CEEX 2008 CONFERENCE INTER-INFLUENCE OF THE VERTICAL AXIS, CROSS-FLOW, MARINE CURRENT TURBINES MOUNTED IN FARMS Andrei-Mugur GEORGESCU 1* , Sanda-Carmen GEORGESCU 2 , Sandor Ianos BERNAD 3 In order to determine the optimal arrangement of vertical axis, cross-flow, marine current turbines in hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in the commercial code COMSOL Multiphysics. The new model proved to save a lot of computational effort. Numerical simulations were performed with the   k turbulence model, and turbine power coefficients were calculated for different arrangements. Some trends with respect to the optimal (or near optimal) arrangement could thus be obtained. Keywords: Achard turbine, cross-flow current turbine, hydro-power farm. 1. Introduction The THARVEST research project [1] of the CEEX Program aims to depict the inter-influence among cross-flow current turbines with vertical axis (called Achard turbines), for different hydropower farm configurations. The main advantage of these turbines is their ability to operate irrespective of the water flow direction. The turbine efficiency depends both on the upstream water velocity, and on the spatial arrangement of the turbines within the farm, described by the distance (gap) between two successive axes. The Achard turbine consists of a runner with three vertical delta blades (Figure 1), sustained by radial supports at mid-height of the turbine. The blades are shaped with NACA 4518 airfoils, while the radial supports are shaped with straight NACA 0018 airfoils. The turbine main geometric dimensions are: the runner diameter 1  D m and the runner height 1  H m. Along each delta blade, the airfoil mean camber line length varies from 0.18 m at mid-height of the turbine, where 0  z , to 0.12 m at the extremities, where 2 H z   . 1 Associate Prof., Hydraulic and Environmental Protection Department, Technical University of Civil Engineering Bucharest, Romania (*Corresponding author) 2 Associate Prof., Hydraulics and Hydraulic Machinery Department, University “Politehnica” of Bucharest, Romania 3 Senior Researcher, Centre of Advanced Research in Engineering Sciences, Romanian Academy – Timişoara Branch, Romania