Experimental Observations and Numerical Simulations of Wave Impact Forces on Recurved Parapets Mounted Above a Vertical Wall

Abstract

Large-scale hydraulic model tests and detail numerical model investigations were conducted on recurved wave deflecting structures to aid in the design of wave overtopping mitigation for vertical walls in shallow water. The incident wave and storm surge conditions were characteristic return period events for an offshore island on the North Slope of Alaska. During large storm events, despite depth-limited wave heights, a proposed vertical wall extension was susceptible to wave overtopping, which could potentially cause damage to equipment. Numeric calculations were conducted prior to the experimental tests and were used to establish the relative effectiveness of several recurved parapet concepts. The numerical simulations utilized the COrnell BReaking waves and Structures (COBRAS) fluid modeling program, which is a Volume-of-Fluid (VOF) model based on Reynolds Averaged Navier-Stokes equations [1] [2]. The experimental testing was conducted in the Large Wave Flume (LWF) at Oregon State University, O.H. Hinsdale Wave Research Laboratory. The experimental test directly measured the base shear force, vertical force, and overturning moment applied to the recurved parapets due to wave forcing. Wave impact pressure on the parapet and water particle velocities seaward of the wall were also measured. Results from the experimental testing include probability of exceedance curves for the base shear force, vertical force, and overturning moment for each storm condition. Qualitative comparisons between the experimental tests and the COBRAS simulations show that the numerical model provides realistic flow on and over the parapet.