Stability analysis of Hoist Vertical Shiplift chamber under pitching motion

Aiming at the stability problem of large Hoist Vertical Shiplift chamber under pitching motion. A fluid dynamic model based on the Housner theory is built to study the sloshing in the ship chamber. The theoretical formulas of the capsizing moments are derived to research the effect of sloshing. To study the whole shiplift pitching stability, the system coupled by pitching motion, torsional vibration of main hoist and sloshing is built. Then, the critical distance of lifting points is obtained by using the Hurwitz theory. Taking seven built typical Hoist Vertical Shiplifts as examples, it is verified that the expression about the critical distance of lifting points is rational. The calculation results show that the sloshing in the ship chamber and the capsizing moment produced by the convective pressure acting on the sidewall of ship chamber could not be neglected in the design of the Hoist Vertical Shiplift. According to the successful experience of the Hoist Vertical Shiplift, it is suggested that the safety factor S of the shiplift under pitching motion should be more than 1.5. (paper)