报告时间: 2019年3月29日（星期五）下午16:00-17:00

报告地点: 轨道交通大楼1楼报告厅(咖啡屋旁)

报告摘要：

Thermo-acoustic (TA) effect did not attract very much attention in the past. Morse and Ingard [1] derived the coupled thermo-acoustic governing equations in 1968. In 2008, Xiao et al. [2] conducted thermo-acoustic experiment for carbon nanotube projectors in air and further in 2010, Aliev et al. [3] extended the work of Xiao [2] underwater. Hu et al. [4] put forward a theoretical explanation on thermo-acoustic emission of different kinds of sound source without taking the influence of heat capacity into consideration. Lim et al. [5] derived and presented thermo-acoustic wave generation for free-standing CNT thin film ignoring the viscosity of fluid.

In this talk, further works on thermo-acoustic wave emission and propagation in viscous media are discussed. The fully coupled thermo-acoustic field is obtained for a free-standing nano-thin film in viscous fluid, which has been usually ignored in the previous works on thermo-acoustic interaction. The influence of heat loss, heat capacity and heat exchange is considered in this investigation. When a sinusoidal alternating current acts on the thin film, the double frequency effect can be determined easily. Subsequently, the thermal wave propagation is decoupled from the acoustic effect by improving the order of differential equations. Then, with appropriate simplification an analytical prediction is derived in which the attenuation coefficient and the classic expression are identical. In addition, the theoretical results agree well with experiment. Compared with Lim et al. [5], an analytical solution of higher-order accuracy is obtained. This work may be helpful to the design of the thermo-acoustic projectors that have shown great potentials for new underwater sonars compared with the electro-acoustic ones traditionally induced by membrane vibration.

报告人简介

Currently a fellow of ASME, ASCE, EMI, HKIE and ISEAM, Ir Professor Lim received a BEng from Univ of Tech. of Malaysia, MEng and PhD from National Univ of Singapore and Nanyang Tech. Univ., respectively. Prior to joining CityU, he was a post-doctoral research fellow at Dept of Civil Eng, The Univ of Queensland and Dept of Mech Eng, The Univ of HK. Professor Lim is also a visiting professor at various universities including the Univ of Western Sydney, Dalian Univ of Tech., Huazhong Univ of Science and Tech., etc. He has expertise in vibration of plate and shell structures, dynamics of smart piezoelectric structures, nanomechanics and symplectic elasticity. He is one of the editors for JoMMS, Assoc Editor (Asia-Pacific Region) for JVET, Assoc Editor for IJBC, subject editor for AMM, etc. and also on the editorial board of a few other international journals. He has published one very well-selling title in Engineering Mechanics entitled “Symplectic Elasticity” and co-authored with W.A. Yao and W.X. Zhong from Dalian Univ of Tech., as recorded in April 2010 by the publisher, World Scientific. He has published more than 250 international journal papers, accumulated more than 3800 independent citations and has an ISI H-index 35. One of his papers was granted the IJSS 2004-2008 most cited article award. He was also awarded Top Referees in 2009, Proc. A, The Royal Society. Professor Lim is also a registered professional engineer in HK.