Relaxation of the Turbulent Boundary Layer After an Abrupt Change From Rough to Smooth Wall (Data Bank Contribution)

1993 ◽  
Vol 115 (3) ◽  
pp. 379-382 ◽  
Author(s):  
R. P. Taylor ◽  
J. K. Taylor ◽  
M. H. Hosni ◽  
H. W. Coleman
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Abrupt Change ◽  
Plate Boundary ◽  
Data Bank ◽  
Skin Friction Coefficient ◽  
Step Change ◽  
Test Surface ◽  
Layer Flow ◽  
Flat Plate Boundary Layer

Measurements of velocity and turbulence intensity profiles and skin friction coefficient are presented for turbulent flat-plate boundary layer flow over a test surface with a rough-to-smooth step change in surface roughness. The first 0.9 m length of the test surface is roughened with 1.27 mm diameter hemispheres spaced 2 base diameters apart in a uniform staggered array, and the remaining 1.5 m length is smooth. The profiles are compared with previous data for all-rough cases under closely matched conditions in the same facility. The skin friction data are compared with previous data for both all-rough and all-smooth cases.

Boundary-layer flow of a micropolar fluid on a continuous moving or fixed surface

2006 ◽  
Vol 84 (5) ◽  
pp. 399-410 ◽  
Author(s):  
Anuar Ishak ◽  
Roslinda Nazar ◽  
Ioan Pop
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Boundary Layer Flow ◽  
Micropolar Fluid ◽  
Plane Surface ◽  
Velocity Ratio ◽  
Skin Friction Coefficient ◽  
Keller Box Method ◽  
Moving Plane ◽  
Layer Flow

The present paper deals with the analysis of boundary-layer flow of a micropolar fluid on a fixed or continuous moving plane surface. Both parallel and reverse moving surfaces to the free stream are considered. The resulting system of nonlinear ordinary differential equations is solved numerically using the Keller-box method. Numerical results are obtained for skin friction coefficient, local Nusselt number, velocity, angular velocity, and temperature profiles. The results indicate that the effect of the material parameter on skin friction and heat transfer depends on the velocity ratio of the plate and the fluid.PACS No.: 47.15.Cb

Heat Transfer in the Turbulent Boundary Layer With a Step Change in Surface Roughness

1991 ◽  
Author(s):  
Robert P. Taylor ◽  
J. Keith Taylor ◽  
M. H. Hosni ◽  
Hugh W. Coleman
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Surface Roughness ◽  
Smooth Surface ◽  
Plate Boundary ◽  
Step Change ◽  
Stanton Number ◽  
Test Surface ◽  
Temperature Profiles ◽  
Boundary Layer Flows

Measurements of Stanton numbers, velocity profiles, temperature profiles, and turbulence intensity profiles are reported for turbulent flat plate boundary layer flows with a step change in surface roughness. The first 0.9 m length of the test surface is roughened with 1.27 mm diameter hemispheres spaced 2 base diameters apart in a staggered array. The remaining 1.5 m length is smooth. The experiments show that the step change from a rough to a smooth surface has a dramatic effect on the convective heat transfer. In many cases, the Stanton number drops below the smooth-wall correlation immediately downstream of the change in roughness. The Stanton number measurements are compared with predictions using the discrete element method with excellent results.

Boundary layer flow near stagnation-points on a vertical surface with slip in the presence of transverse magnetic field

2014 ◽  
Vol 24 (3) ◽  
pp. 643-653 ◽  
Author(s):  
Ibrahim Yakubu Seini ◽  
Daniel Oluwole Makinde
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Boundary Layer ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Stagnation Point ◽  
Vertical Surface ◽  
Skin Friction Coefficient ◽  
Content Type ◽  
Layer Flow

Purpose – The purpose of this paper is to investigate the MHD boundary layer flow of viscous, incompressible and electrically conducting fluid near a stagnation-point on a vertical surface with slip. Design/methodology/approach – In the study, the temperature of the surface and the velocity of the external flow are assumed to vary linearly with the distance from the stagnation-point. The governing differential equations are transformed into systems of ordinary differential equations and solved numerically by a shooting method. Findings – The effects of various parameters on the heat transfer characteristics are discussed. Graphical results are presented for the velocity and temperature profiles whilst the skin-friction coefficient and the rate of heat transfers near the surface are presented. It is observed that the presence of the magnetic field increases the skin-friction coefficient and the rate of heat transfer near the surface towards the stagnation-point. Originality/value – The presence of magnetic field increases the skin-friction coefficient and the rate of heat transfer near the surface towards the stagnation-point.

scholarly journals Modeling of Laminar-Turbulent Transition in Boundary Layers and Rough Turbine Blades

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Liang Wei ◽  
Xuan Ge ◽  
Jacob George ◽  
Paul Durbin
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Skin Friction ◽  
Current Model ◽  
Turbine Blades ◽  
Great Influence ◽  
Plate Boundary ◽  
Freestream Turbulence ◽  
Roughness Effects ◽  
Flat Plate Boundary Layer

A local, intermittency-function-based transition model was developed for the prediction of laminar-turbulent transitional flows with freestream turbulence intensity Tu at low (Tu < 1%), moderate (1% < Tu < 3%), and high Tu > 3% levels, and roughness effects in a broad range of industrial applications such as turbine and helicopter rotor blades, and in nature. There are many mechanisms (natural or bypass) that lead to transition. Surface roughness due to harsh working conditions could have great influence on transition. Accurately predicting both the onset location and length of transition has been persistently difficult. The current model is coupled with the k–ω Reynolds-averaged Navier–Stokes (RANS) model, that can be used for general computational fluid dynamics (CFD) purpose. It was validated on the ERCOFTAC experimental zero-pressure-gradient smooth flat plate boundary layer with both low and high leading-edge freestream turbulence intensities. Skin friction profiles agree well with the experimental data. The model was then tested on ERCOFTAC experimental flat plate boundary layer with favorable/adverse pressure gradients cases, periodic wakes, and flows over Stripf's turbine blades with roughness from hydraulically smooth to fully rough. The predicted skin friction and heat transfer properties by the current model agree well with the published experimental and numerical data.

Boundary Layer Transition Induced by Periodic Wakes

1998 ◽  
Vol 122 (3) ◽  
pp. 442-449 ◽  
Author(s):  
Xiaohua Wu ◽  
Paul A. Durbin
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
Skin Friction ◽  
Plate Boundary ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Layer Transition ◽  
Benchmark Data ◽  
Flat Plate Boundary Layer

Turbulent wakes swept across a flat plate boundary layer simulate the phenomenon of wake-induced bypass transition. Benchmark data from a direct numerical simulation of this process are presented and compared to Reynolds-averaged predictions. The data are phase-averaged skin friction and mean velocities. The predictions and data are found to agree in many important respects. One discrepancy is a failure to reproduce the skin friction overshoot following transition. [S0889-504X(00)00503-1]

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