Hi Saif
"Should I use free stream condition for wind direction? or, should I use local wind direction (close to the facade)?"
Basically, pressure coefficients will vary if you consider one or the other. If your building has surrounding obstacles, and you determine cp's for wind direction near the facade, you will have a certain array of values. But if you build your pressure coefficients according to the wind direction outside the influence of the obstacles, you produce a different set of arrays. So you use the wind directions values for the case at hand. If you determine cp values on CFD simulation near the facade, and you know there are surrounding obstacles, you need to use wind directions obtained (or at least inittially considered) to be the wind direction at the facade level and not at the free stream. This is because each direction on the fream stream will most probably correspond to a different direction at the facade. The same applies to wind speed at different elevations, due to the (likely) variation of the velocity profile of wind with respect to altitude.
"how far I should go from the facade to consider wind direction?"
the distance from the facade, when comes to specify an outside node for wind pressure coefficients, is not taken into consideration in Eplus. You can relate each opening of the building that you need defined to an outside node that helds the values of the pressure coefficients.
Hope this helps.
Pedro.
On 22-05-2011 5:04, saif_1509 wrote:
Hi
I am using CFD to get pressure coefficient for building facades. However, due to surrounding buildings, wind directions are different than free stream condition (or, from weather file data). Should I use free stream condition for wind direction? or, should I use local wind direction (close to the facade)? Due to facades damping effect, wind direction next to facade is almost parallel to the facade. In this case, how far (feet or meter normal to the facade) I should go from the facade to consider wind direction? Any suggestion or guidance will be appreciated. Thank you in advance.
Saif
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