S. Nelmes

Doctor of Philosophy, Oxford University, Trinity Term 1999

The Aerodynamic Characterisation of Shelterbelts

Summary

This thesis describes a series of 1:75 scale wind tunnel experiments and a full-scale experiment, investigating the flow around a shelterbelt. A shelterbelt is a row of trees planted to provide shelter. The experiments were designed to identify a single aerodynamic characterising parameter, which would be uniquely related to the flow behind the shelterbelt. The identification of such a parameter would allow quantification of the shelter effect of a particular shelterbelt without the need for extensive field tests.

Described in this thesis is an aerodynamic characterising parameter known as s. It was identified through wind tunnel tests and was verified through comparison of mean velocity profiles downstream of a full-scale and model shelterbelt. The value of s is calculated from the mean and r.m.s. horizontal velocity measured at two points close to the ground and shelterbelt. In order for a characterising parameter to be worthwhile, it should be easy to measure and robust; these properties are exhibited by s.

The second part of this thesis explores definitions of shelter for different objects, which are necessary to assess the effectiveness of a shelterbelt. Animals, plants, pedestrians and soil were considered, and wind-shelter criteria were established for each object. The results from the wind tunnel tests and the shelter criteria for different objects were combined in a database to produce an indication of the effectiveness of a shelterbelt given its value of s. Construction of the database is described in this thesis.

(no thesis available)