Research On Tapping The Precipitation Potential Based On The Ultra-high Power Cluster Of Sound Waves

Low-frequency acoustic wave is considered a non-contact manipulation technology,based on acoustic energy transfer in the fluid medium and the exchange of kinetic energy between acoustic waves and particles,which can lead to particle vibration,collision and thus accelerate agglomeration,in industrial dust removal,airport fog removal and artificial impact on the weather and other areas of application.China's spatial and temporal distribution of water resources is uneven,especially the river source area water vapor conditions,but the natural precipitation conversion rate is not high,the use of acoustic and other new technologies to enhance the conversion rate of precipitation in the air,effectively increase precipitation on water conservation,increase soil moisture and river runoff is of great importance.The mechanism and critical conditions of acoustic agglomeration rainfall augmentation have been studied,but the acoustic sound source,acoustic propagation and attenuation law under natural conditions are not enough.In this paper,theoretical derivations and numerical simulations are carried out on the sound generation mechanism of a new high-power modulated airflow rotary flute sound source(rotary flute pneumatic sound source),the acoustic propagation law of sound waves in the atmosphere,the attenuation of sound waves propagating in the atmosphere and the effect on the coalescence efficiency of liquid particles in clouds,and the main findings are as follows:(1)The sound frequency of the rotary flute type pneumatic sound source is mainly concentrated between 0?300Hz;meanwhile,as the air chamber pressure of the rotary flute type pneumatic sound source increases,its sound pressure level of the sound waves emitted shows an increasing trend.And the increasing trend slows down and levels off when the air chamber pressure reaches 400,000 Pa.(2)The mathematical derivation of the attenuation coefficient of acoustic wave propagation of point source in the atmosphere was carried out,and the relationship between frequency(20?300Hz),humidity(10?50%)and temperature(-20?25?)related to the change of attenuation coefficient was calculated respectively,and it was concluded that the attenuation coefficient of acoustic wave propagation increased with the increase of atmospheric temperature,but when the relative humidity gradually increased,for lower frequencies,the acoustic wave attenuation coefficient with the increase in temperature is first increased and then decreased.The attenuation values of the total sound pressure level on the center vertical line under different working conditions were analyzed,and it can be seen that the degree of acoustic attenuation increases with the increase of temperature,which is consistent with the calculation results of the acoustic attenuation coefficient.(3)when the sound wavelength corresponding to the sound wave frequency is much larger than the size of the sound source device,the sound wave of this frequency is propagated in a relatively regular spherical form in the semi-free field;otherwise,if the sound wavelength corresponding to the sound wave frequency is close to or less than or equal to the size of the sound source device,the "cluster" effect appears,and the "strip" shape sound wave targeting the sound source device forms near the ground.The higher the frequency IS,the more "strips" form;the sound pressure level on the vertical line at the center of the horn mouth of the sound source device decreases in an exponential form;and the "strip" form sound wave near the ground targeting the sound source device causes that the sound pressure level on the vertical level deviating from the center of the horn mouth of the sound source device increases first and then decreases;the analysis carried out on the attenuation value of the total sound pressure level at the central vertical line under different working conditions shows that the degree of sound wave attenuation increases as the temperature grows,which is consistent with the calculation result of the sound wave attenuation coefficient;(4)in addition,the attenuated cluster of sound wave indeed plays a condensation effect on the liquid particles after atmospheric propagation,and the condensation efficiency obtained is 1.2% by simulation calculation with the frequency of 200 Hz,sound pressure level of 124 d B and the diameter of 50?m.