MEASURING ENERGY DISSIPATION RATESIN A WAVE TANK

摘要

The effectiveness of dispersants is typically evaluated at variousrnscales ranging from the smallest (10 cm, typical of flask tests in thernlaboratory) to the largest (10's to 100's of meters, typical of fieldrnscale open water dispersion tests). This study aims at evaluatingrndispersant effectiveness at intermediate or pilot scale. The hypothesisrnis that the energy dissipation rate per unit mass, ε, plays arnmajor role in the effectiveness of a dispersant. Therefore, it is stipulatedrnthat in fairly general conditions, conservation of ε betweenrnthe wave tank scale and that of the field scale is sufficient to accuratelyrnevaluate the effectiveness of a dispersant to disperse oilrndroplets. A wave tank measuring 16 m long × 0.6 m wide × 2 mrndeep was constructed on the premises of the Bedford Institute ofrnOceanography, Halifax, Nova Scotia. Waves were generated usingrna flap-type wavemaker. Conditions of the breaking waves wererncreated using a dispersive focusing technique in which the wavernmaker is started at high frequency and then the frequencyrndecreased to create breaking waves. Experiments defining thernvelocity profile and energy dissipation rates in the wave tank werernconducted at 2 different induced breaking-wave energies. Energyrnin the wave tank was measured with an Acoustic DopplerrnVelocimeter (ADV) coupled to a data acquisition system. Energy inrnthe lab flasks was measured with a Hot Wire Anemometer.