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Session: Instability and Transition 2
Session starts: Tuesday 25 August, 15:00
Presentation starts: 16:15
Room: Room A

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Shashank H J (Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India)
Sreenivas K R (Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India)

Abstract:
The effect of drag reducing polymers on the onset of instability in a pipe with reverse flow is investigated. Reverse flow is established by using a piston cylinder mechanism, the programmed motion of which imparts a known impulse to the fluid. An inflection point is formed, leading to flow instability above a critical Reynolds number. The effect of the drag reducing polymers (Poly-ethylene oxide, dissolved in water) is observed using dye visualization and PIV. The time of onset of instability and the wavelength of the instability are studied in systems with and without Poly-ethylene Oxide (PEO). The experiments show that the wavelength increases in systems with PEO when compared to water. The flow due to forward motion of the piston is solved analytically to obtain the velocity profiles after the piston stops. Stability analysis is also performed to compare the behaviour of systems with and without PEO.