• Title/Summary/Keyword: Detached-eddy simulation

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Aeroacoustic Investigation of a Cavity with and without Doors by Delayed Detached Eddy Simulation

  • Liu, Yu;Tong, Mingbo
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.1
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    • pp.19-27
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    • 2015
  • In the present study, an effort was made to numerically investigate rectangular cavity aeroacoustics with and without doors. The simulation was performed on an open cavity with an aspect ratio of 5:1:1 at Mach 0.85 using the delayed detached eddy simulation (DDES) approach based on the Spalart-Allmaras model. Two cavity configurations, a clean cavity and a cavity with doors, were modeled. The results obtained from the clean cavity were compared with the experimental sound pressure levels (SPL) and the root mean square for the pressures applied. Furthermore, comparisons of frequencies were made using a modified semi-empirical Rossiter formula. The simulation using DDES precisely predicted the pressure fluctuation and the results matched the experiment quite well. The SPLs at the rear of the cavity were much higher than those in the front due to the instability of the shear layer impinging on the rear wall. Comparisons of DDES for the clean cavity and the doors-on cavity revealed that the SPLs inside the cavity as well as the magnitude of tones are amplified by the side doors. The main focus of this investigation was to obtain a better understanding of the open cavity acoustic resonance phenomenon and investigate the effects of cavity doors on the SPL.

Numerical Simulation of the Flow Around the SUBOFF Submarine Model Using a DES Method (DES법을 이용한 SUBOFF 잠수함 모델 주위 유동 수치해석 연구)

  • Suh, Sung-Bu;Park, Il-Ryong
    • Journal of the Society of Naval Architects of Korea
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    • v.58 no.2
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    • pp.73-83
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    • 2021
  • In this study, the numerical investigation of the flow around the SUBOFF submarine model is performed by using the Detached Eddy Simulation (DES) method which is developed based on the SST k-ω turbulence model. At the DES analysis level, complex vortical flows around the submarine model are caused mainly by the vortices due to the appendages and their interactions with the flows from the hull boundary layer and other appendages. The complexity and scale of the vortical flow obtained from the numerical simulations are highly dependent on the grid. The computed local flow properties of the submarine model are compared with the available experimental data showing a good agreement. The DES analysis more reasonably estimates the physical phenomena inherent in the experimental result in a low radius of the propeller plane where vortical flows smaller than the RANS scale are dominant.

UNSTEADY THREE-DIMENSIONAL ANALYSIS OF TRANSVERSE FUEL INJECTION INTO A SUPERSONIC CROSSFLOW USING DETACHED EDDY SIMULATION (DES를 이용한 초음속 유동내 수직 연료분사 유동의 비정상 3차원 해석)

  • Won, S.H.;Moon, S.Y.;Jeung, I.S;Choi, J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.97-103
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    • 2008
  • Unsteady three-dimensional flowfields generated by transverse fuel injection into a supersonic mainstream are simulated with a DES turbulence model. Comparisons are made with experimental results in term of the temporal eddy position and eddy formation frequency. The vorticity field around the jet exit is also analyzed to understand the formation mechanism of the jet vortical structures. Results indicate that the DES model correctly predicts the convection characteristics of the large scale eddies. However, it is also observed that the numerical results slightly overpredict the eddy formation frequency. The jet vortical structures are developed from the competing vortices in the recirculation region of upstream boundary.

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UNSTEADY THREE-DIMENSIONAL ANALYSIS OF TRANSVERSE FUEL INJECTION INTO A SUPERSONIC CROSSFLOW USING DETACHED EDDY SIMULATION (DES를 이용한 초음속 유동내 수직 연료분사 유동의 비정상 3차원 해석)

  • Won, S.H.;Moon, S.Y.;Jeung, I.S.;Choi, J.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.97-103
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    • 2008
  • Unsteady three-dimensional flowfields generated by transverse fuel injection into a supersonic mainstream are simulated with a DES turbulence model. Comparisons are made with experimental results in term of the temporal eddy position and eddy formation frequency. The vorticity field around the jet exit is also analyzed to understand the formation mechanism of the jet vortical structures. Results indicate that the DES model correctly predicts the convection characteristics of the large scale eddies. However, it is also observed that the numerical results slightly overpredict the eddy formation frequency. The jet vortical structures are developed from the competing vortices in the recirculation region of upstream boundary.

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EFFECT OF LENGTH-SCALE IN DDES FOR BACKWARD-FACING STEP FLOW (후향계단 DDES 해석의 길이척도 영향 분석)

  • Lee, C.Y.;Sa, J.H.;Park, S.H.;Lee, E.S.;Lee, J.I.;Lee, K.S.
    • Journal of computational fluids engineering
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    • v.17 no.4
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    • pp.24-31
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    • 2012
  • Effects of the subgrid length-scale in the Delayed-Detached Eddy Simulation(DDES) are investigated based on the Spalart-Allmaras(S-A) and the k-$\omega$ Shear Stress Transport(SST) turbulence models. Driver & Seegmiller's experimental results are used to validate numerical results. Grid convergence with grid resolution and subgrid length-scale is investigated. The simulation results show that the volume method for the subgrid length-scale is more resistant to unfavorable effects of the grid size in the periodic direction than the maximum method. Using a sufficient grid resolution and an appropriate subgrid length-scale, both S-A based DDES and SST based DDES methods can provide a good correlation with the experimental data.

NUMERICAL ANALYSIS OF PRESSURE PERTURBATION OF DELTA WING VORTEX FLOW AT A HIGH ANGLE OF ATTACK (고 받음각 ONERA 70도 삼각날개 와류 유동의 압력 섭동 분석)

  • Son, M.S.;Sa, J.H.;Park, S.H.;Byun, Y.H.
    • Journal of computational fluids engineering
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    • v.20 no.2
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    • pp.73-80
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    • 2015
  • Delayed Detached-Eddy Simulation was conducted to investigate surface pressure coefficient distribution and surface pressure fluctuation over an ONERA 70-degree delta wing at a high angle of attack. Time-averaged surface pressure distribution is directly affected by the primary vortices, whereas the pressure fluctuation is influenced by the unsteady fluctuating boundary layer over the surface. And pressure coefficient, velocity, pressure fluctuation, and turbulent kinetic energy were analyzed along the vortex core in order to investigate the process of vortex breakdown. Consequently, strong pressure fluctuations were found where the vortex breakdown was occurred at x~620 mm. The turbulent kinetic energy abruptly increased and followed after the vortex breakdown.

A Comparative Study of Numerical Methods on Aerodynamic Characteristics of a Compressor Rotor at Near-stall Condition

  • Kim, Donghyun;Kim, Kuisoon;Choi, Jeongyeol;Son, Changmin
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.2
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    • pp.157-164
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    • 2015
  • The present work performs three-dimensional flow calculations based on Reynolds Averaged Navier-Stokes (RANS) and Delayed Detached Eddy Simulation (DDES) to investigate the flow field of a transonic rotor (NASA Rotor 37) at near-stall condition. It is found that the DES approach is likely to predict well the complex flow characteristics such as secondary vortex or turbulent flow phenomenon than RANS approach, which is useful to describe the flow mechanism of a transonic compressor. Especially, the DES results show improvement of predicting the flow field in the wake region and the model captures reasonably well separated regions compared to the RANS model. Besides, it is discovered that the three-dimensional vortical flows after the vortex breakdown from the rotor tip region are widely distributed and its vortex structures are clearly present. Near the rotor leading edge, a part of the tip leakage flows in DES solution spill over into next passage of the blade owing to the separation vortex flow and the backflow is clearly seen around the trailing edge of rotor tip. Furthermore, the DES solution shows strong turbulent eddies especially in the rotor hub, rotor tip section and the downstream of rotor trailing edge compared to the RANS solution.

Wind Pressure Coefficients and Spectrum Estimation of Dome by Improved Delayed Detached Eddy Simulation (Improved Delayed DES 해석을 통한 돔 형상의 풍압 계수 및 풍압 스펙트럼 산정)

  • Park, Beom-Hee;Jeon, Doo-Jin;Han, Sang-Eul
    • Journal of Korean Association for Spatial Structures
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    • v.19 no.4
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    • pp.95-102
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    • 2019
  • In this study, the reliability of the analysis is evaluated by comparing the average wind pressure coefficient, RMS wind pressure coefficient and wind pressure spectrum with same condition of wind tunnel test which are calculated in the high-Reynolds number range of 1.2×106, 2.0×106 each for the typical curved shape dome structure. And it is examined by the reliability of analysis through Improved delayed detached Eddy Simulation(IDDES), which is one of the hybrid RANS/LES techniques that can analyze the realistic calculation range of high Reynolds number. As a result of the study, it was found that IDDES can be predicted very similar to the wind tunnel test. The distribution pattern of the wind pressure coefficient and wind pressure spectrum showed a similar compared with wind tunnel test.

Dynamic Correction of DES Model Constant for the Advanced Prediction of Supersonic Base Flow (초음속 기저유동의 우수한 예측을 위한 DES 모델상수의 동적 보정)

  • Shin, Jae-Ryul;Choi, Jeong-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.2
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    • pp.99-110
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    • 2010
  • The DES analysis of strong compressibility flow, LES mode is intentionally performed in boundary layer with the conventional empirical constant $C_{DES}$ value of 0.65. In this study, an expression is suggested to determine the $C_{DES}$ value dynamically by using a distribution function of the ratio of turbulence length scale and wall distance which is used in S-A DDES model for RANS mode protection. The application of the dynamic $C_{DES}$ presents better prediction than previous results those used constant but different $C_{DES}$ values.

Unsteady Three-Dimensional Analysis of Transverse Fuel Injection into a Supersonic Crossflow using Detached Eddy Simulation Part II : Reacting Flowfield (DES를 이용한 초음속 유동내 수직 연료분사 유동의 비정상 3차원 해석 Part II : 반응 유동장)

  • Won, Su-Hee;Jeung, In-Seuck;Choi, Jeong-Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.9
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    • pp.879-888
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    • 2009
  • Unsteady three-dimensional reacting flowfield generated by transverse hydrogen injection into a supersonic mainstream is numerically investigated using DES and finite-rate chemistry model. Comparisons are made with experimental results to investigate the turbulent reacting flow physics. The numerical OH distribution describes well the experimental OH-PLIF result, while the numerical ignition delay time shows some disparity due to the restricted available experimental data. The intermittency phenomena are identified by the comparative analysis between RANS and DES. Those effects are also quantified by the temperature distributions along streamlines and superimposed OH mass fraction along with time.