Velocity measurements in a cavitating micro-channel flow

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Submitted on 6 May 2019

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Velocity measurements in a cavitating micro-channel flow

Cyril Mauger, Loïc Méès, Marc Michard, Michel Lance

To cite this version:

Cyril Mauger, Loïc Méès, Marc Michard, Michel Lance. Velocity measurements in a cavitating micro-

channel flow. 51st European Two-Phase Flow Group Meeting, 2013, Lyon, France. �hal-02120617�

Velocity measurements in a cavitating micro-channel flow

C. Mauger

, L. Méès

, M. Michard

, M. Lance

1

Laboratoire de Physique de l'ENS Lyon (Phys-ENS), CNRS UMR5672 – École Normale Supérieure - Lyon

2

Laboratoire de Mécanique des Fluides et d’Acoustique (LMFA), CNRS UMR 5509 – Ecole Centrale de Lyon – INSA de Lyon – Université Claude Bernard – Lyon 1, Ecully

Cavitation is generally known for its drawbacks (noise, vibration, damage).

However, it may play a beneficial role in the particular case of fuel injection, in the atomization [1] process or by reducing nozzle fouling. Studying cavitation in real injection configuration is therefore of great interest, yet tricky because of high pressure, high speed velocity, small dimensions and lack of optical access for instance. A simplified transparent 2D micro-channel (200-400 µm) continuously supplied with test oil at lower pressure (6 MPa) is adopted. A shadowgraph-like imaging system is set-up. It makes it possible to visualize vapor formations as well as density gradients (refractive index gradients) in the liquid phase, including scrambled structures connected to turbulence the same [2]. Space and space-time correlation functions are used to characterize these structures’ evolution. An integral length scale is defined. It tends to decrease as the Reynolds number increases. Once cavitation is reached, the integral length scale seems to slightly increase, suggesting a diminution in smaller (or an increase in larger) turbulent structures. Since these structures are correlated in time, an image correlation algorithm can be used to extract mean velocity field as well as fluctuations, without tracer. A good agreement is found between the flow rate measured with a flowmeter and that deduced from the inter-correlation algorithm. An increase in velocity fluctuations is observed at the channel outlet for a critical normalized length of vapor cavities equals to 40-50 %. A parametric study on channel height and oil temperature is performed: none of them impacts the critical normalized length but larger velocity fluctuations are observed in channel of larger height.

[1] M. Birouk, N. Lekic, Liquid jet breakup in quiescent atmosphere: A review, Atomization and Sprays 19 (6): 501–528 (2009).

[2] C. Mauger, L. Méès, M. Michard, A. Azouzi, S. Valette, Shadowgraph, Schlieren and

Interferometry in a 2D cavitating channel flow, Exp Fluid. 53: 1895-1913 (2012).