Regular and Breaking Waves in Wave Tank for Dispersion Effectiveness Testing

Abstract

The wave tank (32 m long × 2.0 m high × 0.6 m wide) at the Bedford Institute of Oceanography in Nova Scotia was used to simulate the propagation and breaking of deep water waves using a flap-type wavemaker. The water profile and velocity were measured using a wave gauge and an Acoustic Doppler Velocimeter (ADV). The wave periods of interest ranged between 1.18 and 2.08 seconds. A technique for generating breaking waves at the same location in the tank was used to obtain a spilling and a plunging breaker. We evaluated the energy dissipation rate at various depths in the tank for regular and breaking waves. Plunging breaking waves had heights of 0.25m. For the breaking experiments, the energy dissipation rate decreased from around 1.0 10−2 watts/kg a few centimeters below the surface to less than 5.0 10−4 watt/kg 20 cm deep in the water column. The regular waves had, on the average, an energy dissipation rate of 5.0 10−6 watt/kg deep in the water column. This indicates that breaking plays an important role in the dispersion of oil at sea.

Evaluating Chemical Dispersant Efficacy in an Experimental Wave Tank: 1, Dispersant Effectiveness as a Function of Energy Dissipation Rate

“…The energy dissipation rates declined exponentially to approximately 0.001 W Á kg À1 for the two breaking wave conditions at a depth of 30 cm and decreased linearly under regular nonbreaking wave conditions (Wickley-Olsen et al, 2008). The average energy dissipation rates of the three wave conditions that were investigated in this research are similar to the mixing energies observed in the field.…”

“…Plunging breaking waves were produced with a 12-cm flap stroke and alternating trains of high-frequency waves (0.85 Hz, wave length 2.16 m, wave height 26 cm, and duration 20 s) and lowfrequency waves (0.5 Hz, wave length 6.24 m, wave height 9 cm, and duration 5 s). The characterization of the wave tank hydrodynamics has been reported in detail elsewhere (Wickley-Olsen et al, 2008).…”

Theoretical Foundation for Predicting Dispersion Effectiveness Due to Waves

“…It is reasonable to assume that the dispersion of oil due to waves occurs primarily near the water surface, where water velocity is usually highest for any type of waves, and especially breaking waves as can be noted from the results of Rapp and Melville (1990) and our own results (Wickley-Olsen et al, 2007). Thus, one may neglect additional dispersion from deep zones in the wave tank.…”

“…The theory is that long period waves propagate faster than small period waves. Further details about the approach could be found in Wickley-Olsen et al (2007). Our work herein relies on the new results presented in Wickley-Olsen et al(2008), where a plunging breaker resulted.…”

“…fluent.com) to estimate both the transport properties of the plume and the mixing energy at various locations near the water-air interface. The mixing energy is quantified by the dissipation rate of kinetic energy per unit water mass, , which was estimated following the approach of Wickley-Olsen et al (2007) for a smaller tank with different wave conditions. For more discussion on , the reader is urged to consult the works of (Kaku et al, 2002;Kaku et al, 2006a;Kaku et al, 2006b).…”