default wind speed modifiers

[Mathadon]

@kldjonge I just dug into some results where the wind pressure had much less effect than expected. E.g. 3m/s of wind really did not affects the zone tire flow that much. It turns out that these equations:

  pWin = Cs*0.5*CpAct*rho*vWin*vWin;
  Cs = (A0*A0)*((Habs/sim.Hwind)^(2*a))

  parameter Real A0=0.6 "Local terrain constant. 0.6 for Suburban,0.35 for Urban and 1 for Unshielded (Ashrae 1993) "
    annotation(Dialog(group="Wind"));
  parameter Real a=0.28 "Velocity profile exponent. 0.28 for Suburban, 0.4 for Urban and 0.15 for Unshielded (Ashrae 1993) "
    annotation(Dialog(group="Wind"));

are to blame. Cs has a value of 0.11, which seems really low. Furthermore, I'm wondering why we do not have Cs=1 for Habs=sim.Hwind. Wouldn't that be logical.

I propose to revise this implementation or default parameters such that the defaults are more logical for the average user. Perhaps we should create an enumaration where the type of terrain can be selected. We could then use Unshielded as default.

[kldjonge]

Agree!

Unshielded as default is fine for me. I think we decided on this because it was the 'middle' value for A0. No further reason I believe.

[Mathadon]

Okay, let's handle the open issues first before proceeding with this.