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박창환(C. H. Park),박승오(S. O. Park) 한국전산유체공학회 2003 한국전산유체공학회지 Vol.8 No.2
The V2F turbulence model, which has shown very good performance in several test cases at low speeds, has been applied to supersonic ramp flow with 20。 corner angle at the free stream Mach number of 2.79. The flow is known to manifest strong shock wave/turbulent boundary layer interactions. As a comparative study, low-Reynolds k-ε models are also considered. While the V2F model predicts wall-pressure distribution well, it relatively predicts larger separation bubble and higher skin-friction after the reattachment than the experimental data. Although the ellpticity of f equation is the characteristics of incompressible flows, the converged solutions are acquired in the compressible flow with shock waves. The effect of the realizability constraints used in the model is also examined. In contrast to the result of impinging jet flows, the realizability bounds proposed by Durbin deterioate the overall solutions of the supersonic ramp flow.
Ristorcelli의 압축성 난류 모형을 이용한 초음속 유동의 계산
박창환(C. H. Park),박승오(S. O. Park) 한국전산유체공학회 2003 한국전산유체공학회지 Vol.8 No.3
Three-dimensional endwall flow within a linear cascade passage of high performance turbine blade is simulated with a 3-D Navier-Stokes CFD code (MOSA3D), which is based on body-fitted coordinate system, pressure-correction and finite volume method. The endwall flow characteristics, including the development and generation of horseshoe vortex, passage vortex, etc. are clearly simulated, consistent with the generally known tendency. The effects of both turbulence model and convective differencing scheme on the prediction performance of endwall flow are systematically analyzed in the present paper. The convective scheme is found to have stronger effect than the turbulence model on the prediction performance of endwall flow. The present simulation result also indicates that the suction leg of the horseshoe vortex continues on the suction side until it reaches the trailing edge.
전완호(W.H. Jeon),박창환(C.H. Park) 한국전산유체공학회 2017 한국전산유체공학회지 Vol.22 No.2
The Present work describes the prediction method for the unsteady flow field and the aeroacoustic noise of an axial fan which has 3 blades with high sweep angle. Unsteady Reynolds-averaged Navier-Stokes(URANS) and large eddy simulation(LES) numerical approaches were adopted for prediction of unsteady flow field around the axial fan. Ffowcs-Williams and Hawkings equation with dipole assumption was used to calculate the aeroacoustic sound generated from the axial fan. Although both URANS and LES offer good estimates of the overall sound spectrum including blade pass frequency, LES produces more accurate and reliable results especially for the prediction of broadband and tonal noise at high frequency range. Through fast Fourier transform(FFT) analysis of noise source strength, the noise source of tonal peak at 750Hz is identified as the vortex separation at 1/4 position of the blade tip. It is also found that the noise source of broadband peak between 1200Hz and 1400Hz is located from center of tip to trailing edge.