Numerical Simulation Of High Pressure Water Jet Nozzle Combined With Underwater Gas Injection System And Experimental Design

There is a broad hull cleaning market in our country.As a new way of vessel cleaning,high pressure water jet cleaning technology for vessel has attracted more and more vessel cleaning companies due to the advantages of high cleaning quality,high cleaning speed,no pollution and wide application range.In addition,high pressure water jet cleaning technology,which can directly clean ships that are anchored and docked,are arisen to reduce the number of vessels becalmed losses and solve the problem of insufficient dock.But at present there exist some problems,such as high cleaning equipment costs and narrow effective cleaning stand-off distance,in the research of high pressure water jet on underwater cleaning facilities application.The technology of high pressure water jet cleaning combined with underwater gas injection system is proposed in the paper to solve above problems,which are in the process of underwater hull cleaning.And the technology can reduce fluid resistance and improve the range of effective stand-off distance of nozzle under the submerged environment.This paper make the following research to achieve the goal above.Firstly,in this paper,the jet characteristics and cleaning mechanism of high pressure water jet,as well as cavitation phenomenon are discussed briefly,which lay the theoretical foundation for a new type of cleaning technology that is proposed and studied in subsequent content of the paper.Secondly,the technology of high pressure water jet cleaning combined with underwater gas injection system are proposed and the operating principle of it are sketched.Then the nozzle that is related to the technology is also raised and the key structure parameters of the nozzle are determined.And then,the grid of the nozzle and its computational domain are created use the software of Gridgen,and flow field of it under different gas-liquid ratio and at a depth of 10m are numerically simulated use the model of Mixture and SST k-?,that are in the software of CFX.Moreover,the distribution characteristics of velocity and pressure under different gas-liquid ratio are discussed in detail.The general analysis results shows that the effective stand-off distance is increased with the increasing gas-liquid ratio in external circulation,which provides theoretical references for the underwater cleaning operation.Furthermore,a testing device based on this technology,in which underwater cleaning process can be imitate at a depth of 10m or more,is designed.Then the plan of experiment,which is on high pressure water jet combined with underwater gas injection system under different gas-liquid ratio,is designed.And the method of standard specimen erosion is adopted.Finally,after the problems about the numerical simulation of the nozzle and the experimental design of cleaning process are summarized,the paper has put forward to future studies.And the conclusion from the paper provides theoretical references for the design of nozzle.