The linear response of turbulent flow to a volume force: comparison between eddy-viscosity model and DNS

2016 ◽  
Vol 790 ◽  
pp. 104-127 ◽  
Author(s):  
S. Russo ◽  
P. Luchini
Keyword(s):  
Turbulent Flow ◽  
Linear Response ◽  
Eddy Viscosity ◽  
Bottom Topography ◽  
Viscosity Model ◽  
Correct Result ◽  
Mean Velocity ◽  
Volume Force ◽  
Eddy Viscosity Model ◽  
External Volume

We identify a benchmark problem simple enough that it can be solved both by an eddy-viscosity model and by direct numerical simulation: this is the linear response of a turbulent flow’s mean-velocity profile to an external volume force. An example of such a force was found in a study of the perturbation induced by bottom topography by Luchini & Charru (J. Fluid Mech., vol. 656, 2010, pp. 337–341). On the other hand, a modification of the method by Quadrio & Luchini (Proceedings of the IX European Turbulence Conference, Southampton, UK, 2002, pp. 715–718) and Luchini et al. (Phys. Fluids, vol. 18, 2006, 121702) to compute the linear impulse response of a wall-bounded turbulent flow allows the response to a volume force to be computed directly. The comparison exhibits significant differences and suggests that there might be fundamental obstacles to designing an eddy-viscosity model that provides the correct result.

Assessment of Large-Eddy Simulation (LES) Models for Engine Type Flows: Effect of Model Type and Grid Size

2013 ◽  
Author(s):  
Jun Han ◽  
Satbir Singh ◽  
Eric Pomraning
Keyword(s):  
Eddy Viscosity ◽  
Flow Characteristics ◽  
Computer Code ◽  
Viscosity Model ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Large Eddy ◽  
Flow Configurations ◽  
Engine Type

In this paper, large-eddy simulations (LES) of engine type flow are performed using commercially available computer code CONVERGE. First, accuracy of the numerical discretization scheme of the code is assessed using well established laminar flow configurations. Then, two different subgrid scale (SGS) models, an eddy-viscosity model of Vreman (Physics of fluids, 16, 2004) and a non eddy-viscosity model of Pomraning and Rutland (AIAA Journal, 40, 2002) are employed to predict turbulent flow characteristics in a piston-valve assembly. A number of grid resolutions are employed to perform the simulations, with and without the SGS models. The mean velocity and the root-mean-squared (RMS) values of the velocity fluctuations are compared with available experimental data. Although satisfactory comparison of model predictions with measured data is obtained, it is found that the predictions are more influenced by the grid resolution than the SGS model contribution.

A Model of the Turbulent Burst Phenomenon: Fully Developed Transitional Turbulent Flow Between Parallel Plates

1982 ◽  
Vol 49 (4) ◽  
pp. 697-703 ◽  
Author(s):  
L. C. Thomas ◽  
H. M. Kadry
Keyword(s):  
Turbulent Flow ◽  
Eddy Viscosity ◽  
Wall Region ◽  
Parallel Plates ◽  
Burst Frequency ◽  
Mean Velocity ◽  
Eddy Viscosity Model ◽  
Region Model ◽  
High Reynolds ◽  
Turbulent Burst

An analysis is presented for fully developed transitional turbulent flow between parallel plates that features the use of a turbulent burst model for the important wall region. Model closure is accomplished by the specification of the mean burst frequency and, for moderate to high Reynolds numbers, by matching with a classical eddy viscosity model for the turbulent core. Predictions obtained for friction factor and mean velocity distribution are compared with experimental data for fully developed transitional turbulent flow in a channel with large aspect ratio. Predictions are also developed for the eddy viscosity within the wall region for transitional turbulent conditions.

scholarly journals On the extension of the eddy viscosity model to compressible flows

2014 ◽  
Vol 26 (4) ◽  
pp. 041702 ◽  
Author(s):  
M. Germano ◽  
A. Abbà ◽  
R. Arina ◽  
L. Bonaventura
Keyword(s):  
Compressible Flows ◽  
Eddy Viscosity ◽  
Viscosity Model ◽  
Eddy Viscosity Model

An Assessment of Three-Dimensional Turbulent Boundary Layer Prediction Methods

1973 ◽  
Vol 95 (3) ◽  
pp. 415-421 ◽  
Author(s):  
A. J. Wheeler ◽  
J. P. Johnston
Keyword(s):  
Boundary Layer ◽  
Eddy Viscosity ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Boundary Layer Flows ◽  
Mean Velocity ◽  
Eddy Viscosity Model ◽  
Separating Flow ◽  
Dimensional Boundary ◽  
Stress Models

Predictions have been made for a variety of experimental three-dimensional boundary layer flows with a single finite difference method which was used with three different turbulent stress models: (i) an eddy viscosity model, (ii) the “Nash” model, and (iii) the “Bradshaw” model. For many purposes, even the simplest stress model (eddy viscosity) was adequate to predict the mean velocity field. On the other hand, the profile of shear stress direction was not correctly predicted in one case by any model tested. The high sensitivity of the predicted results to free stream pressure gradient in separating flow cases is demonstrated.

Simulation of Multi-Stage Compressor at Off-Design Conditions

2017 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Non Linear ◽  
The Right

Computational Fluid Dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multi-stage, high-speed machines remain challenging. This paper presents the authors’ effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g. blade fillet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and non-linear eddy viscosity models are assessed. The non-linear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The non-linear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated fillet leads to thicker boundary layer on the fillet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed the computations without the shroud cavities fail to predict the major flow features in the passage and this leads to inaccurate predictions of massflow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid result in a credible prediction of compressor matching and performance with steady state mixing planes.

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