ICFD- FSI stress output

- November 7, 2022 at 5:38 pm
  
  Laura Pałys
  Subscriber
  
  Hi, Does anyone know how I could get the results of scalar shear stresses (in a numerical mesh generated automatically in ICFD). I need these values as a criterion for evaluating a medical device. I found a relationship between stresses and velocity gradient. I wonder how to introduce these equations into LS-DYNA.
- November 11, 2022 at 1:34 am
  
  Reno Genest
  Ansys Employee
  
  Hello Laura,
  Have a look at *ICFD_DATABASE_DRAG in the user manual vol III:
  LSDYNA » Manuals (ansys.com)
  
  You can output the drag forces and moments on surfaces. It will split the drap forces into pressures forces (normal to the surface) and viscous forces (tangent to the surface which is what you want). With these forces, you should be able to calculate the shear stresses. Here is what you will find in the manual:
  
  I don't know if it is possible to output shear stresses directly.
  
  Reno.
- November 11, 2022 at 6:52 pm
  
  Reno Genest
  Ansys Employee
  
  Hello Laura,
  You can also fringe the shear vector on the MSMESH part of your choice to visualize the hot spots:
  You can also do this with the MSPOST Explorer:
  
  Reno.
- November 23, 2022 at 2:59 pm
  
  Laura Pałys
  Subscriber
  
  Dear Reno,
  thank you for your response.Unfortunately, I am unable to manage with my problem. I used the DATABASE_DRAG_VOL (I also put 1 for ELOUT card), but but this is still the value for the surface when I want to compute the same value for each element.
  Do you know how can I get the values of individual components (pressure, velocity) in text form? For this, I would also need information about the size of the surface that the element consists of. Additionally, the simulation is transient and the remeshing follows.
- November 23, 2022 at 4:42 pm
  
  Laura Pałys
  Subscriber
  
  I found an interesting option in the post-processing module. But as I mentioned, I don't know how to generate an ifcdrag file.
- November 28, 2022 at 6:21 pm
  
  Reno Genest
  Ansys Employee
  
  Hello Laura,
  Do you have the *ICFD_DATABASE_DRAG keyword in your model? If so, it should create the following drag ASCII files:
  You can read the drag files with a text editor or post-process with LSPP as follows:
  
  Let me know how it goes.
  
  Reno.
- November 30, 2022 at 11:16 am
  
  Laura Pałys
  Subscriber
  
  Hello Reno,
  ICFD_DATABASE_DRAG works well (I've got icfdraga.dat file for surface), but for ICFD_DATABASE_DRAG_VOL I haven't got any output.
  Best,
  Laura
- January 12, 2023 at 7:37 pm
  
  Laura Pałys
  Subscriber
  
  The best solution is to calculate the shear stresses in Ensight or Paraview. The topic can be closed.