A wind loading correlation for an isolated square heliostat, part 1: lift and drag forces

Abstract

A design requirement of a heliostat is the ability to withstand storm loads in the stow position and operational wind loads in any position. To design a heliostat, therefore, one must be able to predict the wind loading on the heliostat for all elevation angles of the heliostat and all wind directions relative to the heliostat coordinate system. Fortunately, experimental wind tunnel force and moment coefficient data in the x, y and z directions exist in tabular format for an isolated heliostat, and are in the public domain, but still require interpolation between different points in a large dataset. This paper shows that the data points fit definable patterns, allowing the use of Fourier analysis to fit a small number of correlations to describe the entire dataset to high accuracy. Correlations for the lift and drag forces are presented. A companion paper presents correlations for the side forces and correlations for moments about the three principal axes, and discusses the behavior of the correlations.