螺旋桨风洞实验气动声学相似准则研究

A New Propeller Aeroacoustic Scaling Law

从气动方程和声学方程两方面共同考虑,结合螺旋桨气动声学风洞实验研究的特点,推导出几何相似螺旋桨风洞实验中应模拟的相似参数。证明了几何相似的低速螺旋桨在临界雷诺数以上时,保证前进比和对应马赫数相等就可以保证声学相似并推导出相似螺旋桨声压级的换算公式。为实际的实验设计和数据处理工作提供了理论依据。

In order to use the results of experiment which are obtained in wind tunnel with small model, propeller aeroacoustic scaling law must be studied. Based on both aerodynamic theory and acoustic theory, a new aeroacoustic scaling law of low speed propeller for far field was derived. This scaling law points out that similar propellers in aeroacoustics must satisfy three conditions： equal advanced ratio; equal Mach number; Reynolds number of propeller is higher than critical number. The derived scaling law is Lp-L′p= 201g（D/D′）＋20lg（r′/r）, where Lp is sound pressure level of large model; L′p is sound pressure level of small model; D is diameter of large model; D′ is diameter of small model; r is distance between large model and sensor; r′ is distance between small model and sensor . Our new scaling law includes the well known Lp-L′p= 20lg（D/D′） as a special case, but is more convenient to use, as it places no limit on the position of point of measurement of noise level. The derived new scaling law gives calculated results that are in close agreement with results of six different types of experiments performed by us.