Question

The fluid layer which is in contact with a smooth wall is called ____________

(a) Inviscid layer

(b) Linear sub-layer

(c) Log-law layer

(d) Wake-law layer

The question was posed to me in an interview for internship.

My question comes from Turbulent Boundary Layer in chapter Turbulence Modelling of Computational Fluid Dynamics

Answer 1

The correct answer is (b) Linear sub-layer

To explain I would say: In the fluid layer which is in contact with a smooth wall, the value of dimensionless velocity and dimensionless cross-stream distance tend to be the same. Because of this linear relationship, the layer is named linear sub-layer.