Abstract:
Turbulent flows over the flat surface undergoing a sudden change
of surface roughness were studied experimently. The experiment
was carried out in a wind tunnel test section, the floor of
which was used as t'lesurface of interest. The surface was artificially
roughned by thin synthetic fibres giving a brush like structure
of average height 23.2 mm (0.913 inch). The flow parameters were
5 5 measured at three Reynolds number viz. B.74XIO , 5.06XIO and
5 2.56XIO .
Measurement of boundary layer parameters was done by pitot static
tube. The flow became fully developed over the .rough surface at
3.5 duct width of the tunnel from the rough-smooth junction.
Sharp pressure drop in the rough-smoothe junction indicates high
dissipation of energy in the transition zone. Friction factor over
the rough surface is found to be dependent on Reynolds number.
The growth of intern~l boundary layer is proportional to xO.49
Origin of the rough surface is observe j 0.6 inch below the crest
of the roughness element, Equivalent sand roughness of the surface
is found to be 3.23 m.m (0.127 inch)
