Applications of Fluid Mechanics to Wind Engineering—A Freeman Scholar Lecture

Abstract

Wind has always had a strong influence, both unfavorable and favorable, upon man and his activities. Within the last decade needs for treatment of wind effects from an engineering point-of-view have increased tremendously. Losses due to wind ($500,000,000 in property damage, 240 deaths and 2600 injuries annually), increased demand and concern for human comfort, serious attempts to control air pollution, and the development and expansion of energy-production capabilities have resulted in applications of engineering to problems for which a body of knowledge has only started to emerge in the United States. The primary elements of this body of knowledge are found in the disciplines of meteorology, fluid mechanics, aerodynamics, and structural mechanics—organizing this knowledge to form a coherent subject-matter base for wind engineering is a real challenge for fluids engineers. The objectives of this review are to establish an initial subject-matter base for wind engineering, to demonstrate current capabilities and deficiencies of this base for an engineering treatment of wind-effect problems, and to indicate areas of research needed to broaden and strengthen the subject-matter base. Focusing of subject matter for wind engineering is accomplished through a historical summary of relevant scientific and technological material, an examination of information on wind characteristics, and a review of current capabilities for physical modeling of winds and wind effects in the laboratory. Current methods and capabilities in wind engineering are demonstrated by a review of problems related to atmospheric advection and dispersion of air pollutants, wind forces on buildings and structures, and control of winds. Research needs are specified separately for each area reviewed -wind characteristics, simulation of the wind, atmospheric transport of air pollutants, wind forces, and wind control. Physical modeling of boundary-layer-type winds and wind effects by measurements on small-scale models placed in long-test-section, meteorological wind tunnels currently provides the most reliable source of data for wind engineering. Coordinated measurements on full-scale systems and their small-scale models are necessary for continued confirmation of similarity for the laboratory data and for development of new modeling capabilities. In particular, development of a tornado simulator is an urgent need to support structural design for nuclear-power-plant facilities. Intensive analytical investigations of three-dimensional, thermally-stratified, turbulent boundary layers; separation of turbulent, unsteady flows; turbulent shear flow over bluff bodies; and interacting turbulent flows with a variety of turbulence characteristics are needed to ensure future progress in wind engineering. These investigations are needed to provide a framework for correlation of both laboratory and full-scale data, to support efforts to develop numerical modeling as a practical tool, and to develop a better understanding of the physical processes involved. These flow problems represent formidable frontiers of turbulent fluid motion. Therefore, investigations in the fluid-mechanics laboratory coupled with measurements on full-scale systems are expected to be the primary sources of information for wind engineering in the immediate future.