Modelling Wind Velocity Patterns for Windbreak Fence De- sign

The use of windbreak fences has become a common practice to reduce wind erosion and soil particle dispersion in potentially risky areas, such as reclaimed lands, harvested fields and sandy beaches. However, the windbreak design in terms of screen porosity, fence height and distance between multiple fences is still determined by empirical knowledge. For the effective and economical use of windbreak fences, this paper introduces a regression model to predict wind speed reduction by windbreak fence according to screen porosity, fence height, fence location and wind speed. The regression model is able to predict the effects of single fence as well as multiple fence array and to provide straightforward procedures for windbreak fence design. The model was developed by non-linear regression analysis based on the data obtained from computational fluid dynamics (CFD) simulations, which was validated in advance by wind tunnel experiments. The porous characteristics of the screen were accurately measured by a small wind tunnel in the forms of the inertial resistance (Cir) and permeability (α) of Darcy-Forchheimer law for specifying porous media. The regression coefficients were estimated by a genetic algorithm. The regression model for single fence showed good agreement to the simulation results with R 2 = 0.997 and 0.999 at leeward and windward, respectively. The model for multiple fences were derived from multiplication of the model for single fence and also showed a good agreement with the simulation results. The regression models for single and multiple fences provided handy charts and a program for users to easily design a windbreak fence or fence array.