高さの分布のある直方体粗度群の抗力係数に関する風洞実験

概要

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The authors systematically investigated a bulk drag force coefficient (C_d) of regularly arrayed rectangular blocks in a wind tunnel by controlling various conditions such as arrangement pattern, plan area density (λ_p) and deviation from average height of the blocks. Using a particular instrument of floating element attached with a load cell, they can directly measure the total drag of roughness in high accuracy. The results can be summarized as follows; 1) C_d of staggered array is larger than that of normal array under a sparse condition owing to the difference of frontal projected area of models. In contrast, C_d of normal array is larger than that of staggered array under a dense condition. This is caused by the fact that a channel flow regime along stream wise streets in normal array phenomenally encourages shear production 2) The height variability among roughness makes C_d large even if the sameλ_p andλ_f (frontal area fraction) of a uniform height case are imposed. This tendency is obvious for dense canopy 3) When the mixture allocation of higher and lower building models is considered (the height deviation is imposed), the effect of arrangement pattern of higher models significantly affects on both C_d and depth of boundary layer.
2007-09-30