In this paper, scouring in confluences was experimentally studied considering the effects of bank slope angle (θ) of the main channel, discharge ratio (Qr) of tributary channel and densimetric Froude number (Frg3) of the post-confluence channel. The experiments were conducted using the constant confluence angle (α) equal to 90° and various bank slope angles including 45°, 60°, 75° and 90°. Applying different Qr and Frg3, the maximum effect of θ on scour depth was observed when the minor Qr was used in the tributary channel. The mildest bank slope angle caused the minimum scour depth for any given Frg3. Generally, the experiment using θ = 45° and Qr = 0.194 showed the best performance and reduced the maximum scour depth by 46%. Considering two obtained empirical relationships, it was concluded that the effect of θ on the height of point bar is more than its effect on the scour depth. Finally, Frg3 and θ demonstrated their greatest influences on dimensionless scour depth (dse/y3) and dimensionless height of point bar (Hse/B3), respectively.
The effect of geometry of channel and flow condition at the confluence on scouring and point bars.
Presenting experimental relationships to estimate the scour depth and the height of point bar.