Abstract:
Particle Image Velocimetry (PIV) is herein used to
investigate the influence of the bed roughness in the
development of unsteady gravity currents, namely in what
concerns the instantaneous two-dimensional velocity and
vorticity fields. Density currents are performed by
lock-release of a fixed volume of saline water into a fresh
water tank. The experiments were conducted in a 3.0 m
long Perspex flume of horizontal bed and rectangular cross
section of 0.20 x 0.30 m2. Four experiments were
performed by varying the bed roughness maintaining the
initial density of the saline water in the lock, the lock length
and the water depth. The analysis of instantaneous velocity
and vorticity maps obtained in the vertical centreline plane
of the channel show that bed roughness reduces the overall
streamwise velocity within the current and confers a
vertically homogenized velocity distribution, therefore
reducing the vorticity magnitude.
