Has anybody had luck (or attempted) to simulate very rough walls in FLOWORKS? I'm currently trying to validate textbook calculations for Rz values in the order of 1E6 - 1E9 micro-inch and I am not getting results that correlate whatsoever.

Thanks for the insight/opinions.

Sorry, typo on the Rz values. I'm only looking at values up to about 3E6 micro-inch. Not 1E9!

3E6 micro-inch is 3 inches. Can you elaborate on the application? How thick is the boundary layer?

John Parry, Research Manager, Flomerics Ltd.

Hello, thanks for the reply. Yes, 3E6 is 3 inches. Is this within the limits of the calculation scheme used by FLOWORKS to calculate wall shear stress and the resultant pressure drop along a flow domain?

The application I'm trying to model is loosely based on ambient airflow through mine shafts with shotcrete finished walls or just blasted/bored. It's large scale models (15 to 30 foot diameters) - I would anticipate bl thickness in the order of 6 inches to perhaps 18 inches. What scheme does FW use for bl approximation?

Additionally, where can I review the residual values after the calculations have finished iterating? The word 'residual' doesn't even show up in the FW help files when I search for it.

Thanks for the assistance,

I've continued to look into wall roughness effects. Not only are my results not lining up hand calcs, pressure drop along a 800 ft section (with fully developed flow) is not even varying for different Rz values.

Do you have access to the validation examples in Floworks? In EFD Lab one of the validation examples is flow over smooth and rough plates. I have just quickly changed the parameters of one of these models and obtained a pressure drop profile. What parameters are you using to check for convergence? The drag coefficent would perhaps be one to use? Cd = F / ((0.5*rho*V^2)*A))

F=drag force, A=surface area, rho=fluid density, V=fluid velocity