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권용훈(Y.H. Kweon),이동훈(D.H. Lee),김희동(H.D. Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
The propagation of the impulse wave discharged from the inclined exit of a pipe is investigated using a<br/> shock tube experiment and by numerical computations. The pressure histories and directivities of the impulse<br/> wave propagating outside from the exits of pipes with several different configurations are analyzed for the<br/> range of the incident shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the<br/> impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational<br/> work. Computations using the two-dimensional, unsteady, compressible, Euler equations are carried out to<br/> represent the experimented impulse waves. Computed Schlieren images predict the experimented impulse<br/> waves with a good accuracy. The results obtained show that for the radial direction the peak pressure of the<br/> impulse wave discharged depends upon the inclined angle of the exit of the pipe, but for the axial direction it<br/> is almost constant regardless of the inclined angle of the pipe exit.
권용훈(Y. H. Kweon),김희동(H. D. Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
The focusing of shock wave over the reflector is numerically investigated using a CFD method. The<br/> Harten-Yee total variation diminishing scheme is used to solve the unsteady, compressible flow governing<br/> equations. The incident shock wave Mach number Ms of 1.1~1.5 are applied to several different types of<br/> reflectors. Detailed focusing characteristics of the shock wave is investigated in terms of peak pressure,<br/> gasdynamical and geometrical foci. The results obtained are compared with the previous experimental results.<br/> The present computational results predict the experimental results with a good accuracy. The results show that<br/> the peak pressure of shock wave focusing and its location depend on the Mach number of the incident shock<br/> wave and the reflector geometry. It is also found that for strong incident shock waves, the gasdynamic focus is<br/> significantly different from the geometrical one.
Helmholtz 공명기 내부를 전파하는 비정상 충격파의 수치해석
이영기(Y.-K. LEE),권용훈(Y.-H. KWEON),신현동(H.-D. SHIN),김희동(H.-D. KIM),靑木俊之(T. AOKI) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
When a shock wave propagates into a Helmholtz resonator, very complicated wave phenomena are formed both inside and outside the resonator tube. Shock wave reflection, shock focusing phenomena and shockvortex interactions cause strong pressure fluctuations inside the resonator, consequently leading to powerful sound emission. In the present study, the wave phenomena inside and outside the Helmholtz resonator are, in detail, investigated with a help of CFD. The Mach number of the incident shock wave is varied below 2.0 and several types of resonators are tested to investigate the influence of resonator geometry on the wave phenomena. A TVD scheme is employed to solve the axisymmetric, compressible, Euler equations. The results obtained show that the configuration of the Helmholtz resonator significantly affects the peak pressure of shock wave focusing, its location, the amplitude of the discharged wave and resonance frequency.
이동훈(Lee, D.H.),이명호(Lee, M.H.),권용훈(Kweon, Y.H.),김희동(Kim, H.D.) 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.12
The propagation of the impulse wave discharged from the Inclined exit of a pipe is investigated through shock tube experiment and numerical computations. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. Computations using the two-dimensional. unsteady, compressible, Euler equations are carried out to represent the experimented impulse waves. Computed Schlieren images predict the experimented impulse waves with a good accuracy. The results obtained show that for the radial direction the peak pressure of the impulse wave discharged depends upon the Inclined angle of the exit of the pipe. but for the axial direction it is almost constant regardless of the inclined angle of the pipe exit.
축소관과 확대관 출구로부터 방출되는 펄스파에 관한 연구
이동훈(Lee, D.H.),이명호(Lee, M.H.),권용훈(Kweon, Y.H.),김희동(Kim, H.D.),박종호(Park, J.H.) 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.5
The present study is to investigate the propagation characteristics of the impulse waves discharged from the exit of the convergent and divergent pipes. An experiment is carried out using a shock tube with an open end and is compared to the computation of the axisymmetric, compressible, unsteady Euler equations, which are solved by the second-order total variation diminishing (TVD) scheme. For the computational work, several initial compression waves are assumed inside the pipe so that those are the same to the experimental ones of the shock tube. The results show that the peak pressures of the impulse waves discharged from the exit of convergent and divergent pipes decrease with an increase in the wavelength of the initial compression wave. All of the impulse waves have a strong directivity toward the pipe axis, regardless of the exit type of the pipe employed. The impulse waves discharged from the divergent pipe are stronger than those from the straight pipe, while the impulse waves of the convergent pipe are weaker than those from the straight pipe. It is found that the convergent pipe can play a role of a passive control to reduce the peak pressure of the impulse wave. The present computations represent the experimented impulse waves with a good accuracy.