Question

For an inviscid flow, if the boundary is stationary and flow is assumed one-dimensional and if V is the velocity of flow then the velocity of layer next to the boundary is:
1. Zero
2. V
3. V/2
4. 2/3 V
5.

Answer 1

Correct Answer - Option 2 : V

Explanation:

(i) When a viscous fluid flows along a fixed impermeable wall, or past the rigid surface of an immersed body, an essential condition is that the velocity at any point on the wall or other fixed surface is zero.

(ii) The extent to which this condition modifies the general character of the flow depends upon the value of the viscosity. If the body is of streamlined shape and if the viscosity is small without being negligible, the modifying effect appears to be confined within narrow regions adjacent to the solid surfaces; these are called boundary layers. Within such layers, the fluid velocity changes rapidly from zero to its main-stream value, and this may imply a steep gradient of shearing stress; as a consequence, not all the viscous terms in the equation of motion will be negligible, even though the viscosity, which they contain as a factor, is itself very small.

For an inviscid flow, there is no viscosity, hence no frictional losses. Hence the velocity throughout is zero.

For real fluid, velocity near the boundary is zero due to no slip condition.