A Study on the Effectiveness of a Built-In Aeration Feature for Navigation Lock Valves

Abstract

The cavitation problem at the valve section of the filling and emptying system is a very prominent hydraulic problem in high-lift navigation locks. Drawing air into the valve section is an economic and effective method to alleviate and even avoid the cavitation problem. However, the existing spatially fixed aeration facilities cannot efficiently solve the cavitation problem arising from the shear flow below the valve lip (called valve lip cavitation problem) for those high-lift navigation locks operated under fluctuating water levels. Thus, a new aeration feature located at the valve lip was proposed, which can move with the valve and draw air to the shear flow. The specific valve lip style and aeration slot style together with its location are determined through analysis on the results of both numerical simulation and a physical model. Dimensional analysis demonstrated that k/ki (relative cavitation parameter k/ki, k is the actual cavitation parameter and ki is the cavitation index at which cavitation is incipient) is mainly affected by n (relative valve opening), H/AV0.5 (H is lock lift and AV is the cross-sectional area of the valve section), and hs/AV0.5 (hs is initial submerged water depth), with a certain structure and size of the culvert system. A total of 16 groups of experiments were conducted and 160 groups of data were analyzed by means of the full factorial method (FFM). With the proposed aeration feature, air can be drawn smoothly into the culvert system under those operating conditions requiring cavitation alleviation. The aeration intensity of the aeration feature is positively related to the severity of valve lip cavitation. Combined with drawing air at the valve slit, the new aeration feature can reduce the submerged depth of the valve section, simplify the culvert style near the valve, and broaden the efficient work head range of locks.