Womersley boundary condition for blood flow simulation
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
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 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- Kurt Sansom
Dear Kurt, Thank you for your help. Here I have a question: *How can I correctly set radius(R)?* Is it a dimensionless quantity? I used to believe that R should be dimensionless quantity and if we use diameter to be our benchmark then R should always be 0.5. If I am wrong, please correct me. I believe this may help to solve this issue. Many thanks! Best, Zhen On Tue, May 28, 2019 at 12:26 PM Kurt Sansom <kayarre@gmail.com> wrote:
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 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- Kurt Sansom
Zhen, Radius is a dimensioned variable unless you have non-dimensionalized your geometry. -Kurt On Tue, May 28, 2019 at 17:22 zxiong@sas.upenn.edu <zxiong@sas.upenn.edu> wrote:
Dear Kurt,
Thank you for your help. Here I have a question: *How can I correctly set radius(R)?* Is it a dimensionless quantity? I used to believe that R should be dimensionless quantity and if we use diameter to be our benchmark then R should always be 0.5. If I am wrong, please correct me. I believe this may help to solve this issue.
Many thanks!
Best,
Zhen
On Tue, May 28, 2019 at 12:26 PM Kurt Sansom <kayarre@gmail.com> wrote:
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 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- Kurt Sansom
-- Kurt Sansom
Dear Kurt, Thank you! Do you think the file I attached is a dimensionless geometry? We just build the geometry model from MRI and import it into Gmsh and use Nekmesh to convert it into xml format to set up simulation. We didn't non-demensionalize geometry but I am not sure if Gmsh will do this automatically. In this case, should I compute the R from Gmsh or still keep it as 0.5? Many thanks! Best, Zhen On Tue, May 28, 2019 at 9:24 PM Kurt Sansom <kayarre@gmail.com> wrote:
Zhen, Radius is a dimensioned variable unless you have non-dimensionalized your geometry.
-Kurt
On Tue, May 28, 2019 at 17:22 zxiong@sas.upenn.edu <zxiong@sas.upenn.edu> wrote:
Dear Kurt,
Thank you for your help. Here I have a question: *How can I correctly set radius(R)?* Is it a dimensionless quantity? I used to believe that R should be dimensionless quantity and if we use diameter to be our benchmark then R should always be 0.5. If I am wrong, please correct me. I believe this may help to solve this issue.
Many thanks!
Best,
Zhen
On Tue, May 28, 2019 at 12:26 PM Kurt Sansom <kayarre@gmail.com> wrote:
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 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
-- Kurt Sansom
-- Kurt Sansom
participants (2)
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Kurt Sansom
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zxiong＠sas.upenn.edu