Abstract: To investigate the impact of ships on open channel flow, we employed point gauges and Particle Image Velocimetry (PIV) systems to measure water depth and flow fields both upstream and downstream of ships under varying draft conditions. We then analyzed velocity distribution characteristics along the longitudinal profile at the midship region. Our findings reveal the following: 1) In comparison to ship-free conditions, the water depth slightly increases upstream of the ship while decreasing slightly downstream. The influence of ships on water depth amplifies with deeper drafts. The maximum and minimum ratios of water depth in the presence of ship to that in the absence of ship are 1.071 and 0.951, respectively. 2) Along the longitudinal vertical axis of the ship, velocity distribution transforms from a “J” shape at the bow, dips near the stern, and returns to a “J” shape. Upstream of the bow and downstream of the stern, rising and diving flow patterns are observed, respectively. 3) At a ship draft of 0.6 h, maximum velocities occur both longitudinally (along the current direction) and vertically (along the water depth direction) under various conditions. The maximum longitudinal velocity, reaching 2.11 times the average longitudinal velocity in the absence of ship, is observed near the bow (x/l=-2/5). The maximum velocity of diving flow is 0.71 times the average longitudinal velocity in the absence of ship, located near the bow (x/l=-0.5). The maximum velocity of rising flow is 0.29 times the average longitudinal velocity in the absence of ship, positioned near the stern (x/l=2/3).

Key words: ships, particle image velocimetry(PIV), depth of water, velocity distribution, open channel flow