scholarly journals Hydromagnetic flow and heat transfer over a bidirectional stretching surface in a porous medium

2011 ◽  
Vol 15 (suppl. 2) ◽  
pp. 205-220 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Manzoor Ahmed ◽  
Zaheer Abbas ◽  
Muhammad Sajid
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Porous Medium ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Mhd Flow ◽  
Heat Transfer Analysis ◽  
Flow And Heat Transfer ◽  
Bidirectional Stretching

In this study, we present a steady three-dimensional magnetohydrodynamic (MHD) flow and heat transfer characteristics of a viscous fluid due to a bidirectional stretching sheet in a porous medium. The heat transfer analysis has been carried out for two heating processes namely (i) the prescribed surface temperature (PST) and (ii) prescribed surface heat flux (PHF). In addition the heat transfer rate varies along the surface. The similarity solution of the governing boundary layer partial differential equations is developed by employing homotopy analysis method (HAM). The quantities of interest are velocity, temperature, skin-friction and wall heat flux. The results obtained are presented through graphs and tabular data. It is observed that both velocity and boundary layer thickness decreases by increasing the porosity and magnetic field. This shows that application of magnetic and porous medium cause a control on the boundary layer thickness. Moreover, the results are also compared with the existing values in the literature and found in excellent agreement.

Direct Experimental Measurements of Heat Transfer Coefficient Augmentation due to Approach Flow Effects

2018 ◽  
Author(s):  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Experimental Program ◽  
The Heat Transfer Coefficient

The injection of film cooling can have a strong impact on the heat transfer coefficient (HTC) between the overflowing freestream gas and the cooled surface. This study investigated the influence of approach flow characteristics, including the boundary layer thickness and character (laminar and turbulent), as well as the approach flow Reynolds number, on the HTC. The influence of these parameters was previously unreported in the open film cooling literature. The figure of merit for this study was the HTC augmentation, that is the ratio of heat transfer coefficients for a cooled vs. uncooled surface. For this work, a direct measurement of the heat transfer coefficient was made, using a heated foil surface which provided a known wall heat flux. Generally for this type of measurement, a flux foil is placed downstream of the coolant hole. However, for this experimental program a heat flux foil was also placed upstream of the film cooling holes, in order to generate an upstream thermal boundary layer which would be more representative of actual engine conditions. Such a configuration has rarely been seen in published studies. An open-literature shaped-hole design was used, known as the 7-7-7 hole, in order to compare with existing results in the literature. A variety of blowing conditions were tested from M = 0.5–3.0. Two elevated density ratios of DR = 1.20 and DR = 1.80 were used. High-resolution IR thermography was used for these measurements, providing a highly-accurate and spatially-resolved measurement of HTC augmentation. The results indicated that turbulent boundary layer thickness had a modest effect on HTC augmentation, whereas a very high level of augmentation was observed for a laminar approach boundary layer. The presence of upstream heating greatly increased the HTC augmentation in the near-hole region, although these effects died out by 10–15 diameters from the holes.

Flow and heat transfer to Sisko fluid with partial slip

2016 ◽  
Vol 94 (8) ◽  
pp. 724-730 ◽  
Author(s):  
Masood Khan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Differential Equations ◽  
Layer Thickness ◽  
Analytical Solutions ◽  
Boundary Layer Thickness ◽  
Velocity Slip ◽  
Partial Slip ◽  
Exact Analytical Solutions ◽  
Flow And Heat Transfer

In this paper we study the partial slip effects on the flow and heat transfer of an incompressible non-Newtonian fluid over a nonlinear stretching sheet. The velocity slip boundary condition based on the Sisko constitutive fluid model is introduced. Suitable dimensionless variables are used to convert the governing partial differential equations into ordinary differential equations. Numerical solutions of these equations are obtained by the Runge–Kutta Fehlberg method. Additionally, the exact analytical solutions are presented in some special cases. The computational results for the velocity, temperature, skin-friction coefficient, and Nusselt number are presented in graphical and tabular forms. To validate the numerical results obtained, a comparison is made with the exact analytical solutions. The analysis of the results obtained shows that enhancement in the velocity slip parameter reduces the velocity as well as the momentum boundary layer thickness. However, quite the opposite is true with the temperature and corresponding thermal boundary layer thickness.

scholarly journals Modelling laminar transport phenomena in a Casson rheological fluid from an isothermal sphere with partial slip in a non-Darcy porous medium

2013 ◽  
Vol 40 (4) ◽  
pp. 469-510 ◽  
Author(s):  
Ramachandra Prasad ◽  
Subba Rao ◽  
Bhaskar Reddy ◽  
Anwar Bég
Keyword(s):  
Boundary Layer ◽  
Porous Medium ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Velocity Slip ◽  
Casson Fluid ◽  
Skin Friction Coefficient ◽  
Partial Slip ◽  
Flow And Heat Transfer ◽  
Fluid Parameter

The flow and heat transfer of Casson fluid from a permeable isothermal sphere in the presence of slip condition in a non-Darcy porous medium is analyzed. The sphere surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite-difference scheme. Increasing the velocity slip parameter is found to decrease the velocity and boundary layer thickness and increases the temperature and the boundary layer thickness. The velocity decreases with the increase the non-Darcy parameter and is found to increase the temperature. The velocity increases with the increase the Casson fluid parameter and is found to decrease the temperature. The Skin-friction coefficient and the local Nusselt number is found to decrease with the increase in velocity and thermal slip parameters respectively.

Flow and Heat Transfer of Jeffrey Fluid Over a Continuously Moving Surface With a Parallel Free Stream

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
T. Hayat ◽  
Z. Iqbal ◽  
M. Mustafa ◽  
S. Obaidat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Free Stream ◽  
Deborah Number ◽  
Jeffrey Fluid ◽  
Stream Velocity ◽  
Moving Surface ◽  
Flow And Heat Transfer

This communication studies the flow and heat transfer characteristics over a continuously moving surface in the presence of a free stream velocity. The Jeffrey fluid is treated as a rheological model. The series expressions of velocity and temperature fields are constructed by applying the homotopy analysis method (HAM). The influence of emerging parameters such as local Deborah number (β), the ratio of relaxation and retardation times (λ2), the Prandtl number (Pr), and the Eckert number (Ec) on the velocity and temperature profiles are presented in the form of graphical and tabulated results for different values of λ. It is found that the boundary layer thickness is an increasing function of local Deborah number (β). However, the temperature and thermal boundary layer thickness decreases with the increasing values of local Deborah number (β).

Boundary Layer Closure and Heat Transfer in Constant Base Pressure and Simple Wave Guns

1978 ◽  
Vol 100 (4) ◽  
pp. 690-696 ◽  
Author(s):  
A. D. Anderson ◽  
T. J. Dahm
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Method Of Characteristics ◽  
Simple Wave ◽  
Momentum Equation ◽  
Base Pressure ◽  
Two Dimensional ◽  
The Method Of Characteristics

Solutions of the two-dimensional, unsteady integral momentum equation are obtained via the method of characteristics for two limiting modes of light gas launcher operation, the “constant base pressure gun” and the “simple wave gun”. Example predictions of boundary layer thickness and heat transfer are presented for a particular 1 in. hydrogen gun operated in each of these modes. Results for the constant base pressure gun are also presented in an approximate, more general form.

Freestream Flow Effects on Film Effectiveness and Heat Transfer Coefficient Augmentation for Compound Angle Shaped Holes

2017 ◽  
Author(s):  
Joshua B. Anderson ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Gas Turbines ◽  
Boundary Layer Thickness ◽  
Adiabatic Effectiveness ◽  
Compound Angle

The use of compound-angled shaped film cooling holes in gas turbines provides a method for cooling regions of extreme curvature on turbine blades or vanes. These configurations have received surprisingly little attention in the film cooling literature. In this study, a row of laid-back fanshaped holes based on an open-literature design, were oriented at a 45-degree compound angle to the approaching freestream flow. In this study, the influence of the approach flow boundary layer thickness and character were experimentally investigated. A trip wire and turbulence generator were used to vary the boundary layer thickness and freestream conditions from a thin laminar boundary layer flow to a fully turbulent boundary layer and freestream at the hole breakout location. Steady-state adiabatic effectiveness and heat transfer coefficient augmentation were measured using high-resolution IR thermography, which allowed the use of an elevated density ratio of DR = 1.20. The results show adiabatic effectiveness was generally lower than for axially-oriented holes of the same geometry, and that boundary layer thickness was an important parameter in predicting effectiveness of the holes. Heat transfer coefficient augmentation was highly dependent on the freestream turbulence levels as well as boundary layer thickness, and significant spatial variations were observed.

scholarly journals Numerical Study of MHD Flow and Heat Transfer Through Porous Medium Between Two Parallel Plates With Hall and Ion Slip Effects

2020 ◽  
Vol 7 ◽  
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Numerical Study ◽  
Mhd Flow ◽  
Parallel Plates ◽  
Electrically Conducting ◽  
Flow And Heat Transfer ◽  
Slip Effects ◽  
Ion Slip ◽  
Temperature And Pressure

This paper studies the effects of Hall and ion slip on two dimensional incompressible flow and heat transfer of an electrically conducting viscous fluid in a porous medium between two parallel plates, generated due to periodic suction and injection at the plates. The flow field, temperature and pressure are assumed to be periodic functions in ti e ω and the plates are kept at different but constant temperatures. A numerical solution for the governing nonlinear ordinary differential equations is obtained using quasilinearization method. The graphs for velocity, temperature distribution and skin friction are presented for different values of the fluid and geometric parameters.

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