Wind Load on Pipe-Towers of Frame Work Structure (Report 4) Case of Drag-Coefficient at Super Critical Region

Abstract

The author has proposed a simple calculation formula capable of determining the wind load which acts on steel pipe towers from any angle of attack. The feature of this calculation formula is that is can be applied not only for the square section of steel pipe towers, but also for other sections, such as rectangles, equilateral triangles, hexagonal triangles, etc. When main pillers and diagonal bracings are exposed to high wind speeds, the drag-coefficients are actually reduced affected by the REYNOLDS number. This is due to the roundness of their structure. On thecontrary, the calculation formula proposed by the author is workable in the subcritical REYNOLDS regions.
Under such circumstances, it was not possible to define the adequate value of the drag-coeffi cients to be used in the case of steel pipe towers in either the critical REYNOLDS region or in the super-critical REYNOLDS region. This paper com-pares the results of conventional studies on dragcoefficients in the critical REYNOLDS region with the author's wind tunnel test results. As a result, the author could identify that dragcoefficients in the square sections would be decreased to about 1.1 in the critical REYNOLDS regions, but increased to about 1.5 in the supercritical REYNOLDS regions. Using these results, the author attempted to come up with a calculation formula capable of determining the dragcoefficients for steel pipe towers in the regions above the critical REYNOLDS regions.