Gap size effects for the Kelvin-Helmholtz instability in a Hele-Shaw cell - art. no. 026308

We report experimental results for the Kelvin-Helmholtz instability between two immiscible fluids in parallel flow in a Hele-Shaw cell. We focus our i nterest on the influence of the gap size between the walls on the instabili ty characteristics. Experimental results show that the instability threshol d, the critical wavelength, the phase velocity, and the spatial growth rate depend on this gap size. These results are compared to both the previous t wo-dimensional analysis of Gondret and Rabaud [Phys. Fluids 9, 3267 (1997)] and the three-dimensional analysis recently derived by Plouraboue and Hinc h [Phys. Fluids (to be published)], showing that the agreement is still not complete especially when gap size increases.