I need help with set up to see if there is any vortices crossing a circular shaft (Von Karman Vortex Street). I have tried to look at a few online example but they just do some initial set up and do not show boundary conditions or goals etc. They just go to the load results after they have ran the CFD analysis. Any help would be appreciated.
do a R'number calc and make sure you are in the range of applicable R'numbers
do a stohal number calc and get the approximate frequency
set study type to external
transient
use the default domain
set velocity under initial conditions.
set time to be 10 x expected period of oscialltion
I have all the information you suggested. I am trying to see if any vortices are created around a cylinder that is inside a pipe. Still use external? I want to see if the fluid subjected to the id of the pipe is affecting the possibility of vortices across the cylinder.
internal is fine then. The 10x of the period is a bit of a guess but signs of life should occur in the time frame - you might have to go longer. Run a 2D calc first as it won't take so long. Then go to the 3D to ccount for spanwise effects or lack there of in your case. The strohal based hand calc assumes an external flow so you might want to use it and test the sim to it just to ensure things are lining up.
Where are you getting stuck?
I am getting stuck on cut plots to show the shedding and the goals i need to set up to view the values of the shedding.
in a transient analysis you need to do a temporal animation to see the shedding - it is not the most elegant interface to get this done. Use the wizard and the help file once inthe animation area.
goals: put a split line on the cynder to allow you to plot force or pressure on the sides that separate parallel to eh flow direction then you can plot the oscillating pressure or force more strongly. If the whoile surface of the cylinder is used it will average out and may not be as strong a signal but probably still visible.
Can a reynolds number be too high? Will a high reynolds number not yield a vortex street across a cylinder?
yes. Above about ~80,000 as I recall. If memory serves me correctly the range is 10,000 to 80,000 or so. See Hoerner ,Fluid Dynamic Drag.
Thank you. Good information on solving this problem.
It was a pleasure. You posed questions that didn't need a novel to answer.
goals: put a split line on the cynder to allow you to plot force or pressure on the sides that separate parallel to eh flow direction then you can plot the oscillating pressure or force more strongly. If the whoile surface of the cylinder is used it will average out and may not be as strong a signal but probably still visible.