Across the normal shock, fluid properties change in such a manner that the: 1) Velocity of flow is subsonic 2) Pressure increases 3) Specific volume decreases 4) Temperature decreases Which of the above are correct?

Option 4 : 1, 2 and 3 only

Explanation:

Shock waves:

• It has been found experimentally that, under some circumstances, it is possible for an almost spontaneous change to occur in a flow, with the velocity decreasing and pressure increasing through this region of sharp change.
• Such regions of sharp change can only occur if the initial flow is supersonic.
• The extremely thin region in which the transition from the initial supersonic waves, relatively low-pressure state to the state that involves low velocity, subsonic and high pressure is known as shock waves.
• A shock wave that is straight and at a right angle to the flow direction is known as Normal shock wave.

Across normal shock fluid properties change as follows:

• Velocity of flow decreases
• Pressure increases
• specific volume decreases
• Temperature increases
• Entropy increases
• Stagnation pressure decreases
• Density increases