HIGH-PRESSURE WATERJETS FOR OIL CONTAINMENT IN CALM AND WAVY WATERS -A PARAMETRIC STUDY

The use of high pressure waterjets (HPWJ) as oil barriers has been pro posed and tesed. It has been shown that a series of waterjets directed horizontally above the free water surface provide an effective means of containing or deflecting oil slicks. The waterjets generate a high speed air flow capable of moving the surface layer of the liquid. A nu merical model is implemented to study the chracteristics of the entrai ned turbulent air flow using the Spectral Element Method (SEM) and an algebraic turbulent model for the Reynolds stresses. A test of the cod e is done for turbulent Couette Flow to check the accuracy of the calc ulated shear stresses against published data. A parametric study is pe rformed to evaluate the HPWJ system performance at various operating a nd design parameters which include manifold pressure, nozzle flow rate , nozzle characteristics, jet height and surface wave conditions. The total driving shear force and power required for effective containment are used as performance measures. Shear stress and the total driving shear force at the air-liquid interface are calculated over a referenc e waterjet distance. Performance is measured under calm and wavy sea c onditions. It is found that the containment pressure required to gener ate a given shear force in wavy surface conditions are 30-50% less tha n those required in calm water. The driving shear force decreases as t he jet height above the liquid surface increased. Shear forces also ap pear to decrease with the reduction of the entrained air flow. The lat ter is governed by nozzle type, spread angle and spacing. The results of the parametric study are consistent with the trends observed experi mentally, and could be used in optimising the system design and perfor mance as well as in setting appropriate operational conditions.