2D LES of vortex shedding from a square cylinder

Bouris, D.; Bergeles, G.

doi:10.1016/s0167-6105(98)00200-1

Cited by 99 publications

(58 citation statements)

References 15 publications

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“…Pr  (11) As constantes empregadas para resolver as equações de transporte adicionais, Equações (8) - (11), são apresentadas na Tabela 1.…”

Section: Modelagem Clássica Da Turbulência (Rans)unclassified

“…Contudo, o custo computacional requerido para as simulações com LES é, ao menos, uma ordem de magnitude maior do que as necessárias com RANS. Para escoamentos externos, Bouris e Bergeles [11] apresentaram um estudo em escoamentos externos sobre corpos rombudos comparando resultados experimentais e numéricos obtidos com RANS e LES. Neste estudo foi verificado que parâmetros médios como os coeficientes de arrasto e sustentação foram razoavelmente preditos com ambas abordagens.…”

Section: Introductionunclassified

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Estudo numérico de escoamentos turbulentos com convecção forçada em cavidades cilíndricas: comparação entre LES e RANS

et al. 2015

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O presente trabalho apresenta um estudo numérico comparando o emprego da Simulação de Grandes Escalas (LES) e Modelagem Clássica (RANS) com o modelo k -ε para a predição dos campos médios e estatísticos em um escoamento turbulento com convecção forçada em cavidades cilíndricas (escoamento de base cisalhante livre) a Re D = 22000 e Pr = 0.71. No âmbito da convecção forçada, o principal propósito é verificar se o uso das diferentes metodologias para abordagem da turbulência pode conduzir a diferenças consideráveis nos fluxos convectivos nas superfícies da cavidade. Além disso, as diferenças dos campos médios e estatísticos de temperatura também são importantes para futuras análises de escoamentos com mecanismos combinados de convecção e radiação térmica em meios participantes, i.e., investigando a influência das Interações Turbulência-Radiação (TRI). As equações de conservação são resolvidas através do Método de Volumes Finitos (FVM). Os resultados revelaram que o jato apresentou uma maior penetração na cavidade cilíndrica para a simulação realizada com LES, enquanto um maior espalhamento radial foi observado no caso com o modelo RANS k -ε. Apesar de apresentarem uma tendência similar, diferenças significativas foram observadas para os campos médios, estatísticos e fluxos convectivos preditos com LES e RANS. Palavras-chave: LES, RANS, turbulência.The present work presents a numerical study comparing the employment of Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes (RANS) with k -ε model for prediction of time-averaged and statistics fields for a forced convective turbulent flow in cylindrical cavities (free shear flow) at Re D = 22000 and Pr = 0.71. In the forced convective framework, the main purpose is to verify whether the use of different methodologies for turbulence approach can led to large differences in convective fluxes in the cavity surfaces. Moreover, the differences between the time-averaged fields of temperature and its statistics predicted with both methods are important for future analyses of turbulent flows with combined convective and radiative transfer in participant medium, i.e., investigating the Turbulence-Radiation Interactions (TRI). The conservation equations are solved by means of Finite Volume Method (FVM). Results revealed that the jet showed a higher penetration into the cylindrical cavity for simulation with LES, while a larger scattering in the radial direction is noticed for the simulations with RANS k -ε. In spite of the qualitatively similarity, it was noticed strongly differences between time-averaged, statistics and convective fluxes predicted with LES and RANS.

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“…Pr  (11) As constantes empregadas para resolver as equações de transporte adicionais, Equações (8) - (11), são apresentadas na Tabela 1.…”

Section: Modelagem Clássica Da Turbulência (Rans)unclassified

Section: Introductionunclassified

Estudo numérico de escoamentos turbulentos com convecção forçada em cavidades cilíndricas: comparação entre LES e RANS

et al. 2015

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“…Particular attention is devoted to how the mismatch between experimental data and LES and RANS simulation results evolves with increasing Reynolds number. In [11], LES is adopted for studying the vortex shedding from a square cylinder at high Reynolds number and a filtering procedure is introduced in the frequency space to separate the periodic from the turbulent fluctuations. In [12], the very high Reynolds number regime (order of 10 6 ) is investigated.…”

Section: Introductionmentioning

confidence: 99%

Diagnosis of vortex induced vibration of a gravity damper

Scappaticci¹,

Castellani²,

Astolfi³

et al. 2018

Diagnostyka

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A gravity damper is a one-way valve, employed for regulating the airflow rate in ducts, generally constituted by a series of rectangular panels (closure sections), connected to an articulated quadrilateral synchronizing the movements. If the device needs to process large masses of high speed air, as common in the case of energy conversion systems, disadvantageous dynamic effects can occur. In this study, vortexinduced vibration (VIV), occurring on a gravity damper for high values of the Reynolds number, is investigated. The analysis of this work couples numerical methods (Computational Fluid Dynamics with Large-Eddy Simulation turbulence model and Finite Element Method) to experiments: a full-scale accelerometric measurement campaign is actually performed at the wind tunnel facilities of the University of Perugia. VIVs are diagnosed and quantified through the experimental vibration analysis, which is interpreted through numerical simulations. The large amplitude of VIV is interpreted as due to a tendency towards lockin because of the approaching of the vortex shedding frequency to a natural vibration mode of the system. The integrated numerical and experimental framework finally inspires two different design solutions for mitigating the amplitude of VIV: these strategies are tested at the wind tunnel and they are indeed shown to be effective.

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“…Figure 9 presents the non-dimensional time-averaged streamwise velocity along the domain centreline of the two present simulation results and can be used to determine the length of the separation zone or the recirculation zone behind the square block. The numerical simulation results of vortex shedding past a square block by Rodi [20] using the Reynolds stress equation model (RSE) and by Bouris [15] using the large eddy simulation (LES) are also included in Figure 9. The experiment measurement of the vortex shedding is available behind the cube and shows that the rotating flow occurred from x/R = 1 until 4, after that o U u / is relatively constant at about 0.6 until the end of the tank.…”

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confidence: 99%

Computation of turbulent flow around a square block with standard and modified k-ε turbulence models

Rusdin¹

2017

Int. J. Automot. Mech. Eng.

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Two-dimensional Reynold Averaged Navier Stokes (RANS) turbulence model simulations for a flow past a square block with Re = 21400 are presented in this paper. An available modified k-ε turbulence model, which is an improved version of the standard k-ε turbulence model, is applied to simulate experiment cases of vortex shedding around a square block. The performance evaluation of the modified model is conducted by assessing its results with the results of the standard k-ε turbulence model based on the similarity with the experiment measurement data. It is found that the modified model improves the drag coefficient by about 16%, the Strouhal number by about 1.5%, and the length recirculation zone by about factor two compared to that of the standard model. The RMSE values indicate a significant improvement of the time averaged velocity along the centre line by about 59% and the velocity profile above the square block by about 6% when the modified model is applied. Generally, the modified k-ε model indicates advantages compared with the standard k-ε model. However, discrepancy is found between the model result and the experiment observation for the free stream velocity at downstream and it may be necessary to consider the 3D effect on turbulent fluctuation in further studies.

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2D LES of vortex shedding from a square cylinder

Cited by 99 publications

References 15 publications

Estudo numérico de escoamentos turbulentos com convecção forçada em cavidades cilíndricas: comparação entre LES e RANS

Estudo numérico de escoamentos turbulentos com convecção forçada em cavidades cilíndricas: comparação entre LES e RANS

Diagnosis of vortex induced vibration of a gravity damper

Computation of turbulent flow around a square block with standard and modified k-ε turbulence models

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