有限长管内包膜微泡在磁-声复合场作用下的振动行为

Vibrational behavior of coated microbubble in finite tube under magneto-acoustic composite field

磁声作用下的包膜微泡在治疗应用中具有极其重要的意义.本文将包膜微泡置于充满磁流体的管中,考虑在磁声场作用下磁流体受到的磁压力,推导了微泡的径向振动方程;并用韦伯数、雷诺数等特征量对其动力学方程无量纲化;采用龙格库塔法分析了磁声场参数及磁流体特性对其振动行为的影响.结果表明,磁场会阻碍微泡塌缩并使其做稳定振荡.声场一定时,磁场能够稳定微泡的振荡,增大振荡微泡的平衡半径;磁场越强,磁流体磁化率x_m对微泡的振动影响越明显,x_m较大时微泡瞬态响应的非线性更强;较大的声场参数会增强振荡微泡对磁场的响应;而磁场越强,声参数对微泡振荡的影响越弱,且微泡瞬态响应非线性明显但稳态响应保持小振幅的往复振荡.可见,通过调控磁声场有利于实现微泡在血管内的稳定振荡并避免塌缩.

The dynamic behavior of coated microbubble in a magneto-acoustic field is very significant for its application to therapy.In this paper,the radial vibration equation of microbubble is derived by placing the coated-microbubbles in a tube filled with magnetic fluid and considering the magnetic pressure on the magnetic fluid under the magneto-acoustic field.The dynamic equation is nondimensionalized by using characteristic quantities such as Weber number and Reynolds number.The effects of magnetic-acoustic field parameters and magnetofluid characteristics on the vibration behavior of the vibration system are analyzed by the Runge-Kutta method.The results show that the magnetic field can prevent the collapse and make bubble oscillate stably.When the acoustic field is constant,the magnetic field can stabilize the oscillation of the microbubble and increase the equilibrium radius of the oscillating microbubble.The stronger the magnetic field is,the more obvious the influence of magnetofluid magnetisability χm on the vibration of the microbubble is and the stronger the nonlinear of the transient response of the microbubble is when the magnetic field is larger.In addition,the larger acoustic field parameters will enhance the response of oscillating microbubble to magnetic field.The larger the magnetic field is,the weaker the influence of acoustic parameters on the oscillations of microbubble is.Also,the transient response of microbubble is obviously nonlinear,but the steady-state response keeps the reciprocating oscillation with small amplitude.It can be seen that the adjusting of the magnetoacoustic field is beneficial to realizing the stable oscillation of microbubble in the blood vessel and avoiding collapse.