Hi Shan, Sorry I have not used this routine for a while. I attach some old notes I had on the derivation but perhaps Kurt is better placed to answer your email. I would guess that - alpha should indeed mean alpha_n. - R is the radius of the Gmsh boundary - T is the time period of the oscillation It is possibly confusing to refer to them as non-dimensional since this depends on how you have set up your mesh and inflow parameters. Cheers, Spencer. On 15 Jun 2019, at 22:33, Shanshan Luo <luoss@sas.upenn.edu<mailto:luoss@sas.upenn.edu>> wrote: Dear all, I'm confused about description of womersley number on Page 150 of user-guide-4.4.1. Can anyone give me some suggestions? On Page 150, for the formulas below: <Screen Shot 2019-06-15 at 5.20.02 PM.png> <Screen Shot 2019-06-15 at 5.20.11 PM.png> How can I calculate 'alpha'? Or it is a typo and should be 'alpha_n'? Also for the formula : <Screen Shot 2019-06-15 at 5.23.19 PM.png>, what does R and T represent? Does R mean RADIUS (the non-dimensional radius of the boundary in Gmsh) or the real radius (with dimension) of the object? Does T mean Period (the non-dimensional cycle time period)? Thank you very much! Best, Shan _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin FREng, FRAeS Head, Aerodynamics, Director of Research Computing Service, Professor of Computational Fluid Mechanics, Department of Aeronautics, s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> South Kensington Campus, Phone: +44 (0)20 7594 5052 Imperial College London, Fax: +44 (0)20 7594 1974 London, SW7 2AZ, UK http://www.imperial.ac.uk/people/s.sherwin/