Stably stratified air with buoyancy frequency and upstream speed approaches a ridge…

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Convection, rotation and geophysical flows · Convection, rotation and geophysical flows

Fluid Dynamics, Ch Stratified flow, double diffusion and geophysical scales

Problem

Stably stratified air with buoyancy frequency N=0.015 s−1N = 0.015\,\mathrm{s^{-1}} and upstream speed U=3.0 m s−1U = 3.0\,\mathrm{m\,s^{-1}} approaches a ridge of height H=900 mH = 900\,\mathrm{m}. The flow is steady, inviscid and Boussinesq, and the approach flow has no horizontal density variation before it meets the ridge. ((a)) Calculate the Froude number Fr=U/(NH)Fr = U/(NH). ((b)) Calculate the dividing-streamline height zdz_d below which the air cannot cross the ridge and instead goes round it. ((c)) Calculate the wind speed that would be needed for all the air to pass over the ridge.

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