrivAer car model on ANSYS Fluent. I have ended up with some really wierd "lightning-like" lines on my plots. I don't know why this is happening and want to know if I'm doing something wrong here. Could anyone point out what's going on? Few details : * K-omega SST turbulence model was used * Inlet velocity was 40m/s and moving ground * DrivAer model without wheels and smooth underbody was used * Domain - 3L in front, 5L in the rear, 3H above and 3W for the side. I have attached pictures for your reference. velocity_plot.jpg Thank you in advance

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August 3, 2022, 12:22		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,195 Blog Entries: 29 Rep Power: 39	I remember having similar issues (a decade ago), which are related to the parallel decomposition, but I honestly don't remember anymore when and why this happened, if it was my fault or Fluent fault, and if there was a fix about it. If I had to point to something, it might be due to the node (as opposed to cell) visualization and the gradients probably not available yet, which probably happens when you first launch Fluent in parallel and go straight to the visualization without computing. Try making a single iteration at least or switching to the cell visualization of the variables