4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

Wave Generation In A Two Dimensional Numerical Wave Tank
Wave energy stands out among the most relevant renewable and sustainable energy resources; This explains the great research and development efforts made in the field of wave energy exploitation, which produced many designs and technologies classified as mensioned in [1]; devices off-shore, near shore, and on shore. Another way to classify the wave energy converters is based on their operating principle: OWC-devices, Surging devices, Overtopping devices [2]. The oscillating water column OWC devices are the most widely used types of wave energy conversion technologies, due to their low operational and maintenance costs. The OWC system consists mainly of two essential components, the air chamber and the air turbine. Basically, the device’s concept consists of a submerged air chamber connected to the atmosphere by means of a circular duct inside which a bidirectional flow turbine is installed The flow rate of air through the turbine is created by the successive incident sea water waves that compress and depressurize air in the chamber by means of the periodic motion of the oscillating free surface. The conversion of this air flow into mechanical energy may be reached by means of a number of devices. For many studies the OWC efficiency improvement was only focused on the air flow field inside the chamber as in [3,4]. However, the recent researches in wave energy conversion domain has been focused on the prediction of experimental results, some of these use numerical wave tanks NWT (an OWC inserted in a wave tank) based on the VOF model to generate the incoming incident wave by either employing the Reynolds Navier Stokes model as in [5] or a velocity potential approach [6,7]. The aim of the present study is to compare regular wave generation inside a 2-dimensional numerical wave tank using three types of wavemakers; piston, plunger, and flap types as indicated in Figure 1. For this, computational fluid dynamics CFD was used to simulate the air flow behavior, and the multiphase VOF model was used to analyze the biphasic (air-water) aspect of the water's free surface inside the wave tank. The results of this study have revealed that the water's free surface elevation experience approximately the same pattern for the three wavemakers with small differences caused by the wave reflection and the interaction of the incoming wave with the OWC front wall.
Keywords: numerical wave tank, OWC device, wave energy, wavemaker
Bouhrim Hafsa, El Marjani Abdellatif