Reynolds-Number Effects on Bridge Aerodynamics

Long span bridges are composed of more or less bluff bodies. A main point of the lecture is the question: In which case does the Re. No. play a significant role, in particular concerning their influence on the propensity to flow induced vibrations. The paper reviews the results of experiments carried out over a wide range of Reynolds numbers ( 104 < Re < 107 ) on 2-D sections. The bodies are a circular cylinder, a bridge section, and a thick airfoil at high angle of attack. In all cases, variation of Re led to dramatic changes in the force coefficients and St. No., caused by changes in the topological structure of the separated flow. The important results are, that there are 2-D sections that behave as a bluff- or streamlined body, depending on Re, and that slender bodies with sharp-edged cross-sections may also suffer pronounced Re. No effects.