The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction for...The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction force of seabed, pontoon buoyancy, and tow force of tugboat can cause large deformation and fatigue damage to the pipeline. In order to keep the pipeline in safety, the lateral and vertical defomlations of pipeline must be controlled within an appropriate range. Theoretical study is carried out in the paper on the environmental forees acting on pipeline, pontoons and chaias, and the confimation of tow parameters including tow forces of tugboat, number of pontoons and length of chains. Then the pipeline in the off-bettom towing process may be simplified into a continuous beam with elastic supports under the concentrated and distributed forces. A finite element method is applied to achieve numerical solutions describing the distributions of deformation and stress along the pipeline. The results show that the lateral shape of the pipeline is like an arc with the maximal deformation appearing at the middle of the pipeline. The distributions of stress are similar between two arbitrary pontoons. Moreover, both deformation and stress have the inverse relation with the tow forces of tugboat.展开更多
The minimum fluid velocity to maintain particles just suspendedwas deduced, and the theoretical analysis shows that the minimumvelocity is influenced by the properties of the solid and liquid, notby the operational co...The minimum fluid velocity to maintain particles just suspendedwas deduced, and the theoretical analysis shows that the minimumvelocity is influenced by the properties of the solid and liquid, notby the operational conditions. For justification, the local minimumvelocity at the bottom of the tank was measured by a bi- electrodeconductivity probe, in a square-sectioned stirred tank (0.75m×0.75×1.0m) with the glass beads-water system. The experiments showed thatthe fluid velocities for the same suspension state were identicaldespite that the power Dissipated per unite mass was not the sameunder different configuration and operation. Both theoreticalanalysis And experimental results indicate that the off-bottomsuspension is controlled by the local fluid flow over the bottom Ofthe stirred tank.展开更多
基金supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2006AA09A105)
文摘The off-bottom tow is an important method to lay pipeline for offshore oil and gas transportation in shallow water area. During the off-bottom towing operation, the actions such as sea current resistance, friction force of seabed, pontoon buoyancy, and tow force of tugboat can cause large deformation and fatigue damage to the pipeline. In order to keep the pipeline in safety, the lateral and vertical defomlations of pipeline must be controlled within an appropriate range. Theoretical study is carried out in the paper on the environmental forees acting on pipeline, pontoons and chaias, and the confimation of tow parameters including tow forces of tugboat, number of pontoons and length of chains. Then the pipeline in the off-bettom towing process may be simplified into a continuous beam with elastic supports under the concentrated and distributed forces. A finite element method is applied to achieve numerical solutions describing the distributions of deformation and stress along the pipeline. The results show that the lateral shape of the pipeline is like an arc with the maximal deformation appearing at the middle of the pipeline. The distributions of stress are similar between two arbitrary pontoons. Moreover, both deformation and stress have the inverse relation with the tow forces of tugboat.
文摘The minimum fluid velocity to maintain particles just suspendedwas deduced, and the theoretical analysis shows that the minimumvelocity is influenced by the properties of the solid and liquid, notby the operational conditions. For justification, the local minimumvelocity at the bottom of the tank was measured by a bi- electrodeconductivity probe, in a square-sectioned stirred tank (0.75m×0.75×1.0m) with the glass beads-water system. The experiments showed thatthe fluid velocities for the same suspension state were identicaldespite that the power Dissipated per unite mass was not the sameunder different configuration and operation. Both theoreticalanalysis And experimental results indicate that the off-bottomsuspension is controlled by the local fluid flow over the bottom Ofthe stirred tank.
