The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics （CFD） method. A moving mesh method was used to more realis...The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics （CFD） method. A moving mesh method was used to more realistically simulate propulsor working conditions, and the thrust, torque, and lateral force coefficients of both propulsors were compared and analyzed. Forces acting on different parts of the propulsors along with the flow field distribution of steady and unsteady results at different advance coefficients were compared. Moreover, the change of the lateral force and the difference between the abovementioned two methods were mainly analyzed. It was shown that the thrust and torque results of both methods were similar, with the lateral force results having the highest deviation展开更多
Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the aut...Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.展开更多
This study investigates the seismic response and failure mode of a pile-structure system in a liquefiable site by employing a numerical simulation model combined with the shaking-table results of a soil-pile-structure...This study investigates the seismic response and failure mode of a pile-structure system in a liquefiable site by employing a numerical simulation model combined with the shaking-table results of a soil-pile-structure dynamic system.The pile and soil responses obtained from the numerical simulations agreed well with the experimental results.The slopes of the dynamic shear-stress-shear-strain hysteretic curves at different positions also exhibited a decreasing trend,indicating that the shear strength of the soil in all parts of the foundation decreased.The peak acceleration of the soil and pile was not clearly amplified in the saturated sand layer but appeared to be amplified in the top part.The maximum bending moments appeared in the middle and lower parts of the pile shaft;however,the shear forces at the corresponding positions were not large.It can be observed from the deformation mode of the pile-group foundation that a typical bending failure is caused by an excessive bending moment in the middle of the pile shaft if the link between the pile top and cap is articulated,and sufficient attention should be paid to the bending failure in the middle of the pile shaft.展开更多
基金Supported by National Natural Science Foundation of China （41176074, 51209048,51379043,51409063） High tech ship research project of Ministry of industry and technology （G014613002） The support plan for youth backbone teachers of Harbin Engineering University （HEUCFQ1408）
文摘The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics （CFD） method. A moving mesh method was used to more realistically simulate propulsor working conditions, and the thrust, torque, and lateral force coefficients of both propulsors were compared and analyzed. Forces acting on different parts of the propulsors along with the flow field distribution of steady and unsteady results at different advance coefficients were compared. Moreover, the change of the lateral force and the difference between the abovementioned two methods were mainly analyzed. It was shown that the thrust and torque results of both methods were similar, with the lateral force results having the highest deviation
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant Nos. 41176074, 51379043 and 51409063）Acknowledgement This project was supported by the National Natural Science Foundation of China （Grant Nos. 41176074,51379043 and 51409063） and was conducted in response to the great support received from a basic research project entitled ＂Multihull Ship Technology Key Laboratory of Fundamental Science for National Defence＂, which was conducted at Harbin Engineering University. The authors would like to extend their sincere gratitude to their colleagues in the towing tank laboratory.
文摘Experimental tests were conducted to evaluate the hydrodynamic performance of an L-type podded propulsor in straight-ahead motion and off-design conditions using an open-water measuring instrument developed by the authors for podded propulsors, a ship model towing tank, and under water particle image velocimetry （PIV） measurement systems. Under the three types of conditions, the main parameters of an L-type podded propulsor were measured, including the propeller thrust and torque, as well as the thrust, side force, and moment of the whole pod unit.In addition, the flow field on the section between the propeller and the strut was analyzed. Experimental results demonstrate that the dynamic azimuthing rate and direction and the turning direction affect the forces on the propeller and the whole pod unit. Forces are asymmetrically distributed between the left and right azimuthing directions because of the effect of propeller rotation. The findings of this study provide a foundation for further research on L-type podded propulsors.
基金supported by the National Science Fund for Excellent Young Scholars of China(Grant No.51722801).
文摘This study investigates the seismic response and failure mode of a pile-structure system in a liquefiable site by employing a numerical simulation model combined with the shaking-table results of a soil-pile-structure dynamic system.The pile and soil responses obtained from the numerical simulations agreed well with the experimental results.The slopes of the dynamic shear-stress-shear-strain hysteretic curves at different positions also exhibited a decreasing trend,indicating that the shear strength of the soil in all parts of the foundation decreased.The peak acceleration of the soil and pile was not clearly amplified in the saturated sand layer but appeared to be amplified in the top part.The maximum bending moments appeared in the middle and lower parts of the pile shaft;however,the shear forces at the corresponding positions were not large.It can be observed from the deformation mode of the pile-group foundation that a typical bending failure is caused by an excessive bending moment in the middle of the pile shaft if the link between the pile top and cap is articulated,and sufficient attention should be paid to the bending failure in the middle of the pile shaft.
