Effect of grid sensitivity on the performance of wall adapting SGS models for LES of swirling and separating–reattaching flows

Arya, Nitish; De, Ashoke

doi:10.1016/j.camwa.2019.03.038

Cited by 32 publications

(7 citation statements)

References 39 publications

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“…In this way, the tracer gas and the target gas were dispersed in the same way. Zhou et al 28 validated the effectiveness of the method by regarding supply air and indoor air as two fluids with the same physical properties.…”

Section: Methodsmentioning

confidence: 99%

Flow characteristics and formation optimization of vortex ring air supply

et al. 2022

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The vortex rings ventilation (VRV) is a new type of air supply system comprising vortex rings. Compared with an air supply jet, a vortex ring reduces the loss of fresh air during transportation because of its stable structure. However, during the formation of the vortex ring, it entrains the ambient air and reduces the fresh air in the vortex ring. In this study, a vortex ring generator with a fresh air cavity is proposed to form confined vortex rings. This improved the fresh air ratio of the VRV. Based on previous experiments, a piston‐orifice axisymmetric model with a dynamic grid was developed to form an air vortex ring. The flow characteristics of free and confined vortex rings during the generation stage were studied. First, the evolution of free vortex rings with different stroke lengths was studied, and the optimal piston stroke length and radial constraint size were determined. Subsequently, the mixing ratios of the free and confined vortex rings were compared and analyzed. The results showed that the mixing ratio of the confined vortex ring formed by the fresh air cavity in the formation stage was zero. Moving to the location of 4.9 times the orifice diameter (D0$$ {D}_0 $$), reduced the mixing ratio of the confined vortex ring by 77.78% compared with that of the free vortex ring. In addition, the influence of three inner diameters and four outlet diameters of fresh air cavities on the vortex rings was studied to optimize the size of the vortex ring generator. The results showed that the inner diameter of the fresh air cavity was greater than 3D0$$ 3{D}_0 $$ and that an outlet diameter greater than 2.5D0$$ 2.5{D}_0 $$ had little influence on the vortex rings.

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Section: Methodsmentioning

confidence: 99%

Flow characteristics and formation optimization of vortex ring air supply

et al. 2022

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“…The

closure model was utilized in conjunction with URANS turbulence model. The wall-adapting local eddy-viscosity subgrid-scale model for LES was used since the previous studies have shown good results for a confined reacting flow [ 44 , 45 ]. In both cases, the wall functions were used for turbulent viscosity

and thermal diffusivity

.…”

Section: Methodsmentioning

confidence: 99%

Validating Confined Flame Noise Simulation Using External Sensor

Williamson

Srivastava²,

Sallam

2022

Sensors

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Advancements in lean premixed combustion have increased the efficiency and reduced the amount of greenhouse gas emissions, but they have led to increased noise emissions due to higher turbulence and mixing fluctuations. This study used an external sensor (microphone) to validate the simulation of the combustion noise of a confined space. An experimental facility with a laboratory-scale furnace was used to carry out the measurement, and the simulation of the confined flame noise was conducted in OpenFOAM. The simulation utilized the Partially Stirred Reactor (PaSR) and a hybrid computational aeroacoustics (CAA) approach using the large eddy simulation (LES)/the Ffwocs Williams–Hawkings (FWH) method. Additionally, unsteady Reynolds-averaged Navier–Stokes (URANS)/the FWH method was tested for a comparison with the LES prediction. A sensor which was placed outside the enclosure for ease of access was then used to validate the results of the numerical model. The sensor data agreed with the LES/FWH results including the amplitude and frequency of the primary combustion peak and the overall sound pressure level (OASPL). This suggested that a sensor which was placed outside the enclosure could serve as a validation tool for the simulation of the confined flames despite the sound reflections from the walls.

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“…The constant C w = 0.325 and V c is the volume of the grid cell. While the WALE model can be overdissipative in strong vortical flows (Bricteux, Duponcheel & Winckelmans 2009), it has been found to perform better than the dynamic Smagorinsky model for simulating flow separation (Arya & De 2019) and flow over rough beds (Lian et al 2019). For this study, the main turbulent generation mechanism is eddies shed from the roughness elements and no strong shear layers formed; therefore, the WALE model is appropriate.…”

Section: Large-eddy Simulation Modelmentioning

confidence: 97%

Boundary layer dynamics and bottom friction in combined wave–current flows over large roughness elements

Rosman

Hench

2021

J. Fluid Mech.

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In the coastal ocean, interactions of waves and currents with large roughness elements, similar in size to wave orbital excursions, generate drag and dissipate energy. These boundary layer dynamics differ significantly from well-studied small-scale roughness. To address this problem, we derived spatially and phase-averaged momentum equations for combined wave–current flows over rough bottoms, including the canopy layer containing obstacles. These equations were decomposed into steady and oscillatory parts to investigate the effects of waves on currents, and currents on waves. We applied this framework to analyse large-eddy simulations of combined oscillatory and steady flows over hemisphere arrays (diameter $D$ ), in which current ( $U_c$ ), wave velocity ( $U_w$ ) and period ( $T$ ) were varied. In the steady momentum budget, waves increase drag on the current, and this is balanced by the total stress at the canopy top. Dispersive stresses from oscillatory flow around obstacles are increasingly important as $U_w/U_c$ increases. In the oscillatory momentum budget, acceleration in the canopy is balanced by pressure gradient, added-mass and form drag forces; stress gradients are small compared to other terms. Form drag is increasingly important as the Keulegan–Carpenter number $KC=U_wT/D$ and $U_c/U_w$ increase. Decomposing the drag term illustrates that a quadratic relationship predicts the observed dependences of steady and oscillatory drag on $U_c/U_w$ and $KC$ . For large roughness elements, bottom friction is well represented by a friction factor ( $f_w$ ) defined using combined wave and current velocities in the canopy layer, which is proportional to drag coefficient and frontal area per unit plan area, and increases with $KC$ and $U_c/U_w$ .

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Effect of grid sensitivity on the performance of wall adapting SGS models for LES of swirling and separating–reattaching flows

Cited by 32 publications

References 39 publications

Flow characteristics and formation optimization of vortex ring air supply

Flow characteristics and formation optimization of vortex ring air supply

Validating Confined Flame Noise Simulation Using External Sensor

Boundary layer dynamics and bottom friction in combined wave–current flows over large roughness elements

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