Item Description

The concept of vortex flows is important in many engineering applications of fluid mechanics. The flow circulates about a fixed center and the stream lines are concentric circles. The classification of vortex flows depends upon the functional relationship between the flow velocity and radius. In the free vortex, the flow velocity is inversely proportional to the radius and the total head in the flow field remains constant. In the forced vortex, the whole body of the fluid rotates as if it is a solid and the flow velocity is directly proportional to the radius. It is essential to demonstrate free and forced vortex flows to understand the basic concepts of fluid mechanics. The Sci-tech Free and Forced Vortices Apparatus Model FM 14is an important experimental set-up necessary for any fluid mechanics and physics laboratories of an educational institution.

The Sci-tech Free and Forced Vortices Apparatus Model FM 14 has been designed to generate free and forced vortices. It is possible to measure surface profiles and total head distributions in the vortex flow field. The apparatus consists of a transparent cylindrical tank having a hole in the center of the base to fix interchangeable push-in orifices while conducting free vortex experiments. The cylinder is mounted on a base plate having leveling screws. The free vortex is generated by discharging water from the tank through the orifice in the base. Two 12mm diameter flow entry tubes placed diametrically opposite near the wall at the base and angled at about 20⁰ to the diameter supply water imparting swirling motion to the liquid entering the vessel. Forced vortex experiments are conducted by closing the orifice at the base by a bushed plug. The forced vortex is generated in the tank by rotating the two bladed paddle positioned at the base.

The paddle rotates on a vertical shaft which is supported by the bushed plug at the base and a suitable hole in the bridge piece fitted across the diameter of the tank at the top. Water jets from the two 8mm diameter flow entry tubes placed diametrically opposite and angled at about 70⁰ to the diameter impinge on the blades and rotate the paddle. Water is drained using the 12mm diameter tubes. The bridge piece accommodates depth gauges required to map the vortex profiles. The total head in the free and forced vortex flow field is measured using a pitot probe. Colored dye can be injected into the flow using hypodermic tubes to visualize streamlines. The FM00 Hydraulic bench or any other standard hydraulic bench models can be used to supply water. A constant head overhead tank can also be used to supply water at controlled flow rate. The complete unit is manufactured from corrosion resistant material.

FREE VORTEX

A free vortex is formed when water flows out of a vessel through a central hole in the base. The degree of the rotation depends on the initial disturbance. In a free cylindrical vortex, the velocity varies inversely with the distance from the axis of rotation.