A Theoretical Study Of Sound Scattering In Different Eddy Current Fields

With the development of industry,a large number of toxic and refractory organic compounds are produced,which cannot be effectively treated by traditional methods,resulting in water pollution and serious ecological problems.As an advanced oxidation process,ultrasonic radiation can rapidly degrade chemical pollutants in water without secondary pollution,so it is introduced into the design of chemical reactor as an important part of new reactors.But at present,all kinds of sonochemical reactors cannot effectively solve the problem of sound field uniform distribution,resulting in standing wave in the reactor,which limits the improvement of reaction rate and efficiency.The existing method is to use composite frequency and increase the number of transducers in the reactor.Considering the efficiency ratio,it causes great waste,and needs to adjust the frequency and change the position of transducers according to the reactants,so the operation is complex.Vortex effect can eliminate the standing wave effect in liquid greatly,which provides a new idea for the design of sonochemical reactor.In this paper,to improve the reaction efficiency and rate of vertical vortex reactor,Taylor vortex reactor and large-scale degradation tank,the sound scattering theory of Rankine compound vortex,Taylor vortex and reverse vortex pair is studied and analyzed respectively,which provides theoretical basis and guidance for more reasonable design of acoustic reactor and degradation tank,making the sound field in the internal liquid evenly distributed and improving the reaction rate and efficiency.Research shows:(1)The scattering characteristics inside and outside the Rankine composite vortex core are different.The phase shift caused by the scattering in the inner region of the vortex core is a small quantity of order ?2,that caused by the scattering outside the vortex core is a small quantity of order ?(?k/2?c=?),and that caused by the scattering in the inner region of the vortex core is a small quantity of higher order,which can be ignored.The scattering characteristics are positively correlated with the change of phase shift,so the scattering of plane acoustic waves into the Rankine composite vortex is mainly caused by the region outside the vortex core.(2)There is a small ? order relationship between the scattering sound pressure of Rankine composite vortex and the incident sound pressure,which corresponds to the small ? order phase shift caused by the scattering outside the vortex core.It is proved that the Rankine composite vortex sound scattering theory is highly consistent and reasonable.The diagram of sound pressure scattered by Rankine composite vortices in Fig.3-4 shows that Rankine composite vortices scatter sound pressure more evenly distribute in the liquid.With the increase of incident wave number,the critical angle tends to decrease,the amplitude of scattered sound pressure increases,and there are more and more scattering oscillation peaks.In each quadrant,the number of oscillation peaks is the same,which is positively related to the incident wave number,that is,Z=kxR/2?.Moreover,the forward scattering amplitude is much larger than the backward scattering amplitude,which is quite different from the solid scattering.(3)There is no singularity in the incident direction of the acoustic wave in the analytical solution of the acoustic pressure equation from Taylor vortex scattering plane acoustic wave.The scattering sound pressure is mainly distributed on both sides of the plane wave incident direction.When kL increases gradually,the position and angle of the maximum amplitude of the scattering sound pressure tend to the incident direction;when kL is small,the backscattering is more obvious,and the scattering sound pressure shows a weak quadrupole effect.With the increase of kL,the ratio of the amplitude of the forward scattering sound pressure and the amplitude of the backscattering sound pressure gradually increases,and the backscattering sound pressure amplitude tends to zero,so a small incident wave number is favorable for the sound wave to be evenly distributed in the liquid.(4)The scattering of plane acoustic waves by backward vortices is anisotropic.When the incident angle of plane sound wave is parallel to the x-axis,the directivity of scattered sound pressure is the strongest.With the increase of the angle between plane sound wave and x-axis,the directivity of scattered sound pressure decreases gradually.When plane sound wave is parallel to the y-axis,the directivity of scattered sound pressure is the smallest.When the incident angle is the same,with the increase of k0d,the directivity of the scattered sound pressure produced by the plane sound wave entering the counter vortex pair increases gradually.Therefore,when the incident wave direction is parallel to the direction of the counter vortex pair,the distribution of the scattered sound wave in the liquid is more uniform when the k0d is smaller.Therefore,it is explained theoretically that how the sound wave is more evenly distributed in the liquid when the reverse vortex pair is added in the vertical vortex reactor,Taylor vortex reactor and large-scale degradation tank,which provides a theoretical basis for the further optimization and design of the acoustic reactor,so as to improve the efficiency and speed of the reactor.