Laboratory measurements of the drag coefficient over a fixed shoaling hurricane wave train

Brian C. Zachry , Chris W. Letchford , Delong Zuo , Andrew B. Kennedy

Abstract

This paper presents results from a wind tunnel study that examined the drag coefficient and wind flow over an asymmetric wave train immersed in turbulent boundary layer flow. The modeled wavy surface consisted of eight replicas of a statistically-valid hurricane-generated wave, located near the coast in the shoaling wave region. For an aerodynamically rough model surface, the air flow remained attached and a pronounced speed-up region was evident over the wave crest. A wavelength-averaged drag coefficient was determined using the wind profile method, common to both field and laboratory settings. It was found that the drag coefficient was approximately 50% higher than values obtained in deep water hurricane conditions. This study suggests that nearshore wave drag is markedly higher than over deep water waves of similar size, and provides the groundwork for assessing the impact of nearshore wave conditions on storm surge modeling and coastal wind engineering.

Key Words

drag coefficient; shoaling wave; wind stress; profile method; log-law

Address

Brian C. Zachry and Delong Zuo — Wind Science and Engineering Research Center, Texas Tech University, Lubbock, TX 79409, USA
Brian C. Zachry — AIR Worldwide, Boston, MA 02116, USA
Chris W. Letchford — Department of Civil and Environmental Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Andrew B. Kennedy — Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA

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