Problem calculating pressure coefficient on facade

#1

Hi all,

I am trying to calculate the wind pressure coefficient, Cp, at specific points on the facade of a test building. This is to validate my setup compared to existing research so I can continue to use it further in my thesis. I made a simple python script to calculate Cp according to the equation Cp = (P - Pref) / (0.5 * rho * Uref^2) however, the results don’t make sense (Cp > 1). I am sampling Pref and Uref at a point 1.5H away from the top of the building. The setup I am emulating specifies U = 12.7m/s at building height (182.88m) which I set in the Create Wind Tunnel Component, however, it seems it still makes 12.7m/s at 10m when I run the analysis.

I tried to follow the advice for getting Cp here: Error with wind simulation when adding awning window panes but BF does not run when I input the function object. I attached my GH file please any help would be appreciated.

PressureCoeffTests.gh (438.5 KB)

#2

Z0 in wind tunnel is currently always set to 0. You can manually edit that value inside the folder. I believe there is an open issue on this topic on GitHub.

#3

@errone92

When you input a velocity value to the wind tunnel component it always corresponds to the 10m wind velocity, thus your findings.

What you can do is use a logarithmic calculator (LB has one or one from the net) and find your 10m wind velocity, for a 12.7m/s velocity at 182.88m. Then plug in that number in BF and all should work okay, assuming your ground starts at 0 (if not then you also have the issue mostapha noted).

Kind regards,
Theodore.