Large-Eddy Simulation of Roughened NACA65 Compressor Cascade

2017 ◽  
Author(s):  
Jongwook Joo ◽  
Gorazd Medic ◽  
Om Sharma
Keyword(s):  
Surface Roughness ◽  
Large Eddy Simulations ◽  
Surface Imaging ◽  
Potential Solution ◽  
Discrete Elements ◽  
Compressor Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Modeling ◽  
The One

Large eddy simulations over a NACA65 compressor cascade with roughness were performed for multiple roughness heights. The experiments show flow separation as airfoil roughness is increased. In LES computations, surface roughness was represented by regularly arranged discrete elements using guidelines from Schlichting. Results from wall-resolved LES indicate that specifying an equivalent sandgrain roughness height larger than the one in experiments is required to reproduce the same effects observed in experiments. This highlights the persisting uncertainty with matching the experimental roughness geometry in LES computations, pointing towards surface imaging and digitization as a potential solution. Some initial analysis of flow physics has been conducted with the aim of guiding the RANS modeling for roughness.

Wall-resolved wavelet-based adaptive large-eddy simulation of bluff-body flows with variable thresholding

2016 ◽  
Vol 788 ◽  
pp. 303-336 ◽  
Author(s):  
Giuliano De Stefano ◽  
Alireza Nejadmalayeri ◽  
Oleg V. Vasilyev
Keyword(s):  
Turbulent Flows ◽  
Bluff Body ◽  
Large Eddy Simulations ◽  
Eddy Simulation ◽  
Computational Mesh ◽  
Large Eddy ◽  
High Reynolds ◽  
The One ◽  
Solid Obstacles ◽  
Bluff Body Flows

The wavelet-based eddy-capturing approach with variable thresholding is extended to bluff-body flows, where the obstacle geometry is enforced through Brinkman volume penalization. The use of a spatio-temporally varying threshold allows one to perform adaptive large-eddy simulations with the prescribed fidelity on a near optimal computational mesh. The space–time evolution of the threshold variable is achieved by solving a transport equation based on the Lagrangian path-line diffusive averaging methodology. The coupled wavelet-collocation/volume-penalization approach with variable thresholding is illustrated for a turbulent incompressible flow around an isolated stationary prism with square cross-section. Wavelet-based adaptive large-eddy simulations supplied with the one-equation localized dynamic kinetic energy-based model are successfully performed at moderately high Reynolds number. The present study demonstrates that the proposed variable thresholding methodology for wavelet-based modelling of turbulent flows around solid obstacles is feasible, accurate and efficient.

Analysis of the Sutton Model for Aero-Optical Properties of Compressible Boundary Layers

2005 ◽  
Vol 128 (2) ◽  
pp. 239-246 ◽  
Author(s):  
Eric Tromeur ◽  
Eric Garnier ◽  
Pierre Sagaut
Keyword(s):  
Boundary Layer ◽  
Density Field ◽  
The Other ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Compressible Boundary Layers ◽  
Optical Effects ◽  
Large Eddy ◽  
The One ◽  
Reference Tool

In order to assess the capability of the Sutton model to evaluate aero-optical effects in a turbulent boundary layer, large-eddy simulation (LES) evolving spatially and Reynolds averaged Navier-Stokes (RANS) computations are carried out at Mach number equal to 0.9. First aerodynamic fields are proved to compare favorably with theoretical and experimental results. Once validated, the characteristics of the boundary layer allow us to obtain information concerning optical beam degradation. On the one hand, the density field is used to compute phase distortion directly and, on the other hand, by means of the Sutton model. Therefore, LES and RANS simulations allow us to study optical models and the validity of their assumptions. Finally, LES is proved to be considered as a reference tool to evaluate aero-optical effects.

Reliable and Accurate Prediction of Three-Dimensional Separation in Asymmetric Diffusers Using Large-Eddy Simulation

2009 ◽  
Author(s):  
Hayder Schneider ◽  
Dominic von Terzi ◽  
Hans-Jo¨rg Bauer ◽  
Wolfgang Rodi
Keyword(s):  
Experimental Data ◽  
Reverse Flow ◽  
Separation Bubble ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

Reynolds-Averaged Navier-Stokes (RANS) calculations and Large-Eddy Simulations (LES) of the flow in two asymmetric three-dimensional diffusers were performed. The numerical setup was chosen to be in compliance with previous experiments. The aim of the present study is to find the least expensive method to compute reliably and accurately the impact of geometric sensitivity on the flow. RANS calculations fail to predict both the extent and location of the three-dimensional separation bubble. In contrast, LES is able to determine the amount of reverse flow and the pressure coefficient within the accuracy of experimental data.

Application of High-Resolution Large Eddy Simulation to Simplified Turbomachinery Flows

2016 ◽  
Author(s):  
Susumu Teramoto ◽  
Takuya Ouchi ◽  
Hiroki Sanada ◽  
Koji Okamoto
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Reynolds Stress ◽  
Sudden Expansion ◽  
Compressor Cascade ◽  
Rans Model ◽  
Eddy Simulation ◽  
Large Eddy

Fully resolved large eddy simulation (LES) is applied to two simple geometry flowfields with well-defined boundary conditions. The LES results are compared with simulations based on a Reynolds-averaged Navier-Stokes (RANS) model with turbulence, and pros and cons of using high-resolution LES for turbomachinery flows are discussed. One flow is a linear compressor cascade flow composed of the tip section of GE rotor B at Rec = 4 × 105 with a clearance, and the other is a Mach 1.76 supersonic turbulent boundary layer at Reδ = 5000 that laminerizes through a 12-degree expansion corner. The grids are prepared fine enough to resolve the turbulent boundary layer through a grid sensitivity study. The liner cascade result shows that all the turbulent shear layers and boundary layers including those in the small tip clearance are well resolved with 800 million grid points. The Reynolds stress derived from the LES results are compared directly with those predicted from the Spalart-Allmaras one-equation RANS turbulence model. The two results agreed qualitatively well except for the shear layer surrounding the tip leakage vortex, demonstrating that the RANS model performs well at least for flowfields near the design condition. From the simulation of the turbulent boundary layer experiencing sudden expansion, noticeable decreases of both Reynolds stress and local friction coefficient were observed, showing that the turbulent boundary layer has relaminarized through the sudden expansion. The boundary layer downstream of the expansion exhibits a nonequilibrium condition and was different from the laminar boundary layer.

scholarly journals Large-eddy simulation of 3-D corner separation in a linear compressor cascade

2015 ◽  
Vol 27 (8) ◽  
pp. 085105 ◽  
Author(s):  
Feng Gao ◽  
Wei Ma ◽  
Gherardo Zambonini ◽  
Jérôme Boudet ◽  
Xavier Ottavy ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Corner Separation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Linear Compressor Cascade

Comparison of Partially Averaged Navier–Stokes and Large-Eddy Simulations of the Flow Around a Cuboid Influenced by Crosswind

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Siniša Krajnović ◽  
Per Ringqvist ◽  
Branislav Basara
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Better Than ◽  
Good Agreement ◽  
Near Wall

The paper presents a partially averaged Navier–Stokes (PANS) simulation of the flow around a cuboid influenced by crosswind. The results of the PANS prediction are validated against experimental data and results of a large-eddy simulation (LES) made using the same numerical conditions as PANS. The PANS shows good agreement with the experimental data. The prediction of PANS was found to be better than that of the LES in flow regions where simulations suffered from poor near-wall resolution.

scholarly journals The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part II: Modeling Particle Trajectories

2015 ◽  
Vol 17 (1) ◽  
pp. 245-255 ◽  
Author(s):  
Matteo Colli ◽  
Luca G. Lanza ◽  
Roy Rasmussen ◽  
Julie M. Thériault
Keyword(s):  
Collection Efficiency ◽  
Time Dependent ◽  
Navier Stokes ◽  
Turbulent Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Efficiency Comparison ◽  
The One ◽  
The Impact

Abstract The use of windshields to reduce the impact of wind on snow measurements is common. This paper investigates the catching performance of shielded and unshielded gauges using numerical simulations. In Part II, the role of the windshield and gauge aerodynamics, as well as the varying flow field due to the turbulence generated by the shield–gauge configuration, in reducing the catch efficiency is investigated. This builds on the computational fluid dynamics results obtained in Part I, where the airflow patterns in the proximity of an unshielded and single Alter shielded Geonor T-200B gauge are obtained using both time-independent [Reynolds-averaged Navier–Stokes (RANS)] and time-dependent [large-eddy simulation (LES)] approaches. A Lagrangian trajectory model is used to track different types of snowflakes (wet and dry snow) and to assess the variation of the resulting gauge catching performance with the wind speed. The collection efficiency obtained with the LES approach is generally lower than the one obtained with the RANS approach. This is because of the impact of the LES-resolved turbulence above the gauge orifice rim. The comparison between the collection efficiency values obtained in case of shielded and unshielded gauge validates the choice of installing a single Alter shield in a windy environment. However, time-dependent simulations show that the propagating turbulent structures produced by the aerodynamic response of the upwind single Alter blades have an impact on the collection efficiency. Comparison with field observations provides the validation background for the model results.

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