Pressure gradients in the inner surf and outer swash zone: a laboratory and numerical investigation
Date
2011
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Publisher
University of Delaware
Abstract
A need exists to understand better coastal processes emphasizing coastal sediment transport. Morphologic variability of shorelines is partially controlled by surf and swash-zone processes. Sediment is transported in the surf and swash zone due to a combination of hydrodynamic elements. The primary mechanisms are the wave characteristics, sediment characteristics and the beach slope. All of these can be categorized as boundary conditions which are imposed on the swash zone by the underlying bed and the surf zone. One possible improvement to models predicting the sediment transport is the inclusion of a pressure gradient term. For this term to be considered important, a thorough lab and model investigation is detailed in this thesis. The presence and magnitude of total pressure gradients is investigated. To do this, a measurement technique that incorporates the total pressure under a wave was developed. The experimental results were compared with the results of a robust 2D numerical model for the test case of a solitary wave propagating over a =typical‘ beach face. 10 solitary wave tests were conducted in a laboratory wave flume to investigate the horizontal pressure gradient under a wave. These experimental tests showed that using the nearbed pressure sensors instead of a proxy yielded a higher shoreward pressure gradient in the surf zone under a passing wave. The numerical model performed well in predicting the experimental pressure gradient and provided a more spatially detailed analysis of the importance of the pressure gradient as the wave propagates through the surf and swash zones.