Effects of adverse and favorable pressure gradients on entropy generation in a transitional boundary layer region under the influence of freestream turbulence

Conditional sampling has been performed on data from a transitional boundary layer subject to high (initially 9%) freestream turbulence and strong (K=ν/U∞2dU∞/dx as high as 9×10−6) acceleration. Methods for separating the turbulent and nonturbulent zone data based on the instantaneous streamwise velocity and the turbulent shear stress were tested and found to agree. Mean velocity profiles were clearly different in the turbulent and nonturbulent zones, and skin friction coefficients were as much as 70% higher in the turbulent zone. The streamwise fluctuating velocity, in contrast, was only about 10% higher in the turbulent zone. Turbulent shear stress differed by an order of magnitude, and eddy viscosity was three to four times higher in the turbulent zone. Eddy transport in the nonturbulent zone was still significant, however, and the nonturbulent zone did not behave like a laminar boundary layer. Within each of the two zones there was considerable self-similarity from the beginning to the end of transition. This may prove useful for future modeling efforts.

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The Effect of Magnetic Field on Compressible Boundary Layer by Homotopy Analysis Method

Journal of the Indian Mathematical Society ◽

10.18311/jims/2021/26517 ◽

2021 ◽

Vol 88 (1-2) ◽

pp. 125

Author(s):

R. Madhusudhan ◽

Achala L. Nargund ◽

S. B. Sathyanarayana

Keyword(s):

Magnetic Field ◽

Boundary Layer ◽

Homotopy Analysis Method ◽

Adverse Pressure Gradient ◽

Analysis Method ◽

Boundary Layer Region ◽

Homotopy Analysis ◽

Curve Singularities ◽

Large Injection ◽

Layer Region

We analyse the effect of applied magnetic field on the flow of compressible fluid with an adverse pressure gradient. The governing partial differential equations are solved analytically by Homotopy analysis method (HAM) and numerically by finite difference method. A detailed analysis is carried out for different values of the magnetic parameter, where suction/ injection is imposed at the wall. It is also observed that flow separation is seen in boundary layer region for large injection. HAM is a series solution which consists of a convergence parameter h which is estimated numerically by plotting <em>h</em> curve. Singularities of the solution are identified by Pade approximation.

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Role of mixed nanofluids on fluid flow and intensify energy transfer in a boundary layer region driven by a free convective force

Heat Transfer-Asian Research ◽

10.1002/htj.21578 ◽

2019 ◽

Vol 48 (8) ◽

pp. 3986-3999 ◽

Cited By ~ 1

Author(s):

B. Ammani Kuttan ◽

S. Manjunatha ◽

S. Jayanthi ◽

B. J. Gireesha

Keyword(s):

Boundary Layer ◽

Energy Transfer ◽

Fluid Flow ◽

Boundary Layer Region ◽

Layer Region

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Jet Impingement of a Non-Newtonian Fluid

Fluids Engineering ◽

10.1115/imece2006-15993 ◽

2006 ◽

Author(s):

Jiangang Zhao ◽

Roger E. Khayat

Keyword(s):

Boundary Layer ◽

Free Surface ◽

Hydraulic Jump ◽

Similarity Solutions ◽

Surface Velocity ◽

Free Surface Velocity ◽

Viscous Boundary Layer ◽

Boundary Layer Region ◽

Layer Region ◽

Viscous Boundary

The similarity solutions are presented for the wall flow which is formed when a smooth planar jet of power-law fluids impinges vertically on to a horizontal plate, and spreads out in a thin layer bounded by a hydraulic jump. This problem is formulated analogous to radial jet flow problem and the solution procedure is accounted for by means of similarity solution of the boundary-layer equation [1] for Newtonian fluids. For the convenience of analysis, the flow may be divided into three regions, namely a developing boundary-layer region, a fully viscous boundary-layer region, and a hydraulic jump region. The similarity solutions of the film thickness and free surface velocity in fully viscous boundary-layer region include unknown constant L, which is solved numerically and approximately in the developing boundary-layer flow region. Comparison between the numerical and approximate solutions leads generally to good agreement, except for severely shear-thinning fluids. The boundary-layer solution depends on two parameters: power-law index n and α, the dimensionless flow parameters. The effect of α on film thickness and free surface velocity is investigated. The relations between the position of the hydraulic jump and dimensionless flow parameter are obtained and the effect of α on the position of the jump is presented.

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Stability of the laminar boundary layer in a streamwise corner

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1984.0048 ◽

1984 ◽

Vol 393 (1804) ◽

pp. 101-116 ◽

Cited By ~ 15

Keyword(s):

Boundary Layer ◽

Boundary Layer Problem ◽

Viscous Incompressible Flow ◽

Boundary Layer Region ◽

Dimensional Boundary ◽

The Mean ◽

Layer Region ◽

The Stability ◽

Infinite Boundary Value Problem ◽

Layer Problem

This work examines the stability of viscous, incompressible flow along a streamwise corner, often called the corner boundary-layer problem. The semi-infinite boundary value problem satisfied by small-amplitude disturbances in the ‘blending boundary layer’ region is obtained. The mean secondary flow induced by the corner exhibits a flow reversal in this region. Uniformly valid ‘first approximations’ to solutions of the governing differential equations are derived. Uniformity at infinity is achieved by a suitable choice of the large parameter and use of an appropriate Langer variable. Approximations to solutions of balanced type have a phase shift across the critical layer which is associated with instabilities in the case of two-dimensional boundary layer profiles.

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Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results

Geospace Mass and Energy Flow - Geophysical Monograph Series ◽

10.1029/gm104p0045 ◽

2013 ◽

pp. 45-49 ◽

Cited By ~ 1

Author(s):

Daniel M. Ober ◽

J. L. Horwitz ◽

D. L. Gallagher

Keyword(s):

Boundary Layer ◽

Outer Magnetosphere ◽

Boundary Layer Region ◽

Layer Region ◽

Initial Results

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Prediction of laminar, transitional and turbulent flow regimes, based on three-equation k-ω turbulence model

The Aeronautical Journal ◽

10.1017/s0001924000002438 ◽

2008 ◽

Vol 112 (1134) ◽

pp. 469-476 ◽

Cited By ~ 1

Author(s):

R. Taghavi-Zenouz ◽

M. Salari ◽

M. Etemadi

Keyword(s):

Boundary Layer ◽

Kinetic Energy ◽

Wind Turbine ◽

Flat Plate ◽

Turbine Blade ◽

Wind Turbine Blade ◽

Freestream Turbulence ◽

Boundary Layer Flows ◽

Laminar Separation ◽

Transitional Boundary Layer

Abstract A recently developed transitional model for boundary-layer flows has been examined on a flat plate and the well-known S809 wind turbine blade. Proposed numerical model tries to simulate streamwise fluctuations, induced by freestream turbulence, in pre-transitional boundary-layer flows by introducing an additional transport equation for laminar kinetic energy term. This new approach can be used for modeling of transitional flows which are exposed to both the freestream turbulence intensity and streamwise pressure gradient, which are known as the most dominant factors in occurrence of transition. Computational method of this model is based on the solution of the Reynolds averaged Navier-Stokes (RANS) equations and the eddy-viscosity concept. The model includes three transport equations of laminar kinetic energy, turbulent kinetic energy and dissipation rate frequency. The present model is capable of predicting either natural or bypass transitional mechanisms, which may occur in attached boundary-layer flows. In addition, the model can simulate transition in the separated free shear layers and the subsequent turbulent re-attachment to form a laminar separation bubble. Flat plate was exposed to different freestream turbulence intensities and streamwise pressure gradients. Wind turbine blade was examined under two different Reynolds numbers, with one of them suitable for the occurrence of laminar separation bubbles on its surfaces. To evaluate the performance of this new model in resolving transitional boundary-layer flows, final results have been compared to those obtained through application of conventional turbulence models. Comparison of final results for the flat plate and the S809 aerofoil with available experimental data show very close agreements.

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