Dependence of boundary layer thickness on layer height in laminar and transient convective regimes

TL;DR

This study investigates how boundary layer thickness in laminar and transient convection regimes depends on layer height, revealing it is primarily influenced by temperature difference and fluid properties rather than layer height.

Contribution

It provides experimental evidence that boundary layer thickness in laminar and transient convection is largely independent of layer height, contrary to common assumptions.

Findings

Boundary layer thickness is mainly determined by temperature difference.

It is almost independent of layer height in laminar and transient regimes.

Results cover a wide range of Rayleigh, Prandtl numbers, and aspect ratios.

Abstract

Dependence of boundary layer thickness on layer height in laminar and transient regimes is studied for convection from localised heat source with an open surface. The measurements of Nusselt number and characteristic frequency of thermal plume formation are done for a wide range of Rayleigh number, different Prandtl numbers and different aspect ratios. The obtained results prove that for the developed (but not turbulent) convective flow the boundary layer thickness is almost independent of the layer height and it is mainly defined by applied temperature difference and physical properties of the fluid.