  We report on experimental observations on the modifications in the
propagation characteristics of precursor solitons due to the different shapes
and sizes of the object over which the dust fluid flows. The experiments have
been performed in a $\Pi$ shaped Dusty Plasma Experimental (DPEx) device where
dusty plasma is created in a DC glow discharge Ar plasma using kaolin
particles. A floating copper wire installed radially on the cathode, acts as a
charged object in the plasma environment. The flow on the dust fluid is
initiated by suddenly lowering the potential of the charged object from
grounded potential to close to floating potential. The size (height and width)
of the potential hill is then varied by drawing current from the wire through a
variable resistance. With a decrease in the height of the potential hill, the
amplitude, velocity and the number of exciting precursor solitons are found to
decrease whereas the widths of the solitons are seen to increase. It is found
that below a threshold value these solitary waves are not excited and the dust
fluid simply flows over the hill. To examine the effect due to the shape of the
potential profiles, the wire is replaced by a triangular object. Only trailing
wakes are seen to be excited when the dust fluid faces the linearly increasing
slope of the potential profile whereas both solitons and wakes get excited when
the object is placed with the sharp edge facing the flow. All the experimental
findings qualitatively agree with numerical solutions obtained with different
source terms in the forced-Korteweg de Vries (f-KdV) model equation.
