GENERALIZED LAW OF THE WALL AND EDDY VISCOSITY MODEL FOR WALL BOUNDARY LAYERS

1966 ◽  
Author(s):  
Gdalia Kleinstein
Keyword(s):  
Boundary Layers ◽  
Eddy Viscosity ◽  
Viscosity Model ◽  
Law Of The Wall ◽  
Eddy Viscosity Model ◽  
Wall Boundary

scholarly journals An Analytical Model of Wave Bottom Boundary Layers Incorporating Turbulent Relaxation and Diffusion Effects

2002 ◽  
Vol 32 (9) ◽  
pp. 2441-2456 ◽  
Author(s):  
Qingping Zou
Keyword(s):  
Shear Stress ◽  
Boundary Layers ◽  
Turbulent Diffusion ◽  
Eddy Viscosity ◽  
Viscoelastic Model ◽  
Outer Region ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
And Diffusion ◽  
Viscoelastic Term

Abstract To calculate the effects of turbulent relaxation on oscillatory turbulent boundary layers, a viscoelastic term is added to an eddy viscosity model. The viscoelastic term parameterizes the lag of turbulent properties in response to imposed oscillatory shear and is proportional to the ratio between the timescales of eddy dissipation and of the oscillating flow. It is found that the turbulent relaxation plays an important role in the phase variations of velocity and shear stress with elevation, and that it decreases the friction factor and the phase lead of bed shear stress over free stream velocity. To assess the effects of turbulent diffusion in this problem, the viscoelastic model is extended by further introducing a turbulent diffusion term in the model. The comparisons between these two models indicate that turbulent diffusion significantly reduces the magnitudes of shear stress and velocity perturbation in the outer region of the boundary layer. It is also found that the effects of turbulent relaxation and diffusion increase with increasing relative roughness. As a result, the analytical solutions demonstrate an overall improvement over the eddy viscosity model in predicting the observed temporal evolution of velocity and shear stress profiles; this improvement is more distinct for rough beds than smooth beds.

An Improved Version of the Cebeci-Smith Eddy-Viscosity Model

1978 ◽  
Vol 29 (3) ◽  
pp. 207-225 ◽  
Author(s):  
M.J. Nituch ◽  
S. Sjolander ◽  
M.R. Head
Keyword(s):  
Pressure Gradient ◽  
Skin Friction ◽  
Boundary Layers ◽  
Eddy Viscosity ◽  
Adverse Pressure Gradient ◽  
Turbulent Boundary Layers ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Smith Method

SummaryAlthough the Cebeci-Smith method of calculating turbulent boundary layers is widely used and generally gives acceptably accurate results, highly inaccurate skin-friction values are obtained for relaxing flows and equilibrium layers in strong adverse pressure gradient. In the present paper, these anomalies are removed by suitable modifications to the basic eddy-viscosity model.

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

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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