Measurements of the Aerodynamic Forces Acting on Porous Screens

摘要

An assessment of the value of porous screens for turning air through an angle depends on a knowledge of their aerodynamic properties when set obliquely to the stream. The present note furnishes measurements of the normal and lateral force coefficients of three wire gauzes, representing different degrees of blockage. Other data relating specifically to the resistance of screens at right angles to the stream, are included. It is shown that the drag coefficient, x80°, at speeds in the neighbourhood of'30 ft./sec. where the " speed effect " has almost vanished, may be expressed by the relation where β is the coefficient of porosity. It is indicated how this expression may be reconciled with a formula given in the Appendix.