• Title/Summary/Keyword: Cavity Flow

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A Computational Study of the Supersonic Cavity Flow (초음속 Cavity 유동에 관한 수치해석적 연구)

  • Jung Sung-Jae;Gwak Jong-Ho;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.23-26
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    • 2004
  • A computational analysis has been conducted to investigate the detailed flow structure inside a supersonic cavity. The free stream Mach number and Reynolds number are 1.83 and $6.02\times10^5$ respectively. In the present study, the depth and width of the cavity are changed to investigate the effect of the cavity dimensions. A fully implicit finite volume scheme is applied to solve the three-dimensional, steady, unsteady, compressible, Navier-Stokes equations. The computed results are validated with the previous experimental data available. The present computation provides reasonable predictions of the cavity flow, compared with experimental results. The obtained results show that a shock wave is generated in front of the downstream edge of the cavity and the dominant frequencies of the pressure oscillations inside the cavity were obtained.

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Design Analysis in a Cavity with Leadframe during Semiconductor Chip Encapsulation (반도체 칩 캡슐화(encapsulation)를 위한 트랜스퍼 금형 캐비티(cavity)에서의 설계 해석 및 실험에 관한 연구)

  • Han, Sejin;Huh, Yong-Jeong
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.12
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    • pp.91-99
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    • 1995
  • An effort has been made to more accurately analyze the flow in the chip cavity, particularly to model the flow through the openings in the leadframe and correctly treat the thermal boundary condition at the leadframe. The theoretical analysis of the flow has been done by using the Hele- Shaw approximation in each cavity separated by a leadframe. The cross-flow through the openings in the leadframe has been incorporated into the Hele-Shaw formulation as a mass source term. The temperature of the leadframe has been calculated based on energy balance in the leadframe. The flow behavior in the leadframe has been verified experimentally. In the experiment, a transparent mold and clear fluid have been used for flow visualization. Comparisons were made between the calculation and experimental results which showed a good agreement.

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Hybrid RANS/LES Simulation of Subsonic Cavity Flow (Hybrid RANS/LES 방법을 이용한 이음속 공동 유동의 수치적 모사)

  • Chang K. S.;Park S. O.;Choi S. K.
    • Journal of computational fluids engineering
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    • v.9 no.2
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    • pp.23-29
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    • 2004
  • A numerical simulation of an incompressible cavity flow is conducted using the hybrid turbulence model. The model adopted is a modified type of DES using k- ε two-equation model. Cavity geometry and flow condition are based on Cattafesta's experiment. Computational results are compared with the results of Cattafesta's experiment. The simulation successfully predicts the oscillatory features and the Strouhal number of the oscillation compares very favorably with that of the dominant mode of experimental data. Vorticity contours obtained from the simulation data are consistent with the smoke visualization of the Cattafesta's experiment. The coherent structures of cavity flow are also investigated using Q criterion.

Aeroacoustic Characteristics of Cavity Resonance on Very Low Subsonic Flows (저아음속 유동에 놓여진 개방형 공동의 공력소음 특성)

  • Koh, Sung-Ryong;Moon, Young-June
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1921-1926
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    • 2004
  • The tone generation mechanism and aeroacoustic characteristics have been investigated for flow over open cavities using direct acoustic numerical simulations. Physically the tone generation mechanism of open cavity is more complicated when flow instabilities are excited by the correlation effects of flow parameters. From non-dimensional parameter studies in very low Mach number range, it is shown that characteristics of cavity resonance inherently involve typical acoustic pattern at each discrete tone frequency, and especially in laminar flow the fundamental tone frequency is determined within flow instability criterion of laminar shear layer as well as cavity geometry, length to depth ratio.

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Control of the Pressure Oscillations in Supersonic Cavity Flows (초음속 공동유동에서 발생하는 압력변동의 제어)

  • Lee Young-Ki;Jung Sung-Jae;Kim Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.117-120
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    • 2005
  • The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

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SIMULATION OF LID DRIVEN CAVITY FLOW WITH DIFFERENT ASPECT RATIOS BY MULTI-RELAXATION-TIME LATTICE BOLTZMANN METHOD (다중완화시간 격자 볼츠만기법을 이용한 다양한 종횡비의 리드드리븐 공동유동 수치해석연구)

  • Huang, Tingting;Song, Juhun;Lim, Hee-Chang
    • Journal of the Korean Society of Visualization
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    • v.18 no.3
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    • pp.42-51
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    • 2020
  • This study performs a numerical simulation of lid driven rectangular cavity flow with different aspect ratios of k = 0.5 to 4 under Reynolds 100, 1,000, 10,000 by using multi-relaxation time (MRT) Lattice Boltzmann Method (LBM). In order to achieve better convergence, well-posed boundary conditions in the domain should be defined such as no-slip condition on side and bottom solid wall surfaces and uniform horizontal velocity on the top of the cavity. This study focuses on the flow inside different shape of rectangular cavity with the aim to observe the effect of the Reynolds number and aspect ratio on the flow characteristics and primary/secondary vortex formation. In order to validate the study, the results have been compared with existing works. The result shows that the Reynolds number and the aspect ratio both has substantial effects on the flow inside the lid-driven rectangular cavity.

Flow Characteristics in a Supersonic Combustor with a Configuration of a Cavity (초음속 연소기 내 공동 형상에 따른 유동 특성)

  • Yim, Geon Wook;Roh, Tae-Seong;Lee, Hyoung Jin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.2
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    • pp.1-11
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    • 2021
  • The cavity inside the combustor increases the mixing efficiency of fuel and air by inducing a oscillation of the flow and the recirculation area with a low speed, and enables continuous combustion by maintaining the flame. In this study, the characteristics of the internal flow by change in the shape parameters of the cavity were analyzed through experiments and two-dimensional computational analysis. It was observed that the flow in the supersonic combustor was greatly influenced by various shape parameters of cavity besides L/D. Even with the same L/D, it was confirmed that the flow type varies depending on the depth of the cavity, either open or closed type, and the aft ramp angle of the cavity and the height of the combustor also affect the flow characteristics. As a result, the change in the shape parameters of the cavity had a great influence on the total pressure loss.

LARGE EDDY SIMULATION OF THE COMPRESSIBLE FLOW OVER A CAVITY WITH HIGH ASPECT RATIO

  • Oh Keon Je
    • Journal of computational fluids engineering
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    • v.9 no.1
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    • pp.1-9
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    • 2004
  • Large eddy simulation is used to investigate the compressible flow over a cavity with high aspect ratio. The sub-grid scale stresses are modeled using the dynamic model. The compressible Navier-Stokes equations are solved with the sixth order accurate compact finite difference scheme in the space and the 4th order Runge-Kutta scheme in the time. The buffer Bone techniques are used for non-reflecting boundary conditions. The results show the shear layer oscillation over the cavity. The votical disturbances, the roll-up of vorticity, and impingement and scattering of vorticity at the downstream cavity edge can be seen in the shear layer. Several peaks for the resonant frequencies are found in the spectra of the vertical velocity at the center-line. The most energetic Peak near the downstream edge is different from that at the center part of the cavity The pressure has its minimum value in the vortex core inside the cavity, and becomes very high at the downstream face of the cavity. The variation of the model coefficient predicted by the dynamic model is quite large between 0 and 0.3. The model coefficient increases in the stream-wise evolution of the shear layer and sharply decreases near the wall due to the wall effect.

Frequency Analysis of the Sweepback Cavity in the Scramjet Engine (스크램제트 엔진 내 후퇴각 공동의 주파수 특성 분석)

  • Jeong, Eun-Ju;Jeung, In-Seuck;O'Byrne, Sean;Houwing, A.F.P.;Kang, Sang-Hun;Yang, Soo-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.11a
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    • pp.293-296
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    • 2007
  • Using the T3 free-piston shock tunnel in ANU, the cavity frequency and flow characteristics of no mass-injection, inclined mass-injection before the cavity, parallel or reverse mass-injection in the cavity are investigated in the case of Mach 3.7 inflow condition. No mass-injection doesn't have the harmonic frequencies but has high amplitude of pressure spectrum at 10 kHz. Inclined mass-injection attenuates the cavity flow fluctuation as disturbing the shear layer reflection at the trailing edge. Parallel mass-injection flow reflects at the trailing edge of the cavity directly hence, increases the cavity flow fluctuation at high injection pressure.

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