The effect of surface curvature on the development of a two-dimensional
wall jet
was investigated experimentally. A comparison was made between a wall jet
flowing
around a circular cylinder and its plane equivalent. Velocity surveys and
surface
pressure measurements in the curved wall jet suggest the existence of two
primary
regions of interest. The first region, ranging from the end of the potential
core to
an approximate angular position of θ=120°, is characterized by
a constant surface
pressure and a self similarity of the mean flow. The second region is marked
by an
adverse pressure gradient leading to separation around θ=230°.
The rate of spread
of this flow, even in the initial region, is much higher than in the plane
wall jet and
so are the levels of turbulence and Reynolds stress. The dominant lengthscale
in this
flow is the radius of curvature R and the dominant velocity scale
is the square root
of the kinematic jet momentum divided by the radius of curvature. Entrainment
of
ambient fluid which causes the jet to adhere to the curved surface is also
the main
reason for its separation which is preceded by a rapid rate of spread of
the flow
leading to the failure of the boundary-layer approximation.
A Study on the Three-Dimensional, Round Wall Jet along a Circular Cylinder. Effects of Ejection Angle.
