What Does "Lead the Boat to the Higher Side of Water Flow and Then Sail it Towards the Lower Side Bank"

To sail a boat through a river bend is highly skill demanding and the instruction " lead the boat to the higher side of the water flow and then sail it towards the lower side bank when passing through a river bend downwards" is commonly followed in inland water navigation. In order to better understand the instruction, the process of passing through a bending reach of the Yangtze River is studied quantitatively. The flow field at the bending reach is measured and the law of ship motion in the area is analyzed. The analysis shows that appropriately setting the deviation to upper side of the water flow and the ship drift angle can effectively compensate the influence of the water flow on ship course and make a ship safely pass through the river bend. Typical operation experiences are investigated and the deviation and the drift angle used by skillful navigators are compared with those calculated.