Toward Cost-Effective Boundary Layer Transition Computations With Large-Eddy Simulation

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Solkeun Jee ◽  
Jongwook Joo ◽  
Ray-Sing Lin
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Stability Theory ◽  
Boundary Layer Stability ◽  
Computational Domain ◽  
Nonlinear Interactions ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Large Eddy

An efficient large-eddy simulation (LES) approach is investigated for laminar-to-turbulent transition in boundary layers. This approach incorporates the boundary-layer stability theory. Primary instability and subharmonic perturbations determined by the boundary-layer stability theory are assigned as forcing at the inlet of the LES computational domain. This LES approach reproduces the spatial development of instabilities in the boundary layer, as observed in wind tunnel experiments. Detailed linear growth and nonlinear interactions that lead to the H-type breakdown are well captured and compared well to previous direct numerical simulation (DNS). Requirements in the spatial resolution in the transition region are investigated with connections to the resolution in turbulent boundary layers. It is shown that the subgrid model used in this study is apparently dormant in the overall transitional region, allowing the right level of the growth of small-amplitude instabilities and their nonlinear interactions. The subgrid model becomes active near the end of the transition where the length scales of high-order instabilities become smaller in size compared to the given grid resolution. Current results demonstrate the benefit of the boundary-layer forcing method for the computational cost reduction.

Subgrid-scale modelling for the large-eddy simulation of high-Reynolds-number boundary layers

1997 ◽  
Vol 336 ◽  
pp. 151-182 ◽  
Author(s):  
BRANKO KOSOVIĆ
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Boundary Layers ◽  
Nonlinear Model ◽  
High Reynolds Number ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

It has been recognized that the subgrid-scale (SGS) parameterization represents a critical component of a successful large-eddy simulation (LES). Commonly used linear SGS models produce erroneous mean velocity profiles in LES of high-Reynolds-number boundary layer flows. Although recently proposed approaches to solving this problem have resulted in significant improvements, questions about the true nature of the SGS problem in shear-driven high-Reynolds-number flows remain open.We argue that the SGS models must capture inertial transfer effects including backscatter of energy as well as its redistribution among the normal SGS stress components. These effects are the consequence of nonlinear interactions and anisotropy. In our modelling procedure we adopt a phenomenological approach whereby the SGS stresses are related to the resolved velocity gradients. We show that since the SGS stress tensor is not frame indifferent a more general nonlinear model can be applied to the SGS parameterization. We develop a nonlinear SGS model capable of reproducing the effects of SGS anisotropy characteristic for shear-driven boundary layers. The results obtained using the nonlinear model for the LES of a neutral shear-driven atmospheric boundary layer show a significant improvement in prediction of the non-dimensional shear and low-order statistics compared to the linear Smagorinsky-type models. These results also demonstrate a profound effect of the SGS model on the flow structures.

Large-eddy simulation of flow over an axisymmetric body of revolution

2018 ◽  
Vol 853 ◽  
pp. 537-563 ◽  
Author(s):  
Praveen Kumar ◽  
Krishnan Mahesh
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Axisymmetric Body ◽  
The Body ◽  
Computational Domain ◽  
Body Of Revolution ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Self Similar

Wall-resolved large-eddy simulation (LES) is used to simulate flow over an axisymmetric body of revolution at a Reynolds number, $Re=1.1\times 10^{6}$, based on the free-stream velocity and the length of the body. The geometry used in the present work is an idealized submarine hull (DARPA SUBOFF without appendages) at zero angle of pitch and yaw. The computational domain is chosen to avoid confinement effects and capture the wake up to fifteen diameters downstream of the body. The unstructured computational grid is designed to capture the fine near-wall flow structures as well as the wake evolution. LES results show good agreement with the available experimental data. The axisymmetric turbulent boundary layer has higher skin friction and higher radial decay of turbulence away from the wall, compared to a planar turbulent boundary layer under similar conditions. The mean streamwise velocity exhibits self-similarity, but the turbulent intensities are not self-similar over the length of the simulated wake, consistent with previous studies reported in the literature. The axisymmetric wake shifts from high-$Re$ to low-$Re$ equilibrium self-similar solutions, which were only observed for axisymmetric wakes of bluff bodies in the past.

scholarly journals A Nested Multi-Scale System Implemented in the Large-Eddy Simulation Model PALM model system 6.0

2020 ◽  
Author(s):  
Antti Hellsten ◽  
Klaus Ketelsen ◽  
Matthias Sühring ◽  
Mikko Auvinen ◽  
Björn Maronga ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Large Eddy Simulation ◽  
Model System ◽  
Computational Domain ◽  
Convective Boundary ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Parent Domain

Abstract. Large-eddy simulation provides a physically sound approach to study complex turbulent processes within the atmospheric boundary layer including urban boundary layer flows. However, such flow problems often involve a large separation of turbulent scales, requiring a large computational domain and very high grid resolution near the surface features, leading to prohibitive computational costs. To overcome this problem, an online LES-LES nesting scheme is implemented into the PALM model system 6.0. The hereby documented and evaluated nesting method is capable of supporting multiple child domains which can be nested within their parent domain either in a parallel or recursively cascading configuration. The nesting system is evaluated by simulating first a purely convective boundary layer flow system and then three different neutrally-stratified flow scenarios with increasing order of topographic complexity. The results of the nested runs are compared with corresponding non-nested high- and low-resolution results. The results reveal that the solution accuracy within the high-resolution nest domain is clearly improved as the solutions approach the non-nested high-resolution reference results. In obstacle-resolving LES, the two-way coupling becomes problematic as anterpolation introduces a regional discrepancy within the obstacle canopy of the parent domain. This is remedied by introducing canopy-restricted anterpolation where the operation is only performed above the obstacle canopy. The test simulations make evident that this approach is the most suitable coupling strategy for obstacle-resolving LES. The performed simulations testify that nesting can reduce the CPU time up to 80 % compared to the fine-resolution reference runs while the computational overhead from the nesting operations remained below 16 % for the two-way coupling approach and significantly less for the one-way alternative.

scholarly journals A nested multi-scale system implemented in the large-eddy simulation model PALM model system 6.0

2021 ◽  
Vol 14 (6) ◽  
pp. 3185-3214
Author(s):  
Antti Hellsten ◽  
Klaus Ketelsen ◽  
Matthias Sühring ◽  
Mikko Auvinen ◽  
Björn Maronga ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Large Eddy Simulation ◽  
Model System ◽  
Computational Domain ◽  
Convective Boundary ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Parent Domain

Abstract. Large-eddy simulation (LES) provides a physically sound approach to study complex turbulent processes within the atmospheric boundary layer including urban boundary layer flows. However, such flow problems often involve a large separation of turbulent scales, requiring a large computational domain and very high grid resolution near the surface features, leading to prohibitive computational costs. To overcome this problem, an online LES–LES nesting scheme is implemented into the PALM model system 6.0. The hereby documented and evaluated nesting method is capable of supporting multiple child domains, which can be nested within their parent domain either in a parallel or recursively cascading configuration. The nesting system is evaluated by first simulating a purely convective boundary layer flow system and then three different neutrally stratified flow scenarios with increasing order of topographic complexity. The results of the nested runs are compared with corresponding non-nested high- and low-resolution results. The results reveal that the solution accuracy within the high-resolution nest domain is clearly improved as the solutions approach the non-nested high-resolution reference results. In obstacle-resolving LES, the two-way coupling becomes problematic as anterpolation introduces a regional discrepancy within the obstacle canopy of the parent domain. This is remedied by introducing canopy-restricted anterpolation where the operation is only performed above the obstacle canopy. The test simulations make evident that this approach is the most suitable coupling strategy for obstacle-resolving LES. The performed simulations testify that nesting can reduce the CPU time up to 80 % compared to the fine-resolution reference runs, while the computational overhead from the nesting operations remained below 16 % for the two-way coupling approach and significantly less for the one-way alternative.

Sensitivity Analysis of Heat Transfer in a Honeycomb Acoustic Liner to Inlet Conditions With Large Eddy Simulation

2017 ◽  
Author(s):  
Florent Duchaine
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Flat Plate ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Computational Domain ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Acoustic Liner ◽  
Inlet Conditions

This article presents a parametric numerical study to analyze the sensitivity of wall heat fluxes on an academic acoustic liner to inlet conditions. Large Eddy Simulation (LES) is used to simulate an array of 20 aligned honeycomb cells on a flat plate with 10% porosity characteristic of installed liners. The computational domain is periodic in the span direction comprising 2 honeycomb cells. The operating conditions are representative of cruise with a Mach number of 0.5 at ambient pressure and temperature. Comparisons of heat fluxes obtained on a none perforated flat plate with the honeycomb liner are proposed with different inlet conditions: steady laminar boundary layer profile, turbulence injection and acoustic perturbation injection at different frequencies. Results show that for the operating condition and the boundary layer thickness used, large differences are observed on the first cells of the liners resulting from different transition to turbulence processes. A first important difference exists from laminar and turbulent conditions where turbulent conditions exhibits higher heat fluxes as expected. Then, case pulsed at the resonant frequency of the honeycomb shows higher heat fluxes than other frequencies. Finally, after a given number of cells, the heat fluxes reach an asymptotic behavior at the same level which seems to be controlled by the turbulence generated by the interaction of the flow and the perforations whatever the inlet conditions.

scholarly journals Study of Realistic Urban Boundary Layer Turbulence with High-Resolution Large-Eddy Simulation

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 201 ◽  
Author(s):  
Mikko Auvinen ◽  
Simone Boi ◽  
Antti Hellsten ◽  
Topi Tanhuanpää ◽  
Leena Järvi
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Large Scale ◽  
Urban Canopy ◽  
Local Scale ◽  
Urban Environments ◽  
Computational Domain ◽  
Time Frequency ◽  
Eddy Simulation ◽  
Large Eddy

This study examines the statistical predictability of local wind conditions in a real urban environment under realistic atmospheric boundary layer conditions by means of Large-Eddy Simulation (LES). The computational domain features a highly detailed description of a densely built coastal downtown area, which includes vegetation. A multi-scale nested LES modelling approach is utilized to achieve a setup where a fully developed boundary layer flow, which is also allowed to form and evolve very large-scale turbulent motions, becomes incident with the urban surface. Under these nonideal conditions, the local scale predictability and result sensitivity to central modelling choices are scrutinized via comparative techniques. Joint time–frequency analysis with wavelets is exploited to aid targeted filtering of the problematic large-scale motions, while concepts of information entropy and divergence are exploited to perform a deep probing comparison of local urban canopy turbulence signals. The study demonstrates the utility of wavelet analysis and information theory in urban turbulence research while emphasizing the importance of grid resolution when local scale predictability, particularly close to the pedestrian level, is sought. In densely built urban environments, the level of detail of vegetation drag modelling description is deemed most significant in the immediate vicinity of the trees.

scholarly journals Hybrid RANS/LES Turbulence Model Applied to a Transitional Unsteady Boundary Layer on Wind Turbine Airfoil

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 128
Author(s):  
Di Zhang ◽  
Daniel R. Cadel ◽  
Eric G. Paterson ◽  
K. Todd Lowe
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Model Problem ◽  
Local Flow ◽  
Flow Angle ◽  
Eddy Simulation ◽  
Large Eddy

A hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) turbulence model integrated with a transition formulation is developed and tested on a surrogate model problem through a joint experimental and computational fluid dynamic approach. The model problem consists of a circular cylinder for generating coherent unsteadiness and a downstream airfoil in the cylinder wake. The cylinder flow is subcritical, with a Reynolds number of 64,000 based upon the cylinder diameter. The quantitative dynamics of vortex shedding and Reynolds stresses in the cylinder near wake are well captured, owing to the turbulence-resolving large eddy simulation mode that was activated in the wake. The hybrid model switched between RANS and LES modes outside the boundary layers, as expected. According to the experimental and simulation results, the airfoil encountered local flow angle variations up to ±50°. Further analysis through a phase-averaging technique found phase lags in the airfoil boundary layer along the chordwise locations, and both the phase-averaged and mean velocity profiles collapsed into the Law-of-the-wall in the range of 0 < y + < 50 . The features of high blade-loading fluctuations due to unsteadiness and transitional boundary layers are of interest in the aerodynamic studies of full-scale wind turbine blades, making the current model problem a comprehensive benchmark case for future model development and validation.

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