Numerical procedure for static and dynamic analysis of fluid-conveying submarine pipeline span on linear elastic seabed

Based on the Hamilton principle, dynamic differential equation of the submarine pipeline span, under the interaction of internal flow and external environmental loads, is established. A constraint-equivalent method is used to deal with the boundary conditions of pipeline span on the linear elastic seabed. Effects of the internal flow velocity and seabed stiffness on the pipeline’s lateral deformation and bending stress are studied by the static analysis, while the preliminary relationships between the internal flow velocity and the foundation stiffness to the natural frequency of pipeline span are investigated by the dynamic analysis. It is found that the lateral deformation increases with the increment of internal flow velocity, but decreases with the increment of seabed stiffness. The bending stress at the ends of span increases with the increment of internal fluid velocity and the seabed stiffness, however the stress at the middle of the span shows the converse tendency. Moreover, increasing the seabed stiffness or decreasing the internal flow velocity can lead to higher natural frequency. The dynamics response of midpoint of span at different foundations and internal fluid velocities are also given in this paper.     

Numerical hydro-acoustic prediction of marine propeller noise

A source-to-far-field computation procedure aiming at predicting the noise generated by the underwater propeller was presented. Detached eddy simulation (DES) was used to resolve the unsteady flow field, which was taken as input data as noise propagation. Far-field sound radiation was performed by means of Ffowcs Williams-Hawkings (FW-H) equation. The computation procedure was finally applied to a typical marine propeller, David Taylor Model Basin (DTMB) 4118. The sound pressure and directivity patterns of this propeller were discussed.     

Numerical study of damage potential in buildings due to excavations

Evaluation industrial factory building damage potential due to ground movements caused by excavations inside the building is a critical design consideration when reconstructing the underground equipment of the industrial factory building. In this paper,the behavior of a support system for a reconstruction project of underground equipment of the industrial factory building in Shanghai and its effects on a pile-foundation supported building are presented. The 8.1 m deep excavation is made through soft clay to...     

Vertical bearing behavior of cast-in-place diaphragm wall in Shanghai

When diaphragm wall is used as the permanent vertical bearing structure,design standard of the bored pile adopted has to induce the risk or iste. The vertical load transfer mechanism and bearing capacity of the diaphragm wall are examined by a field testing program at the site in Shanghai soft clays. Test results indicate that the diaphragm wall almost behaves as a rigid body under the vertical load. It induces that the skin friction and the toe resistance of the wall develop simultaneously. The skin fricti...     

Research on flow loss of inlet duct of marine waterjets

In the process of performance prediction of waterjet system,the flow loss of inlet duct is usually reckoned by the rule of thumb. But its value is often overestimated to some extent,resulting in error of prediction accuracy. This paper introduces a new method to determine the flow loss by means of computational fluid dynamic (CFD). Firstly,the fluid field around waterjet system is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations using commercial CFD code Fluent. Then an additional U...     

Coupled analysis of multi-body motions in offshore connecting process

The coupled dynamic responses of two pontoons while connecting with each other in irregular waves are calculated by means of 3D potential flow theory. The computation is used to find the optimal status for connecting at certain sea state. On the basis of the relative motion of two pontoons in irregular waves,visual FORTRAN programming language,as well as open graphics library (OpenGL),is used to develop a set of virtual reality system,which is fully interactive and with realistic effect. The transfinite int...     

Development of a twin-accumulator hydro-pneumatic suspension

A twin-accumulator hydro-pneumatic suspension has been developed based on the off-road vehicle in order to meet the requirements of ride comfort. The working principle and elements construct of the developed suspension are studied. And then,a mathematical model of the developed suspension is built. The influence of twin-accumulator hydro-pneumatic suspension parameters on the vehicle body vertical acceleration,suspension travel and dynamic tyre load is studied by simulation based on a quarter off-road vehic...     

Low cost and reliable anonymity protocols in P2P reputation systems

In peer-to-peer (P2P) reputation systems,each peer's trustworthiness is evaluated based on its pseudonym's rating values given by other peers. Since it is assumed that each peer has a long lived pseudonym,all the transactions conducted by the same peer may be linked by its pseudonym. Therefore,one of the fundamental challenges in P2P reputation systems is to protect peers' identity privacy. In this paper,we present two independent anonymity protocols to achieve all the peers' anonymity by changing pseudonym...     

Numerical study of the forming process of high frequency welded pipe

The roll forming process is applied to the manufacturing of high frequency welded (HFW) pipes,section steels,etc. In this paper,the roll forming process of the HFW pipe is simulated with the finite element method (FEM). A user-defined material routine of the commercial finite element code ABAQUS/Explicit is developed,and the mixed hardening constitution model is realized through the user-defined material routine. Based on the mixed hardening constitutive equation,the numerical simulation of roll forming pro...     

Performance research of a micro-CCHP system with adsorption chiller

This paper describes a new micro-combined cooling,heating and power(CCHP) system,which is especially suitable for domestic and light commercial applications. It mainly consists of a natural gas-fired internal combustion engine,a silica gel-water adsorption chiller and other heat recovery units. In order to study the energy effciency and economic feasibility,an experimental investigation has been carried out. The experimental system has a rated electricity power of 12 kW,a rated cooling capacity of 9 kW and a rated heating capacity of 28 kW. Evaluation and analysis of the system are discussed in detail. The testing results show that the energy effciency of the overall system depends on different modes. The overall thermal and electrical effciency is over 70%. Higher heat load supplied causes higher effciency of the system. Economic evaluation shows that the micro-CCHP system enjoys a small capital cost and short payback period,which is easily accepted by customers. At current natural gas price of 1.9 RMB/m3(nominal condition) and electric price of 0.754 RMB/(kW·h) ,the total capital cost is only 90 000 RMB with a payback period of 3.21 years.