The interaction between waves and an overlying airflow
File(s)
Author(s)
Black, Duncan
Type
Thesis
Abstract
This dissertation examines the interaction between a series of progressive gravity waves
and an overlying airflow. A critical review of the existing literature is made, from which
it is concluded that although a large number of wind-wave interactions have been
proposed, few have been verified experimentally. Furthermore, virtually no
consideration has been given to the effect of the airflow on the underlying wave motion.
A comprehensive experimental investigation of the interaction between wind and waves
has therefore been undertaken. In respect of the airflow, a complete set of kinematics measurements, involving both
horizontal and vertical velocity data, is presented. The mean, wave-induced and
fluctuating velocities are presented in a wave-following frame of reference. The flow
streamlines are deduced from the measured velocity data, and the structure of the
airflow examined in detail. Analysis of the velocity profiles using boundary layer theory
enables the effects of the flow structure identified above to be quantified and an
assessment of the surfece stresses made.
A corresponding set of kinematics measurements were undertaken in the underlying
water flow. The wind-induced currents and wave kinematics are examined. Numerical
models to predict the wave motion in combined wind-wave field are developed. The
models incorporate the effects of a wind-induced current and the varying surface
stresses, and allow the relative importance of each of these effects to be investigated.
Furthermore, measurements of the water surface elevation are used to investigate the
modification to the underlying long waves caused by the airflow, and the nature of the
superposed wind-waves. The variation in the properties of the wind-generated waves
with the phase of the long waves are also examined. Finally, the fundamental
mechanisms of wind-wave interaction are considered, and the relative importance of the
various mechanisms assessed. The implications for the oflfehore engineer, in terms of wind loading, gas ventilation and wave loading are outlined.
and an overlying airflow. A critical review of the existing literature is made, from which
it is concluded that although a large number of wind-wave interactions have been
proposed, few have been verified experimentally. Furthermore, virtually no
consideration has been given to the effect of the airflow on the underlying wave motion.
A comprehensive experimental investigation of the interaction between wind and waves
has therefore been undertaken. In respect of the airflow, a complete set of kinematics measurements, involving both
horizontal and vertical velocity data, is presented. The mean, wave-induced and
fluctuating velocities are presented in a wave-following frame of reference. The flow
streamlines are deduced from the measured velocity data, and the structure of the
airflow examined in detail. Analysis of the velocity profiles using boundary layer theory
enables the effects of the flow structure identified above to be quantified and an
assessment of the surfece stresses made.
A corresponding set of kinematics measurements were undertaken in the underlying
water flow. The wind-induced currents and wave kinematics are examined. Numerical
models to predict the wave motion in combined wind-wave field are developed. The
models incorporate the effects of a wind-induced current and the varying surface
stresses, and allow the relative importance of each of these effects to be investigated.
Furthermore, measurements of the water surface elevation are used to investigate the
modification to the underlying long waves caused by the airflow, and the nature of the
superposed wind-waves. The variation in the properties of the wind-generated waves
with the phase of the long waves are also examined. Finally, the fundamental
mechanisms of wind-wave interaction are considered, and the relative importance of the
various mechanisms assessed. The implications for the oflfehore engineer, in terms of wind loading, gas ventilation and wave loading are outlined.
Version
Open Access
Date Issued
1998-03
Date Awarded
1998
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Swan, Chris
Publisher Department
Civil Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Author Permission
Permission granted