Investigation of a Turbulent Radial Wall Jet

1967 ◽  
Vol 34 (2) ◽  
pp. 457-463 ◽  
Author(s):  
M. Poreh ◽  
Y. G. Tsuei ◽  
J. E. Cermak
Keyword(s):  
Eddy Viscosity ◽  
Outer Region ◽  
Maximum Velocity ◽  
Viscosity Model ◽  
Wall Friction ◽  
Wall Jet ◽  
Wall Region ◽  
Reynolds Stresses ◽  
Radial Wall ◽  
Eddy Viscosity Model

In this paper measurements are presented of mean velocities, turbulence intensities, Reynolds’ stresses, and the wall friction in a radial wall jet formed by an impinging circular jet on a smooth flat plate. The mean velocities of the wall jet are found to be similar and can be correlated with the maximum velocity and jet thickness at each station, except for a mild Reynolds number dependence near the wall. The dimensionless radial velocity profile is in good agreement with the form suggested by Glauert [1] although the variation of the thickness of the jet does not conform to his predictions. It is shown here that this discrepancy follows from Glauert’s use of the Prandtl eddy viscosity model in describing the Reynolds’ stress distribution. Our measurements show that the shear stress does not vanish where the velocity gradient is zero, as in the case with a free jet, or as required by the eddy viscosity model. The wall friction in the wall jet is found to be larger than the corresponding friction pipe flow. This increase is probably due to the large turbulent fluctuations in the outer region of the jet, which affect the structure of the wall region.

Full Field Algebraic Anisotropic Eddy Viscosity Model for the Film Cooling Flows

2012 ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Wall Region ◽  
Mean Flow ◽  
Experiment Data ◽  
Anisotropic Models ◽  
Eddy Viscosity Model

The algebraic anisotropic eddy viscosity model proposed by the authors is further developed to make it suitable to the full flow field in order to focus not only in the near wall region but also in the main flow field. The three anisotropic eddy viscosity ratios for u′v′, u′w′, v′w′ are determined from the eddy viscosity hypothesis and algebraic Reynolds stress transport equations and expressed in Cartesian coordinate system. This model is applied to four isotropic two-equation turbulence models to make them anisotropic. These anisotropic models are validated with the experiment data from Sinha et al.[1]. Thorough tests are performed with all these isotropic and anisotropic turbulence models for film cooling on a flatplate with different blowing ratios. Detailed analyses of computational simulations are presented. The predicted adiabatic film cooling effectiveness and mean flow field show that the algebraic anisotropic eddy-viscosity turbulence models agree better with the experiment data. Among the four anisotropic models, the anisotropic models based on the realizable k-ε and RNG k-ε models stand out as the most promising models for flatplate film cooling predictions. It’s a big advantage of this model that it deals with the whole flow field and can be combined with different turbulence models.

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.

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.

Improved compressor corner separation prediction using the quadratic constitutive relation

2017 ◽  
Vol 231 (7) ◽  
pp. 618-630 ◽  
Author(s):  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Constitutive Relation ◽  
Eddy Viscosity ◽  
Pressure Coefficient ◽  
Momentum Equation ◽  
Viscosity Model ◽  
Corner Separation ◽  
Pressure Loss Coefficient ◽  
Eddy Viscosity Model ◽  
Relation Model ◽  
Separation Size

This work presents the implementation and study of the quadratic constitutive relation nonlinear eddy-viscosity model with representative compressor application, for which the corner separation has been poorly predicted with the widely used linear Boussinesq eddy-viscosity model. With the introduction of the Reynolds stress anisotropy, the secondary flow of the second kind and its effect on the corner flow can be well captured and this results in greatly improved prediction of pressure coefficient, total pressure loss coefficient and the corner separation size. Without the quadratic constitutive relation model, the separation size and loss are generally over-estimated. The mechanism of the improvement is studied using both the vortex dynamics and the momentum equation. It is proved that quadratic constitutive relation model consumes low CPU time and provides much improved compressor corner separation prediction without worsening the convergence property.

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