Original scientific paper

A LINEAR THEORY FOR LEEWAVE ROTORS

P.F. Sheridan ; Met Office FitzRoy Road Exeter EX1 3PB UK
S.B. Vosper ; Met Office FitzRoy Road Exeter EX1 3PB UK

Abstract

A linear theory for the prediction of rotor formation under trapped lee waves has been developed. The theory is based on the assumption that the flow can be divided into two layers: an outer region in which the flow is inviscid, and an inner region close to the ground where turbulent stresses are important. The flow in the inner region is driven by the pressure gradient due to lee waves aloft. A simple mixing-length turbulence closure is assumed and for a given lee-wave pressure field, analytic solutions to the inner-region flow are obtained. Results from the linear theory are compared with a series of two-dimensional numerical simulations in which a sharp temperature inversion is present upwind of a ridge. Lee waves may form on the inversion, which when of sufficient amplitude, give rise to flow separation and rotors underneath the wave crests. The point at which linear theory predicts flow separation underneath the wave crests is shown to correspond, approximately, to the occurrence of lee-wave rotors in the numerical results and a flow regime diagram based on linear theory is constructed and compared to that obtained from the simulations.

Keywords

rotors; linear theory

Hrčak ID:

64527

URI

https://hrcak.srce.hr/64527

Publication date:

15.12.2005.

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