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Effect of vortex generator on unsteady flow around cylindrical protrusion
Vignesh Ram P S,Heuy Dong Kim 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
Numerical simulation on the effect of vortex generator on unsteady flow around the cylindrical protrusion was studied. All simulation were carried out at Mach number 2.0 and the Reynolds number 3.6×10<SUP>7</SUP>/m. Three dimensional steady and unsteady RANS simulation with k-w turbulence model is carried out. The flow field properties around the cylindrical protrusion from the present numerical results is compared with the existing experimental result for steady pressure data. Good agreement between the numerical and experimental result has been achieved. Use of vortex generator shows reduction of peak pressure acting on the cylindrical protrusion. The power spectral analysis for cylinder is obtained at a point on cylinder rear face which shows a shedding frequency of 2143 Hz.
DSMC Study of Hypersonic Flows
Vignesh Ram P S,Kim Heuy Dong 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
The hypersonic flow around rectangular cylinder is studied using in-house developed DSMC solver. When the flow becomes rarefied the shock system will be affected and also the cases with high Knudsen number will be difficult to simulate using Navier – Stokes equation. DSMC method can provide accurate result for high Knudsen or rarefied flow regimes. In the present simulation the rectangular cylinder of 6 x 6 mm is investigated for a range of Mach number 2.0 – 5.0. The results shows that the shock gets smeared with increasing Knudsen number. Also the increasing Knudsen number shows that pressure load acting on the rectangular cylinder gets reduced.
Control of Shock Train in the Isolator of Hypersonic Engine
Vignesh Ram PS,Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.11
The Isolator plays a critical role in scramjet engine situated between the inlet and the combustion chamber. The supersonic flow decelerated to subsonic speed achieved by compression waves. The flow filed is more complex with shock–shock interaction and shock boundary layer interaction. The series of shock wave occurs inside the isolator is called as shock train. In the present work the characteristic of shock train flow field in a constant area isolator and its control using suction is studied numerically. The results shows that the suction of boundary layer can influence the shock train length and with the optimum pressure ratio the shock train can become a single normal shock. The total pressure loss also improved by boundary layer suction.
Vignesh Lakshmanan,PUSHPAK DOIPHODE,Indraneel Samanta 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.1
Invertier air conditioners are being widely used in the air conditioning sector for energy saving pirposes. These air conditioners use an inverter of a variable frequency dirive(VFD) to control the compressor operating speed based on cooling or heating load fluctuations. If the heat generated by the electronic components of the VFD is not dissipated properly, it can lead to failure of the VFD. In general, a heat sink is used for dissipating the heat gererated by the electronic components of the VFD. The heat sink can be either air cooled of liquid cooled. Using computational fluid dynamics(CFD), the present paper deals with optimization of the thermal performance of an air cooled plate fin heat sink with rectangular fins used in a residential split inverter air conditioner. Commercially availavle CFD tool has been used for simulations. It has been observed that enhancing fluid flow around heat sink and inproving heat transfer area of the fins significantly improce the thermal performance of the heat sink. By using heat sink with rectagular fins having a stepped profile, it has been possible to improve the heat transfer from the baseline case by 27%. Whereas, by using hollow fins, heat transfer improvement of 20% has been achieved.
Effect of Throat Area Ratio on Micro Nozzle Flows Using DSMC
Vignesh Ram P.S.,Heuy Dong Kim 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
Study of effect of throat area ratio on micro nozzle flows is carried out by using Direct Simulation Monte Carlo (DSMC) method. This method can be applied to a wide range of rarefied flows and is more appropriate to the flow regime where Kn>0.1. The objective of this study is to understand the flow features inside the micro nozzle by changing the throat area ratio. DSMC simulations are carried out by considering a non-reacting gas Nitrogen (N2) for various pressure ratios. Molecular collision is modeled by the variable hard sphere model and Larsen-Borgnakke statistical model is used to model energy exchange between kinetic and internal modes of species. This study revealed that at micro scale the exit pressure is matched without undergoing several shocks and by increasing the exit area shows the separation flow from the nozzle wall.
Unsteady Aerodynamics of Supersonic Cylindrical Protrusion Flows with a Vortex Generator
Vignesh Ram P. S.,Heuy Dong Kim(김희동) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Numerical simulation on the effect of vortex generator on unsteady aerodynamics of cylindrical protrusion was studied. All simulation were carried out at Mach number 2.0 and the Reynolds number 3.6×10⁷/m. Three dimensional steady and unsteady LES simulation is carried out. The flow field properties around the cylindrical protrusion from the present numerical results is compared with the existing experimental result for steady pressure data. Good agreement between the numerical and experimental result has been achieved. Use of vortex generator shows reduction of peak pressure acting on the cylindrical protrusion. The comparison of power spectral density for cylindrical protrusion with VG is obtained which clearly indicates that the high frequency power spectra can be reduced and also helps in reduction of pressure drag acting on the cylinder.