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
Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fiel...Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fields.With fish-like propulsion systems,it is important to pay more attention to complex flow fields.In this paper,the influence of vortices on the hydrodynamic performance of 2-D flapping-foils was investigated.The flapping-foil heaved and pitched under the influence of inflow vortices generated by an oscillating D-section cylinder.A numerical simulation was run based the finite volume method,using the computational fluid dynamics(CFD) software FLUENT with Reynolds-averaged Navier-Stokes(RANS) equations applied.In addition,dynamic mesh technology and post processing systems were also fully used.The calculations showed four modes of interaction.The hydrodynamic performance of flapping-foils was analyzed and the results compared with experimental data.This validated the numerical simulation,confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices.展开更多
This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were an...This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were analyzed and designed for a range of water depths using different mooring line materials.These were steel wire rope, polyester rope and HMPE (high modulus poly ethylene).The mooring analysis was carried out using the advanced fully coupled time domain analysis method in the computer software package HARP.Diffraction analysis was first applied to solve the hydrodynamic properties of the vessel and then the motion equations of the complete dynamic system including the drilling rig, the mooring lines and risers were developed and solved in the time domain.Applying the advanced analysis method, a matrix of mooring systems was developed for operating in water depths of 1000 m, 1500 m, and 2 000 m using various mooring materials.The development of mooring systems was conducted in accordance with the commonly adopted mooring design code, API RP 2SK and API RP 2SM.Fresh attempts were then made to comparatively evaluate the mooring system's characteristics and global performance.Useful results have been obtained in terms of mooring materials, water depths, and key parameters of mooring configurations.The results provide in-depth insight for the design and operation of deepwater mooring systems in the South China Sea environment.展开更多
Offloading application to cloud can augment mobile devices' computation capabilities for the emerging resource-hungry mobile application, however it can also consume both much time and energy for mobile device off...Offloading application to cloud can augment mobile devices' computation capabilities for the emerging resource-hungry mobile application, however it can also consume both much time and energy for mobile device offloading application remotely to cloud. In this paper, we develop a newly adaptive application offloading decision-transmission scheduling scheme which can solve above problem efficiently. Specifically, we first propose an adaptive application offloading model which allows multiple target clouds coexisting. Second, based on Lyapunov optimization theory, a low complexity adaptive offloading decision-transmission scheduling scheme has been proposed. And the performance analysis is also given. Finally, simulation results show that,compared with that all applications are executed locally, mobile device can save 68.557% average execution time and 67.095% average energy consumption under situations.展开更多
The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Das...The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.展开更多
This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic d...This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic disciplines. The present investigation was performed within the framework of the 2-D slender body method （SBM） by calculating the resistance of three symmetric trimaran series moving in a calm free surface of deep water. Each trimaran series comprises of 4681 configurations generated by considering 151 staggers （-50%≤a≤＋ 100%）, and 31 separations （100%≤β≤400%） for 81 Froude numbers （0.20≤Fn≤ 1.0）. In developing the three trimaran series, Wigley-st. AMECRC-09, and NPL-4a models were used separately for both the main and side hulls of each individu;d series models. A computer macro named Tri-PL was created using the Visual Basic for Applications~. Tri-PL~ sequentially interfaced Maxsurfe then Hullspeed to generate the models of the three trimaran series together with their detailed hydrostatic particulars, followed by their resistance components. The numerical results were partially validated against the available published numerical calculations and experimental results, to benchmark the Tri-PL macro and hence to rely on the analysis outcomes. A graph template was creaLed within the framework of SigmaPlot to visualize the significant results of the Tri-PL properlv.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Supported by the National Natural Science Foundation of China under Grant No.50579007,50879014the specialized research fund for the doctoral program of higher education under Grant No.200802170010
文摘Fish are able to make good use of vortices.In a complex flow field,many fish continue to maintain both efficient cruising and maneuverability.Traditional man-made propulsion systems perform poorly in complex flow fields.With fish-like propulsion systems,it is important to pay more attention to complex flow fields.In this paper,the influence of vortices on the hydrodynamic performance of 2-D flapping-foils was investigated.The flapping-foil heaved and pitched under the influence of inflow vortices generated by an oscillating D-section cylinder.A numerical simulation was run based the finite volume method,using the computational fluid dynamics(CFD) software FLUENT with Reynolds-averaged Navier-Stokes(RANS) equations applied.In addition,dynamic mesh technology and post processing systems were also fully used.The calculations showed four modes of interaction.The hydrodynamic performance of flapping-foils was analyzed and the results compared with experimental data.This validated the numerical simulation,confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices.
基金Supported by China National 111 Project under Grant No.B07019
文摘This paper addresses the need for systematic evaluation of the station keeping systems of deepwater drilling semi-submersibles.Based on the selected drilling semi-submersible configuration, the mooring systems were analyzed and designed for a range of water depths using different mooring line materials.These were steel wire rope, polyester rope and HMPE (high modulus poly ethylene).The mooring analysis was carried out using the advanced fully coupled time domain analysis method in the computer software package HARP.Diffraction analysis was first applied to solve the hydrodynamic properties of the vessel and then the motion equations of the complete dynamic system including the drilling rig, the mooring lines and risers were developed and solved in the time domain.Applying the advanced analysis method, a matrix of mooring systems was developed for operating in water depths of 1000 m, 1500 m, and 2 000 m using various mooring materials.The development of mooring systems was conducted in accordance with the commonly adopted mooring design code, API RP 2SK and API RP 2SM.Fresh attempts were then made to comparatively evaluate the mooring system's characteristics and global performance.Useful results have been obtained in terms of mooring materials, water depths, and key parameters of mooring configurations.The results provide in-depth insight for the design and operation of deepwater mooring systems in the South China Sea environment.
基金supported by National Natural Science Foundation of China (Grant No.61261017, No.61571143 and No.61561014)Guangxi Natural Science Foundation (2013GXNSFAA019334 and 2014GXNSFAA118387)+3 种基金Key Laboratory of Cognitive Radio and Information Processing, Ministry of Education (No.CRKL150112)Guangxi Key Lab of Wireless Wideband Communication & Signal Processing (GXKL0614202, GXKL0614101 and GXKL061501)Sci.and Tech.on Info.Transmission and Dissemination in Communication Networks Lab (No.ITD-U14008/KX142600015)Graduate Student Research Innovation Project of Guilin University of Electronic Technology (YJCXS201523)
文摘Offloading application to cloud can augment mobile devices' computation capabilities for the emerging resource-hungry mobile application, however it can also consume both much time and energy for mobile device offloading application remotely to cloud. In this paper, we develop a newly adaptive application offloading decision-transmission scheduling scheme which can solve above problem efficiently. Specifically, we first propose an adaptive application offloading model which allows multiple target clouds coexisting. Second, based on Lyapunov optimization theory, a low complexity adaptive offloading decision-transmission scheduling scheme has been proposed. And the performance analysis is also given. Finally, simulation results show that,compared with that all applications are executed locally, mobile device can save 68.557% average execution time and 67.095% average energy consumption under situations.
文摘The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.
文摘This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic disciplines. The present investigation was performed within the framework of the 2-D slender body method （SBM） by calculating the resistance of three symmetric trimaran series moving in a calm free surface of deep water. Each trimaran series comprises of 4681 configurations generated by considering 151 staggers （-50%≤a≤＋ 100%）, and 31 separations （100%≤β≤400%） for 81 Froude numbers （0.20≤Fn≤ 1.0）. In developing the three trimaran series, Wigley-st. AMECRC-09, and NPL-4a models were used separately for both the main and side hulls of each individu;d series models. A computer macro named Tri-PL was created using the Visual Basic for Applications~. Tri-PL~ sequentially interfaced Maxsurfe then Hullspeed to generate the models of the three trimaran series together with their detailed hydrostatic particulars, followed by their resistance components. The numerical results were partially validated against the available published numerical calculations and experimental results, to benchmark the Tri-PL macro and hence to rely on the analysis outcomes. A graph template was creaLed within the framework of SigmaPlot to visualize the significant results of the Tri-PL properlv.
