Experimental investigation of wake flow field and wind comfort characteristics of fractal wind fences

Wind fences are frequently utilized in many areas from agriculture to traffic safety in order to provide a sheltered region behind. The conventional geometry of wind fences are usually porous with circular or rectangular holes. Recent studies on fractal/multiscale grid geometries, i.e. a geometry that consists of smaller scales that are copies of the whole, show interesting results, indicating a potential towards using these types of grids as wind fences. Thus, the main purpose of this study is to investigate the performance of fractal grids as wind fences. For this purpose, four different types of wind fences, three of which have fractal grids, all having the same porosity ratio of 40%, are tested in a wind tunnel. Results of the two-dimensional PIV measurements downstream of each fence are presented. Comparisons of the details of the wake flow structure as well as quantitative comparisons of wind comfort and shelter characteristics up to 10H downstream of fences, where H is the fence height, are also presented. Results show that the jet-wake-wall interactions within the near wake of the fences have a major impact on wind comfort characteristics further downstream. These interactions can potentially be manipulated by custom designing fractal grid fences based on given wind comfort requirements in order to obtain required mean flow and sheltering characteristics

Investigation of Circular Woven Composite Preforms for Composite Pipes

The main traditional technique for commercial manufacturing of composite pipes is filament winding in which the winding angle and the discontinuity of the structure (caused by starting and ending points of the winding process) are two important matters of concern. In the present study, circular woven fabric with its orthogonal net-shaped continuous structure was produced from polyester yarns. Fabric was wet with epoxy and hand lay-up was used to manufacture the composite pipes. Composite pipes were subjected to internal hydrostatic pressure and their burst strength was recorded. In addition, tensile strength of flat laminas was assessed in the warp and weft directions. We estimated and analysed the failure strength of composite pipes using Tresca’s failure criterion and Finite Element (FE) modeling. The experimental burst strength was almost 23% more than the FE model and 77% more than the theoretical estimate