The CFD investigations also indicated that the wave height of the surface wave created by the net in this position would be on the order of a few millimeters and can be considered negligible. Based on preliminary CFD investigations, it was decided to position the net panel in the center of the cross-section of the tank. The net panel was positioned well below the water surface (0.73 m) to minimize drag forces from surface wave creation due to the pressure difference between the front and the back of the net panel. The velocity of the carriage was measured using a set of light gates measuring travel time over a set distance. The water speed relative to the carriage and net was measured using an acoustic doppler velocimeter (ADV) in different positions behind the net, mostly in the wake region, but also outside the wake. Drag force (parallel to velocity) and lift force (perpendicular to velocity) were measured using a loadcell arrangement. 1 was constructed and used in the tank to support the net panel and measure the forces. A series of measurements of drag and lift forces on a net panel and velocity reduction behind the net panel were conducted in the University of New Hampshire (UNH) 37 m long, 3.66 m wide and 2.44 m deep tow/wave tank as described by Patursson (2007). More detailed information about the software is provided by Fluent (2006, 2007). Wall boundaries were modeled using the standard wall functions. The velocity at the inlet was constant across the inlet face and values of k and e were specified in the inlet water. The grid was generated by the meshing software Gambit 2.3 from ANSYS Inc., and two grid generation methods were employed - TGrid that generates meshes from tetrahedral cells and Hex Core that generates mixed meshes using tetrahedral and hexahedral cells. Ferziger and Peric ́, 2002) method was employed for the pressure–velocity coupling. The momentum equation was discretized using a second order upwind scheme, derivatives were evaluated using the node based formulation, and the SIMPLE (e.g. (1) and (2) were discretized using a finite volume approach and solved using the segregated iterative solver employing an algebraic multigrid method with under relaxation. The volume integrated steady state versions of Eqs. These general equations were solved using the CFD software FLUENT 6.3 from ANSYS Inc. the local axes of the porous media are not aligned with the global coordinate axes, a tensor rotation approach has to be employed.
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