• Title/Summary/Keyword: 후향계단

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Flow Control using DBD Plasma on Backward-facing Step (DBD 플라즈마를 이용한 후향계단 아음속 유동 제어)

  • Song, Ji-Woon;Park, Sul-Ki;Kim, Tae-Hwan;Cho, Hyung-Hee
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.433-436
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    • 2011
  • The effect of plasma on flow characteristics in subsonic flow in backward-facing step is studied. The velocty of main flows are 0.5 m/s. DBD plasma is using for flow control. Stainless foil and polymide films are used as an electrode and dielectric material. The change of flow characteristics are shown by different of plasma generation region in fluid flow.

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Reduced Order Modeling of Backward-Facing-Step Flow Field (후향계단 유동장 축약모델링 기법)

  • Lee, Jin-Ik;Lee, Eun-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.10
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    • pp.833-839
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    • 2012
  • In this paper, we analyze the reconstruction error in the modeling of flow field on BFS(Backward Facing Step). In order for the mathematical modelling of a density on the field, the spatial and temporal modes are extracted by POD(Proper Orthogonal Decomposition) method. After formulating the modeling error, we summarize the relationship between the energy strength and the reconstruction errors. Moreover the allowable modeling error limits in the flow control point of view are confined by analysing in the frequency domain as well as time domain of the reconstructed data.

EXAMPLES OF REDUCED ORDER MODELLING FOR A 3D BACKWARD FACING STEP FLOW USING POD TECHNIQUE (POD를 사용한 3차원 후향계단 유동장 분석 예제)

  • Lee, K.S.;Lee, E.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.40-42
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    • 2010
  • Unsteady CFD results of the backward facing step (BFS) flow field is reconstructed by the low-dimenstional modes using the POD (Proper Orthogonal Decomposition) technique. Flow responses to the blowing or suction with various frequencies and amplitudes applied at the edge of the BFS can also be analysed using the same technique. The present technique can be effectively applied to the feedback flow control device.

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ARX Design Technique for Low Order Modeling of Backward-Facing-Step Flow Field (후향계단 유동장 저차 모델링을 위한 ARX 설계 기법)

  • Lee, Jin-Ik;Lee, Eun-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.10
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    • pp.840-845
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    • 2012
  • An ARX(Auto-Regressive eXogenous) modeling technique for vortex dynamics in the BFS(Backward Facing Step) flow field is proposed in this paper. In order for the modeling of the dynamics, the spatial and temporal modes are extracted through POD(Proper Orthogonal Decomposition) analysis. Determining the orders of the inputs and outputs for an ARX structure is carried out by the spectrum analysis and temporal mode analysis, respectively. The order of input delay terms is also determined by the flow velocity. Finally the coefficients of the ARX model are designed by using an artificial neural network.

Design Study of a Dual-Mode Ramjet Engine with Large Backward-Facing Step (큰 후향 계단이 있는 이중 모드 램젯 엔진의 설계 연구)

  • Yang, Inyoung;Lee, Yang-Ji;Lee, Kyung-Jae
    • Journal of the Korean Society of Propulsion Engineers
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    • v.19 no.6
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    • pp.33-41
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    • 2015
  • Scaled model of a dual-mode ramjet engine with large backward-facing step, as a component of the rocket-based combined cycle engine, was designed. Design parameters were derived for this engine with the consideration of application for the rocket-based combined cycle engine. Design methodology was established for these design parameters. The design was partially verified through numerical study. Flow characteristics of the dual-mode ramjet engine with large backward-facing step was investigated experimentally. The design methodology for relevant design parameters established in this study was verified as feasible.

Numerical Study of Unsteady Supersonic Flow Behind a Rearward-Facing Step with Slot Injection (측면제트분사가 있는 후향계단 후류의 비정상초음속유동에 대한 수치적 연구)

  • Kim,Jong-Rok;Kim,Jae-Su
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.1
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    • pp.97-103
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    • 2003
  • Numerical research has been done for the transverse jet behind a rearward-facings step in turbulent supersonic flow without chemical reaction. Purpose of transverse jet is to enhance mixing of the fuel in the combustor. Two-dimensional unsteady flowfields generated by slot injection into supersonic flow are numerically simulated with the Navier-Stokes equations with two-equation k-$\varepsilon$ turbulence model. Numerical method is used high-order upwind TVD scheme. Eight cases are computed for different slot momentum flux ratios and slot position at downstream of the step. The flow is very similar to the cavity flow, because the jet acts as an obstacle. The numerical results thus show the periodic phenomenon.

Cross-Spectral Characteristics of Wall Pressure Fluctuations in Flows over a Backward-Facing Step (후향계단 주위의 난류 박리재부착유동에서의 벽압력변동의 통계적 특징)

  • Lee, In-Won;Sung, Hyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.2
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    • pp.280-287
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    • 2000
  • Laboratory measurements were made of wall pressure fluctuations in a separated and reattaching flow over a backward-facing step. An array of 32 microphones along the streamwise direction was utilized. Various statistical properties of pressure fluctuations were scrutinized. The main emphasis was placed on the flow inhomogeneity along the streamwise direction. One point statistics such as the streamwise distribution of rms pressure and autospectra were shown to be generally consistent with other studies. The coherences and wavenumber spectra in the streamwise directions were indicative of the presence of dual modes in pressure; one is the large-scale vortical structure in low frequency and the other is the boundary-layer-like decaying mode in high frequency.

Prediction of a Backward-Facing Step Flow with Modified Turbulence Models (수정 난류모델에 의한 후향계단 유동예측)

  • 명현국;백인철;한화택
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.11
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    • pp.3039-3045
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    • 1994
  • The k-$\varepsilon$ turbulence models by Launder et al.(1977, LPS) and Leschziner and Rodi(1981, LR) are modified to account for the secondary straining effect with having a generality in the present paper. The modified models are obtained by replacing the gradient Richardson number used to account for the secondary straining effect in the original models by a new parameter with a tensor-invariant correction form. These two modified models are used to predict the turbulent flow over a backward-facing step. In contrast to both standard and modified LR models, the modified LPS model is found to predict the reattachment point fairy well, as well as mean velocity, wall static pressure, turbulent kinetic energy and Reynolds shear stress in the recirculating region.

Assessment of Reynolds Stress Turbulence Closures for Separated Flow over Backward-Facing Step (후향계단을 지나는 박리류에 대한 레이놀즈응력 모델의 성능 평가)

  • ;;Oh, Myung-Taek
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.11
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    • pp.3014-3021
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    • 1995
  • This study is carried out in order to evaluate the performances of the Reynolds stress turbulence models such as SSG and GL models in the calculation of separated flow over backward-facing stepp.In addition, two slow return-to-isotropy models, YA and Rotta models combined with rapid part of SSG model are also tested. The finite volume method is used to discretize the governing differential equations, and the power-law scheme is used to approximate the convection terms. The SIMPLE algorithm is used for pressure correction in the governing equations. The results show that SSG model gives the better prediction near the reattachment point than GL model. In cases that the rapid term of SSG model is combined with Rotta and YA slow models, the results show the better predictions of stress components in recirculation zone, but indicate inaccuracy in the predictions of mean velocity.