scholarly journals Adaptive downstream tensorial eddy viscosity for hybrid large‐eddy simulations‐Reynolds‐averaged‐Navier–Stokes simulations

2021 ◽  
Author(s):  
Wanjia Zhang ◽  
Tom I‐P. Shih
Keyword(s):  
Eddy Viscosity ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Assessment of the validity of RANS knock prediction using the resonance theory

2019 ◽  
Vol 21 (4) ◽  
pp. 610-621 ◽  
Author(s):  
Corinna Netzer ◽  
Lars Seidel ◽  
Frédéric Ravet ◽  
Fabian Mauss
Keyword(s):  
Numerical Simulations ◽  
Direct Numerical Simulations ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Post Processing ◽  
Resonance Theory ◽  
Auto Ignition ◽  
Engine Knock ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Following the resonance theory by Bradley and co-workers, engine knock is a consequence of an auto-ignition in the developing detonation regime. Their detonation diagram was developed using direct numerical simulations and was applied in the literature to engine knock assessment using large eddy simulations. In this work, it is analyzed if the detonation diagram can be applied for post-processing and evaluation of predicted auto-ignitions in Reynolds-averaged Navier–Stokes simulations even though the Reynolds-averaged Navier–Stokes approach cannot resolve the fine structures resolved in direct numerical simulations and large eddy simulations that lead to the prediction of a developing detonation. For this purpose, an engine operating point at the knock limit spark advance is simulated using Reynolds-averaged Navier–Stokes and large eddy simulations. The combustion is predicted using the G-equation and the well-stirred reactor model in the unburnt gases based on a detailed gasoline surrogate reaction scheme. All the predicted ignition kernels are evaluated using the resonance theory in a post-processing step. According to the different turbulence models, the predicted pressure rise rates and gradients differ. However, the predicted ignition kernel sizes and imposed gas velocities by the auto-ignition event are similar, which suggests that the auto-ignitions predicted by Reynolds-averaged Navier–Stokes simulations can be given a meaningful interpretation within the detonation diagram.

Hybrid Reynolds-Averaged Navier-Stokes/Large-Eddy Simulations of Supersonic Turbulent Mixing

AIAA Journal ◽  
2003 ◽  
Vol 41 (2) ◽  
pp. 218-229 ◽  
Author(s):  
Nicholas J. Georgiadis ◽  
J. Iwan D. Alexander ◽  
Eli Reshotko
Keyword(s):  
Turbulent Mixing ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Flow and Heat Transfer in an Internally Ribbed Duct With Rotation: An Assessment of Large Eddy Simulations and Unsteady Reynolds-Averaged Navier-Stokes Simulations

2004 ◽  
Vol 127 (2) ◽  
pp. 306-320 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Density Ratio ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Flow And Heat Transfer ◽  
Number Ratio ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Large eddy simulations (LES) and unsteady Reynolds averaged Navier-Stokes (URANS) simulations have been performed for flow and heat transfer in a rotating ribbed duct. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The LES results are based on a higher-order accurate finite difference scheme with a dynamic Smagorinsky model for the subgrid stresses. The URANS procedure utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The URANS computations have been carried out for a wide range of Reynolds number (Re=12,500-100,000), rotation number (Ro=0-0.5) and density ratio (Δρ∕ρ=0-0.5), while LES results are reported for a single Reynolds number of 12,500 without and with rotation (Ro=0.12,Δρ∕ρ=0.13). Comparison is made between the LES and URANS results, and the effects of various parameters on the flow field and surface heat transfer are explored. The LES results clearly reflect the importance of coherent structures in the flow, and the unsteady dynamics associated with these structures. The heat transfer results from both LES and URANS are found to be in reasonable agreement with measurements. LES is found to give higher heat transfer predictions (5–10% higher) than URANS. The Nusselt number ratio (Nu∕Nu0) is found to decrease with increasing Reynolds number on all walls, while they increase with the density ratio along the leading and trailing walls. The Nusselt number ratio on the trailing and sidewalls also increases with rotation. However, the leading wall Nusselt number ratio shows an initial decrease with rotation (till Ro=0.12) due to the stabilizing effect of rotation on the leading wall. However, beyond Ro=0.12, the Nusselt number ratio increases with rotation due to the importance of centrifugal-buoyancy at high rotation.

Reynolds-Averaged Navier-Stokes/Large-Eddy Simulations of Supersonic Base Flow

AIAA Journal ◽  
2006 ◽  
Vol 44 (11) ◽  
pp. 2578-2590 ◽  
Author(s):  
Franck Simon ◽  
Sébastien Deck ◽  
Philippe Guillen ◽  
Pierre Sagaut
Keyword(s):  
Base Flow ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes
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