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Journal Articles International Journal of Multiphase Flow Year : 2014

Velocity measurements based on shadowgraph-like image correlations in a cavitating micro-channel flow

Abstract

Cavitation is generally known for its drawbacks (noise, vibration, damage). However, it may play a beneficial role in the particular case of fuel injection, by enhancing atomization processes or 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. In this paper, the authors proposed a simplified and transparent 2D micro-channel (200-400 µm), supplied with test oil at lower pressure (6 MPa), allowing the use of non-intrusive and accurate optical measurement techniques. A shadowgraph-like imaging arrangement is presented. It makes it possible to visualize vapor formations as well as density gradients (refractive index gradients) in the liquid phase, including scrambled grey-level structures connected to turbulence. This optical technique has been already discussed in a previous paper (Mauger et al., 2012), together with a Schlieren and an interferometric imaging technique. In this paper, the grey-level structures connected with turbulence are considered more specifically to derive information on flow velocity. The grey-level structure displacement is visualized through couples of images recorded within a very short time delay (about 300 ns). At first, space and space-time correlation functions are calculated to characterize the evolution of grey-level structures. Space-time correlations provide structure velocity that slightly underestimates the real flow velocity deduced from flowmeter measurements. Since the grey-level structures remain correlated in time, a second velocity measurement method is applied. An image correlation
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Dates and versions

hal-01166554 , version 1 (23-06-2015)

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Cyril Mauger, Loïc Méès, Marc Michard, Michel Lance. Velocity measurements based on shadowgraph-like image correlations in a cavitating micro-channel flow. International Journal of Multiphase Flow, 2014, 58, pp.301-312. ⟨10.1016/j.ijmultiphaseflow.2013.10.004⟩. ⟨hal-01166554⟩
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