Pressure, sonar profiling, and current measurements were recorded at 5.5-, 8-, and 13-m water depths in the outer surf zone and inner continental shelf region off the coast of Duck, North Carolina. This unique data set was analyzed to investigate wave evolution by comparing estimates from linear wave theory with field measurements. Energy flux calculations combining shoaling and refraction theory showed smaller measured than predicted energy flux values at the two inshore locations (sometimes by more than one third), emphasizing the importance of considering energy loss in engineering design and planning calculations. A wave friction factor for each record was determined by accounting for frictional energy loss in the energy flux calculation, using velocity time series measured 0.20, 0.55, and 1.50 m above the sea floor. Calculated friction factors varied throughout storm events, but most fell within a range of 0 to 0.1. Wave friction factors calculated using the total measured velocity time series showed a narrower range (0 to 0.05) than those calculated from demeaned velocities (0 to 0.1). Representative wave friction factors of 0.053 (demeaned velocity) and 0.0209 (total velocity) were identified for this location using a least squares fit between energy flux decay and |ub|3Δx over all storm events.
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1 November 2006
Wave Friction Factors from Energy Flux Comparisons Outside of the Surf Zone
Jodi L. Eshleman,
Robert G. Dean,
Kent K. Hathaway
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energy dissipation
Energy flux
Nearshore
Wave shoaling