纵向加速流场中风速管系数的理论修正

THE THEORETICAL CORRECTION OF PITOT TUBE COEFFICIENT IN LONGITUDINALLY ACCELERATED FLOW

基于理想不可压轴对称位流理论，求得一任意椭球在纵向加速流场中绕流的精确解。并以一根细长的棉球近似模拟风速管，求得均匀流中风速管系数理论值，以及在纵向加速流中它的相对偏差值。以两个长细比各为32和250的椭球为算例，得知在一般风洞实验段内存在的速度梯度下，风速管系数的相对偏差量很小。文中表1、表2所列不同加速下风速管系数的相对偏差值，可近似用来修正实际风速管，或根据流场加速程度选择合适的风速管外径的大小。

Based on the axisymmetrical potential flow theory of an inviscid,incompressible fluid,the exact solutions of the longitudinally accelerated and uniform flow passing the ellipsoids were obtained respectively. The conventional pitot tube was approximately modeled by a slender ellipsoid,then,the theoretical values of pitot tube coefficient in both flows were calculated,and the relative deviation of the coefficients was determined. As an example,two slender ellipsoids with slenderness radio 32 and 250 were analysed. It is concluded that the relative deviation of pitot tube coefficient are small enough in conventional wind tunnel with longitudinal velocity gradient. The relative deviation with various accelerating gradients was listed,which may be used to make practical Correction or to determine the appropriate diameter of pitot tube for various accelerating cases.