Mixed convection heat and mass transfer along a vertical wavy surface

Publisher Summary This chapter discusses the onset and development of thermal convection in fully developed shear flows. The subject of thermal convection in shear flows is rich in results that have both basic interest and practical importance in science and engineering. Although the field has matured greatly during the part 15 years, many topics still need study. For instance, the effects of channel sidewalls on both the initial instability and the instability of longitudinal rolls need to be clarified both theoretically and experimentally. More effort should be devoted to the use of controlled disturbances in studying the onset of instability due to the convective nature of the instability. Such studies might prove useful also in suggesting how turbulent convection can be promoted or postponed in shear flows. This chapter presents an in-depth account of the basic concepts and of some of the major results that have occurred during the past 15 years. It focuses primarily on simple basic states involving a Boussinesq fluid and fully developed forced flows, mainly of the Couette or Poiseuille type. The chapter also provides some references to similar phenomena in other basic flows, for example, when the basic flow itself is due to natural (or “free”) convection.

The Onset and Development of Thermal Convection in Fully Developed Shear Flows

https://hal-upec-upem.archives-ouvertes.fr/hal-00695272/document

Revue bibliographique sur les écoulements de Poiseuille–Rayleigh–Bénard : écoulements de convection mixte en conduites rectangulaires horizontales chauffées par le bas

Return flows in horizontal MOCVD reactors studied with the use of TiO2 particle injection and numerical calculations

Near-wall structures in turbulent natural convection at Rayleigh numbers of $10^{10}$ to $10^{11}$ at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR= 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. the mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log–normal probability distribution function, independent of the rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-rayleigh-number turbulent natural convection are likely to be laminar mixed convection type.

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J.R. Maughan

Papers

Experiments on mixed convection heat transfer for airflow in a horizontal and inclined channel

Regions of heat transfer enhancement for laminar mixed convection in a parallel plate channel