Measurements of the Flowfield Interaction Between Tandem Cylinders

†This paper presents the most recent measurements from an ongoing investigation of the unsteady wake interference between a pair of circular cylinders in tandem. The purpose of this investigation is to help build an in-depth experimental database for this canonical flow configuration that embodies the effects of component interaction in landing gear noise. This new set of measurements augments the previous database at the primary Reynolds number (based on tunnel speed and cylinder diameter) of 1.66 × 10 5 in four important respects. First, better circumferential resolution of surface pressure fluctuations is obtained via cylinder “clocking”. Second, higher resolution particle image velocimetry measurements of the shear layer separating from the cylinders are achieved. Third, the effects of simultaneous boundary layer trips along both the front and rear cylinders, versus front cylinder alone in the previous measurements, are studied. Lastly, on-surface and off-surface characteristics of unsteady flow near the “critical” cylinder spacing, wherein the flow switches intermittently between two states that are characteristic of lower and higher spacings, are examined. This critical spacing occurs in the middle of a relatively sudden change in the drag of either cylinder and is characterized by a loud intermittent noise and a flow behavior that randomly transitions between shear layer attachment to the rear cylinder and constant shedding and rollup in front of it. Analysis of this bistable flow state reveals much larger spanwise correlation lengths of surface pressure fluctuations than those at larger and smaller values of the cylinder spacing.

[1]  Thomas F. Brooks,et al.  Aeroacoustic Simulations of Tandem Cylinders with Subcritical Spacing , 2008 .

[2]  Thomas F. Brooks,et al.  Tandem Cylinder Noise Predictions , 2007 .

[3]  Meelan Choudhari,et al.  Measurements of Unsteady Wake Interference Between Tandem Cylinders , 2006, 36th AIAA Fluid Dynamics Conference and Exhibit.

[4]  T. Brooks,et al.  Noise Radiation from Single and Multiple Rod Configurations , 2006 .

[5]  Yueping Guo,et al.  Airframe Noise Source Locations of a 777 Aircraft in Flight and Comparisons with Past Model-Scale Tests , 2003 .

[6]  B. Sunden,et al.  Free-stream turbulence and tube spacing effects on surface pressure fluctuations for two tubes in an in-line arrangement , 1991 .

[7]  M. M. Zdravkovich,et al.  Flow induced oscillations of two interfering circular cylinders , 1985 .

[8]  Masaru Kiya,et al.  Pressure Fluctuations on the Surface of Two Circular Cylinders in Tandem Arrangement , 1983 .

[9]  M. M. Zdravkovich,et al.  Interference between two circular cylinders; Series of unexpected discontinuities , 1977 .

[10]  P.O.A.L. Davies,et al.  An experimental investigation of the unsteady pressure forces on a circular cylinder in a turbulent cross flow , 1975 .

[11]  A. Roshko.  Experiments on the flow past a circular cylinder at very high Reynolds number , 1961, Journal of Fluid Mechanics.

[12]  Luther N. Jenkins,et al.  Simulations of Bluff Body Flow Interaction for Noise Source Modeling , 2006 .

[13]  Luther N. Jenkins,et al.  Unsteady Flowfield Around Tandem Cylinders as Prototype for Component Interaction in Airframe Noise , 2005 .

[14]  Luther N. Jenkins,et al.  Characterization of Unsteady Flow Structures Around Tandem Cylinders for Component Interaction Studies in Airframe Noise , 2005 .

[15]  J S Bendat and A G Piersol.  Random Data Analysis and Measurement Procedures , 2000 .

[16]  Scott O. Kjelgaard,et al.  The Basic Aerodynamics Research Tunnel - A facility dedicated to code validation , 1988 .

[17]  Atsushi Okajima,et al.  Flows around Two Tandem Circular Cylinders at Very High Reynolds Numbers , 1978 .