How to calculate OSI, Ig factor, Area averaged wall shear and time averaged wall shear in Ansys fluent?

Calculating the Oscillatory Shear Index (OSI), Ig factor, Area Averaged Wall Shear Stress (AAWSS), and Time Averaged Wall Shear Stress (TAWSS) in ANSYS Fluent involves several steps. Here's a general guide to help you with the process:

1. **Oscillatory Shear Index (OSI)**:

   - OSI is a measure of the directional change of wall shear stress over time and can be calculated using the formula:

     

   - In Fluent, you may need to write a User-Defined Function (UDF) to calculate OSI based on the wall shear stress values obtained during your simulation⁶.

2. **Ig Factor**:

   - The Ig factor, or the index of hemolysis, is typically calculated based on the shear stress and exposure time. You might need to use a UDF to integrate these values over the simulation time.

3. **Area Averaged Wall Shear Stress (AAWSS)**:

   - AAWSS is the average of the wall shear stress over a specified area. This can be calculated in Fluent by using surface integrals or custom field functions to average the wall shear stress over the area of interest⁷.

4. **Time Averaged Wall Shear Stress (TAWSS)**:

   - TAWSS is the average of wall shear stress over a period of time. In Fluent, you can calculate this by setting up data sampling for time statistics and then post-processing the sampled data to obtain the time-averaged values¹².

For detailed steps and to ensure accuracy, it's recommended to refer to the ANSYS Fluent documentation and tutorials, which provide comprehensive instructions on setting up and calculating these parameters. Additionally, the ANSYS user forums and discussion threads can be a valuable resource for specific questions and user experiences related to these calculations⁴⁶.

Source:

(1) OSI, AAWSS, TAWSS calculation -- CFD Online Discussion Forums. https://www.cfd-online.com/Forums/fluent/216127-osi-aawss-tawss-calculation.html.

(2) ANSYS FLUENT 12.0 Theory Guide - 20.3.1 Computing Surface Integrals - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node416.htm.

(3) How to calculate/visualize contour Time Average data (Wall shear stress .... https://forum.ansys.com/forums/topic/how-to-calculate-visualize-contour-time-average-data-wall-shear-stress-on-ansys-cfd-post/.

(4) How can I display wall shear stress based on 'time averaged velocity .... https://ansyskm.ansys.com/forums/topic/how-can-i-display-wall-shear-stress-based-on-time-averaged-velocity-in-cfd-post/.

(5) How do you calculate TAWSS, OSI, and RRT using ANSYS CFD-Post?. https://forum.ansys.com/forums/topic/how-do-you-calculate-tawss-osi-and-rrt-using-ansys-cfd-post/.

(6) Time Averaged Shear Stress -- CFD Online Discussion Forums. https://www.cfd-online.com/Forums/cfx/97793-time-averaged-shear-stress.html.

(7) Time-averaged Wall Metrics in EnSight from LS-DYNA FSI Results - Ansys .... https://forum.ansys.com/forums/topic/time-averaged-wall-metrics-in-ensight-from-ls-dyna-fsi-results/.

(8) UDF for calculating Oscillatory Shear Index (OSI) - CFD Online. https://www.cfd-online.com/Forums/fluent-udf/113815-udf-calculating-oscillatory-shear-index-osi.html.

(9) https://www.youtube.com/watch?v=SsORGWCg1ss.

(10) https://www.youtube.com/watch?v=E6VyM_aEGeE.

(11)  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v192/cfd_post/i1300348.html.

(12)  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v202/en/flu_ug/flu_ug_solver_steady_stats.html?q=data%20sampling.