登陆海底管道近岸段预挖沟

海底管道大都是由深水到浅水,经过潮差段登上陆地的。为确保海底管道在登陆段的稳定和生产期间的安全,一般都是采用预挖沟埋设的方法。本文根据近年来管道施工的经验,对管道登陆段的预挖沟方法、测量定位以及挖沟质量控制等做了详细地介绍。     

小口径长输管道高地下水位段单侧沉管施工技术

为了解决高地下水位段由于地表承载力差,采用传统的沟上组焊吊装下沟的施工方法难度较大的问题。笔者结合沙漠段沉管下沟的方法在工程中的应用,在高地下水位段采用单侧沉管下沟的施工工艺。工程实践结果表明,该工艺成功解决了高地下水位段小口径长输管道施工面临的困难,极大地提高工程进度的同时保证了施工安全且减少了项目成本,可为同类地区的管道施工提供借鉴。     

掏槽法在黄麦岭磷矿掘双壁沟爆破中的应用

在黄麦岭磷矿露天开采的掘沟爆破中，根据掏槽法的机理，使用大孔径深孔掏槽，采用多排微差挤压爆破，一次形成开采所需的双壁沟，提高了掘沟效率，扩大了掏槽法的应用范围。     

High-speed water impacts of flat plates in different ditching configuration through a Riemann--ALE SPH model

The violent water entry of flat plates is investigated using a Riemann-arbitrary Eulerian-Lagrangian(ALE) smoothed particle hydrodynamics(SPH) model. The test conditions are of interest for problems related to aircraft and helicopter emergency landing in water. Three main parameters are considered: the horizontal velocity, the approach angle(i.e., vertical to horizontal velocity ratio) and the pitch angle, a. Regarding the latter, small angles are considered in this study. As described in the theoretical work by Zhao and Faltinsen(1993), for small a a very thin, high-speed jet of water is formed, and the time-spatial gradients of the pressure field are extremely high. These test conditions are very challenging for numerical solvers. In the present study an enhanced SPH model is firstly tested on a purely vertical impact with deadrise angle α=4°. An in-depth validation against analytical solutions and experimental results is carried out, highlighting the several critical aspects of the numerical modelling of this kind of flow, especially when pressure peaks are to be captured. A discussion on the main difficulties when comparing to model scale experiments is also provided. Then, the more realistic case of a plate with both horizontal and vertical velocity components is discussed and compared to ditching experiments recently carried out at CNR-INSEAN. In the latter case both 2-D and 3-D simulations are considered and the importance of 3-D effects on the pressure peak is discussed for α=4° and α=10°.     

乌兰布和沙漠小口径长输管道施工技术

宁夏石化成品油外输管道工程全线近1/3处于乌兰布和沙漠,管道沿线沙丘承载力低,严重制约了管沟开挖和管道下沟作业。经过现场踏勘及论证,决定采用单侧沉管施工方法。实践证明,采用单侧沉管方法成功解决了小口径管道沙漠地段下沟问题,同时该技术施工工艺简单、能减少风险、节约成本、使作业更加流畅及可靠等特点。     

驳载拖橇式滩海海底挖沟敷缆装置

针对渤海埕岛滩海油田开发的需要,胜利石油管理局工程建设一公司研制了驳载拖橇式滩海海底挖沟敷缆装置。在报道该装置在极浅水域成功应用的同时,介绍了该装置的结构特点、工作原理及技术指标。     

滑移动网格在波浪水面迫降数值模拟中的应用

为研究飞机在波浪中迫降时不同航向对迫降性能的影响,在刚性动网格和滑移网格方法的基础上,开发出将两者相结合的滑移动网格方法,在保证自由面处于网格加密区的同时,可以模拟飞机在复杂海况下的任意姿态.数值模拟三维平板斜向冲击入水,将数值模拟的垂向运动历程及表面压强分布与实验数据进行对比分析,验证数值方法的有效性并得到网格参数的设置经验;用滑移动网格方法对飞机平静水面迫降进行数值模拟,将数值模拟的运动历程与实验数据进行对比,验证滑移动网格方法的有效性;在应用数值造波的基础上,模拟研究飞机迎浪、顺浪和平行于波浪3种不同航向的迫降,对比分析3种工况下飞机的运动历程和各部件受力情况.模拟结果表明:波浪中迫降的最优航向是平行于波浪,其垂向冲击力峰值比平静水面迫降大12%,滚转和偏航运动造成的影响也较小;迎浪迫降会产生较大的俯仰角峰值,垂向冲击力峰值比平静水面迫降大149%,并且会遭受多次波浪冲击作用,是最危险的迫降航向.     

基于重叠网格法的飞机水上降落水动力砰击载荷研究

为分析飞机在水上降落过程中的砰击载荷及运动规律,基于数值模拟研究NACA TN2929飞机水上降落过程,考查飞机的初始速度、初始仰角对降落过程的影响。求解雷诺平均纳维-斯托克斯方程(RANS)模拟飞机与水的相互作用,采用VOF方法捕捉自由面,采用重叠网格技术及DFBI模型模拟飞机与流体的耦合运动。通过计算楔形体和圆锥体自由入水过程验证模型的可靠性,通过网格和时间步长的收敛性分析确定合适的网格和时间步大小,与实验结果对比确定计算结果的正确性。模拟飞机以不同初始速度与不同仰角的着水过程,分析飞机底部压力的变化规律,研究飞机初始速度、初始仰角对砰击载荷及运动姿态的影响规律。数值计算结果表明飞机在入水0.2 s左右砰击载荷会达到峰值,载荷峰值与飞机着水的速度的平方线性相关;飞机机身底部压力峰值出现在水面与机身的正向交界处;飞机初始仰角增加,砰击载荷峰值会有所减小。     

巡航导弹海上生存能力模型研究

首先,深入研究了海上阵风、海浪以及巡航导弹垂直平面内飞行和高度控制等数学模型．给出了阵风、海浪的仿真方法。在此基础上，提出计算巡航导弹生存能力的计算方法．并画出了计算流程图。此外．上述模型对于巡航导弹飞行仿真也是适用的。能够为巡航导弹海上飞行的其它相关研究提供帮助。     

SIMULATION OF FLUID-SOLID INTERACTION ON WATER DITCHING OF AN AIRPLANE BY ALE METHOD

Ditching is considered as one of the important aspects of safety performances of airplanes.It is related primarily with the fluid-solid interaction,whose studies mainly depend on experiments at the present time.Numerical and analytical methods for fluid-solid interaction by using 3-D full scale airplane’s model will reduce the dependence on the expensive model tests.Numerical studies can be used to estimate the safety of ditching and provide a reference for the crashworthiness design.This article proposes a 3-D dynamical structural model after the real shape of an airplane and an Arbitrary Lagrange-Euler (ALE) fluid-field model,to simulate the fluid-solid interactions caused by low speed ditching.The simulation is based on interaction computational methods,within LS-DYNA nonlinear finite-element code.The results of pressure distributions and accelerating time histories of the airplane’s subfloor are discussed in the context of the safety of ditching,and the simulation results and the analytical methods are verified.