The fluid flowing over a solid surface has zero relative velocity at the surface. The fluid which is in direct contact with the surface does not move(or moves with the surface) and it sticks to the surface. This is known as a no-slip condition.

If the fluid did not stick to the surface at the surface then, the fluid would have slipped over the surface and the viscosity effects/shear stresses/frictional losses at the solid-fluid boundary would have been completely avoided.

What can you do with this information?

Having knowledge about no-slip condition can be helpful when designing airplane wings, car aerodynamics, etc. The frictional effect of air over these surfaces plays a vital role in deciding their shapes and sizes. If you know about the no-slip condition and the boundary layer height, you can calculate shear stresses on the surface and these stresses can be optimized/minimized by changing shapes through trial and error (CFD).

The no-slip boundary condition also helps to calculate heat transfer between solid and fluid. As the fluid is assumed stationary with respect to the surface, the heat is transferred as conduction between the solid and fluid layer at the surface. The amount of heat transferred through convection by the fluid layers adjacent to the stationary layer at the surface is exactly equal to the amount of heat that is conducted at the surface.

The fluid flowing over a solid surface has zero relative velocity at the surface. The fluid which is in direct contact with the surface does not move(or moves with the surface) and it sticks to the surface. This is known as a no-slip condition.

If the fluid did not stick to the surface at the surface then, the fluid would have slipped over the surface and the viscosity effects/shear stresses/frictional losses at the solid-fluid boundary would have been completely avoided.

What can you do with this information?Having knowledge about no-slip condition can be helpful when designing airplane wings, car aerodynamics, etc. The frictional effect of air over these surfaces plays a vital role in deciding their shapes and sizes. If you know about the no-slip condition and the boundary layer height, you can calculate shear stresses on the surface and these stresses can be optimized/minimized by changing shapes through trial and error (CFD).

The no-slip boundary condition also helps to calculate heat transfer between solid and fluid. As the fluid is assumed stationary with respect to the surface, the heat is transferred as conduction between the solid and fluid layer at the surface. The amount of heat transferred through convection by the fluid layers adjacent to the stationary layer at the surface is exactly equal to the amount of heat that is conducted at the surface.