Journal of Fluid Mechanics

Papers

Internal gravity waves generated by convective plumes

JOSEPH K. ANSONGa1 and BRUCE R. SUTHERLANDa2 c1

a1 Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, T6G 2G1, Canada

a2 Departments of Physics and of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, T6G 2G7, Canada

Abstract

We present experimental results of the generation of internal gravity waves by a turbulent buoyant plume impinging upon the interface between a uniform density layer of fluid and a linearly stratified layer. The wave field is observed and its properties are measured non-intrusively using axisymmetric Schlieren. In particular, we determine the fraction of the energy flux associated with the plume at the neutral buoyancy level that is extracted by the waves. On average, this was found to be approximately 4%. Within the limits of the experimental parameters, the maximum vertical displacement amplitude of waves were found to depend linearly upon the maximum penetration height of the plume beyond the neutral level. The frequency of the waves was found to lie in a narrow range relative to the buoyancy frequency. The results are used to interpret the generation of waves in the atmosphere by convective storms impinging upon the tropopause via the mechanical oscillator effect.

(Received July 09 2009)

(Revised October 30 2009)

(Accepted November 01 2009)

Correspondence:

c1 Email address for correspondence: bruce.sutherland@ualberta.ca

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