TITLE:
Experimental Study of Two Impinging Jets Aligned With a Crossflow
AUTHORS:
Jorge M. M. Barata, Fernando M. S. P. Neves, Diana F. C. Vieira, André R. R. Silva
KEYWORDS:
Impinging Jets, Crossflow
JOURNAL NAME:
Journal of Modern Physics,
Vol.5 No.16,
October
30,
2014
ABSTRACT: Laser
Doppler measurements provide information on the flowfield created by twin
impinging jets aligned with a low velocity crossflow. The experiments were
carried out for a Reynolds number based on the jet exit conditions of Rej = 4.3 × 104,
an impingement height of 20.1 jet diameters and for a velocity ratio between
the jet exit and the crossflow VR = Vj/Uo of 22.5, and an inter-jet spacing of S = 6D. The
results show a large penetration of the first (upstream) jet that is deflected
by the crossflow and impinges on the ground, giving rise to a ground vortex due
to the collision of the radial wall and the crossflow that wraps around the
impinging point like a scarf. The second jet (located downstream) is not so
affected by the crossflow in terms of deflection, but due to the downstream
wall jet that flows radially from the impinging point of the first jet it does
not reach the ground. The results indicate a new flow pattern not yet reported
so far, that is most relevant for a VSTOL aircraft operating in ground vicinity
with front wind or small forward movement may result in enhanced under
pressures in the aft part of the aircraft causing a suction down force and a
change of the pitching moment towards the ground.