This study analyzed the effect of changing the diameter of a downstream cylinder on the unsteady flow and vortex shedding of an upstream cylinder in a yawed-tandem cylinder arrangement. Microphones were used to measure surface pressure on the upstream cylinder at various yaw angles and downstream diameters. The Strouhal numbers calculated from the measurements showed that the vortex shedding from the upstream cylinder was sensitive to the diameter of the angled downstream cylinder, with different Strouhal numbers observed for different downstream diameters at the same yaw angle.

1. Frequency Analysis of the Unsteady Surface Pressure From Yawed-Tandem Circular
Cylinder Arrangements with Varying Downstream Diameters
Jesse A. MacArthur Stephen J. Wilkins Joseph W. Hall
Department of Mechanical Engineering, University of New Brunswick, Fredericton NB, Canada
Summary of Results
Mic. # θ = 90° θ = 80° θ = 60°
11 St = 0.153 St = 0.182 St = 0.196
5 St = 0.153 St = 0.182 St = 0.206
1 St = 0.153 St = 0.182 St = 0.210
Introduction
The objective of this research is to look at the effect of
changing the size of the downstream cylinder on the
unsteady flow around an upstream cylinder in a yawed-
tandem configuration. This research is an extension of
Wilkins et al. (2013), which looked at the vortex-shedding
from two yawed-tandem circular cylinders with the same
diameters.
• Cylinders had an upstream diameter of Du = 4.2cm, and
downstream diameters of Dd = 2.5cm and 4.8cm. The
Reynolds number of the upstream cylinder was 56,000.
• The yaw angle of the rear cylinder was varied from θ = 90°,
80° & 60°.
• Pressure was measured along the span of the upstream
cylinder using 11 microphones.
• The Strouhal numbers were calculated with: St = f DU /Vs
Experimental Set-Up
Closing Remarks
• The ability of an angled rear cylinder to
manipulate the vortex shedding from an
upstream cylinder has been shown.
• The vortex shedding from the front cylinder
seems to be sensitive to the diameter of the rear
angled cylinder. Further investigation is required
to fully understand this behaviour.
Small & Large Cylinders Downstream at θ = 60°Small & Large Cylinders Downstream at θ = 80°
Mic. # θ = 90° θ = 80° θ = 60°
11 St = 0.147 St = 0.214 St = 0.195
5 St = 0.147 St = 0.214 St = 0.178
1 St = 0.147 St = 0.214 St = 0.176
Mic. # θ = 90° θ = 80° θ = 60°
11 St = 0.183 St = 0.191 St = 0.201
5 St = 0.183 St = 0.191 St = 0.201
1 St = 0.183 St = 0.174 St = 0.201
Downstream Cylinder: 4.8cm
Downstream Cylinder: 4.2cm (Wilkins et al., 2013)
Downstream Cylinder: 2.5cm
Reference: Wilkins, S., Hogan, J., & Hall, J. (2013). Vortex Shedding in a Tandem Circular Cylinder System With a Yawed Downstream Cylinder. Journal of Fluids Engineering J. Fluids Eng., 071202.