水下防喷器组控制系统深水模拟试验装置研制

防喷器组控制系统在深水环境的工作可靠性一直是海洋钻井业高度关注的问题。研制了用于水下防喷器组控制系统及其阀件功能测试和可靠性研究的深水模拟试验装置,包括模拟3 000m水深的大型高压舱,用于控制系统原理样机的深水模拟试验;模拟4 200m水深的小型高压舱,用于深水电磁阀和深水液压阀的深水功能试验和寿命试验。介绍了该试验装置的液控系统、电控系统、水下监控系统的设计原理。试验结果表明:该试验装置能够满足深水防喷器组控制系统的测试要求。

小当量炸药深水爆炸气泡脉动模拟实验

为在实验室内开展深水爆炸气泡脉动规律研究,通过增加水面大气压强来模拟水中静水压的方法,建立可模拟深水环境的爆炸容器。开展不同模拟水深条件下的3种当量炸药的水下爆炸实验,得到了气泡脉动过程图像,验证小当量深水爆炸模拟实验与自由场实验的等效性,分析气泡脉动周期与最大半径同模拟水深的关系。实验结果表明:容器壁面反射效应对气泡脉动过程的影响可以忽略不计,模拟实验可等效为自由场实验;深水爆炸气泡脉动周期及最大半径随流体静力深度增加的衰减系数分别为-0.83和-0.364。

深水下岩石切割的模拟试验研究

通过自行开发设计的一套深水环境条件模拟试验装置,进行一系列深水环境条件下磨料水射流切割岩石的试验研究。针对岩石切割深度的主要影响因素,分别进行一系列的靶距变化、切割次数变化、射流横移速度变化和不同水深的模拟试验,从而揭示在深水环境条件下岩石切割深度与各主要切割参数的关系和规律,以及水深对岩石切割深度的影响。在深水环境条件下岩石切割技术的生产实际应用中,要综合考虑切割次数和射流横移速度与效率的关系;岩石等材料的合理靶距是一个关键性技术问题,应控制在有效靶距范围内才具有实际意义。

模拟深水环境下雷管铅土寿扩孔实验研究

利用模拟深水爆炸容器,以8号雷管为爆源,进行了从0.6m到110.6m水深条件下雷管铅土寿扩孔实验。通过测量扩孔值来衡量装药的作功能力。研究得出:随着模拟水深的增加,扩孔值减小,并且堵塞方式不同,其扩孔值也不同。

数码电子雷管深水起爆性能试验研究

采用密封压力罐中注入一定量的水,然后施加不同气压的方法模拟数码电子雷管在一定水深下的工况,通过系列试验研究模拟相应工况下的起爆能力。试验结果证明:所用数码电子雷管在40 m水深处放置48 h,其抗水性、起爆能力、延期精度均不会受水深的影响,可满足工程需要。通过系列试验,弥补了现有工程资料数据的不足,为类似工程提供了必要的试验数据和依据。

水下爆破岩石破碎块度的实验研究

基于武汉科技大学与中铁港航局联合研制的10 g TNT当量水介质爆炸容器,在爆炸罐内施加不同压强,模拟不同水深梯度,进行多组素混凝土试块的水下爆炸实验,统计炸药爆炸后的各种块度,发现随着水深增大岩石的大块率增加,且水深是主要影响因素。由于水介质的压力作用,改变了岩石中的轴向压力作用,受到水的围压作用,炸药爆炸后需分配一部分能量用于克服水压作用,而且水深越大,岩石外部围压越大,因此破碎程度远不如同等条件下的陆地爆破,得到相同破碎程度,需要更大的单耗,水深越大所需单耗越大,研究结果可供实际工程参考。

Freak wave simulation based on nonlinear model and the research on the time-frequency energy spectrum of simulation results

VOF （volume of fluid） method has been used to make the numerical simulation of freak wave come true. The comparisons between the numerical results and linear theoretical results corresponding to Eq.（5） have been carried out to show that the numerical results have a better exhibition of nonlinear characteristics. Wavelet analysis method has been adopted to investigate the time-frequency energy spectrum of simulation freak waves and the results reveal strong nonlinear interaction enables energy to be transferred to high harmonics during the progress of its formation. Varying water depth can enhance the nonlinear interaction, making much more energy be transferred to high harmonics and freak waves with higher asymmetry be generated.

Modeling underwater transport of oil spilled from deepwater area in the South China Sea

Based on a Lagrangian integral technique and Lagrangian particle-tracking technique,a numerical model was developed to simulate the underwater transport of oil from a deepwater spill. This model comprises two submodels: a plume dynamics model and an advection-diffusion model. The former is used to simulate the stages dominated by the initial jet momentum and plume buoyancy of the spilled oil,while the latter is used to simulate the stage dominated by the ambient current and turbulence. The model validity was verified through comparisons of the model predictions with experimental data from several laboratory flume experiments and a field experiment. To demonstrate the capability of the model further,it was applied to the simulation of a hypothetical oil spill occurring at the seabed of a deepwater oil/gas field in the South China Sea. The results of the simulation would be useful for contingency planning with regard to the emergency response to an underwater oil spill.

Analysis of Water Insulating Effect of Compound Water-Resisting Key Strata in Deep Mining

The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the key strata is established given the structural characteristics and the mechanical properties of the roof rock layers of the working face in a particular coal mine. Four other models were derived from this model by rearranging the order of the layers in the key strata. The distribution characteristics of stress, deformation, pore pressure and the flow vector of all the models are computed using the analytical module of fluid-structure interaction in the FLAC software and the corresponding risks of a water-burst are analyzed. The results indicate that the water-insulating ability of the key strata is related to the arrangement of soft and hard rocks. The water-insulating ability of the compound water-resisting key strata (CWKS) with a hard-hard-soft-hard-soft compounding order is the best under the five given simulated conditions.

Numerical Simulation of 3-D Wave Crests

A clear definition of 3-D wave crest and a description of the procedures to detect the boundary of wave crest are presented in the paper. By using random wave theory and directional wave spectrum, a MATLAB-platformed program is designed to simulate random wave crests for various directional spectral conditions in deep water. Statistics of wave crests with different directional spreading parameters and different directional functions are obtained and discussed.

基于大型卡箍结构的设计方法对比分析

基于某大型卡箍结构的基本性能指标要求,通过使用三种设计方法分别对卡箍紧固结构的尺寸进行计算,并进行了相应的对比,得出相应的结论,为以后大型卡箍设计提供了指导。

Physical and Numerical Modelling Applied to a Major New Port Development and Impacts of Its Deep Navigational Channel

This paper describes the use of a numerical and physical modelling study in the design of large breakwaters for a new port and dry dock complex on the southern coast of Oman. The numerical modelling was carried out to optimise the entrance channel layout with respect to wave penetration into the port and to refine design conditions for the sizing of the primary armour on the breakwaters. Wave conditions inside and outside of the port have been assessed using the 2-dimensional numerical wave penetration model MIKE21 EMS （Elliptic Mild-Slope）. As part of the design process, 3D physical modelling studies were also undertaken at Delft Hydraulics in the Netherlands to confirm the stability of the armour on the trunk and roundhead of the breakwaters and to verify the influence of the deep approach channel on stability. The opportunity was taken to extend the physical model tests to assess the influence of the deep channel on wave penetration through the port entrance. The paper focuses on the influence of the deep channel on wave conditions in the entrance to the port and compares the results from the numerical and physical modelling.

Experimental investigation on dynamic response of chamber to simulate deepwater explosive

Experimental investigation was conducted for the dynamic response of a real spherical explosive chamber that can simulate 200 m deepwater explosive loaded 10 g TNT equivalent.The vibration characteristics and dynamic strength of the chamber were analyzed by measuring the strain profiles of six characteristic points on the chamber.The research results revealed the rule of the dynamic response of the chamber on different explosive loads and static pressures.It provides references for the design and development of the chamber to simulate deepwater explosion.

Numerical simulation of deepwater deployment for offshore structures with deploying cables

Deepwater deployment of offshore structures in different sea states was investigated. The whole deployment system was modeled as a lumped mass model, and discretization scheme for cable geometry and methodology for calculating the internal and external force acting on deploying cable were presented. The deployment model suitable for the time-varying length of deploying cable was specified. The free-surface flow fields together with the ship motions were used to calculate dynamic tension in the deploying cable during deployment of the structure. The deployment of deep sea mining system which was a typical subsea working system was employed. Based on lumped mass analysis model and parameters of deep sea mining system, numerical simulations were performed, and dynamic load and dynamic amplification factor(DAF) with different cable parameters, deploying velocities and sea states were obtained. It is shown that cable parameters and amplitudes of ocean waves can significantly influence the dynamic load and DAF, and the time-varying natural period of deploying system is a dominant factor, while the effect of deploying velocity is not obvious.

Vibration mechanism research of large-scale and deep-water caisson

According to the construction method of Taizhou Bridge, numerical simulation is conducted to analyze the vibration of caisson under wind and water flows to determine the main factors of the caisson vibration. Meanwhile, the localization system of caissons and anchors of Taizhou Bridge is modeled in order to summarize the vibration mechanism of caissons under deep-water and jet-flow condition, and further pertinent vibration-control measures are proposed. The obtained results are well verified in engineering practice, and consequently the safety risk of positioning the caisson is reduced.

Prediction of water table depths under soil water-groundwater interaction and stream water conveyance

Water table over an arid region can be elevated to a critical level to sustain terrestrial ecosystem along the natural channel by the stream water conveyance. Estimation of water table depth and soil moisture on river channel profile may be reduced to a two-dimensional moving boundary problem with soil water-groundwater interaction. The two-dimensional soil water flow with stream water transferred is divided into an unsaturated vertical soil water flow and a horizontal groundwater flow. Therefore, a prediction model scheme for water table depths under the interaction between soil water and groundwater with stream water transferred is presented, which includes a vertical soil water movement model, a horizontal groundwater movement model, and an interface model. The synthetic experiments are conducted to test the sensitivities of the river elevation, horizontal conductivity, and surface flux, and the results from the experiments show the robustness of the proposed scheme under different conditions. The groundwater horizontal conductivity of the proposed scheme is also calibrated by SCE-UA method and validated by data collected at the Yingsu section in the lower reaches of the Tarim River, which shows that the model can reasonably simulate the water table depths.

Sound propagation from the shelfbreak to deep water

Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at shallower depths,we study sound propagation from the transitional area(shelfbreak)to deep water.Numerical simulations with different source depths are first performed,from which we reach the following conclusions.When the source is located near the sea surface,sound will be strongly attenuated by bottom losses in a range-independent oceanic environment,whereas it can propagate to a very long range because of the continental slope.When the source is mounted on the bottom in shallow water,acoustic energy will be trapped near the sound channel axis,and it converges more evidently than the case where the source is located near the sea surface.Then,numerical simulations with different source ranges are performed.By comparing the relative energy level in the vertical direction between the numerical simulations and the experimental data,the range of the air-gun source can be approximated.