CFD analysis of wind loads on permeable low-rise structures

Current screen enclosure building codes are based on the experimental wind tunnel studies and, to a smaller extent, full scale open terrain studies conducted at Virginia Tech and Clemson University. There are still widespread wind damages to pool and patio enclosures during wind storms. Experimental studies based on simulation comparison of wind load on a low-rise structure in general, continue to show large discrepancies based on NIST data. Accounting for the many parameters which are essential to achieve an accurate simulation through experimentation is daunting. Reynolds number, spectrum density, large and small turbulent scales, viscous shear layer, and flow intermittency are a few of those parameters. Numerical simulation (CFD) provides an attractive parametric study and offers a richer, higher resolution data output. In this work, flow around a screen enclosure embedded within the atmospheric boundary layer is investigated numerically. The flow is governed by Navier-Stokes equations with a momentum sink that follows Darcy equations and incorporating the eddy viscosity K-S turbulent closure model. The pressure drop that is computed provides the basis of evaluating wind load on the screen structure. The evaluated load is compared to the Florida Building Code ASCE7 provision and is used to conduct structural analysis on common baseline enclosures to assess their reliability. The structure is analyzed using Bernoulli-Euler beam elements having cross sections according to the code and subjected to forces and moments with 6 (3displacements and 3 rotational) degrees of freedom.