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반사경 내부 유동의 초점 형성에 관한 고해상도 수치 해석
정연규(Y.G. Jung),장근식(K.S. Chang) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
Shock focusing is related with explosive release of shock wave energy on a narrow spot in a short duration of time triggering a spontaneous high pressure near the focal point. It is well known that reflection of planar incident shock wave from the metallic concave mirror such as ellipsoidal, paraboloidal or hemispherical cavities will focus on a focal point. We intend to improve the computational results using a wave propagation algorithm and to resolve the mushroom-like structure. For computation of the concave cavity flow, it is not easy to use a single-block mesh because of the many singular points in geometry and coordinates. We have employed a uniform Cartesian-grid method for the wave propagation algorithm.
내장 카티지안 경계법과 파동전파 알고리즘을 사용한 충격파 집속 현상의 수치적 시뮬레이션
정연규(Y.G. Jung),장근식(K.S. Chang) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.2
Shock-focusing concave reflectors can have parabolic, circular or elliptic cross-sections. They produce effectively a very high pressure at the focusing point. In the past, many optical images have been obtained on shock focusing via experiments. Measurement of field variables is, however, difficult in the experiment. Using the wave propagation algorithm and the Cartesian embedded boundary method, we have successfully obtained numerical Schlieren images that appear very much like the experimental results. In addition, we obtained the detailed field variables such as pressure, velocity, density and vorticity in the unsteady domain. The present numerical results have made it possible to understand the shock focusing phenomenon in more detail than before.
장세명(S.M. Chang),정연규(Y.G. Jung),김사지(S.J. Kim),송찬이(C.Y. Song),장근식(K.S. Chang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Extracorporeal Shock Wave Therapy (ESWT) is known a very effective clinical treatment against persistent musculo-skeletal pains that do not respond with the conservative medical therapy. In the hydroelctric type ESWT, shock waves are generated by the electric sparks between two electrodes a few milimeters apart charged in tens of thousand volts, immersed in water and located at the first focal point of an ellipsoidal reflector. Then the shock is focused at the second focal point of the reflector for clinical use. The shock wave is bombarded thousand of times on the target area positioned at the second focal point. In this medical equipment, there is lots of obscurity in the physical and biological effect. We first make CFD analysis to expound the shock focusing process of this pressure device.