Experimental Study on Towing Characteristics of Composite Bucket Wellhead Platform

With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfield development.However,traditional simple wellhead platforms are often discarded after a single use.In pursuit of a more costeffective approach to developing marginal oilfields,this paper proposes a new offshore oil field development facility—an integrated bucket foundation for wellhead platform.To verify the safety of its towing behavior and obtain the dynamic response characteristics of the structure,this paper takes a bucket integrated bucket foundation for wellhead platform with a diameter of 40 m as the research object.By combining physical model tests and numerical simulations,it analyzes the static stability and dynamic response characteristics of the structure during towing,complete with the effects of the draft,wave height,wave period,and towing point height,which produce the dynamic responses of the structure under different influence factors,such as roll angle,pitch angle,heave acceleration and towing force as well as the sensibility to transport variables.The results show that the integrated bucket foundation for wellhead platform is capable of self-floating towing,and its movement is affected by the local environment,which will provide a reference for actual projects.

Trajectory planning for multi-robot coordinated towing system based on stability

Given the unconstrained characteristics of the multi-robot coordinated towing system,the rope can only provide a unidirectional constraint force to the suspended object,which leads to the weak ability of the system to resist external disturbances and makes it difficult to control the trajectory of the suspended object.Based on the kinematics and statics of the multi-robot coordinated towing system with fixed base,the dynamic model of the system is established by using the Newton-Euler equations and the Udwadia-Kalaba equations.To plan the trajectories with high stability and strong control,trajectory planning is performed by combining the dynamics and stability of the towing system.Based on the dynamic stability of the motion trajectory of the suspended object,the stability of the suspended object is effectively improved through online real-time planning and offline manual adjustment.The effectiveness of the proposed method is verified by comparing the motion stability of the suspended object before and after planning.The results provide a foundation for the motion planning and coordinated control of the towing system.

基于TOWS分析的农村集体经营性建设用地入市研究

采用TOWS理论,结合在河北、江苏等地的实地调研成果,分析我国农村集体经营性建设用地入市的挑战、机遇、劣势和优势。分析认为,当前农村集体经营性建设用地入市存在地区差异大、收益难分配、村民乡土情结深厚、政策宣传不到位等问题,但得益于乡村振兴政策和城乡一体化进程,入市改革又存在着很强的发展潜力。入市改革不宜“指标化”的无序推进,而应以农民根本利益为核心,从有序扩大入市规模、放活入市标准、完善收益分配、强化政校联动等方面入手,推动集体经营性建设用地入市工作的进一步展开。

Towing characteristics of large-scale composite bucket foundation for offshore wind turbines

In order to study the towing dynamic properties of the large-scale composite bucket foundation the hydrodynamic software MOSES is used to simulate the dynamic motion of the foundation towed to the construction site.The MOSES model with the prototype size is established as the water draft of 5 and 6 m under the environmental conditions on site.The related factors such as towing force displacement towing accelerations in six degrees of freedom of the bucket foundation and air pressures inside the bucket are analyzed in detail.In addition the towing point and wave conditions are set as the critical factors to simulate the limit conditions of the stable dynamic characteristics.The results show that the large-scale composite bucket foundation with reasonable subdivisions inside the bucket has the satisfying floating stability.During the towing process the air pressures inside the bucket obviously change little and it is found that the towing point at the waterline is the most optimal choice.The characteristics of the foundation with the self-floating towing technique are competitive for saving lots of cost with few of the expensive types of equipment required during the towing transportation.

Air-Floating Towing Behaviors of Multi-Bucket Foundation Platform

Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）.

Mechanical Analysis of Submarine Pipeline During off-Bottom Towing Operation

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.

Integrated Towing Transportation Technique for Offshore Wind Turbine with Composite Bucket Foundation

Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine construction and installation has been largely reduced.Foundation stability is the key technology in the process of towing transportation.Field observation data can reflect the real state of the foundation.In this paper,the influence of water depth and towing speed on liquid level,the compartment pressure,and the pitch angles during towing of composite bucket foundation are studied.These data are analyzed based on the field measurements data from a 3.3 MW offshore wind power project in China.The results show that with varied water depths and towing speeds,the compartment pressure changes are small during the bucket foundation towing process.The offshore wind turbine composite bucket foundation is stable while being towed in the ocean.

Influence of towing speed on effectiveness of rolling dynamic compaction

The influence of towing speed on the effectiveness of the 4-sided impact roller using earth pressure cells(EPCs)is investigated.Two field trials were undertaken;the first trial used three EPCs placed at varying depths between 0.5 m and 1.5 m with towing speeds of 9-12 km/h.The second used three EPCs placed at a uniform depth of 0.8 m,with towing speeds of 5-15 km/h.The findings from the two trials confirmed that towing speed influences the pressure imparted to the ground and hence compactive effort.This paper proposes that the energy imparted to the ground is best described in terms of work done,which is the sum of the change in both potential and kinetic energies.Current practice of using either kinetic energy or gravitational potential energy should be avoided as neither can accurately quantify rolling dynamic compaction(RDC)when towing speed is varied.

Cooperative Multi-Agent Control for Autonomous Ship Towing Under Environmental Disturbances

Among the promising application of autonomous surface vessels(ASVs)is the utilization of multiple autonomous tugs for manipulating a floating object such as an oil platform,a broken ship,or a ship in port areas.Considering the real conditions and operations of maritime practice,this paper proposes a multi-agent control algorithm to manipulate a ship to a desired position with a desired heading and velocity under the environmental disturbances.The control architecture consists of a supervisory controller in the higher layer and tug controllers in the lower layer.The supervisory controller allocates the towing forces and angles between the tugs and the ship by minimizing the error in the position and velocity of the ship.The weight coefficients in the cost function are designed to be adaptive to guarantee that the towing system functions well under environmental disturbances,and to enhance the efficiency of the towing system.The tug controller provides the forces to tow the ship and tracks the reference trajectory that is computed online based on the towing angles calculated by the supervisory controller.Simulation results show that the proposed algorithm can make the two autonomous tugs cooperatively tow a ship to a desired position with a desired heading and velocity under the(even harsh)environmental disturbances.

Test Research on Influence of Draft on Towing Behaviors of 3-Bucket Foundation Platform

To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.

Research on the Motion Track of Ocean Towing System

In this paper, a method for predicting the position of towline is presented. The location of the finite node is determined by installing fixed spaced attitude sensors in towline arrays, then the appropriate objective functions are selected for water depth profile and course profile respectively, and the interpolation fitting method is combined with the determined predicted positions. Through the hydrodynamic analysis of the existing towing cable’s underwater motion, the position of the towing cable under the steady state motion is obtained as the reference basis, and two methods are put forward, which are improved spline interpolation method, polynomial fitting method and multivariate nonlinear regression analysis. In the case of steady state motion, the two methods are compared and compared with the hydrodynamic simulation results. Finally, a more suitable method is selected as the basis of cable location inversion and applied to deep-sea towing operations.

基于遗传算法的不等间距阵优化方法

阵元数一定情况下,针对不等间距拖线阵高频信号处理存在的空间增益和无栅瓣兼容问题,提出一种基于遗传算法的不等间距拖线阵阵型优化方法。该方法以频带交互下最大旁瓣级最小作为约束因子,通过模拟生物自然进化过程搜索全局最优解,得到优化后的阵元位置。优化后阵型在保证低频信号处理空间增益不变情况下,实现对高频信号高空间增益、无栅瓣处理。计算机仿真结果表明:相比未优化阵型,在高频信号处理方面,优化后阵型在无栅瓣情况下,空间增益提升值近似理论值提升值;在低频信号处理方面,优化后阵型具有相同的空间增益。为实际不等间距拖线阵阵型优化和应用提供了一种思路。

“深海一号”半潜式生产储油平台长距离湿拖方案论证

针对“深海一号”半潜式生产储油平台拖航方案设计及工程实施面临拖航距离远、拖航路径环境恶劣、拖船资源选择少,以及作业风险高等众多技术难题,通过对比分析平台干拖和湿拖方案,重点分析湿拖过程中的拖航路线、平台吃水、湿拖阻力、拖船配置等关键技术问题,通过水池模型试验验证该方案的可行性,顺利实施了“深海一号”平台的长距离湿拖工作。

飞机高速牵引滑行制动模式分析

在传统牵引车牵引飞机的运动过程中,其制动行为是通过牵引车独立制动来完成的,主要用于低速推出牵引和轻载中速维护牵引工况。针对未来飞机牵引滑行的高速重载新特征,仅靠牵引车实施制动能否满足牵引系统制动性能需要重新评估。为此,文中考虑了由飞机和牵引车联合制动的新模式,即由飞机主起落架机轮刹车系统和牵引车轮刹车系统同时制动,通过分配制动力来实现牵引车-飞机系统的制动行为。建立了飞机牵引滑行时制动过程的动力学模型,并以B737-200型飞机和TBL-180型牵引车为例,分析对比了牵引车单独制动和牵引车-飞机联合制动两种模式下的系统制动性能和制动安全性。结果表明:牵引车-飞机联合制动时的制动性能远优于牵引车单独制动时的制动性能,是飞机高速牵引滑行时紧急制动的优选模式;在安全性方面,牵引车-飞机联合制动时的前起落架横向载荷也远小于牵引车单独制动,会为飞机前起落架结构保留更大的横向冲击安全裕度。

基于LightGBM的拖曳系统动力响应预报方法

针对传统数值仿真计算方法耗时长、占用计算机资源多等缺点,提出基于LightGBM算法的拖曳系统动力响应进行评估的回归预测模型,以已有的OrcaFlex数值模拟得到的数据为样本,以拖曳系统上的海洋环境条件、拖船航速和下放缆长为特征,以动力响应为目标,引入LightGBM算法,对拖曳缆顶端张力最大值等动力响应进行预测分析。与传统数值模拟方法相比,LightGBM算法在保证结果准确性的同时大幅度提高了计算效率。通过与随机森林(RF)、极限梯度提升(XGBoost)算法相比,其准确度和计算效率的表现更好。最后提出了贝叶斯参数优化的LightGBM算法,准确度进一步提高,为提前采取措施保障拖曳系统的作业安全提供了一条高效的技术途径,同时为建立拖曳系统数字孪生体提供了有力的技术支撑。

拖曳水池教学实验室拖车设计与研制

按照“设计—研制—标定”的思路,完成了船模拖曳水池拖车系统研制。设计阶段结合教学科研需求完成拖车结构设计、最大航速确定和拖车重量预估,并用数值模拟方法完成强度校核和模态分析;研制阶段先在工厂进行分段制造,后运输至实验室现场组装调试,完成了机械调试和电路调试两部分;标定阶段完成了拖车振动测试、标模阻力测试和敞水测试。将新拖车用于本科教学,提高了教学效率,丰富了教学手段,有助于提升学生对实验现象的观察与知识点的理解。

海上风电单柱复合筒型基础拖航性能研究

单柱复合筒型基础结合了单桩基础与筒型基础的优点,能有效缩短施工期、降低成本且对环境友好。拖航是单柱复合筒型基础可重复利用、便于运输和安装的关键技术,需对拖航性能进行深入研究,为实际拖航过程提供技术指导。使用MOSES软件建立单柱复合筒型基础水动力模型,对单柱复合筒型基础的拖航过程进行数值模拟。计算结果表明,单柱复合筒型基础拖航性能较好,其运动响应受波浪和浮运条件影响显著,应避免横浪和大浪,且不宜在波浪周期接近基础固有周期时段拖航;通过调整系缆点高度、吃水深度及拖航速度可提升结构拖航稳性。

特种机编队下的雷达牵引探测建模与效能分析

针对编队作战使用的需求,为实现对特种机编队条件下的双/多机传感器的有效管理,使之协同工作并发挥出最大效能。本文基于特种机双机雷达牵引探测的场景,进行了牵引流程设计、交接班概率计算和效能分析,并进行了仿真验证,证明了双机雷达牵引探测流程的有效性。

基于AQWA的船舶拖航耦合动力响应分析

船舶在长期航行中,会遇到船舶发生故障以及穿过狭窄航道的情况,需要拖船牵引船舶航行。本文以船舶拖航为研究对象,利用AQWA分析时域耦合过程中不同拖缆数目和不同拖速对船舶拖航的影响。从拖缆张力和运动响应2个方面进行对比分析,结果表明,在相同环境条件下,2根拖缆比1根拖缆时最大张力平均减少49.18%,拖速4 kn比拖速8 kn时拖缆最大张力平均减少53.78%,拖速6 kn比拖速8 kn时拖缆最大张力平均减少29.39%。

曳引摇枝式板栗落果装置设计与试验

针对当前丘陵山地板栗采摘困难、人工收获工作强度大、采收效率低等问题,设计了一种由柔性钢丝绳曳引振动的小型摇枝式板栗落果装置。建立板栗果实-果枝单摆动力学模型,分析果实脱落条件,得到板栗果实振动脱落切向加速度为285.36 m/s~2,得出影响板栗果实脱落的主要因素为果枝振动频率、振幅、振动时间;进行板栗果枝振动特性试验,用Default Shaker液压振动台以0~30 Hz扫频方式确定垂直方向上板栗果枝共振频率,并在频率7~15 Hz段进行驻频试验,得出振动落果较优频率为10~12 Hz。根据果枝振动试验结果,利用ADAMS软件对摇振机构进行仿真,结果表明,摇杆振幅大于95 mm时,果枝末端加速度可满足板栗果振动脱落的加速度条件,确定了落果装置参数设计的合理性。设计了三因素三水平正交试验,试验结果表明,板栗落果最佳作业参数组合为摇振频率11 Hz、振幅135 mm、摇振时间30 s,此时板栗落果率为91.9%,树皮损伤率为8.8%,满足农业机械推广鉴定标准中树皮损伤标准。