Measurements of Turbulent Mixed Convection Flow Over a Vertical Forward-Facing Step

2003 ◽  
Author(s):  
H. I. Abu-Mulaweh ◽  
B. F. Armaly ◽  
T. S. Chen
Keyword(s):  
Mixed Convection ◽  
Free Stream ◽  
Free Stream Velocity ◽  
Heated Wall ◽  
Laser Doppler Velocimeter ◽  
Convection Flow ◽  
Stream Velocity ◽  
Convection Boundary Layer ◽  
Turbulent Natural Convection ◽  
Forward Facing Step

Measurements of turbulent mixed convection boundary-layer air flow over a two-dimensional, vertical forward-facing step are presented. The upstream and downstream walls and the step itself were heated to a uniform and constant temperature. Air velocity and temperature distributions and their turbulent fluctuations are measured simultaneously by using a two-component laser-Doppler velocimeter (LDV) and a cold wire anemometer were used, respectively. The present study treats buoyancy-dominated mixed convection over a vertical forward-facing step and examines the effect of a small free stream velocity on turbulent natural convection. It was found that the reattachment length increases while the heat transfer rate from the downstream heated wall decreases as the small free stream velocity increases.

Bioconvection in Casson nanofluid flow with Gyrotactic microorganisms and variable surface heat flux

2019 ◽  
Vol 12 (04) ◽  
pp. 1950041 ◽  
Author(s):  
I. S. Oyelakin ◽  
S. Mondal ◽  
P. Sibanda ◽  
D. Sibanda
Keyword(s):  
Heat Flux ◽  
Vertical Plate ◽  
Free Stream ◽  
Free Stream Velocity ◽  
Convection Flow ◽  
Stream Velocity ◽  
Constant Density ◽  
Gyrotactic Microorganisms ◽  
Casson Nanofluid ◽  
Variable Surface

This paper presents a two-dimensional unsteady laminar boundary layer mixed convection flow heat and mass transfer along a vertical plate filled with Casson nanofluid located in a porous quiescent medium that contains both nanoparticles and gyrotactic microorganisms. This permeable vertical plate is assumed to be moving in the same direction as the free stream velocity. The flow is subject to a variable heat flux, a zero nanoparticle flux and a constant density of motile microorganisms on the surface. The free stream velocity is time-dependent resulting in a non-similar solution. The transport equations are solved using the bivariate spectral quasilinearization method. A grid independence test for the validity of the result is given. The significance of the inclusion of motile microorganisms to heat transfer processes is discussed. We show, inter alia, that introducing motile microorganisms into the flow reduces the skin friction coefficient and that the random motion of the nanoparticles improves the rate of transfer of the motile microorganisms.

scholarly journals Mixed convection slip flow with temperature jump along a moving plate in presence of free stream

2015 ◽  
Vol 19 (1) ◽  
pp. 119-128 ◽  
Author(s):  
Gurminder Singh ◽  
Oluwole Makinde
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Free Stream ◽  
Slip Flow ◽  
Convection Flow ◽  
Stream Velocity ◽  
Physical Parameters ◽  
Local Similarity ◽  
Moving Plate ◽  
Linear Ordinary Differential Equations

In this paper, we examine the mixed convection flow with slip and convective heat transfer along a continuously moving vertical plate in the presence of uniform free stream. The plate and free stream velocity being in the same direction. The governing equations of continuity, momentum and energy for this boundary-layer flow are transformed into one set of coupled non-linear ordinary differential equations using the local similarity transformation and are then solved using the fourth-order Runge-Kutta method along with the shooting technique. The fluid flow and heat transfer distributions are discussed and presented graphically. Skin-friction and the Nusselt number at the plate surface are obtained for various values of the physical parameters and presented in tabular form and the physical aspects of these results are discussed.

Laminar Natural Convection Flow Over a Vertical Backward-Facing Step

1995 ◽  
Vol 117 (4) ◽  
pp. 895-901 ◽  
Author(s):  
H. I. Abu-Mulaweh ◽  
B. F. Armaly ◽  
T. S. Chen
Keyword(s):  
Natural Convection ◽  
Free Stream ◽  
Heated Wall ◽  
Laser Doppler Velocimeter ◽  
Convection Flow ◽  
Reattachment Length ◽  
Backward Facing Step ◽  
Natural Convection Flow ◽  
Temperature Distributions ◽  
Laminar Natural Convection

Measurements and predictions of laminar boundary-layer air flow in natural convection over a vertical two-dimensional backward-facing step are reported. The upstream and downstream walls and the step itself were heated to a uniform and constant temperature. The experiment was carried out for the ranges of step heights 3.5 mm ≤ s ≤ 9 mm, temperature differences of 5.8°C ≤ ΔT ≤ 23°C between the heated wall and the free stream (corresponding to 2.238 × 107 < Grxi < 8.877 × 107), and reference velocities of 0.24 m/s ≤ u* ≤ 0.47 m/s. Laser-Doppler velocimeter and cold-wire anemometer were utilized to measure, respectively, the velocity and the temperature distributions simultaneously. Flow visualization was also performed to determine the reattachment length. Measurements compare favorably with predictions. These results reveal that the step height significantly affects the velocity and temperature distributions, the friction coefficient, and the rate of heat transfer downstream of the backward-facing step.

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