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박선호(S. Park),이신형(S.H. Rhee) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.3
In the present study, a practical method to predict cavitation erosion, which caused a critical damage on hydraulic machineries, was developed. Impact and critical velocities were defined to develop a practical method for the prediction of cavitation erosion. To develope the practical method, the computational fluid dynamics (CFD) was introduced. Cavitating flows with erosion in a converging-diverging nozzle and around a hydrofoil were simulated by developed and validated code. Based on the CFD results, the cavitation erosion coefficient was derived by a curve fitting method. The cavitation erosion coefficient was formulated as the function of the cavitation and Reynolds numbers. A cavitating flow in an axisymmetric nozzle followed by radial divergence was simulated to validate the developed practical method. For the application to a propeller, a cavitating flow around a propeller was simulated. Predicted damage extent showed similar with damaged full-scale propeller blade.
박선호(S.H. Park),이신형(S.H. Rhee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
Cavitation erosion can be observed on hydraulic mechanical devices and has long been studied, yet a difficult research subject for many years. In the present study, the practical formula to predict the cavitation erosion was developed, and the CFD analyses were performed to determine the cavitation erosion coefficient. Cavitating flows were studied using an Reynolds-averaged Navier-Stokes solver based on a cell-centered finite volume method. To verify and validate cavitating flows, sheet, cloud and super cavitating flows were simulated and compared against existing experimental data. Through the simulations, the computational methods were studied carefully and the simulation of cavitating flows was validated. The cavity length and surface pressure distribution were compared with experimental data and analytic solutions. To develop the cavitation erosion coefficient, cavitating flows in a converging and diverging nozzle and around a hydrofoil were simulated. Cavitation erosion extents were studied for various cavitating flow conditions including various cavitation and Reynolds numbers. By comparison with, existing experimental data, a practical equation for the prediction of cavitation erosion, which is a function of the cavitation number, was developed. The developed practical formula helps predict cavitation erosion observed on the blades of pumps, turbines, and marine propellers.
반구형 전두부 실린더에서 발생하는 캐비테이션 유동의 압축성 효과에 대한 수치해석 연구
박선호(S. Park),이신형(S.H. Rhee),신병록(B.R. Shin) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
Cavitation on an axi-symmetric hemispherical head-form body was studied using an Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To consider compressibility effects on the vapor phase and cavity interface, a pressure-based compressible flow CFD code was developed. To validate the developed CFD code, cavitating flow around the hemispherical head-form body was simulated using pressure-based incompressible and compressible CFD codes and validated against existing experimental data in the three-way comparison. The cavity shedding behavior, length of re-entrant jet, drag history, and Strouhal number of the hemispherical head-form body were compared between two CFD codes. The results, in this paper, suggested that the computations of cavitating flow with compressibility effects improve the description of cavity dynamics.
반구형 전두부 실린더에서 발생하는 캐비테이션 유동의 압축성 효과에 대한 수치해석 연구
박선호(S. Park),이신형(S.H. Rhee),신병록(B.R. Shin) 한국전산유체공학회 2013 한국전산유체공학회지 Vol.18 No.4
Cavitation on an axi-symmetric hemispherical head-form body was studied using an Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To consider compressibility effects on the vapor phase and cavity interface, a pressure-based compressible flow CFD code was developed. To validate the developed CFD code, cavitating flow around the hemispherical head-form body was simulated using pressure-based incompressible and compressible CFD codes and validated against existing experimental data in the three-way comparison. The cavity shedding behavior, length of re-entrant jet, drag history, and Strouhal number of the hemispherical head-form body were compared between two CFD codes. The results, in this paper, suggested that the computations of cavitating flow with compressibility effects improve the description of cavity dynamics.
2차원 및 축대칭 운동체 주위의 초공동 현상에 대한 수치해석
박선호(S. Park),이신형(S. H. Rhee) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
Super-cavitating flows around under-water bodies are being studied for drag reduction and dramatic speed increase. In this paper, high speed super-cavitating flow around a two-dimensional symmetric wedge-shaped body were studied using an unsteady Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To verify the computational method, flow over a hemispherical head-form body was simulated and validated against existing experimental data. Various computational conditions, such as different wedge angles and caviation numbers, were considered for the super-cavitating flow around the wedge-shaped body. Super-cavity begins to from in the low pressure region and propagates along the wedge body. The computed cavity lenths and velocities on the cavity boundary with varying cavitation number were validated by comparing with analytic solution.
수평축 조류발전 터빈의 비 설계 조건을 고려한 수치 해석 기법 개발
박세완(S.W. Park),박선호(S. Park),이신형(S.H. Rhee) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
To design a better tidal stream turbine being operated in off-design condition, analyses considering the effect of blade deformation and non-conventional inflow condition are essential. Flow load causes deformation on the blade, and the deformation affects the turbine performance. Also, non-conventional inflow conditions, such as inclined inflow and vertically sheared inflow could influence the turbine performance. In the present study, CFD analysis procedures were developed to predict performance of horizontal axis tidal stream turbine (HATST). The developed procedures were verified by comparing the results with existing experimental results. Fluid-structure interaction (FSI) analysis method, based on the verified CFD procedure, carried out to estimate the turbine performance for a turbine with flexible composite blades, and then the results were compared with that for rigid blades. Moreover, the effects on turbine performance with non-conventional inflow conditions were investigated with the extended numerical method.