流体中速度场,声场检测方案(粒子图像测速)

Although acoustics consists in the propagation of an oscillatory disturbance of local pressure, particle velocity, density and temperature, sound measurement is often assimilated to pressure measurement. This is because for decades only pressure fluctuations were accessible and because their relation with the other oscillatory quantities is well known under linear acoustic approximation and in simple configurations. Such a correct description of the origins of sound has long been known from the theory of sound, but there is a bad habit of acousticians to use the descriptions of sound as acoustic pressure only. Meanwhile, a sound wave is a form of energy transport in the field and has the vectors features. Sound intensity (SI) as a vector variable inseparably couples the acoustic particle velocity (called also acoustic velocity). and acoustic pressure (Ia=p v) and represents a stream of acoustic energy flowing in the field. This vector parameter of acoustic wave can be measured with special sound intensity probe and can be easily shown in a graphical form.