Control of Radial Miscible Viscous Fingering Using a Finite Blob-An Experimental Study.

We experimentally demonstrate the control of miscible viscous fingering instability in a novel way. We consider the less viscous fluid initially in a circular blob of finite radius r$_{\mathrm{0}}$ displacing the surrounding more viscous fluid in the radial Hele-Shaw cell. Experiments only with a point source (r$_{\mathrm{0}} \quad =$0) are available in the literature. Getting initial finite circular blob is a huge experimental challenge. For each r$_{\mathrm{0}}$, a flow rate is wisely calculated so as to have a stable displacement up to radius r$_{\mathrm{0}}$. Also, a diligently designed T- junction is utilized in the Hele-Shaw experimental set-up to ease the fluid injection. The experiments depict the initial radius of the circular blob (r$_{\mathrm{0}}_{\thinspace })$ as a controlling parameter. A delay in instability is observed for experiments with non-zero r$_{\mathrm{0}}$ in comparison to those performed with a point source. Further, a reduced instability is evident with an increase in r$_{\mathrm{0}}$, which is in agreement with the numerical simulations performed.