Modelling of wind shear downwind of mountain ridges at Hong Kong International Airport

Abstract

A theoretical and computational study is presented of the wind flow over the mountain ridges to the south of Hong Kong International Airport given the upwind profiles of 'mean' velocity and temperature. A sensitivity study shows how large variations in wind speed, wind shear and wind direction occur on the approach path when the upwind flow from the southeast is stably stratified above the boundary layer with a significant inversion no more than a few hundred metres above the ridge (height about 450 m). The Froude number is close to unity. The effects of vertical wind shear across the inversion layer reduce the speed-up, and directional wind shear changes the surface flow direction. The observed horizontal length scales along the approach are about equal to the projected widths of the predominant features of the ridges and valleys. For an extreme wind event there was found to be satisfactory agreement between the wind speed measured by a landing aircraft and the predictions of the fast quasi-linear analytically based computer model FLOWSTAR. This suggests that near real time application of the model and near real time monitoring with remote and in situ instruments can be used to predict these extreme flow events and hence give warnings about them. Conclusions are drawn about how such predictive modelling could be developed.

FLOWSTAR-Energy: a high resolution wind farm wake model

“…Carruthers et al, 2014, Stocker et al, 2016, CERC, 2016, it has so far not been used in detail to predict energy yields from 10 wind farms in complex terrain. This will be the subject of a further validation study for FLOWSTAR-Energy.…”

“…FLOWSTAR has previously been described (Carruthers et al, 1988) and validated (Carruthers et al, 2014, Stocker et al, 2016, CERC, 2016-Askervein Hill Wind Energ. Sci.…”

Optimized use of real‐time vertical‐profile wind data and fast modelling for prediction of airflow over complex terrain

“…The main drawback of this modelling approach is that it is not possible to incorporate the RAMS into an operational nowcasting system due to restrictive computation times, and the inability to use local data within the computational domain. A very fast analytical approach, FLOWSTAR, as described in Carruthers et al () and Carruthers et al () with underlying theory from Hunt et al (), has been used in many complex terrain studies in which the input data used are from locations outside the domain. FLOWSTAR is a linear, steady‐state perturbation model.…”

“…Carruthers et al () demonstrated good qualitative agreement between changes in the modelled and observed headwind values (refer to Figure 12 in that work). However, the magnitude of the headwind speed was overestimated.…”

“…A particular wind event, which occurred on 27 December 2009, caused a number of landing aircraft to be diverted. This event has been reported previously (Chan, ); initial modelling of one of the aborted landings was undertaken by Carruthers et al () using the FLOWSTAR model (Carruthers et al , ) with input wind data from outside the computational domain. In the present study, the model is developed to take better account of vertical wind shear and also to incorporate the real‐time upwind profile data recorded at a small island upwind of Lantau Island.…”