Vortex Instability of Mixed Convection Flow over a Horizontal Flat Plate

1981 ◽  
Vol 103 (2) ◽  
pp. 257-261 ◽  
Author(s):  
A. Moutsoglou ◽  
T. S. Chen ◽  
K. C. Cheng
Keyword(s):  
Mixed Convection ◽  
Flat Plate ◽  
Wave Mode ◽  
Longitudinal Vortex ◽  
Linear Stability Theory ◽  
Convection Flow ◽  
Spanwise Direction ◽  
Mixed Convection Flow ◽  
Vortex Instability ◽  
Laminar Mixed Convection

The vortex instability of laminar, mixed-convection flow over an isothermal, horizontal flat plate is investigated analytically by the linear stability theory. In the analysis, the main flow and thermal fields are treated as non-parallel and the disturbances are assumed to have the form of a stationary longitudinal vortex roll that is periodic in the spanwise direction. Numerical results for the critical Grashof and Reynolds numbers that predict the first occurrence of the vortex rolls are obtained for fluids with Prandtl numbers of 0.7 and 7. It is found that the flow becomes more susceptible to vortex mode of instability as the buoyancy force increases. The present results are compared with available experimental data and also with analytical results from the wave mode of instability.

Coupled Thermal Radiation and Mixed Convection Step Flow of Nongray Gas

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
M. Atashafrooz ◽  
S. A. Gandjalikhan Nassab ◽  
K. Lari
Keyword(s):  
Mixed Convection ◽  
Radiative Transfer Equation ◽  
Convection Flow ◽  
Mixed Convection Flow ◽  
Discrete Ordinate ◽  
Full Spectrum ◽  
Step Flow ◽  
Laminar Mixed Convection ◽  
Gray Medium ◽  
Hydrodynamic Behaviors

The main goal of this paper is to analyze the thermal and hydrodynamic behaviors of laminar mixed convection flow of a nongray radiating gas over an inclined step in an inclined duct. The fluid is considered an air mixture with 10% CO2 and 20% H2O mole fractions, which is treated as homogeneous, absorbing, emitting, and nonscattering medium. The full-spectrum k-distribution (FSK) method is used to handle the nongray part of the problem, while the radiative transfer equation (RTE) is solved using the discrete ordinate method (DOM). In addition, the results are obtained for different medium assumptions such as pure mixed convection and gray medium to compare with the nongray calculations as a real case. The results show that in many cases, neglecting the radiation part in computations and also use of gray simulations are not acceptable and lead to considerable errors, especially at high values of the Grashof number in mixed convection flow.

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