Further experiments and analysis on flow instability in eccentric annular channels

Gap instability (GI), an inviscid, Kelvin-Helmholtz type, was investigated experimentally and numerically in an eccentric annular channel with an inner-to-outer diameter ratio $d/D=0.5$ and a length of 320 hydraulic diameters, under conditions not sufficiently documented in the literature, namely, low and moderate eccentricities ($02000$. A stability map was constructed and an improved physical model of the gap vortex street was proposed.