Abstract
An experimental study has been performed by using particle image velocimetry to investigate the effect of nozzle-to-plate separation distance (
L
) and jet impingement angle on the flow characteristics of an obliquely inclined submerged water jet. Measurements were taken for
L
= 1
D
, 2
D
, 4
D
and 6
D
(where
D
is the diameter of the nozzle) for the jet impingement angle (
θ
) of 45° and 26°, and the flow characteristics in the uphill and the downhill regions are investigated at Reynolds number of 2600 (based on the nozzle diameter
D
and the jet velocity
U
o
). It is observed that surface spacing has an opposite effect in the uphill and the downhill regions in terms of wall jet flow. In the uphill region, the tendency of the wall jet to grow increases with increase in
L
/
D
. However, in the downhill region, the jet velocity and its thickness are observed to reduce as the separation distance is increased. The distance between the stagnation point and the geometric centre is observed to decrease with increase in
L
/
D
because of jet–ambient fluid interaction in the uphill region. The jet width is observed to grow for
θ
= 45° in the downstream of the plate due to enhanced jet–ambient fluid interaction. Flow at
θ
= 26° shows that after impingement the entire jet deviates towards the downhill side, which indicates the existence of a critical impingement angle below which there is no flow of the jet in the uphill region. RMS velocity fluctuations and shear stress show an increased turbulence level downstream of the plate in the downhill region for smaller impinging distance implying higher jet–ambient fluid interaction and increased jet width. They, along with the negative turbulence production term, reveal the region of flow separation and reattachment. The decrease in the peak value of Nusselt number can be related to the drop in the jet momentum at the stagnation point with increase in the surface spacing.
Graphic abstract