[3nhu1]

Hello, would be grateful for some advice, a novice here and I am trying to run CFD simulations in bifurcations of arteries. These were meshed in simpleware and then run in CFX.

However for some of the models (5 out of total 70) - They have errors at the inlet - either an object on the face or multiple arrows, a colleague adviced smoothing the bifurcations and cutting the finite planes more perpendicular, I could only fix one, would be grateful for your advice as I am now stuck! We are unkeen to change meshing parameters as it would mean rerunning all the models. Thank you in advance

Pictures attached
multiplearrows.jpg

objonface.jpg

[ghorrocks]

What error are you getting? Are you getting the error in CFX-Pre or the solver? If the solver please attach your output file.

[Opaque]

Separate advice here:
1 - You can get a nice image from the CFX-Pre viewer by right clicking on the viewer, and select Save Picture
2 - or if using Windows, use the "snipping tool" to get a snapshot of the viewer and panel of interest

[3nhu1]

Thank you for getting back which is appreciated. To clarify I can run the simulation in CFX pre and get an output, however the inlet looks very odd and whilst we can get values they are off. We should be getting wall shear stress values between 1 - 7 Pa for coronary blood flow which is what we have generally obtained for all the other models, but when these ones with abnormal inlets are run values of more than 30-40++ Pa even are obtained.

I have attached another image with better resolution of the inlet with multiple arrows near the edges (on the left) and another model which was correct (on the right). Am just posting this hear to see if any one had an idea of potential issues and solutions. One thing that has helped variably fixing 1-2 of them this afternoon was recutting the inlet plane boundary much more perpendicular when meshing in simpleware before exporting to CFX but this solution is variable still and often does not work.

[Opaque]

I think you modified the markers rendering options in CFX-Pre

You can right-click in the viewer, and select Markers, you should get a Markers and Labels Option tab.. Press apply defaults.

You will notice several sliders, and probably they are at their maximum, or the limits are deactivated.

[ghorrocks]

With regard your accuracy question, see the FAQ: https://www.cfd-online.com/Wiki/Ansy..._inaccurate.3F

Note the inlet boundary condition is likely to be important here. If you just define a constant velocity over the whole inlet patch you are going to get huge wall shear stresses until the flow establishes itself. To fix this you need to impose an inlet condition which better matches developed flow, or extend the inlet boundary upstream to allow it to develop.

[3nhu1]

Thanks all for getting back, I managed to fix two more models by editing manually the stl file and mask (very tedious) - there probably is some issue as we are using multiple softwares and also the mesh settings at the boundary may be too detailed. Have 3 more to go but will try and fix it this way for now, thank you again