Experimental Study of the Front Velocity in an Interfacial flow across a U-shaped tube

The pressure-driven displacement flow of two immisciblefluids (water and diesel) is experimentally studied in a Ushapedtube. The diesel is injected to the U-tube which isfilled with water, discharging it from another end. The flowpatterns and the local front velocity (Vf) as a function ofReynolds number and the flow curvature (θ) are examined.At low Reynolds numbers, buoyancy force of water exertedto the diesel front is dominant. The Kelvin-Helmholtzinstabilities disturb the interface. By increasing theReynolds number, the inertia force of diesel graduallyovercomes the buoyancy. Depending on the Reynoldsnumber the bamboo waves can be observed. It was foundthat Vf is highly dependent on the Reynolds number alongthe flow. Using a normalized front velocity, an empiricalrelationship is developed to express the front velocity interms of θ.