拖式吊舱推进器的非定常水动力性能

应用升力面理论涡格法和面元法,建立了拖式吊舱推进器非定常水动力性能的数值计算方法。螺旋桨桨叶采用升力面理论涡格法计算,吊舱舱体及支架采用HESS-SMITH面元法计算,螺旋桨与吊舱及支架之间的相互影响通过迭代计算来处理。针对拖式吊舱推进器,通过系统的计算和分析,研究了螺旋桨负荷、吊舱和支架诱导速度各分量以及标称与实效诱导速度对其水动力性能的影响。研究表明,就吊舱及支架的实效诱导速度而言,轴向及周向诱导速度主要由支架引起,径向诱导速度主要由吊舱舱体引起。当考察吊舱推进器的定常水动力性能时,可略去吊舱诱导速度的径向及周向分量;考察非定常性能时,可略去径向分量,但应考虑周向分量的影响。以吊舱及支架的标称诱导速度作为进流,将导致非定常推力、扭矩的平均值降低,脉动量幅值减小,因此,虽然标称诱导速度容易得到,但据此进行吊舱推进器的性能预报或设计都会引起一定的误差。非定常水动力的脉动幅值取决于船尾伴流与吊舱诱导速度的相对比例,略去吊舱诱导速度会导致桨叶非定常力的变化特征发生较大变化。

Research on Unsteady Hydrodynamic Performances of Puller Type Podded Propulsors

Based on potential flow theory,a numerical method is proposed for predicting the steady and unsteady hydrodynamic performances of puller type podded propulsors.In the method,the hydrodynamic forces on propeller blades are calculated with a vortex lattice method,while the hydrodynamic forces on the pod and strut are calculated with the Hess-Smith method.Hydrodynamic interactions between the propeller and the pod and strut are treated via iterative calculations.Based on the method,a computation program is designed,written and tested,and then is used to investigate the hydrodynamic characteristics of podded propulsors.The influence of the propeller loads,nominalinduced velocity,effective induced velocity of the pod and strut,and their components on the unsteady hydrodynamic performances of podded propulsors is investigated systemically.The results show that for the effective induced velocity of the pod and strut,the axial and tangential components are mainly induced by the strut,while the radial component is mainly induced by the gondola.It is feasible to neglect the effects of the radial and circumferential components of the induced velocity of the pod when the steady hydrodynamic performance of a podded propulsor is investigated,and to neglect the effect of the radial component for unsteady performance.The nominal induced velocity of the pod can be obtained easily,but some errors will appear when the design or performance prediction of a podded propulsor is dealed with based on this.The fluctuation amplitudes of the unsteady hydrodynamic forces and moments depend upon the ratio between the hull wake and the induced velocity of the pod,while the characteristics of the unsteady forces will vary noticeably when the induced velocity of the pod is neglected.