## WSS calculations directly from SimVascular

Provides a system for patient-specific cardiovascular modeling and simulation.
Atefeh Razavi
Posts: 23
Joined: Sun Mar 04, 2018 10:47 am

### WSS calculations directly from SimVascular

Hello,

I was wondering to know how I may extract (calculate) WSS values directly from SimVascular not Paraview.

Thank you and looking forward to your reply,
Ati

David Parker
Posts: 142
Joined: Tue Aug 23, 2005 2:43 pm

### Re: WSS calculations directly from SimVascular

Hi Ati,

WSS is calculated from the simulation results using the svPost program, which is part of the svSolver programs. You could have a look at the source code to see how the values are calculated (see https://github.com/SimVascular/svSolver ... ver/svPost).

Cheers,
Dave

Atefeh Razavi
Posts: 23
Joined: Sun Mar 04, 2018 10:47 am

### Re: WSS calculations directly from SimVascular

Hi Dave!

I looked at the code, however due to high number of variables, I did not figure out which variables were used to calculate WSS.
As defined, WSS is the velocity derived tangential stress. I was interested to see if I can calculate WSS from the velocity as well as the normal to the cell and then compare it with the WSS values given in Paraview.

Thanks,
Atefeh

David Parker
Posts: 142
Joined: Tue Aug 23, 2005 2:43 pm

### Re: WSS calculations directly from SimVascular

Hi Atefeh,

Sorry, I mislead you! The WSS calculation is actually done in the solver in solver_subroutines.f at line 1667:

Code: Select all

``````
rtmp = zero
wallssVec  = zero

do i=1, numnp
if (invflx(i) .ne. 0) then
rtmp(i,2:4) = flxres(i,1:3) !viscous flux
c     calculate the WSS
tn = flxres(i,1) * flxnrm(i,1)
&            + flxres(i,2) * flxnrm(i,2)
&            + flxres(i,3) * flxnrm(i,3)

wallssVec(i,1) = flxres(i,1) - tn * flxnrm(i,1)
wallssVec(i,2) = flxres(i,2) - tn * flxnrm(i,2)
wallssVec(i,3) = flxres(i,3) - tn * flxnrm(i,3)
endif
enddo
``````
where flxnrm is the outward normal and flxres is the viscous flux.

Cheers,
Dave