Research Papers

Measurement of a Bluff Body Aerodynamic Yaw Moment Magnification and Damping Using a Dynamic Wind Tunnel Facility

[+] Author and Article Information
Shuhaimi Mansor

 Universiti Teknologi Malaysia, 81310 UTM Skudai Johor, Malaysia

Martin Passmore

 Loughborough University, Leicestershire L11 3TU, UK

J. Appl. Mech 78(3), 031004 (Feb 07, 2011) (6 pages) doi:10.1115/1.4003347 History: Received August 15, 2009; Revised December 13, 2010; Posted January 04, 2011; Published February 07, 2011; Online February 07, 2011

This paper describes a technique for determining the dynamic aerodynamic yaw moment derivative based on the time response data using an oscillating model rig. The aerodynamic yaw moment derivatives are initially estimated using oscillation frequency and amplitude decay. The results from the dynamic measurement are compared with conventional static test and presented in the form of aerodynamic magnification. The yaw moment derivative exceeds that determined statically across reduced frequency range measured. The yaw damping derivative was found to be a function of freestream speed; at low velocities it is negative but progressively increases to a positive value. With further increases in speed, a self-sustained oscillation is observed with almost constant frequency and amplitude. This result is attributed to coupling between the model wake and the model stability; however, the exact behavior of the interaction is not fully understood; this phenomenon is under further investigation.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 10

Yaw moment derivative against Reynolds number

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Figure 11

Yaw damping derivative against Reynolds and wind speed

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Figure 12

Yaw moment derivative magnification (20 deg slant)

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Figure 1

Loughborough University low-speed open circuit wind tunnel

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Figure 2

Schematic of an oscillating model rig in a wind tunnel working section

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Figure 3

Davis model geometry

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Figure 4

Yaw moment coefficients against yaw angle at different wind speeds

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Figure 5

Frequency ratio versus reduced frequency for Springs S1–S5 for four repeat tests showing collapse of data onto a single curve

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Figure 6

Time response for a single Spring S1 over a range of tunnel speeds

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Figure 7

Yaw moment derivative against reduced frequency from four repeat tests

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Figure 8

Yaw damping derivative against reduced frequency at 10 m/s of three repeat tests (20 deg slant)

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Figure 9

Yaw damping derivative against reduced frequency at 15 m/s and 20 m/s of three repeat tests




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