Abstract
The purpose of this study is to investigate the behavior of airflow in urban area and to obtain some information on the points mentioned below. 1) Calculation of natural ventilation. 2) Precise estimation of heat road for building air conditioning. 3) Protection against air pollution due to gas emission from auto-mobiles and buildings. 4) Prevension of public nuisance due to strong wind around tall buildings. For the purpose, several wind tunnel experiment were made. At first, we arranged many city-block models regularly in the wind tunnel and measured wind velocity, momentum flux, mixing length and so on. As a result, following remarks may be made. 1) Wind profiles above the streets to which wind direction is at right angles are nearly conform to the log-low in upper part (Z≧Z_0), but above the streets with which wind direction is in parallel, those are not necessarily conform to log-low. 2) The pattern of vertical distribution of friction velocity u_* is that in lower part (Z≦Z_0) the value of u_* is small, but in upper part u_* increases and becomes constant (u_*≃0.2). [cf. Fig.35, 36] 3) Mixing lengths increase in proportion to height (Z) in upper part (Z≧Z_0), but near the limit of boundary layer, they decrease to zero. [cf. Fig.37, 38] and so on.
