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流体通过涡激振动机翼的声辐射研究 总被引:1,自引:0,他引:1
为了有效地降低涡激噪声,研究了粘性流体通过涡激振动机翼的声辐射。采用Navier-Stokes方程描述二维机翼的流固耦合运动,用弹簧系统代替实际固体变形产生的回复力和力矩,翼型的运动是两个自由度,即垂直于来流的振荡和转动振荡;为了模拟涡激振动,机翼的初始攻角取得比较大,以便产生周期性的旋涡脱落及周期性的流体动力,后者与弹簧系统相耦合,引起振动,用Lighthill声比拟方法研究了由此引起的声辐射。计算结果表明:当涡脱频率和机翼的固有的振动频率一致时,发生锁定的现象,此时的声辐射达到最大。 相似文献
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Estimation of temperature elevation generated by ultrasonic irradiation in biological tissues using the thermal wave method 下载免费PDF全文
In most previous models,simulation of the temperature generation in tissue is based on the Pennes bio-heat transfer equation,which implies an instantaneous thermal energy deposition in the medium.Due to the long thermal relaxation time τ(20 s-30 s) in biological tissues,the actual temperature elevation during clinical treatments could be different from the value predicted by the Pennes bioheat equation.The thermal wave model of bio-heat transfer(TWMBT) defines a thermal relaxation time to describe the tissue heating from ultrasound exposure.In this paper,COMSOL Multiphysics 3.5a,a finite element method software package,is used to simulate the temperature response in tissues based on Pennes and TWMBT equations.We further discuss different factors in the bio-heat transfer model on the influence of the temperature rising and it is found that the temperature response in tissue under ultrasound exposure is a rising process with a declining rate.The thermal relaxation time inhibits the temperature elevation at the beginning of ultrasonic heating.Besides,thermal relaxation in TWMBT leads to lower temperature estimation than that based on Pennes equation during the same period of time.The blood flow carrying heat dominates most to the decline of temperature rising rate and the influence increases with temperature rising.On the contrary,heat diffusion,which can be described by thermal conductivity,has little effect on the temperature rising. 相似文献
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2005年津、鲁、浙、苏三省一市声学学术会议暨全国物理声学学术会议于2005年10月22日至24日在南京市南京大学召开,由江苏省声学学会和南京大学声学研究所承办。应邀参加会议的有南京大学党委副书记、校长助理张荣教授、中国声学学会秘书长宗健教授、中国科学院院士张淑仪教授、会议承办单位的有关领导以及与会代表等共70余人。会议得到三省一市及全国各地声学工作者的热烈响应,积极投稿,共收到论文摘要90余篇,接受论文70篇,其中有57篇论文在会议上进行了宣读。 相似文献
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Scheme of negative acoustic radiation force based on a multiple-layered spherical structure 下载免费PDF全文
Acoustic radiation force(ARF), as an important particle manipulation method, has been extensively studied in recent years. With the introduction of the concept of “acoustic tweezers”, negative acoustic radiation has become a research hotspot. In this paper, a scheme of realizing negative ARF based on the multiple-layered spherical structure design is proposed. The specific structure and design idea are presented. Detailed theoretical calculation analysis is carried out.Numerical simulations have... 相似文献
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A numerical method is developed to analyse and to correct the diffraction effect in the measurement of acoustic nonlinearity parameter B/A at high frequencies. By using the KZK nonlinear equation and the superposition approach of Gaussian beams, an analytical model is derived to describe the second harmonic generation through multi-layer medium SiO2/liquid specimen/SiO2. Frequency dependence of the nonlinear characterization curve for water in 110-155 MHz is numerically and experimentally investigated. With the measured dip position and the new modal, values of B/A for water are evaluated. The results show that the present method can effectively correct the diffraction effect in the measurement. 相似文献
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