다양한 출구조건과 받음각이 적용된 초음속 흡입구 공력불안정성 수치적 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 계산과학전공, 2013. 2. 김종암.The present study numerically investigates the flow instability around supersonic inlet, called inlet buzz. Though the flow conditions change linearly, behavior of inlet buzz alters hysteretically. In order to simulate the inlet buzz hysteretic character, computations are conducted with varying mass flow rate and angle of attack. The mass flow rate condition is controlled by an exit throttling plug which moves back and forth to change an exit area. For angle of attack study, three dimensional inviscid simulations are conducted. Firstly, a set of simulation with mass flow control is presented. This simulation focuses on hysteretic buzz characteristics of supersonic inlet according to mass flow and the historic path of the mass flow change. Before the set of simulation, an inlet without a center-body is calculated to validate basic resonance mode results. In the next, an inlet buzz case with decreasing mass flow rate is simulated. In this process, the inlet buzz characteristic changes from the first mode of a low frequency regime to the second mode of a high frequency regime. Lastly, the effect of the increasing mass flow rate on the inlet buzz is examined. This case shows another kind of the buzz transition that the buzz frequency becomes higher in the third mode. The hysteretic inlet buzz has many similarities to the fundamentals of a pipe-type musical instrument such as self-excited feed-back mechanism and overblowing. Considering the similarities, the hysteretic characteristics of an inlet buzz is discussed in the instrumental acoustic point of view. In the second step, an investigation of angle of attack effects on inlet pressure oscillation is carried out with three-dimensional inviscid simulation intended to examine a tendency of inlet buzz briefly. It is seen that the major physical characteristic of the inlet pressure oscillation can be obtained by inviscid computations and the computed flow patterns inside and around the inlet are qualitatively consistent with the experimental observations. It is found that patterns of pressure oscillation histories and distortion due to asymmetric (or three-dimensional) shock structures are substantially affected by angle of attack. The dominant frequency of the existing inlet pressure oscillation does not change noticeably even in regards to a wide range of angle of attacks. However, the increasing angle of attack condition initiates a pressure oscillation from a steady state of inlet at low angle of attack.Chapter I Introduction 1 1.1 Inlet Buzz Transition under Varying Mass flow condition 2 1.2 Asymmetry Behavior of Inlet Flow Oscillation at Attack Angled flow 5 1.3 Outline of Thesis 7 Chapter II Instrumental Acoustics 9 2.1 Edge Tone 10 2.2 Positive feedback 11 2.3 Over-blowing 12 Chapter III Numerical Approach 14 3.1 Governing Equations 14 3.2 Turbulence Model 19 3.2.1 The original k-ω model 20 3.2.2 The Transformed k-ε Model 20 3.2.3 The Standard Menters k-ω Shear Stress Transport (SST) Model 21 3.2.4 The Menters k-ω SST Model from 2003 (k-ω SST-2003) 24 3.3 Spatial Discretization 26 3.3.1 Roes Flux Difference Splitting 27 3.3.2 RoeM Scheme 29 3.3.3 AUSMPW+ 31 3.3.3 Higher order spatial accuracy 34 3.3.4 Compact Scheme for Viscous Fluxes 36 3.4 Time Integration Method 37 3.4.1 Pseudo-Time Discretization 38 3.4.2 LU-SGS Scheme 40 3.4.3 Dual Time Stepping 42 3.5 Geometric Modeling and Boundary Condition 44 3.5.1 Axisymmetric Inlet Modeling for Viscous Computation 44 3.5.2 Modeling of Varying Exit Area for Mass Flow Control 46 3.5.3 Three-dimensional Inlet Modeling for Inviscid Computation 47 Chapter IV Inlet Buzz Simulation with Throttling Ratio Control 50 4.1 Case1 - Validation by Inlet Configuration without Center Body 50 4.2 Case2 - Inlet under Decreasing Mass Flow (T.R) Condition 57 4.2.1 Large Throttling Ratio (2.41 ~ 1.42) 57 4.2.2 Medium Throttling Ratio (1.14 ~ 0.79) 60 4.2.3 Small Throttling Ratio (0.67 ~ 0) 64 4.3 Case3 - Inlet under Increasing Mass Flow (T.R) Condition 71 4.4 Summary of Inlet Buzz Simulation Results with Mass flow control 78 4.5 Hysteretic Behavior of inlet buzz with Varying Mass Flow Rate 80 4.5.1 Required factors for overblowing 81 4.5.2 Vortex role for resonation and relation with throttling ratio 84 Chapter V Inlet Buzz Simulation at Angle of Attacks 87 5.1 Steady State Simulation at T.R 2.41 89 5.2 Inlet Pressure Oscillation Simulation with Zero Angle of Attack 92 5.3 Inlet Pressure Oscillation Simulation with Moderate Angle of Attack 96 5.4 Angle of Attack Effects on Inlet Pressure Oscillation 105 5.4.1 Pressure oscillation transition from small to big amplitude 105 5.4.2 Dynamic Distortion 110 Chapter VI Concluding Remarks 113 References 118Docto

수치해석을 이용한 이어도 기지 구조물이 해수 유동에 미치는 영향 분석과 해류 관측 평가 및 보정방안 연구 = Numerical Investigation, Calibration Method of the Interaction between Ieodo Ocean Research Station and Ocean Current

이어도에 건설된 다목적 해양과학기지에서는 주위 대류 및 해류의 데이터 수집을 통해 기상, 어장예보 등의 기초 자료를 제공하는 것을 한 가지 목적으로 한다. 그런데 이어도 기지 구조물에 의한 해수 유동의 변화는 과학기지의 관측 데이터에 영향을 주어 정확한 자료 수집을 어렵게 하므로, 이어도 기지 구조물이 주위 유동에 미치는 영향을 분석하고 유동 정보 관측을 평가/보정하는 방법에 대한 연구가 필요하다. 본 연구에서는 이를 위한 기초연구로, 해류와 구조물 사이의 상호 작용을 모사할 수 있는 알고리즘을 연구, 적용방법을 논의한다. 그 결과, 3차원 전산유체역학을 이용한 수치해석을 통해 이어도 기지 구조물 및 수중암초가 주위 유동에 미치는 영향을 연구하고 정확한 데이터 측정방법을 제안한다. = One of the main function of Ieodo Ocean Research Station is to service the information about the weather and fishing grounds condition which are collected through calibrating convection flow and ocean current around the station. However, due to the influence of the station"s structure below sea level, it is difficult to obtain the exact flow data. Therefore, it is required to research on the effect of the structure and the method to evaluate and revise the observed data. In this paper, as a basic study, it deals with the algorithm that simulate the interaction between ocean current and the station structure, followed by discussions about the way to applicate the algorithm. Through 3-dimensional computational fluid dynamics analyses (using Navier-Stokes equations with K-turbulence model), the influence of the station and submerged rocks are quantitatively evaluated, and we would suggest methods how to obtain accurate flow information from the measured rough data.본 연구는 한국해양연구원의 이어도 종합해양과학기지구축 및 활용연구(KORDI PM43000)사업의 지원으로 수행되었음

NUMERICAL ANALYSIS OF FLOW CHARACTERISTICS AROUND 3-D SUPERSONIC INLET AT VARIOUS ANGLE OF ATTACK

받음각(AOA, angle of attack)이 있는 3차원 초음속 흡입구의 비점성 유동해석을 수행하였다. 받음각은 0°, 3°의 작은 각과 5°, 7°, 10°의 높은 받음각이 있는 경우에 대해 계산을 수행하였다. 또한 5개의 받음각에 대해 입출구비를 0.00에서 2.42까지 변화시켜가며 계산을 수행하였다. 입출구비는 입구에서 가장 작은 면적을 가지는 목의 넓이와 출구의 가장 좁은 목 넓이의 비로 정의 하였다. 받음각이 높아짐에 따라 흡입구 내부 벽면에 작용하는 압력 비대칭성과 주진동수 변화의 경향성에 대해 알아보았다. 또한 특정 단면에서 물성치 분포를 관찰하였고 이로 인한 유동패턴을 분석하였다.본 연구는 2011년도 정부(교육과학기술부)의 재원으로 국가수리과학연구소의 주요사업 (No. A21001), 한국연구재단을 통해 교육과학기술부의 우주기초원천기술개발 사업(NSL, National Space Lab, 과제번호 20100028975) 지원으로 수행되었음.OAIID:oai:osos.snu.ac.kr:snu2011-01/104/0000004648/31SEQ:31PERF_CD:SNU2011-01EVAL_ITEM_CD:104USER_ID:0000004648ADJUST_YN:NEMP_ID:A001138DEPT_CD:446CITE_RATE:0FILENAME:받음각이_있는_3차원_초음속_흡입구_주위의_유동진동_해석.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

수치해석을 이용한 이어도 기지 구조물이 해수 유동에 미치는 영향 분석과 해류 관측 평가 및 보정방안 연구 = Numerical investigation, calibration method of the interaction between Ieodo ocean research station and ocean current

이어도에 건설된 다목적 해양과학기지에서는 주위 대류 및 해류의 데이터 수집을 통해 기상, 어장예보 등의 기초 자료를 제공하는 것을 한 가지 목적으로 한다. 그런데 이어도 기지 구조물에 의한 해수 유동의 변화는 과학기지의 관측 데이터에 영향을 주어 정확한 자료 수집을 어렵게 하므로, 이어도 기지 구조물이 주위 유동에 미치는 영향을 분석하고 유동 정보 관측을 평가/보정하는 방법에 대한 연구가 필요하다. 본 연구에서는 이를 위한 기초연구로, 해류와 구조물 사이의 상호 작용을 모사할 수 있는 알고리즘을 연구, 적용방법을 논의한다. 그 결과, 3차원 전산유체역학을 이용한 수치해석을 통해 이어도 기지 구조물 및 수중암초가 주위 유동에 미치는 영향을 연구하고 정확한 데이터 측정방법을 제안한다. = One of the main function of Ieodo Ocean Research Station is to service the information about the weather and fishing grounds condition which are collected through calibrating convection flow and ocean current around the station. However, due to the influence of the station"s structure below sea level, it is difficult to obtain the exact flow data. Therefore, it is required to research on the effect of the structure and the method to evaluate and revise the observed data. In this paper, as a basic study, it deals with the algorithm that simulate the interaction between ocean current and the station structure, followed by discussions about the way to applicate the algorithm. Through 3-dimensional computational fluid dynamics analyses (using Navier-Stokes equations with K-turbulence model), the influence of the station and submerged rocks are quantitatively evaluated, and we would suggest methods how to obtain accurate flow information from the measured rough data

A new FVM-based analysis on pipeline fluid system

OAIID:oai:osos.snu.ac.kr:snu2010-01/104/0000004648/38SEQ:38PERF_CD:SNU2010-01EVAL_ITEM_CD:104USER_ID:0000004648ADJUST_YN:NEMP_ID:A001138DEPT_CD:446CITE_RATE:0FILENAME:파이프라인_유체시스템_분석을_위한_새로운_유한체적법.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]:

Study on Concept Design of Supersonic Inlet and Flow Control of Bleeding under Operating Condition

본 연구에서는 간단한 압축성 유체이론에 기초하여 렘젯 엔진의 초음속 흡입구를 개념 설계하고 보다 넓은 범위의 운영조건에서 안정적인 성능을 내도록 블리딩 유동제어 연구를 수행하였다. 초음속 흡입구의 성능을 개선시키기 위해서는 충격파 안정성, 충격파-경계층 상호작용 및 유동 박리를 적절히 제어할 수 있어야 한다. 비점성 해석을 통해 얻어진 1차 기초설계 형상으로부터 점성을 고려하여 충격파의 강도와 경계층 및 박리의 효과가 반영된 2차 수정설계를 수행하였다. 그 결과 설계조건에서 충격파가 안정화되고 목표 흡입유량을 만족하는 형상을 얻었다. 흡입구가 탈 설계조건 내에서도 성능이 유지되도록 하기위해 블리딩을 적용하였다. 질량유량 경계조건을 이용하여 블리딩 효과를 모델링 하였으며 위치와 개수를 조절해가며 성능변화를 관찰하였다.The present paper deals with concept design of supersonic inlet based on compressible flow theory and flow control of bleeding in order to guarantee stability of supersonic inlet of ramjet engine in broad range of operating conditions. Shock instability, shock wave-boundary layer interaction and flow separation should be properly controlled to improve performance of the supersonic inlet. Considering shock strength, boundary layer and flow separation, the supersonic inlet is modified from the basic model which is designed under inviscid theory. Consequently, shock is stabilized, and required mass flow rate is obtained. Furthermore, bleeding is applied to the supersonic inlet to maintain performance in off-design conditions. Mass flow condition is adopted for modeling of bleeding effect, and performance of the supersonic inlet is evaluated by changing bleeding locations and numbers.OAIID:oai:osos.snu.ac.kr:snu2012-01/102/0000004648/7SEQ:7PERF_CD:SNU2012-01EVAL_ITEM_CD:102USER_ID:0000004648ADJUST_YN:YEMP_ID:A001138DEPT_CD:446CITE_RATE:0FILENAME:초음속 흡입구 개념 설계와 운영조건 내의 블리딩(bleeding) 유동제어 연구.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]_YN:NCONFIRM:

Study of flow control character using synthetic jet

학위논문(석사) --서울대학교 대학원 :기계항공공학부,2007.Maste

NUMERICALL STUDY OF FLOW OSCILLATION AROUND SUPERSONIC INTAKE UNDER STATIC AND DYNAMIC THROTTLING CONDITION

Ramjet engine has small throttling ratio in initial launching state and pressure around the engine oscillates in high frequency. Moreover, at that time, throttling ratio is changed abruptly. The flow unsteadiness from throttling ratio changing could bring result in engine unstart or even structure damage to engine. A numerical study was conducted to simulate the pressure oscillation phenomenon that is occurred in small throttling ratio. Simulation and analysis of flow charateristics are not only nuder static throttling condition but also under dynamic throttling condition. Generally, throttling ratio is defined as ratio of throat area and exit area. Throttling ratio 0.70 is threshold between high frequency boundary and low frequency boundary in the present geometry[1] research. Numerical simulation is conducted in 0.55 throttling ratio case and 0.00 that is below 0.70. By the way, the result shows high frequency oscillation between 300 and 400 Hz. Dynamic throttling condition is assumed that throttling ratio can be moved in the range between 0.00 and 0.70. Numerical analysis and discussion of result is conducted for the changing of flow oscillation characteristics under the dynamic throttling condition from the initial condition that pressure oscillation has been already onset.OAIID:oai:osos.snu.ac.kr:snu2010-01/104/0000004648/39SEQ:39PERF_CD:SNU2010-01EVAL_ITEM_CD:104USER_ID:0000004648ADJUST_YN:NEMP_ID:A001138DEPT_CD:446CITE_RATE:0FILENAME:정적__동적_출구조건에서의_초음속_흡입구_유동진동_해석_연구.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]: