1. Wall temperatures in natural convection flow with laminar longitudinal vortices

1999 ◽  
Vol 2 (1) ◽  
pp. 3-3
Author(s):  
P. Jeschke ◽  
R. Biertümpfel ◽  
H. Beer
Keyword(s):  
Natural Convection ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Longitudinal Vortices

Flow Visualization Studies on Vortex Instability of Natural Convection Flow Over Horizontal and Slightly Inclined Constant-Temperature Plates

1988 ◽  
Vol 110 (3) ◽  
pp. 608-615 ◽  
Author(s):  
K. C. Cheng ◽  
Y. W. Kim
Keyword(s):  
Natural Convection ◽  
Flow Visualization ◽  
Ambient Air ◽  
Convection Flow ◽  
Turbulent Regime ◽  
Natural Convection Flow ◽  
Number Range ◽  
Grashof Number ◽  
Vortex Instability ◽  
Longitudinal Vortices

Flow visualization experiments were performed in a low-speed wind tunnel to study vortex instability of laminar natural convection flow along inclined isothermally heated plates having inclination angles from the horizontal of θ = 0, 5, 10, 15 and 20 deg. The temperature difference between plate surface and ambient air ranged from ΔT = 15.5 to 37.5°C and the local Grashof number range was Grx = 1.02×106 to 2.13×108. Three characteristic flow regimes were identified as follows: a two-dimensional laminar flow, a transition regime for developing longitudinal vortices, and a turbulent regime after the breakdown of the longitudinal vortices. Photographs are presented of side and top views of the flow and of cross-sectional views of the developing views of the developing secondary flow in the postcritical regime. Instability data of critical Grashof number and wavelength are presented and are compared with the theoretical predictions from the literature.

Longitudinal vortices in natural convection flow on inclined plates

1969 ◽  
Vol 37 (2) ◽  
pp. 251-255 ◽  
Author(s):  
E. M. Sparrow ◽  
R. B. Husar
Keyword(s):  
Natural Convection ◽  
Secondary Flow ◽  
Colour Change ◽  
Transition Process ◽  
Convection Flow ◽  
Inclined Plate ◽  
Natural Convection Flow ◽  
Longitudinal Vortices ◽  
Tollmien Schlichting ◽  
Inclined Plates

Experiments are performed to demonstrate the occurrence and explore the characteristics of a secondary flow superposed upon the natural convection main flow on an inclined plate. A flow visualization technique is employed whereby the flow pattern is made visible by local changes of colour of the fluid itself, the colour change being brought about by a change in pH. The secondary flow consists of longitudinal vortices or rolls distributed more or less periodically across the width of the plate. The number of such vortices increases with the temperature difference between the surface and the ambient fluid, but appears to be relatively insensitive to the inclination angle of the plate. The secondary flow results from the destabilizing effect of the buoyancy force component, which acts normal to the plate surface. The longitudinal vortices are the first stage of the laminarturbulent transition process. This is in contrast to the case of natural convection on a vertical plate, where the first stage of transition is Tollmien-Schlichting waves.

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