Wind pressure on circular cylinders and chimneys

Abstract

In this paper a summary is given of the published model experiments on the wind pressure on cylinders and of some previously unpublished experiments made at the National Bureau of Standards on models, on a large cylinder in natural winds, and on the power plant chimney in natural winds. This information is collected and analyzed for the purpose of estimating the wind pressure on chim-neys and other cylindrical structures at known wind speeds. The new experiments are in large measure determinations of the local distribu-tion of pressure over the entire surface of the cylinder in the model experiments, and over a suitably chosen section in the experiments in natural winds. In addi-tion, the overturning moment on a 10 by 30 foot cjdinder in the natural wind was directly measured. The general conclusions are as follows: 1. The wind pressure on a chimney is a function of the ratio of the height of the chimney to its diameter and possibly of the roughness of the surface. 2. Model experiments can not be directly utilized because of a large scale effect. 3. A wind pressure corresponding to 20 lbs. /ft. 2 of projected area at a wind speed of 100 miles per hour is a safe value to use in designing chimneys of which the exposed height does not exceed ten times the diameter. 4. The pressure may reach large values locally and this may require considera-tion in the design of thin-walled stacks of large diameter. CONTENTS Page I. Introduction 653 II. Summary of aerodynamic data on cylinders 655 III. Model experiments at the Bureau of Standards 660 1. Apparatus 660 2. General procedure 661 3. Results 664 4. Discussion and comparison with other published data 666 5. Summary of model experiments 677 IV. Experiments in natural winds 677 1. The interpretation of experiments in natural winds 677 2. Experiments on a cylindrical stack, 10 feet in diameter and 30 feet high 679 (a) Distribution of pressure, stack 10 feet in diameter and 30 feet high 679 (6) Overturning moment, stack 10 feet in diameter and 30 feet high 683 (c) Summary, stack 10 feet in diameter and 30 feet high_ 686 3. Power-plant chimney