This research focuses on resuspension and transport of
sediments in a partially standing water wave. The flow regime was generated
using a pneumatic piston wavemaker in a small-scale laboratory glass flume.
Particle Image Velocimetry (PIV) was used for simultaneous visualization and
velocity measurements. Observations reveal that sediment particles resuspend
intermittently at a location, which changes dynamically within a small limited
range, and form coherent well-defined narrow streaks of sediments. Velocity
vector fields across vertical cross sections along the flume centerline for
both sediment and neutrally buoyant particles were obtained. The measured velocities
were used to calculate the periodic velocity, drift velocity, shear stresses,
vorticity, Lagrangian velocity, particle trajectories and turbulent field. A
good correlation was found between the resuspension location and the location
of maximum velocity gradient, ðu/ðy . A topological similarity was
identified when comparing the pattern of suspended matter and velocity related
properties such as time average velocity field, Lagrangian velocity field,
vorticity and particle trajectories. The velocity fields of the neutrally
buoyant and of the sediment particles were almost identical. This indicates
that flow modulation by the sediment particles is minimal and the convective
flow field plays a major role in the transport of the sediments. The existence
of a narrow particle streak and the particular shape it forms may indicate that
a phase correlation exists between the resuspension of particles, the periodic
field, maximum shear, and the instantaneous location of the particles streak.
It is not clear yet what causes the resuspension intermittency. An analysis of
the turbulent velocity field shows that it consists of long-lived vortex-like
structures, which maintain their coherence for many wave periods. It is not
clear what is the exact time history of these structures within the wave
period. To answer this question, measurements at higher frequency are required.
