Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Geological and Atmospheric Sciences

First Advisor

Eugene Takle

Abstract

The present study investigates basic aspects of the flow of a density-stratified fluid past three-dimensional obstacles for Froude number ~ O(1) and isolated surface thermal forcing representative of diurnally varying mesoscale flows past mountainous islands such as Hawaii. In order to minimize parameter space, we have excluded the effects of friction, rotation, nonuniform ambient flow, and the complexities of realistic surface boundary layer and terrain. Through simple scaling arguments, we deduce that the parameter [eta][superscript]* [[eta][superscript]*≡L[superscript]*[macron] Q[over] Uh≤ft([partial][macron][theta][over][partial] z)[superscript]-1 ~ O(1) for mesoscale flows]controls thermally forced flows for a given Froude number, and we provide crude estimates of a flow response for a range of [eta][superscript]*. The principal question addressed is for what values of [eta][superscript]* will a transition occur from the low-Froude-number flow regime, characterized by the stagnation and splitting of the lower upwind flow, to the regime in which flow passes over rather than around the obstacle. We show that the linear theory captures such a tendency consistently with simple scaling arguments. To provide quantitative measures of flow variability with the Froude number and [eta][superscript]*, we employ an efficient isentropic numerical code and summarize the results of numerous simulations in the form of a regime diagram. The principal result is a simple criterion for the transition of a heated flow from the blocked to unblocked flow regime. We illustrate the relevance of the idealized study to natural flows with an example of applications to a flow past the Hawaiian Archipelago.

DOI

https://doi.org/10.31274/rtd-180813-11102

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Jon Reisner

Language

en

Proquest ID

AAI9311529

File Format

application/pdf

File Size

104 pages

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