wind energy resource evaluation in a site of central italy ... - WindSim

3.5 Investigation of a flow over a 2D roughly hilly terrainThis paragraph presents an investigation of a flow over a two–dimensional roughlyhilly terrain. Two cases have been realized, to highlight the behavior of an attachedflow and a separated flow, by varying the slope of the hill. A comparison betweenexperimental [3] and numerical data has been done, showing good agreement.The numerical simulations are based on the solution of Reynolds Averaged Navier-Stokes (RANS) equations, by the software WindSim, with the k-ε turbulencemodel. The realized numerical grid is in both cases non orthogonal body fitted type,while the solver which better produces a good level of convergence in the solution isthe segregated, enriched with the “yap” correction of the k-ε turbulence model.3.5.1 Description of the test caseThe experimental data comes from the tests conducted in an open-circuit boundarylayerwind tunnel, having a test section of width, height and length of 1.2, 1.2 and 6meters respectively. A neutrally stratified boundary layer is developed using equallyspaced 0.25 m height triangular spire-type vortex generators and artificial grass of 5mm height. In these experiments, a fully-developed turbulent boundary layer of 0.25m height is generated, and has a typical wind profile over an open flat area (fitting toa log-law profile).The shape of the hill is described by the following equation3.5.1) = ∙ 1+ ∙ ,where:H [m] is the height of the hillL 1 [m] is the half-length of the hill at the upwind mid-height of thehillThe slope of the hill S is defined as the average slope for the top half of the hillupstream of the crest, through the equation37