Explain the hydraulically smooth and rough bounday surface.

If the irregularities on any actual surface are such that the effects of projections do not penetrate through the viscous sublayer, the surface is called hydraulically Smooth.

If the irregularities on any actual surface are such that the effects of projections extend beyond the viscous sub-layer so that the laminar layer is broken up, then such surface are hydraulically Rough surface.

From Nikuradse's experiment,

• If `e/delta_v  < 0.25`, the surface is smooth.

• If `e/delta_v > 0.25`, the surface is rough.

where, `delta_v` is the thickness of viscous sublayer.

For hydraulically smooth pipe flow, the friction factor f is a function of Reynolds Number only.

For hydraulically Rough surface, the friction factor f is a function of only relative roughness ratio.

With increasing Reynolds Number, .... Show More

If the irregularities on any actual surface are such that the effects of projections do not penetrate through the viscous sublayer, the surface is called hydraulically Smooth.

If the irregularities on any actual surface are such that the effects of projections extend beyond the viscous sub-layer so that the laminar layer is broken up, then such surface are hydraulically Rough surface.

From Nikuradse's experiment,

• If `e/delta_v  < 0.25`, the surface is smooth.

• If `e/delta_v > 0.25`, the surface is rough.

where, `delta_v` is the thickness of viscous sublayer.

For hydraulically smooth pipe flow, the friction factor f is a function of Reynolds Number only.

For hydraulically Rough surface, the friction factor f is a function of only relative roughness ratio.

With increasing Reynolds Number, there is a gradual transition from smooth to rough flow.