Local similarity relationships in a horizontally inhomogeneous boundary layer

1990 ◽  
Vol 52 (1-2) ◽  
pp. 17-40 ◽  
Author(s):  
Yaping Shao ◽  
J�rg M. Hacker
Keyword(s):  
Boundary Layer ◽  
Local Similarity ◽  
Similarity Relationships ◽  
Horizontally Inhomogeneous

Local Similarity Relationships In The Urban Boundary Layer

2002 ◽  
Vol 102 (1) ◽  
pp. 63-82 ◽  
Author(s):  
M. H. Al-Jiboori ◽  
Yumao Xu ◽  
Yongfu Qian
Keyword(s):  
Boundary Layer ◽  
Urban Boundary Layer ◽  
Local Similarity ◽  
Similarity Relationships

scholarly journals The Cessation of Continuous Turbulence as Precursor of the Very Stable Nocturnal Boundary Layer

2012 ◽  
Vol 69 (11) ◽  
pp. 3097-3115 ◽  
Author(s):  
B. J. H. Van de Wiel ◽  
A. F. Moene ◽  
H. J. J. Jonker
Keyword(s):  
Boundary Layer ◽  
Time Scale ◽  
Nocturnal Boundary Layer ◽  
Surface Heat ◽  
Heat Extraction ◽  
Local Similarity ◽  
Temporary Reduction ◽  
Turbulent Friction ◽  
Near Surface ◽  
Flow Acceleration

Abstract The mechanism behind the collapse of turbulence in the evening as a precursor to the onset of the very stable boundary layer is investigated. To this end a cooled, pressure-driven flow is investigated by means of a local similarity model. Simulations reveal a temporary collapse of turbulence whenever the surface heat extraction, expressed in its nondimensional form h/L, exceeds a critical value. As any temporary reduction of turbulent friction is followed by flow acceleration, the long-term state is unconditionally turbulent. In contrast, the temporary cessation of turbulence, which may actually last for several hours in the nocturnal boundary layer, can be understood from the fact that the time scale for boundary layer diffusion is much smaller than the time scale for flow acceleration. This limits the available momentum that can be used for downward heat transport. In case the surface heat extraction exceeds the so-called maximum sustainable heat flux (MSHF), the near-surface inversion rapidly increases. Finally, turbulent activity is largely suppressed by the intense density stratification that supports the emergence of a different, calmer boundary layer regime.

Non-Darcian Boundary Layer Flow and Forced Convective Heat Transfer Over a Flat Plate in a Fluid-Saturated Porous Medium

1990 ◽  
Vol 112 (1) ◽  
pp. 157-162 ◽  
Author(s):  
A. Nakayama ◽  
T. Kokudai ◽  
H. Koyama
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Porous Medium ◽  
Flat Plate ◽  
Similarity Solution ◽  
Temperature Fields ◽  
Solid Boundary ◽  
Local Similarity ◽  
Viscous Term ◽  
Inertia Term

The local similarity solution procedure was successfully adopted to investigate non-Darcian flow and heat transfer through a boundary layer developed over a horizontal flat plate in a highly porous medium. The full boundary layer equations, which consider the effects of convective inertia, solid boundary, and porous inertia in addition to the Darcy flow resistance, were solved using novel transformed variables deduced from a scale analysis. The results from this local similarity solution are found to be in good agreement with those obtained from a finite difference method. The effects of the convective inertia term, boundary viscous term, and porous inertia term on the velocity and temperature fields were examined in detail. Furthermore, useful asymptotic expressions for the local Nusselt number were derived in consideration of possible physical limiting conditions.

Boundary Layer Analysis of Exothermic and Endothermic Kind of Chemical Reaction in the Flow of Non-Darcian Unsteady Micropolar Fluid along an Infinite Vertical Surface

2017 ◽  
Vol 28 ◽  
pp. 90-101 ◽  
Author(s):  
O.K. Koriko ◽  
A.J. Omowaye ◽  
Isaac Lare Animasaun ◽  
Idris O. Babatunde
Keyword(s):  
Boundary Layer ◽  
Differential Equations ◽  
Chemical Reaction ◽  
Micropolar Fluid ◽  
Local Heat Transfer ◽  
Flow Region ◽  
Local Similarity ◽  
Suction Parameter ◽  
Boundary Layer Analysis ◽  
Layer Analysis

The problem of unsteady non – Newtonian flow past a vertical porous surface in the presence of thermal radiation is investigated. Using the theory of boundary layer analysis, the flow of micropolar fluid in the presence of exothermic and endothermic kind of chemical reaction is considered. It is assumed that the relationship between the flow rate and the pressure drop as the fluid flows over a porous medium is non – linear. Using local similarity transformation, the governing partial differential equations of the physical model are reduced to ordinary differential equations. The corresponding boundary value problem is solved numerically using shooting method along with Runge-Kutta Gill method together with quadratic interpolation. It is found that increase in micro-rotation parameter increases the velocity while the micro- rotation decreases across the flow region. Maximum micro-rotation of tiny particles is guaranteed at higher values of suction parameter. Local heat transfer rate decreases with an increase in exothermic /endothermic parameter.

scholarly journals The Critical Richardson Number and Limits of Applicability of Local Similarity Theory in the Stable Boundary Layer

2012 ◽  
Vol 147 (1) ◽  
pp. 51-82 ◽  
Author(s):  
Andrey A. Grachev ◽  
Edgar L Andreas ◽  
Christopher W. Fairall ◽  
Peter S. Guest ◽  
P. Ola G. Persson
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Richardson Number ◽  
Similarity Theory ◽  
Local Similarity ◽  
Stable Boundary ◽  
Critical Richardson Number ◽  
Local Similarity Theory

scholarly journals Effects of Binary Chemical Reaction and Activation Energy on MHD Boundary Layer Heat and Mass Transfer Flow with Viscous Dissipation and Heat Generation/Absorption

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Kh. Abdul Maleque
Keyword(s):  
Activation Energy ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Differential Equations ◽  
Heat And Mass Transfer ◽  
Viscous Dissipation ◽  
Chemical Reaction ◽  
Heat Generation ◽  
Porous Plate ◽  
Local Similarity

We study an unsteady MHD free convection heat and mass transfer boundary layer incompressible fluid flow past a vertical porous plate in the presence of viscous dissipation, heat generation/absorption, chemical reaction, and Arrhenius activation energy. The plate is moving with uniform velocity. The chemical reaction rate in the function of temperature is also considered. The governing partial differential equations are reduced to ordinary differential equations by introducing local similarity transformation (Maleque (2010)) and then are solved numerically by shooting method using the Nachtsheim-Swigert iteration technique. The results of the numerical solution are then presented graphically as well as the tabular form for difference values of the various parameters.

Sign in / Sign up

Export Citation Format

Share Document