Unveröffentlichtes Dokument,
Unsteady near-shore natural convection induced by ramped isothermal surface heating
(01.03.2012)
Zusammenfassung
The present investigation is concerned with natural convection induced by ramped
isothermal heating at the water surface in a wedge-shaped coastal domain. A
semi-analytical approach coupled with scaling analysis and numerical simulation is
adopted to resolve the problem. It is revealed that the flow domain is composed of
two distinct sub-regions, a conductive region near the shore which finally becomes isothermal and stationary and a convective region offshore which eventually maintains a steady flow velocity. Different scenarios are revealed through the comparison between the ramp duration P and the characteristic time scales tc. For the conductive region, the characteristic time scale is the time for the thermal boundary layer formed at the surface to reach the local bottom. For the convective region, it is the steady state time when convection balances conduction. If P < tc, no steady state is reached before the ramp finishes. On the other hand, if P > tc, for both sub-regions, a quasi-steady state is reached before the ramp finishes. For the conductive region, the quasi-steady state is characterized by a steady flow velocity and the same local temperature growth rate as the water surface. For the convective region, the quasi-steady state is characterized by a change in the growth rate of velocity. The maximum velocity for the conductive region and the steady-state velocity for the convective region are the same as the corresponding constant isothermal heating case.
Major time and velocity scales governing the flow development in both regions are proposed by semi-analytical solution coupled with scaling and verified by the numerical simulation.
