MODELING THE UNSTEADY LIFT AND DRAG ON A FINITE-LENGTH CIRCULAR CYLINDER IN CROSS-FLOW |
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| Institution: | 1. Pennsylvania State University, Applied Research Laboratory, 30, State College, PA, 16804, U.S.A.;2. Pennsylvania State University, Graduate Program in Acoustics and Applied Research Laboratory, 30, State College, PA, 16804, U.S.A.;1. Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801, United States;2. School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China;3. Department of Aerospace Engineering, University of Illinois, Urbana, IL 61801, United States;4. Department of Civil and Environmental Engineering, University of Illinois, Urbana, IL 61801, United States;1. Department of Aerodynamics, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing, Jiangsu 210016, China;2. National Key Laboratory of Science and Technology on Hydrodynamics, China Ship Scientific Research Center, Wuxi, Jiangsu 214082, China;1. IITB-Monash Research Academy, India;2. Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India;3. Department of Mechanical Engineering, Monash University, 3800, Clayton, Australia;1. Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta T6G2G1, Canada;2. Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G2G8, Canada |
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| Abstract: | Semi-empirical models for unsteady lift and drag are developed to predict the spectral features of the unsteady forces on a finite-length, right circular cylinder in cross-flow. In general, the models consist of two parts; the spatial variation of r.m.s wall pressure on the cylinder, and the correlation lengths which describe the spatial extent of the correlation of the unsteady wall pressures. Experiments were conducted in a low noise wind tunnel as a function of cylinder diameter Reynolds number (19 200<Re<32 000) and the Strouhal number (0·05< St<3·33), to measure the statistics of the unsteady wall pressures on a model cylinder. These results are incorporated into the theoretical models, and predictions of the spectral characteristics of the lift and drag are made. The r.m.s. wall pressures on the cylindrical surface are found to have the largest amplitude near the cylinder end-cap, and on the rearward portion of the cylinder body. The high levels in these locations are attributed to the separated flow region over the end-cap. The circumferential and axial length-scales decrease exponentially with Strouhal number. Both length-scales exhibit maxima near the Strouhal shedding frequency of St=0·21. The axial length-scales are found to depend on the measurement reference location due to the three-dimensional flow and separated flow region near the end-cap. The unsteady lift and drag predictions using the models developed in this work agree well with previously measured unsteady force data measured on inertial hydrophones exposed to flow. The broadband unsteady lift is found to be greater than the broadband unsteady drag by nominally 3dB. |
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