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Title: Numerical Investigation of Hydrodynamic Stability of Inward Radial Rayleigh-Bènard-Poiseuille Flow
Since the generation of green and clean renewable energy is a major concern in the modern era, solar energy conversion technologies such as the solar chimney power plant are gaining more attention. In order to accurately predict the performance of these power plants, hydrodynamic instabilities that can lead to large-scale coherent structures which affect the mean flow, have to be identified and their onset has to be predicted accurately. The thermal stratification of the collector flow (resulting from the temperature difference between the heated bottom surface and the cooled top surface) together with the opposing gravity can lead to buoyancy-driven instability. As the flow accelerates inside the collector, the Reynolds number can get large enough for viscous (Tollmien-Schlichting) instability to occur. A new highly accurate compact finite difference Navier-Stokes code in cylindrical coordinates has been developed for the spatial stability analysis of such radial flows. The new code was validated for a square channel flow. Stability results for different stable and unstable Reynolds/Rayleigh number combinations were in good agreement with temporal stability simulations as well as linear stability theory. To investigate the radial flow effect, spatial stability simulations were then carried out for a computational domain with constant streamwise extent and different outflow radii. The Reynolds and Rayleigh number were chosen such that buoyancy-driven instability occured. For cases with significant radial flow effect, the spatial growth rates of the azimuthal modes were found to vary considerably in the streamwise direction.  more » « less
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2018 AIAA Aerospace Sciences Meeting
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Sponsoring Org:
National Science Foundation
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  5. null (Ed.)
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