UDF Format 8th Order Poly Fit

Jason

I am writting a UDF to model the Womersly solution for a tube. I have fit 8th order polynomials to the Bessel functions. When I use my code in MatLab I obtain the correct answer. When I format it for the UDF applied at the inlet velocity b.c. I beleif the problem to be associated with my 8th order polynomial fit. After ploting the velocity points from both the Matlab version and from Fluent, they match very closely from r/R = 0 to r/R = .5 but after that are radicaly different. Is there anyway of dealing with these "higher frequencies"? I interpert it with no error messages. I can send you the UDF and the MatLab m.file if anyone is interested in helping. Thanks, Jason