Isothermal Jet Suction Through the Lateral Openings of a Cylindrical Funnel

This paper discusses the computation of air entrainment in to the louvers of a cylindrical funnel as a result of a high-velocity isothermal air jet placed inside the funnel having different lengths of protrusion and different funnel diameters. The experimental setup consists of a cylindrical Perspex tube with circular louvers cut around it. The flow through the nozzle is measured with a rotameter, and the velocity at the cylinder outlet is measured with a hot wire anemometer. The numerical simulation is carried out by solving the conservation equations of mass and momentum for the funnel with a surrounding computational domain so that the suction can take place at the louver entry. The resulting equations have been solved numerically using finite volume technique in an unstructured grid employing eddy viscosity based two-equation k-e turbulence model of Fluent 6.3. It has been found from the experiment and the CFD computation that there exists an optimum funnel diameter for which the mass ingress into the funnel is highest, and also there exists an optimum protrusion length of the nozzle that entrains maximum air flow into the funnel. For isothermal air suction the mass ingress into the funnel does not depend on the inclination of the funnel, whereas for low velocity and high temperature of the nozzle fluid the mass ingress in to the funnel depends on the inclination of the funnel. After a critical nozzle velocity (Gr/Re2 < 0.5), the mass ingress into the funnel does not again depend on the inclination of the funnel. An approximate relation for the entrance length of a sucking pipe has also been developed from the present CFD solution. The original contribution of the paper is the setting of a computational methodology for computing various conditions of suction flow in to a funnel while having the numerical confidence by comparing the CFD result with a small-scale experimental measurement in the laboratory.