Numerical investigation of the flow around lightweight solar modules. Determination of the uplift forces by means of CFD modeling and wind tunnel validation.

Abstract

Anglès: Present developments in construction engineering are aiming towards bigger and more slender structures, where wind loading becomes an even more decisive factor in its design. These structures are very often conceived with special geometrical shape that leads to highly difficult (sometimes impossible) approaches to determine the wind load effects. Therefore wind tunnel investigations have been regularly used to get a reliable approach to the real wind conditions on and around the structure. The appearance in early 1960’s of Computational fluid dynamics (CFD) let us predict the fluid fields and other physics in detail for an application of interest by using numerical methods and algorithms. Before the appearance of CFD the fluid mechanics advancements where done with the combination of experiments and basic theoretical analyses, which have the disadvantage of not including all the required physics of the flow. But now, the role of CFD in engineering predictions has become so strong, that today it can be seen as a new “third dimension” in fluid dynamics. CFD had rapidly become a popular tool in engineering analyses. CFD calculations in civil engineering are still an immature alternative to wellestablished methods like wind tunnel. The large computational effort and timeconsuming calculations together with the difficulties of modeling the atmospheric boundary layer and its turbulent structures had been the main drawbacks for dealing with wind effects on structures. Nevertheless in the latest years, an always increasing computer power has opened the possibilities of simulation in the field structural aerodynamics, as they start giving accurate results with affordable time expense. One of the main deficiencies of CFD is the CFD solutions of turbulent flows. These solutions contain turbulence models which are just approximations of the real physics. Therefore, all CFD solutions of turbulent flows are subject to inaccuracy. CFD community is directly attacking this problem in the most basic sense. There is work today on the direct computation of turbulence. This is currently a wide open area of CFD research. It is the purpose of this study to compare the CFD solutions of a turbulent flow with the solutions obtained in a wind tunnel experiment, in order to validate its use. This study focuses on generating a suitable model for a lightweight solar module and carry out a numerical investigation of the flow around it and determining the uplift forces using computational fluid dynamics (CFD) calculations. Finally the results will be validated with the results obtained in the experiments done in a wind tunnel by the Institute of Steel Construction of the RWTH University of Aachen.