Influence of Reynolds number and forcing type in a turbulent von Karman flow
Article dans une revue avec comité de lecture
We present a detailed study of a global bifurcation occuring in a turbulent von Kármán swirling flow. In this system, the statistically steady states progressively display hysteretic behaviour when the Reynolds number is increased above the transition to turbulence. We examine in detail this hysteresis using asymmetric forcing conditions—rotating the impellers at different speeds. For very high Reynolds numbers, we study the sensitivity of the hysteresis cycle—using complementary particle image velocimetry and global mechanical measurements—to the forcing nature, imposing either the torque or the speed of the impellers. New mean states, displaying multiple quasi-steady states and negative differential responses, are experimentally observed in torque control. A simple analogy with electrical circuits is performed to understand the link between multi-stability and negative responses. The system is compared to other, similar 'bulk' systems, to understand some relevant ingredients of negative differential responses, and studied in the framework of thermodynamics of long-range interacting systems. The experimental results are eventually compared to the related problem of Rayleigh–Bénard turbulence.
Showing items related by title, author, creator and subject.
Article dans une revue avec comité de lectureSAINT-MICHEL, Brice; DUBRULLE, Bérengère; MARIÉ, Louis; RAVELET, Florent; DAVIAUD, François (American Physical Society, 2013)We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of ...
Article dans une revue avec comité de lectureRAVELET, Florent; DUBRULLE, Bérengère; DAVIAUD, François; RATIÉ, Pierre-Arthur (American Physical Society, 2012)We provide experimental and numerical evidence of in-blades vortices in the von Karman swirling flow. We estimate the associated kinematic α-effect tensor and show that it is compatible with recent models of the von Karman ...
Article dans une revue avec comité de lectureZAARAOUI, Abdelkader; RAVELET, Florent; MARGNAT, Florent; KHELLADI, Sofiane (Elsevier, 2013)A prototype device for measuring the volumetric flow-rate by counting vortices has been designed and realized. It consists of a square-section pipe in which are placed a two-dimensional bluff body and a strain gauge force ...
Experimental and Numerical Analysis of the Flow Inside a Configuration Including an Axial Pump and a Tubular Exchanger Communication avec acteSOLIS, Moises; RAVELET, Florent; KHELLADI, Sofiane; BAKIR, Farid (ASME, 2010)In centrifugal and axial pumps, the flow is characterized by a turbulent and complex behavior and also by physical mechanisms such as cavitation and pressure fluctuations that are mainly due to the strong interactions ...
Article dans une revue avec comité de lectureTOMOV, Petar; KHELLADI, Sofiane; RAVELET, Florent; SARRAF, Christophe; BAKIR, Farid; VERTENOEUIL, P. (Elsevier, 2015)The injection of bubbles into an already cavitating flow is a way of influencing the typical cavitating behavior. The present article deals with experiments on aerated and non-aerated cavitation in a transparent horizontal ...