1. Vortex Shedding from a Group of
Cylinders
ENG 3163: BEng Final Year
Project
Individual work carried by: Youssef Sayed
Project Supervisor: Dr. Matteo Carpentieri

2. Problem Statement
 Flow around a circular cylinder has been a classic problem
in the fluid mechanics field where lots of experiments have
been carried on to understand the flow around it.

3. Research Objectives
 This project aims to investigate experimentally and discuss
theoretically the behaviour of the wake resulting from
different cylinder formations:
- Side by side
- Tandem
- Staggered
 Optimise the visualisation technique and the recording
systems used during the experiments.
 Forming a library of video-clips to be added to the existing
set of the EnFlo laboratory album.

4. Wake Configuration
Wake Configuration has been debated between many
engineers:
-Williamson (1985) discussed the two types of wake configuration
-Landweber (1942) found that all the vortex shedding are mainly inphase
-Thomas & Kraus (1964) detected the formation of inphase and antiphase
shedding
-Bearman & Wadcock (1973) and Quadflieg (1977) found preponderance
of the antiphase type of shedding.

5. Side by side Configuration
Two main approximations are the diameter of the cylinders
which is noted by ‘D’ and the gap width between the cylinders
noted by ‘T’

6. Side by side Configuration
Three observations have been noted by Sumner (2010)
regarding these formed patterns.
(a) The single bluff body ( T/D< 0.2)
(b) The based flow pattern (0.2< T/D < 2)
(c) Parallel vortex pattern ( T/D> 2)

7. Tandem Configuration
Two main approximations are the diameter of the cylinders,
noted by ‘D’, and the distance between the centre of the
cylinders, known as the centre width noted by ‘L’

8. Staggered Configuration
Three observations have been noted by Sumner (2010)
regarding these formed patterns.
Regime Zdravkovich (1987) Zhou & Yiu (2006)
Extended Body
Regime
1< L/D <1.2-1.8 1< L/D <2
Extended Body
Regime
1.2-1.8< L/D <3.4-3.8 2< L/D <5
Extended Body
Regime
L/D >3.4-3.8 L/D >5

9. Staggered Configuration
The staggered configuration is arrangement of two circular
cylinders; the geometry of this configuration is set by the
P/D dimensionless ratio and the angle of incidence α

10. Staggered Configuration
Four Groups identified by Sumner (2010)

11. Experimental Methodology Modification
1. New towing tank filling mechanism

12. Optimising the Recording Mechanism:
1. New flow control device
Experimental Methodology Modification

13. Optimising the Recording Mechanism:
2. Introducing the white sheet
Experimental Methodology Modification

14. Support Arms (Tandem configuration)
Experimental Methodology Modification

15. Results
The results were divided between two phases:
First phase experiments:
– Response from one cylinder
• (a) Testing best angle of injection
• (b) Effect of Reynolds number
• (c) Development of Vortex Street
– Response of cylinders arranged in side by side configuration
• (a) Effect of Proximity
• (b) Increase Reynolds number
• (c) Effect of Increasing Reynolds number with proximity
Second phase includes:
– Response of cylinders arranged in tandem configuration
• (a) Effect of Proximity
• (b) Effect of Increasing Reynolds number with proximity

16. Phase One Results
Results from the response of one cylinder
Selected flow options:
Injection =180 deg (Immediate Shedding)
Reynolds number =185 (Clear Flow)

17. Phase One Results
Results from the response of two cylinder (proximity effect)
Cylinders =2
Re =185
proximity=4D
Cylinders =2
Re =185
proximity=2D
Cylinders =2
Re =185
proximity=1D
Cylinders =2
Re =185
proximity=0.5D

18. Phase One Results
Results from the response of two cylinder (Re number effect)
Cylinders =2
Re =320
proximity=1D
Cylinders =2
Re =450
proximity=1D
Cylinders =2
Re =450
proximity=2D
Cylinders =2
Re =320
proximity=2D

19. Phase One Results
Results from the response of multiple cylinders (Increase
number of cylinders effect)
Cylinders =3
Re =185
proximity=1D
Cylinders =4
Re =185
proximity=1D
Cylinders =5
Re =185
proximity=1D

20. Phase Two Results
Results from the response of two cylinders (proximity effect)
Dis=1L/D Dis=2L/D Dis=3L/D Dis=3.5L/D Dis=4.5L/D Dis=5.5L/D

21. Phase Two Results
Results from the response of two cylinders (proximity effect)
Dis=1L/D Dis=3.5L/D Dis=4.5L/D Dis=5.5L/D
• Re= 320
• Re= 450

22. Conclusion and Observations
The results were divided between two phases:
Phase one observations:
 Predominance of the antiphase shedding wake configuration proving the
theory of Bearman & Wadcock (1973) and Quadflieg (1977).
 Proximities tested using two cylinders (side by side configuration) verified the
three flow pattern
 Intermediate cylinder using odd number of cylinders, showed anti-phase
shedding to both sides of the cylinder.
 When an even number of bodies were tested, the two cylinders spaced close
together showed an anti-phase shedding nature
Phase two observations :
 The proximities tested verified three regimes and demonstrated values that
are closer to Zhou & Yiu (2006)
 The co-shedding system recognised by Igrashi (1981) can have either
symmetrical or unsymmetrical mixing.

23. Thank you for your attention