April 13, 2024 at 12:39 am
robert reis
Subscriber

Hi Rob,

Thanks for taking the time to have a look at this.  You have asked 2 very good questions which I think will help me understand bigger picture.

I have purposely set the face size of the yellow strut in this example to the same as the horizontal plates.  As noted there is minimal refinement compared to the opposite end.  I am fine with this in principle - the flow is from left to right.  There is separation at left side and for the velocities I am looking at the flow does not re-attach at right. But as you say the refinemement is a result of the settings on the struts.

Secondly, the analysis is intended to parametrically look at the force on the struts for various size openings (solidity of strut). I was thinking of it this way - the force on the horizontal plates in almost a "constant", and not of large concern.  Yes there will be some boundary layer variation due to the recirculation between upper and lower plates due to solidity of the struts and resulting velocities, but I thought I could go coarser on the face sizing for the horizontals compared the verticals which will influence result more.  Where the struts intersect the horizontals is perfectly as expected with the refinement at the corner.  The issue the top most plate with the reflected refinement which I think is not required.

To add, in order to test my concern I have been running a grid independence study varying the face sizing of the vertical and horizontal plates,  but keeping rest of domain constant.  I have been using total force in X-direction as the dependent variable.  As I decrease the face size the total force increases, up to a point and then it begins to reduce.  For example see below - horizontal axis is cell count and vertical is total force.

So I'm thinking thios is pretty weird and needed to find an explanation.  Are we seeing a variation in force due to the refinement of the top face cells?  As we go to 4M cells, the top face becomes more consistent and uniform rather than banded as shown in my pics above which are from the 1.5M cell version.

What I need to do is re-run the simulations to capture the X-force component of just the top plate to see how that varies with the mesh issues above.

However if I could isolate that top face from the mesh refinement of the struts below and not have the banding would be awesome.

Happy for your thoughts?

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