Laboratory Apparatus #4521161

Forces acting on bodies which are moving in a Fluid (for example air) are important parameters required in order to analyze and design the bodies and vehicles for their aerohydro dynamic characteristics. These forces are largely estimated by measurement on scaled models of the bodies kept in a wind tunnel operating at a suitable wind speed. The forces are then extrapolated to the full scale. The measurements of these forces are conveniently made by appropriate balances which are designed to suit certain specifications. These specifications normally depend on the loads to be measured, size of the models and size of the wind tunnel etc. The three component balance -WBAL00103- manufactured by Sunshine measurements is suitable for use in a wind tunnel having a 600mm x 600mm test section and a maximum speed of 50msec. The estimated maximum loads that are likely to occur on typical suitable model of wings, vehicles, etc kept in the wind tunnel of the above size are of the order as follows. Lift: 10 kgDrag: 2 kgPitching moment: 5kg-mm The Sunshine measurement Balance system suits the above specifications and can be mounted conveniently in 600mm x 600mm test sections.

The apparatus is show in figure (1). It consists of two plates one Perspex and the other glass plate held together with a small gap of 1mm. Water flows through this gap from a tank above and flows out in to a small tank below. Flow is controlled by a tap in the bottom tank. Models can be inserted in to the gap from a plug hole on the perplex sheet and the model can be rotated. Colored die can be injected in to the flow through an adjoining small tank connected to a pipe which leads the die to small holes drilled in the Perspex sheet at the top. The die comes out through the holes as streaks when the flow is properly controlled. There is a vent provided to the bottom tank for removing air locks in the bottom tank. Potassium permanganate dissolved in water can be used as a die.