Towards prediction of wind load on pylons for a neutral atmospheric boundary layer flow over two successive hills

Abstract

In strong wind situations for a neutral atmospheric boundary layers, wind loads on pylons depend on both the mean velocity and the turbulence fluctuations, predicted by analytical models only for simple topographies. For complex topographies, only experiments or numerical simulations give access to the local flow conditions around the pylon. We present experimental and numerical results using a RANS model for the parametric study of the flow near two successive hills of height H and width L for varying distance λ between the tops. We focus on the modification of flow conditions on the second hill by the presence of the first hill. For λ/H≥19.2, the first hill does not modify the flow structure around the second hill. For decreasing values of λ/H below 19.2, a secondary turbulence intensity peak appears on the frontal part of the second hill. It is associated with the impact of the mixing layer generated at the top of the first hill, whose development is well described by analytical models of the planar mixing layer. These analytical models yields simple estimations of the turbulent kinetic energy k for the pylon’s wind load calculations. Different hill slopes and height ratios are also investigated.