The flume is made of transparent glass, precision-built toensure parallel walls and a consistently accurate cross section along itslength. The Viscosity and Particle Drag apparatus is a simplefalling-sphere viscometer. The self-standing unit holds two glass tubes filled with the test fluids, for comparisons and to minismise draining and refillingof the fluids after experimentation. A sturdy steel square-section firmly supports the channel throughoutits length. It has a floor-standing frame that supports the working section ata convenient eye-level position for students. The back plate has a low-voltage backlightso students can easily see the test spheres through the fluid. Students fillthe two tubes with their chosen test fluid, then select a sphere of the correctdensity and size for the fluid. They drop the sphere into the test fluid at thetop of the glass tube. The valve systemminimises the fluid loss from the tube and helps when draining the tube afterthe tests are complete. Students may also make their own use shapes to test inthe unit. The shapes must fi t through the valve at the base (maximum 8 mm inany single dimension). They then use a stopwatch (included) to measure the timetaken for the sphere to fall a set distance down the tube. When the test spherereaches the bottom of the tube, it enters a valve that the students turns,dropping the sphere into a collection vial for recovery. The apparatus can be used with any fluid that can besafely handled and is chemically compatible with the wetted parts of theequipment - glass and PTFE. Suitable test fluids include water, thin machine oil,castor oil and motor oil.
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