Hi Zhen,

  Are the inlets to your domain cylindrical? VMTK has a widget that allows you to add cylindrical flow extensions. This would allow you have a more precise inlet, and womersley as implemented is only valid for a cylinder. 

If there is a analytical solution to womersley of an arbitrary inlet crossection please let me know.

One thing to consider is that that analytical solution depends on the radius of the vessel, make sure R is the same units as the domain, and if the radius of the mesh inlet exceeds the radius, R for the  Womersley solution, then failures would be expected.

I do similar simulations in fluent and have found that rounding to single precision in the womersley parameters avoids this issue.

~Kurt 

On Mon, May 27, 2019 at 10:45 PM zxiong@sas.upenn.edu <zxiong@sas.upenn.edu> wrote:

Dear all,

We are trying to do blood flow simulation on a vessel geometry model. When we try to apply Womersley boundary condition to the inlet, we meet some problems.

In Womersley boundary condition, we need to specify the property "axispoint" which should be the center of the vessel's inlet and the property "axisnormal" which should be the flow direction. However, we can only estimate these two value because they are not in the standard position(all the numbers are floating points). This causes the failure of simulation. So I want to know does Nektar++ require 100% accuracy in these two property? If so, does anyone have some suggestion? 

Many thanks!

Best,

Zhen

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Kurt Sansom