THERMAL INSTABILITY IN THERMAL ENTRANCE REGION OF PLANE COUETTE FLOW HEATED UNIFORMLY FROM BELOW

1986 ◽  
Author(s):  
C. K. Choi ◽  
С. B. Shin ◽  
S. T. Hwang
Keyword(s):  
Couette Flow ◽  
Thermal Instability ◽  
Entrance Region ◽  
Plane Couette Flow ◽  
Thermal Entrance Region ◽  
Thermal Entrance

Transient Analysis on the Onset of Thermal Instability in the Thermal Entrance Region of a Horizontal Parallel Plate Channel

1991 ◽  
Vol 113 (2) ◽  
pp. 363-370 ◽  
Author(s):  
F. S. Lee ◽  
G. J. Hwang
Keyword(s):  
Peclet Number ◽  
Parallel Plate ◽  
Transient Analysis ◽  
Thermal Instability ◽  
Entrance Region ◽  
Wave Number ◽  
Péclet Number ◽  
Thermal Entrance Region ◽  
Plate Channel ◽  
Thermal Entrance

A transient analysis on the onset of thermal instability in the thermal entrance region of a horizontal parallel plate channel, where the lower plate is heated isothermally, is presented. A novel time-dependent approach based on a three-dimensional linear stability theory is developed to determine the neutral stability position, where a disturbance neither grows nor decays with time. The range of parameters Pe=30, 40, 60, 80, and 100, and Pr=0.2, 0.7, 1.0, and 7.0 are covered in the study. One finds that increasing Prandtl number has a destabilizing effect on the flow for a fixed Peclet number along the streamwise direction. On the other hand, increasing Peclet number or Reynolds number tends to stabilize the flow. As the onset of thermal instability moves upstream, the critical Rayleigh number and the critical wave number are increased. The result shows a good agreement with the previous experimental investigations.

Periodic Forced Convection in a Darcy Metallic Foam: The LTNE Model

2012 ◽  
Author(s):  
Eugenia Rossi di Schio ◽  
Antonio Barletta
Keyword(s):  
Forced Convection ◽  
Outer Boundary ◽  
Method Of Lines ◽  
Mean Value ◽  
Entrance Region ◽  
Solid Matrix ◽  
Metallic Foam ◽  
The Method Of Lines ◽  
Thermal Entrance Region ◽  
Thermal Entrance

The present paper studies the thermal entrance region in a concentric annular duct filled by a fluid saturated porous metallic foam, with reference to steady forced convection and to a thermal boundary condition given by a wall temperature longitudinally varying with a sinusoidal law. The effect of viscous dissipation in the fluid is taken into account, and a two-temperature model is employed in order to evaluate separately the local fluid and solid matrix temperatures. The governing equations in the thermal entrance region are solved numerically by the method of lines. The Nusselt numer and its mean value in an axial period is evaluated, with reference both to the inner and the outer boundary.

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