The waterjet propulsion is widely applied in the marine vessels over 30 knots,and the intake duct is considered as an essential component that strongly relates to the propulsion performance.This paper sheds light on t...The waterjet propulsion is widely applied in the marine vessels over 30 knots,and the intake duct is considered as an essential component that strongly relates to the propulsion performance.This paper sheds light on the flow features inside an intake duct under mooring conditions by using the particle image velocimetry(PIV)technique with three-dimensional(3D)numerical simulations.The hydraulic loss gradually increase as the flow-rate increases.According to analyses via the Bernoulli equation,the hydraulic loss is composed of the frictional head loss(h_(f)~V^(1.75))and the local head loss(h_(j)~V^(2.0)).A recirculation region is observed near the duct lower wall with a high-velocity flow near the upper wall,and subsequently a shear flow presents in the horizontal straight pipe with an obvious velocity gradient.Three-dimensional simulations demonstrate that the vortex pair is very strong in the recirculation region and then it gradually decreases as the fluid flows downstream.With the flow-rate increasing,the non-uniformity at the duct outlet firstly increases to a peak and then slightly decreases,while the perpendicularity at the duct outlet dramatically decreases to a minimum and then increases.This work not only reveals some physics of the waterjet propulsion under mooring conditions,but also promotes its efficient operation.展开更多
By solving the three-dimensional incompressible Reynolds-averaged Navier-Stokes equations,numerical simulations of the viscous flow within a flush type intake duct of a waterjet under different motion conditions are c...By solving the three-dimensional incompressible Reynolds-averaged Navier-Stokes equations,numerical simulations of the viscous flow within a flush type intake duct of a waterjet under different motion conditions are carried out.Therein,the effects of the steering and reversing unit as well as the impeller shaft on the flow field are taken into account.The numerical results show that the static pressure under backward conditions with the reversing jet flow is the lowest,and the cavitations are most likely to occur within the intake duct.The flow field under forward conditions is less uniform because of the shaft,while the velocity uniformity under backward conditions is improved.The shaft rotation causes an asymmetric secondary flow above the shaft under all conditions.The pressure contours under backward conditions with the reversing jet flow are sensitive to the presence of the shaft.This study can provide some references for the design optimization of waterjet propulsion system.展开更多
基金the National Natural Science Foundation of China(Grants 52006232 and 11772340)the Science and Technology on Water Jet Propulsion Laboratory(Grant 6142223190101).
文摘The waterjet propulsion is widely applied in the marine vessels over 30 knots,and the intake duct is considered as an essential component that strongly relates to the propulsion performance.This paper sheds light on the flow features inside an intake duct under mooring conditions by using the particle image velocimetry(PIV)technique with three-dimensional(3D)numerical simulations.The hydraulic loss gradually increase as the flow-rate increases.According to analyses via the Bernoulli equation,the hydraulic loss is composed of the frictional head loss(h_(f)~V^(1.75))and the local head loss(h_(j)~V^(2.0)).A recirculation region is observed near the duct lower wall with a high-velocity flow near the upper wall,and subsequently a shear flow presents in the horizontal straight pipe with an obvious velocity gradient.Three-dimensional simulations demonstrate that the vortex pair is very strong in the recirculation region and then it gradually decreases as the fluid flows downstream.With the flow-rate increasing,the non-uniformity at the duct outlet firstly increases to a peak and then slightly decreases,while the perpendicularity at the duct outlet dramatically decreases to a minimum and then increases.This work not only reveals some physics of the waterjet propulsion under mooring conditions,but also promotes its efficient operation.
基金the Fund of Key Laboratory of Waterjet Propulsion Technology of MARIC(No.61422230301162223010)。
文摘By solving the three-dimensional incompressible Reynolds-averaged Navier-Stokes equations,numerical simulations of the viscous flow within a flush type intake duct of a waterjet under different motion conditions are carried out.Therein,the effects of the steering and reversing unit as well as the impeller shaft on the flow field are taken into account.The numerical results show that the static pressure under backward conditions with the reversing jet flow is the lowest,and the cavitations are most likely to occur within the intake duct.The flow field under forward conditions is less uniform because of the shaft,while the velocity uniformity under backward conditions is improved.The shaft rotation causes an asymmetric secondary flow above the shaft under all conditions.The pressure contours under backward conditions with the reversing jet flow are sensitive to the presence of the shaft.This study can provide some references for the design optimization of waterjet propulsion system.
