Numerical Visualization of Supersonic Microjet Flows

신춘식(Choon Sik Shin),이종성(Jong Sung Lee),김희동(Heuy Dong Kim) 한국가시화정보학회 2009 한국가시화정보학회 학술발표대회 논문집 Vol.2009 No.11

Supersonic microjets acquire considerable research interest from a fundamental fluid dynamics perspective, in part because the combination of highly compressible flow at low-to-moderate Reynolds number is not very common, and in part due to the complex nature of the flow itself. In addition, microjets have a great variety engineering applications such as micro-propulsion, MEMS (Micro-Electro Mechanical Systems) components, microjet actuators and fine particle deposition and removal. Numerical simulations have been carried out at moderate nozzle pressure ratios and for different nozzle exit diameters to investigate and to understand in-depth of aerodynamic characteristics of supersonic microjets.

초음속 공동내부의 압력진동 제어에 미치는 기류 마하수의 영향

신춘식(Choon Sik Shin),Abhilash Suryan,김희동(Heuy Dong Kim) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5

본 연구에서는 2차원 초음속 공동유동에서 발생하는 압력진동을 제어하기 위하여 수치해석적 연구를 수행하였다. 본 계산에서는 압력진동을 제어하기 위하여 보조공동의 형상을 변화시켰으며, 유동의 마하수를 1.50, 1.83 그리고 2.50로 변화시켰다. 그 결과, 보조공동은 압력진동을 상당히 감소시켰으며, 압력진동의 제어효과는 유동의 마하수와 보조공동의 상세형상에 크게 의존함을 알았다. Numerical computations were carried out to analyze the effect of inlet Mach number and sub-cavity on the control of cavity-induced pressure oscillations in two-dimensional supersonic flow. A passive control method wherein a sub-cavity was introduced on the front wall of a square cavity was studied for Mach numbers 1.50, 1.83 and 2.50. The results showed that sub-cavity is effective in reducing the oscillations at different inlet Mach numbers. The resultant amount of attenuation of pressure oscillations depended on the inlet Mach number, length of the flat plate, and the depth of the sub-cavity used as an oscillation suppressor.

이중목 노즐을 이용한 추력벡터 제어에 관한 기초적 연구

신춘식(Choon Sik Shin),김희동(Heuy Dong Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5

최근 이중목 노즐(Dual Throat Nozzle, DTN)을 사용하여 추진체의 추력을 제어하는 방법이 많은 주목을 받고 있다. 이중목 노즐은 공동을 사이에 두고 두 개의 노즐 목을 가지도록 설계된다. 본 연구에서는 DTN의 유동특성을 조사하기 위하여, 수치해석적인 방법을 적용하였으며, 2차유동의 질량 유량을 변화시켰다. 수치해석에서는 2차원, 압축성 Navier-Stokes방정식을 풀기 위하여, 유한체적법을 적용하였다. 그 결과 본 수치해석은 실험결과를 잘 예측하였으며, DTN을 이용한 추력벡터 제어는 추력계수와 유출계수의 항으로 상세하게 설명하였다. Dual throat nozzle(DTN) is recently attracting much attention as a new concept of the thrust vectoring technique of propulsion jet. This DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze the performance of a dual throat nozzle(DTN) at various mass flow rate of secondary flow. Two-dimensional, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. The present computational results were validated with some experimental data available. Based upon the present results, Thrust-vector contro

이중목 노즐에서 발생하는 초음속유동 특성에 관한 연구

신춘식(Choon Sik Shin),김희동(Heuy Dong Kim) 한국추진공학회 2010 한국추진공학회지 Vol.14 No.5

Dual throat nozzle(DTN) is recently attracting much attention as a new concept of the thrust vectoring technique. This DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze a fundamental performance of a dual throat nozzle(DTN) at various nozzle pressure ratios(NPR) and throat area ratios. Two-dimensional, axisymmetric, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. NPR was varied in the range of NPR from 2.0 to 10.0, at different throat area ratios. The present computational results were validated with some experimental data available. Based upon the present results, the performance of DTN is discussed in terms of the discharge coefficient and thrust efficiency.

상류막 방식과 하류막 방식의 Ludwieg Tube에서 발생하는 유동특성에 관한 연구

신춘식(Choon Sik Shin),김희동(Heuy Dong Kim) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.11

여러 형태의 풍동장치 중에서 Ludwieg Tube(LT)는 높은 레이놀즈수 유동을 실현할 수 있는 가장 적합한 장치로 알려져 있다. 일반적으로 LT는 격막의 위치에 따라 두 종류로 구분된다. 본 연구에서는 상류막 방식과 하류막 방식 LT의 작동특성을 조사하기 위하여, 수치해석적인 방법을 적용하였다. 수치해석에서는 2차원 축대칭, 비정상, 압축성 Navier-Stokes 방정식에 유한체적법을 적용하였다. 그 결과, 본 수치해석은 시동과정의 유동 메커니즘을 파동선도를 이용하여 상세하게 설명하였으며, 시동시간과 작동시간의 특성을 조사하였다. Among the many different types of wind tunnels, Ludwieg Tube(LT) is the most suitable facility for high Reynolds number testing. Depending on the location of diaphragm, there are two types of LTs. In the present study, a computational work has been carried out to compare the operation characteristics of upstream- and downstream-diaphragm LTs. Two-dimensional, axisymmetric, unsteady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. Based on the present results, the flow mechanism of the starting process was discussed in detail using wave diagrams and characteristics of starting time and working time were investigated.

충격파관 유동의 파막과정에 관한 수치 시뮬레이션

신춘식(Choon Sik Shin),정준창(June Chang Jeong),Abhilash Suryan,김희동(Heuy Dong Kim) 한국추진공학회 2009 한국추진공학회지 Vol.13 No.1

Shock tube flow measurement has been often hampered a finite opening time of diaphragm, but there is no systematic work to investigate its effect on the shock tube flow. In the present study, both the experimental and computational works have been performed on the shock tube flows at low pressure ratios. The computational analysis has been performed using the two-dimensional, unsteady, compressible Navier-Stokes equations, based upon a TVD MUSCL finite difference scheme. It is known that the present computational results reproduce the experimental data with good accuracy and simulate successfully the process of diaphragm opening as a function of time. The concept of an imaginary center is introduced to quantify the non-centered expansion wave due to a finite opening time of diaphragm. The results obtained show that the diaphragm opening time is reduced as the initial pressure ratio of shock tube increases, leading to the effect of a finite opening time of diaphragm to be more remarkable at low pressure ratios.

A Study on the Reduction of Supersonic Cavity Pressure Oscillations Using a Sub-Cavity System

신춘식(Choon Sik Shin),정준창(June Chang Jeong),Abhilash Suryan,김희동(Heuy Dong Kim) 한국추진공학회 2009 한국추진공학회지 Vol.13 No.5

Numerical computations were carried out to analyze the effect of a sub-cavity at several inlet Mach numbers on the control of cavity-induced pressure oscillations in two-dimensional supersonic flow. The present passive control method, the sub-cavity applied to the front wall of a square cavity, was studied for the inlet Mach numbers of 1.50, 1.83 and 2.50. The results show that the sub-cavity is effective in reducing the oscillations, and a resultant amount of the reduction depended on the inlet Mach number, the length of flat plate, and the depth of sub-cavity used as an oscillation suppressor.

Numerical Visualization of Supersonic Microjet Flows

신춘식(Choon Sik Shin),이종성(Jong Sung Lee),김희동(Heuy Dong Kim) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.7 No.2

Supersonic microjets acquire considerable research interest from a fundamental fluid dynamics perspective, in part because the combination of highly compressible flow at low-to-moderate Reynolds number is not very common, and in part due to the complex nature of the flow itself. In addition, microjets have a great variety engineering applications such as micro-propulsion, MEMS(Micro-Electro Mechanical Systems) components, microjet actuators and fine particle deposition and removal. Numerical simulations have been carried out at moderate nozzle pressure ratios and for different nozzle exit diameters to investigate and to understand in-depth of aerodynamic characteristics of supersonic microjets.

Ludwieg Tube의 시동과정에 관한 수치해석적 연구

신춘식(Choon Sik Shin),김희동(Heuy Dong Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4

매우 다양한 풍동장치 중에서 Ludwieg tube는 높은 레이놀즈수를 실현할 수 있는 가장 적합한 장치이다. 본 연구에서는 Ludwieg tube의 시동과 작동시간을 조사하기 위하여, 수치해석적인 방법을 적용하였다. 수치해석에서는 축대칭 비정상 압축성 Navier-Stokes 방정식을 풀기 위하여, 유한체적법을 적용하였다. 그 결과 본 수치해석은 실험결과를 잘 예측하였으며, 시동과정의 유동 메커니즘을 파동선도를 통해서 상세하게 설명하였다. Among many different types of wind tunnels, Ludwieg tube is the most suitable facility for high Reynolds number wind tunnel testing, In the present study, a computational work has been carried out to analyze the starting and operating time of a Ludwieg, Two-dimensional, axisymmetric, unsteady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme, The present computational results were validated with some experimental data available. Based upon the present results, the wave diagrams showing the starting process were fabricated, and the flow mechanism of the starting process was discussed in detail.

초음속 마이크로제트 유동특성에 관한 연구

신춘식(Choon-Sik Shin),김희동(Heuy-Dong Kim),Toshiaki Setoguchi 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11

Supersonic microjets acquire considerable research interest from a fundamental fluid dynamics perspective, in part because the combination of highly compressible flow at low-to-moderate Reynolds number is not very common, and in part due to the complex nature of the flow itself. In addition, microjets have a great variety engineering applications such as micro-propulsion, MEMS (Micro-Electro Mechanical Systems) components, microjet actuators and fine particle deposition and removal. Numerical simulations have been carried out at moderate nozzle pressure ratios and for different nozzle exit diameters to investigate and to understand in-depth of aerodynamic characteristics of supersonic microjets.