Couette-Poiseuille flow experiment with zero mean advection velocity: Subcritical transition to turbulence

Abstract

We present a new experimental set-up that creates a shear flow with zero mean advection velocity achieved by counterbalancing the nonzero streamwise pressure gradient by moving boundaries, which generates plane Couette-Poiseuille flow. We carry out the first experimental results in the transitional regime for this flow. Using flow visualization we characterize the subcritical transition to turbulence in Couette-Poiseuille flow and show the existence of turbulent spots generated by a permanent perturbation. Due to the zero mean advection velocity of the base profile, these turbulent structures are nearly stationary. We distinguish two regions of the turbulent spot: the active, turbulent core, which is characterized by waviness of the streaks similar to traveling waves, and the surrounding region, which includes in addition the weak undisturbed streaks and oblique waves at the laminar-turbulent interface. We also study the dependence of the size of these two regions on Reynolds number. Finally, we show that the traveling waves move in the downstream (Poiseuille)

Statistical transition to turbulence in plane channel flow

“…In plane Couette flow [28,49], the upstream and downstream spatial decay rates are equal, by virtue of symmetry, while those of pipe flow show a strong dependence of the upstream decay rate on Reynolds number [50]. Asymmetry between upstream and downstream spatial decay rates is also seen in turbulent spots in boundary layer flow [51] and in Poiseuille-Couette flow [52].…”

Decay of streaks and rolls in plane Couette–Poiseuille flow

“…It has previously been described in detail by Klotz et al. (2017). It consisted of two parallel vertical glass plates set 14 mm apart and these form a connected channel between two filled water reservoirs.…”

“…The threshold at which turbulence is self-sustained in experiments is estimated approximately at ; the turbulence becomes featureless at (Klotz et al. 2017). Since the geometry of CPF is similar to that of PCF and PPF, it is anticipated that there will be common features in the transition processes in all three flows.…”

Laminar–Turbulent Intermittency in Annular Couette–Poiseuille Flow: Whether a Puff Splits or Not

“…As an experimental study, Nakabayashi et al [ 47 ] also measured the turbulence statistics of a plane Couette–Poiseuille flow at high Reynolds numbers, and classified the flow field into a Couette- or Poiseuille-type depending on the base flow. In addition, Klotz et al [ 48 , 49 ] eliminated the net flow in a plane Couette–Poiseuille flow (pCPf), allowing localized turbulence to be tracked for long periods of time while stationary in the observation window. A recent quench experiment on the decay of Couette–Poiseuille turbulence is likely to approach the crossover of the decay rate, that is, the quantitative identification of [ 50 ].…”