simpleFoam 2D plate flow with obstacle errors between hex blocks

CoolHand · February 19, 2014, 19:23

I am new to OpenFOAM and I've been having this problem with several different simulations I've tried. I want to examine the turbulence from an obstacle on a plate in a flow. It's a very simple geometry with just 3 blocks, but it seems like no matter what I do there is something wrong happening where the hex blocks meet. It's as if the calculation starts over every time it reaches a new block. If anyone has any insight into this I would be incredibly grateful.

Here's my case:

Google Drive with case files.

This includes all files from my 0, system, and constant folders and also includes a checkMesh.log and a 7zip archive containing all the files.

Here are images of my mesh and the velocity contours around the obstacle (which I've been referring to as a "speed bump").

Mesh Screenshot
Velocity Contours Screenshot

chegdan · February 20, 2014, 15:04

What solver are you using?
What do you mean by " It's as if the calculation starts over every time it reaches a new block"?
Also, rescale your final result in paraview because your picture shows some stair-stepping because it is visualizing data outside the range you started with.

CoolHand · February 20, 2014, 15:51

I'm using simpleFoam. What I mean is I can see a boundary layer develop and then when it reaches anew block the boundary layer stops abruptly and starts developing again in the new block until it reaches the next block. Does the paraView data range explain that?

chegdan · February 20, 2014, 16:41

About your BL
Your y+ has an average of 468 and a max of over 1000 on the lower wall. Firstly, you will need to use wall functions and/or refine your mesh to fit into the criteria that makes your turbulence model valid t capture the correct physics. Your results will not be remotely correct without this and you will need to resolve the mesh much finer (y+ < 3 ) if you really want to capture the BL at higher Reynolds numbers + use a low Re turbulence model like Lam Bremhorst.

Paraview
What I mean about paraview and scaling is that paraview picks a color based on the range of data when its loaded or prescribed by the user. So your colors in your surface plot are chosen based on time 0 (or your start time). When you advance to later times, the color scheme is still in the range of your start. If the data is above the range...it will give it the color of the highest value it was originally scaled by. The same is true for values lower than the what was assigned in the surface plot colors...i.e. it will assign the color of the lowest value color. To get past this, you need to tell paraview to reassign colors based on the new range...i.e. rescale the color range.

February 19, 2014, 19:23	simpleFoam 2D plate flow with obstacle errors between hex blocks	#1
CoolHand New Member Join Date: Jan 2014 Location: South Florida Posts: 20 Rep Power: 12	I am new to OpenFOAM and I've been having this problem with several different simulations I've tried. I want to examine the turbulence from an obstacle on a plate in a flow. It's a very simple geometry with just 3 blocks, but it seems like no matter what I do there is something wrong happening where the hex blocks meet. It's as if the calculation starts over every time it reaches a new block. If anyone has any insight into this I would be incredibly grateful. Here's my case: Google Drive with case files. This includes all files from my 0, system, and constant folders and also includes a checkMesh.log and a 7zip archive containing all the files. Here are images of my mesh and the velocity contours around the obstacle (which I've been referring to as a "speed bump"). Mesh Screenshot Velocity Contours Screenshot

February 20, 2014, 16:41		#4
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	About your BL Your y+ has an average of 468 and a max of over 1000 on the lower wall. Firstly, you will need to use wall functions and/or refine your mesh to fit into the criteria that makes your turbulence model valid t capture the correct physics. Your results will not be remotely correct without this and you will need to resolve the mesh much finer (y+ < 3 ) if you really want to capture the BL at higher Reynolds numbers + use a low Re turbulence model like Lam Bremhorst. Paraview What I mean about paraview and scaling is that paraview picks a color based on the range of data when its loaded or prescribed by the user. So your colors in your surface plot are chosen based on time 0 (or your start time). When you advance to later times, the color scheme is still in the range of your start. If the data is above the range...it will give it the color of the highest value it was originally scaled by. The same is true for values lower than the what was assigned in the surface plot colors...i.e. it will assign the color of the lowest value color. To get past this, you need to tell paraview to reassign colors based on the new range...i.e. rescale the color range. Last edited by chegdan; February 20, 2014 at 16:55. Reason: clarity and formatting

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February 20, 2014, 15:04		#2
chegdan Senior Member Daniel P. Combest Join Date: Mar 2009 Location: St. Louis, USA Posts: 621 Rep Power: 0	What solver are you using? What do you mean by " It's as if the calculation starts over every time it reaches a new block"? Also, rescale your final result in paraview because your picture shows some stair-stepping because it is visualizing data outside the range you started with.

February 20, 2014, 15:51		#3
CoolHand New Member Join Date: Jan 2014 Location: South Florida Posts: 20 Rep Power: 12	I'm using simpleFoam. What I mean is I can see a boundary layer develop and then when it reaches anew block the boundary layer stops abruptly and starts developing again in the new block until it reaches the next block. Does the paraView data range explain that?