pipe flow
 

Does anybody have any explanation for the fact that some low Reynolds number models (e.g. Launder & Sharma, 1974) accurately predict the friction velocity in turbulent pipe flow, yet do not return the correct axial pressure gradient? My simulation results are definitely grid independent, I have ensured that the first five near wall nodes are located at yplus<1.0 and the pressure gradient was calculated using the predicted data near the pipe exit where the flow is fully-developed. Any comments/hints would be greatly appreciated.

Richard Carroni