Explain the construction and working of Reddy’s shock tube. Mention any three applications of shock waves.

1. b) With a neat diagram, explain the construction and working of Reddy’s shock tube. Mention any three applications of shock waves.

Answer:

Construction: Reddy tube operates on the principle of conventional piston driven shock tube. Reddy shock tube is made of simple medical syringe with the following dimensions.

• Compression chamber is of length 60mm and diameter 12.8mm.
• A plastic piston with plunger with outer diameter 12.8mm fitted closely inside the compression chamber.
• O-rings on the piston head prevent the leakage of leaking of gas.
• The driven tube is a 30 mm long SS tube of 1 mm internal diameter and wall thickness of 0.8 mm.
• The compression tube and the shock tube (hypodermic needle) are separated by a 50 μm thick plastic diaphragm.
• The elliptic free end of the hypodermic needle (shock tube) is made circular by grinding and is open to atmospheric air

Working :

Diaphragm and the needle are detached from the compression tube and the piston is moved outwards to fill the compression chamber with ambient air at atmospheric pressure. The diaphragm and the needle are attached to the compression tube. The piston is pushed into the compression chamber so that the air inside is compressed and pressure builds. As the piston moves the pressure increases and finally the diaphragm ruptures resulting in the very high speed flow of the compressed air. Schlieren images of the flow at the exit of the Reddy tube confirm the generation of shock waves. Thus shock waves of mach 1.5 to 2.0 are generated at the tip of the needle.

Applications of Shock waves: (Any 3)

1. Mach reflection of a shock wave is used to remove micron size dust particles from the surface of silicon wafers.
2. Shock waves are used in medical therapy in orthopedics and for breaking kidney stones.
3. Shock waves are used in pencil industries to impregnate preservatives into wood slats.
4. Shock waves are used in sandal oil extraction.
5. Shock waves are used in cell transformation.
6. Shock waves are used in geophysics.