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Turbulence model adaptability at critical Reynolds numbers and applications in wake control via fairings 临界雷诺数下的湍流模型适应性及在整流罩尾流控制中的应用
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-18 DOI: 10.1016/j.apor.2024.104263
Yigang Gong , Jiasong Wang
<div><div>The water-drop shaped fairings with varying shape angles are attached to a circular cylinder to achieve wake control and vortex suppression at critical Reynolds numbers. To ensure the capability of Reynolds averaged Navier–Stokes (RANS), detached eddy simulation (DES) and large eddy simulation (LES) models at the critical Reynolds number region, three representative turbulence models are employed: LES with <span><math><mi>σ</mi></math></span> subgrid-scale (SGS) model, delayed DES model with improved wall-modeling capability (IDDES) and shear stress transport (SST) <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> RANS model. These models are utilized to simulate flow around a circular cylinder at Reynolds number <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. The solver used in this paper is further developed based on the high-resolution algorithm platform for incompressible flow (HRAPIF). The comparative analysis of the results from the three turbulence models has been rigorously validated and investigated. An exhaustive examination of the mean flow field, Reynolds stresses, characteristic lengths, and instantaneous flow fields among the models reveals instructive insights. The IDDES and <span><math><mi>σ</mi></math></span>-LES models predict the hydrodynamic forces, the so-called ‘drag crisis’, alongside the pressure distribution and skin friction coefficient with high precision. The <span><math><mi>σ</mi></math></span>-LES model stands out for its superior accuracy, while the IDDES model is also a viable alternative, offering commendable accuracy with a reduced demand for mesh density. Subsequently, the IDDES model is selected for wake control calculations using fairings with five distinct shape angles (<span><math><mrow><mn>3</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>4</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>6</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup><mo>,</mo><mn>7</mn><msup><mrow><mn>5</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span> and <span><math><mrow><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>) at <span><math><mrow><mtext>Re</mtext><mo>=</mo><mn>2</mn><mo>.</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. In-depth comparisons to the bare cylinder and subcritical results reveal that the wake control effect varies at the critical Reynolds region. The fairing with a 30° shape angle substantially suppresses hydrodynamic forces. The lift coefficient experiences a remarkable decrease of approximately 96%, while the drag coefficient diminishes by about 90%. Concurrently, fairings with angles from 45° to 90° lead to reductions in drag coefficient of 11.6%, 10%, 3% and
不同形状角度的水滴形整流罩被固定在圆筒上,以实现临界雷诺数下的尾流控制和涡流抑制。为确保雷诺平均纳维-斯托克斯(RANS)、分离涡模拟(DES)和大涡模拟(LES)模型在临界雷诺数区域的能力,采用了三种具有代表性的湍流模型:带有 σ 子网格尺度(SGS)模型的 LES、带有改进壁面建模能力(IDDES)的延迟 DES 模型和剪应力传输(SST)k-ω RANS 模型。这些模型用于模拟雷诺数 Re=2.5×105 时圆形圆柱体周围的流动。本文使用的求解器是在不可压缩流高分辨率算法平台(HRAPIF)的基础上进一步开发的。本文对三种湍流模型的结果进行了严格的验证和研究。对模型间的平均流场、雷诺应力、特征长度和瞬时流场的详尽研究揭示了具有启发性的见解。IDDES 和 σ-LES 模型可以高精度地预测流体动力,即所谓的 "阻力危机",以及压力分布和表皮摩擦系数。σ-LES 模型以其卓越的精度脱颖而出,而 IDDES 模型也是一种可行的替代方案,它在提供值得称道的精度的同时降低了对网格密度的要求。随后,在 Re=2.5×105 条件下,使用五种不同形状角(30∘、45∘、60∘、75∘ 和 90∘)的整流罩,选择 IDDES 模型进行尾流控制计算。与裸气缸和亚临界结果的深入比较显示,尾流控制效果在临界雷诺区域有所不同。形状角为 30° 的整流罩大大抑制了流体动力。升力系数显著降低了约 96%,而阻力系数降低了约 90%。同时,角度为 45° 至 90° 的整流罩可使阻力系数分别降低 11.6%、10%、3% 和 4%。即使是形状角 α=90∘ 的短整流罩,升力系数也降低了 75%,这对工业设计可能是一个有意义的指导。
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引用次数: 0
Three-dimensional numerical simulation of vortex-induced vibration of a free spanning submarine cable in uniform currents 匀速水流中自由跨越海底电缆涡流诱发振动的三维数值模拟
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-18 DOI: 10.1016/j.apor.2024.104268
Haidong Zhao , Chao Wang , Junjie Zhu , Ping Dong , Bing Ren , Pengzhi Lin
The free spanning submarine cable, a slender and flexible structure with a certain sag, exhibits unique vortex-induced vibration (VIV) characteristics in currents compared to offshore risers and submarine pipelines. To study the VIV of the cable, a three-dimensional numerical model based on the finite difference method (FDM) and the finite element method (FEM) is established. The large eddy simulation method is employed to close the turbulent motion equations in the hydrodynamic model, while the beam element method is used to solve the structural motion equations in the structural dynamic model. An analytical mapping method is adopted for the reconstruction of the structure surface in the fixed Cartesian fluid grids, and the immersed boundary method is used to deal with boundary conditions at fluid-solid interfaces. Since simulating VIV of a submarine cable with sag requires extensive local grid refinement near the cable's surface, a partition parallel algorithm with multi-GPU nodes is developed to enhance the computational efficiency, where the parallel efficiency of a single GPU can reach 80–90%. The numerical model is validated by a laboratory experiment on the VIV of a submarine cable, where the transverse response amplitudes and frequencies obtained by numerical simulation agree well with the experimental results. The streamwise vibration responses that are not measured in the experiment are analyzed by the numerical simulation. It is found that when the cable's equilibrium profile is deflected in the streamwise direction by the drag force, the streamwise vibration with the same frequency as the transverse vibration occurs, and the streamwise vibration amplitude increases with sag. The detailed flow field information provided by numerical simulation indicates that the size of the vortex structures gradually increases with the velocity, and the shape of the vortex structure has a strong correlation with the transverse vibration mode of the cable.
自由跨越海底电缆是一种具有一定下垂度的细长柔性结构,与海上立管和海底管道相比,在水流中表现出独特的涡流诱发振动(VIV)特性。为研究海缆的 VIV,建立了基于有限差分法(FDM)和有限元法(FEM)的三维数值模型。在流体动力学模型中,采用大涡流模拟法关闭湍流运动方程;在结构动力学模型中,采用梁元法求解结构运动方程。在固定笛卡尔流体网格中,采用分析映射法重建结构表面,并使用沉浸边界法处理流固界面的边界条件。由于模拟下垂海底电缆的 VIV 需要在电缆表面附近进行大量的局部网格细化,因此开发了一种多 GPU 节点的分区并行算法,以提高计算效率,其中单 GPU 的并行效率可达 80-90%。数值模拟得到的横向响应振幅和频率与实验结果非常吻合。数值模拟分析了实验中未测量到的流向振动响应。结果发现,当缆索的平衡剖面在阻力作用下发生流向偏转时,会产生与横向振动频率相同的流向振动,且流向振动振幅随下垂度的增加而增大。数值模拟提供的详细流场信息表明,涡流结构的大小随速度的增加而逐渐增大,涡流结构的形状与缆索的横向振动模式密切相关。
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引用次数: 0
Experiments on the effect of wall distances for bubble collapse characteristics 气泡坍塌特性的壁距影响实验
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-18 DOI: 10.1016/j.apor.2024.104277
Wei Xu , Yuanyuan Zhao , Guohui Zhao , Fujian Zhao , Xiuli Wang , Chuan Wang
At present, the energy released by bubble collapse can be used for the surface treatment of workpieces and can also be used to degrade pollutants. However, the mechanism of action between bubble collapse and a nearby wall has yet to be accurately explained. In order to grasp the relationship between the wall distance and collapse characteristics, the methods of spark discharge, high-speed photography, and pressure acquisition are used to study bubble shapes and the dynamic variation during pressure release with different wall distances in this paper. The results show that with the increasing of the distance L, the shape of a bubble changes from oblate to spherical and its collapse time shortens. The proportion of the total collapse time consumed by the slow collapse stage shows an increasing trend. In an experiment with two contractions, the time proportion of the slow collapse stage of the first contraction is much larger than that of the second contraction. The existence of the wall delays the collapse of the bubble. As the distance L increases, the bubble goes from undergoing one collapse to two collapses and then to one collapse again. The proportion of the duration of the slow collapse stage of the first contraction decreases rapidly, and the proportion of the slow collapse stage of the second contraction increases slowly, but the time proportion of second contraction decreases. When the distance L increases from 4.5 mm to 11 mm, the pressure received by the wall gradually decreases 28.19 MPa to 18.01 MPa. With an increase in the distance S from 0 to 8 mm, the maximum pressure received by the wall gradually decreases from 19.77 MPa to 9.37 MPa. The relationship found between the slow collapse stage (ta), the second contraction (tb), and the distance (L) can provide guidance for the effective application of the energy released by bubble collapse.
目前,气泡坍塌释放的能量可用于工件的表面处理,也可用于降解污染物。然而,气泡塌陷与附近壁面之间的作用机理尚未得到准确解释。为了掌握壁距与塌陷特性之间的关系,本文采用火花放电、高速摄影和压力采集等方法,研究了不同壁距下的气泡形状和压力释放过程中的动态变化。结果表明,随着壁距 L 的增大,气泡的形状由扁圆形变为球形,塌陷时间缩短。缓慢坍缩阶段所消耗的时间占总坍缩时间的比例呈上升趋势。在两次收缩的实验中,第一次收缩的慢速塌缩阶段所占的时间比例远远大于第二次收缩。气泡壁的存在延迟了气泡的坍缩。随着距离 L 的增加,气泡会从一次塌缩变成两次塌缩,然后再变成一次塌缩。第一次收缩的缓慢塌缩阶段的持续时间比例迅速减少,第二次收缩的缓慢塌缩阶段的比例缓慢增加,但第二次收缩的时间比例减少。当距离 L 从 4.5 mm 增加到 11 mm 时,壁面承受的压力逐渐从 28.19 MPa 减小到 18.01 MPa。当距离 S 从 0 毫米增加到 8 毫米时,墙体承受的最大压力从 19.77 兆帕逐渐减小到 9.37 兆帕。缓慢塌陷阶段 (ta)、第二次收缩 (tb) 和距离 (L) 之间的关系可为有效利用气泡塌陷释放的能量提供指导。
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引用次数: 0
An effective boundary element model to calculate the interaction between waves and flexible membrane 计算波浪与柔性膜相互作用的有效边界元模型
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-17 DOI: 10.1016/j.apor.2024.104267
Chaofan Lv , Shiming Yao , Xizeng Zhao , Hualong Luan , Mengyu Li , Kaiyuan Zheng , Geng Qu
Flexible membranes are widely used in marine engineering, but how to calculate their hydrodynamic performance under wave action remains a challenging problem. In this paper, a new model based on the eigenfunction expansion boundary element method (EEBEM) is proposed to calculate the wave-membrane interaction under two-dimensional conditions. A general dynamic boundary condition suitable for linear and arcuate membranes is established based on the membrane’s constitutive equations under cylindrical coordinates. This condition considers the dynamic tension and curvature of the membrane, and an integral expression for the dynamic tension is also derived. Subsequently, the dynamic boundary condition is transformed into a function of the velocity potential and applied to the EEBEM, overcoming the difficulty of the coupled solutions for the arcuate membrane’s motion and the flow field. Moreover, a generalized solution framework for wave-structure interaction is established by constructing a fully closed form of the water wave equations, which effectively shortens the modeling time and expands the application scope. After verifying the accuracy and effectiveness of the model, the hydrodynamic performance (wave force, membrane tension and wave transmission coefficient) and motion response of a submerged flexible membrane breakwater (SFMB) are investigated. The results demonstrate that the model exhibits high accuracy, which is beneficial for elucidating the mechanism of wave-membrane interaction and providing robust support for related research fields.
柔性膜在海洋工程中应用广泛,但如何计算其在波浪作用下的水动力性能仍是一个具有挑战性的问题。本文提出了一种基于特征函数扩展边界元法(EEBEM)的新模型,用于计算二维条件下波与膜的相互作用。根据圆柱坐标下的膜构成方程,建立了适用于线性和弧形膜的一般动态边界条件。该条件考虑了膜的动态张力和曲率,并推导出动态张力的积分表达式。随后,将动态边界条件转化为速度势函数并应用于 EEBEM,从而克服了弧形膜运动和流场耦合求解的困难。此外,通过构建水波方程的全封闭形式,建立了波与结构相互作用的广义求解框架,有效缩短了建模时间,扩大了应用范围。在验证了模型的准确性和有效性后,研究了水下柔性膜防波堤(SFMB)的水动力性能(波力、膜张力和透波系数)和运动响应。结果表明,该模型具有很高的精度,有利于阐明波-膜相互作用的机理,并为相关研究领域提供有力支持。
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引用次数: 0
A non-local formulation for simulating the fully nonlinear Serre–Green–Naghdi equations for a solitary wave interaction with a variable slope 模拟具有可变斜率的孤波相互作用的全非线性塞雷-格林-纳格迪方程的非局部公式
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-14 DOI: 10.1016/j.apor.2024.104220
T.S. Jang , H.G. Sung , Jinsoo Park
In this paper, we simulate a solitary wave interaction with a variable slope with reflection on a vertical wall by integrating the fully nonlinear Serre–Green–Naghdi (SGN) equations. To this end, we first provide an iterative solution process for the SGN equations so that we can simulate a solitary wave propagating over variable bathymetry. For the purpose of the study, we examine two physical problems. The first is of a solitary wave interaction with a constant slope with reflection on a vertical wall. The simulated solutions are in good agreement with other numerical and experimental data, confirming the validity of the current work. The second is concerned with a perturbation of the first problem, where the constant slope of the first problem is varied; i.e., a variable slope is taken into account. We compare the simulated solutions of the two problems and observe the (physically realistic) effect of the variable slope on shoaling and reflection by the vertical wall.
在本文中,我们通过对完全非线性的 Serre-Green-Naghdi (SGN) 方程进行积分,模拟了孤波与可变坡度的相互作用以及在垂直壁上的反射。为此,我们首先提供了 SGN 方程的迭代求解过程,从而可以模拟在可变水深上传播的孤波。为此,我们研究了两个物理问题。第一个问题是孤波与恒定斜坡相互作用,并在垂直墙壁上产生反射。模拟解与其他数值和实验数据十分吻合,证实了当前工作的有效性。第二个问题涉及第一个问题的扰动,即改变第一个问题的恒定坡度,也就是考虑可变坡度。我们对两个问题的模拟解进行了比较,并观察了可变坡度对垂直壁的滑动和反射的(物理现实)影响。
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引用次数: 0
Cumulative strain intelligent evaluation of marine soil from offshore wind farms based on enhanced machine learning 基于增强型机器学习的海上风电场海洋土壤累积应变智能评估
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-13 DOI: 10.1016/j.apor.2024.104265
Zhishuai Zhang, Xinran Yu, Bo Han, Song Dai
Accurate evaluation of cumulative strains in marine soils under long-term cyclic loading is essential for the design and safe operation of offshore wind turbines. This study proposes an enhanced machine learning model to predict the cumulative strain in marine soils subjected to cyclic loading. Cumulative strains of marine soils from five offshore wind farms under long-term cyclic loading were tested. Four prediction models for cumulative strains were developed and evaluated based on test results using the Back Propagation Neural Network (BP-NN), Random Forest (RF), Support Vector Regression (SVR), and eXtreme Gradient Boosting (XGBoost) models, each combined with the Particle Swarm Optimization (PSO) algorithm. The prediction model with the highest accuracy was further analyzed using the SHapley Additive exPlanations (SHAP) method. Results show that the RF and XGBoost algorithms have higher prediction accuracy, with R² values above 0.99, compared to the BP-NN and SVR models. Furthermore, dynamic triaxial test parameters significantly influence the cumulative strain predictions more than the soil properties. This study provides a more efficient method for cumulative strain assessment of marine soils under long-term cyclic loading.
准确评估海洋土壤在长期循环荷载作用下的累积应变对于海上风力涡轮机的设计和安全运行至关重要。本研究提出了一种增强型机器学习模型,用于预测循环加载下海洋土壤的累积应变。对五个海上风电场的海洋土壤在长期循环荷载下的累积应变进行了测试。根据测试结果,使用反向传播神经网络 (BP-NN)、随机森林 (RF)、支持向量回归 (SVR) 和极梯度提升 (XGBoost) 模型,结合粒子群优化 (PSO) 算法,开发并评估了四种累积应变预测模型。使用 SHapley Additive exPlanations (SHAP) 方法对准确率最高的预测模型进行了进一步分析。结果表明,与 BP-NN 和 SVR 模型相比,RF 和 XGBoost 算法的预测精度更高,R² 值超过 0.99。此外,动态三轴试验参数对累积应变预测的影响比土壤特性更大。这项研究为海洋土壤在长期循环荷载下的累积应变评估提供了一种更有效的方法。
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引用次数: 0
Research on ice-breaking characteristics of underwater explosion bubbles based on an effective coupled model 基于有效耦合模型的水下爆炸气泡破冰特性研究
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-11 DOI: 10.1016/j.apor.2024.104259
Ming He , Jiale Yan , Pengyu Lv , Huiling Duan , A-Man Zhang
The use of underwater explosion bubbles for ice breaking represents an efficient technological advance that is critical for polar exploration. In this paper, we propose an effective numerical methodology for investigating this pertinent issue. By combining the advantages of peridynamics and the Eulerian finite element method, we establish a coupled model for investigating the integral ice-breaking characteristics of underwater explosion bubbles. Our model is capable of accurately simulating the formation of bifurcated ice cracks and capturing the evolution patterns of both ice cracks and crushed ice under various complex working conditions. When the extreme standoff parameter is set to zero, multiple crushed ice formations are effectively generated during contact explosion, and the changes in the height and width of this crushed ice exhibit a predominantly increasing trend over time. Furthermore, our results elucidate the destructive mechanism of the bubble jet on the ice structure. We find that when the initial bubble does not have a strong destructive effect, the jet’s impact becomes more pronounced. The conclusions from this study offer valuable technical support for real-world polar exploration problems.
利用水下爆炸气泡破冰是一项高效的技术进步,对极地探索至关重要。在本文中,我们提出了一种有效的数值方法来研究这一相关问题。通过结合周动力学和欧拉有限元法的优势,我们建立了一个耦合模型,用于研究水下爆炸气泡的整体破冰特性。我们的模型能够精确模拟分叉冰裂缝的形成,并捕捉各种复杂工况下冰裂缝和碎冰的演化规律。当极端间距参数设置为零时,在接触爆炸过程中会有效地产生多个碎冰层,并且这些碎冰层的高度和宽度的变化主要呈现出随时间增加的趋势。此外,我们的结果还阐明了气泡喷射对冰结构的破坏机制。我们发现,当初始气泡不具有很强的破坏作用时,喷流的影响会变得更加明显。这项研究的结论为现实世界中的极地勘探问题提供了宝贵的技术支持。
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引用次数: 0
Online parameter identification and real-time manoeuvring prediction for a water-jet USV based on weighted multi-innovation prediction error method integrated with dynamic window strategy 基于动态窗口策略的加权多创新预测误差法的喷水式 USV 在线参数识别和实时操纵预测
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-11 DOI: 10.1016/j.apor.2024.104260
Zaopeng Dong , Baolin Wang , Fei Tan , Wenjie Zhou , Yuanchang Liu
Research on online parameter identification and real-time manoeuvring prediction for a class of water-jet unmanned surface vehicle (USV) is carried out in this paper. Utilizing actual sailing data from a water-jet USV, the weighted multi-innovation prediction error method integrated with dynamic window strategy is proposed to identify the manoeuvring parameters of the USV model online. Subsequently, real-time prediction of the water-jet USV's motion is achieved based on the established time-varying model. The thrust generation of water-jet propulsion system and the effect of rotational current on the USV's motion are analyzed simultaneously, and then a three-degree-of-freedom mathematical model is established for the water-jet USV equipped with two water-jet propulsion systems. Due to the weakening of the correction ability of the prediction error method in the later stage, an adaptive step factor with phase adjustment is designed to improve the response accuracy to the error innovation and maintain the algorithm's correction ability. Since the prediction error method updates the identification value using only a single innovation each time, incorporating multi-innovation theory enhances the utilization of historical data, allowing the algorithm to more accurately reflect the current state or trend. In order to fully consider the differences between data points, an adaptive weighting strategy is developed to assign weights according to the contribution of the data in the innovation window to USV modeling, so as to enhance the tracking performance of the time-varying parameters. Aiming at the outliers in the collected data, a dynamic innovation window strategy is designed, and then the data in this window is filtered by Quartile algorithm and the outliers are detected by local outlier factor, so that the window could contain more effective sailing state information. A large amount of actual test data analysis demonstrates that, the algorithm proposed in this paper could achieve more accurate online identification of water-jet USV model parameters and more precise real-time prediction of USV motion, which would provide strong support for safe navigation and efficient control of USV.
本文对一类喷水式无人水面航行器(USV)进行了在线参数识别和实时操纵预测研究。利用喷水式无人水面航行器的实际航行数据,提出了加权多创新预测误差法与动态窗口策略相结合的方法,在线识别无人水面航行器模型的操纵参数。随后,基于建立的时变模型,实现了喷水式 USV 运动的实时预测。同时分析了喷水推进系统产生的推力和旋转电流对 USV 运动的影响,然后建立了配备两个喷水推进系统的喷水 USV 的三自由度数学模型。由于后期预测误差法的修正能力减弱,设计了一种带有相位调整的自适应阶跃因子,以提高对误差创新的响应精度并保持算法的修正能力。由于预测误差法每次更新识别值时只使用一次创新,因此结合多创新理论可以提高对历史数据的利用率,使算法更准确地反映当前状态或趋势。为了充分考虑数据点之间的差异,开发了一种自适应加权策略,根据创新窗口中的数据对 USV 建模的贡献来分配权重,从而提高时变参数的跟踪性能。针对采集数据中的离群值,设计了动态创新窗口策略,然后利用四分位算法对该窗口中的数据进行过滤,并利用局部离群因子对离群值进行检测,从而使该窗口包含更多有效的航行状态信息。大量实际测试数据分析表明,本文提出的算法可以实现更准确的喷水式 USV 模型参数在线识别和更精确的 USV 运动实时预测,为 USV 的安全航行和高效控制提供有力支持。
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引用次数: 0
Thermal-mechanical sequence coupling analysis on the ultimate bearing capacity of embedded foundations in polar marine permafrost 极地海洋冻土中嵌入式地基极限承载力的热力学序列耦合分析
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-10 DOI: 10.1016/j.apor.2024.104256
Xiaofei Hu , Long Yu , Qing Yang , Xiao Han
This study presents the results of the numerical simulation analysis, aiming to investigate the temperature effects on the vertical ultimate bearing capacity of the three types of foundations, namely generic spudcan (SGEN), skirted and pile foundations, at different embedded depth ratios H/D (H/D = 1/3, 2/3, and 1 or H/D = 10/3, 5, and 20/3) and strength reduction coefficients su,T/su0 (su,T/su0 = 0.1, 0.5). The latent heat effects on foundation bearing capacities are studied by small strain finite element analysis (FEA). The findings from this investigation and previous research indicate that the foundations' vertical ultimate bearing capacity decreases with time, while it increases with increasing the foundation's embedment ratio. For the foundations, the strength reduction coefficient plays an important role in the vertical ultimate bearing capacity. Notably, as the strength reduction coefficient decreases from 0.5 to 0.1, the reduction rate of the vertical ultimate bearing capacity increases by ∼ 3 to 6 times accordingly. Consequently, a normalized bearing capacity coefficient model has been proposed to provide an optimization tool for engineering design in permafrost regions.
本研究介绍了数值模拟分析的结果,旨在研究在不同的埋深比 H/D(H/D = 1/3、2/3 和 1 或 H/D = 10/3、5 和 20/3)和强度折减系数 su,T/su0 (su,T/su0 = 0.1、0.5)条件下,温度对三种地基(即通用铲形地基 (SGEN)、裙式地基和桩基)垂直极限承载力的影响。通过小应变有限元分析 (FEA) 研究了潜热对地基承载力的影响。本次调查和之前的研究结果表明,地基的竖向极限承载力随时间的推移而减小,但随着地基嵌固率的增大而增大。对于地基而言,强度折减系数对竖向极限承载力起着重要作用。值得注意的是,当强度折减系数从 0.5 降到 0.1 时,竖向极限承载力的折减率会相应增加 3 到 6 倍。因此,提出了归一化承载力系数模型,为冻土地区的工程设计提供了优化工具。
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引用次数: 0
The properties of cement stabilized dredged sludge solidifying in seawater and its application in the protection of subsea pipelines 在海水中固化的水泥稳定疏浚淤泥的特性及其在海底管道保护中的应用
IF 4.3 2区 工程技术 Q1 ENGINEERING, OCEAN Pub Date : 2024-10-09 DOI: 10.1016/j.apor.2024.104264
Zhong Xiao , Bo Hou , Zhe Chang , Xian Wei , Zehuan Song , Haitao Li
Hundreds of millions of tons of dredged sludge are generated by waterway dredging worldwide every year. Traditional disposal of dredged sludge, such as in-situ stockpiling and offshore dumping, cannot avoid the waste of land resource and the pollution to marine environment. Sludge stabilization/solidification treatment currently used can achieve the reuse of drudged sludge but requires large investment and time. Therefore, how to turn waste into treasure in an effective, environmentally friendly and cheap way is a notable problem. In this study, the variation of strength of solidified sludge cured in air with water-cement ratio, water content and curing time by unconfined compression test was investigated, and the inner mechanism of strength influenced by water-cement ratio and water content was revealed by XRD test, which offered an optimal working condition. Also, solidified sludge with the maximum strength in the optimal working condition was immersed into seawater at different times, which showed the 7d strength after mixing completion for 8 h immersed into seawater could reach 20.60 MPa (1.37 times of the strength in air), and the prediction formulas considering all the parameters mentioned above were established. At last, a field test of solidified dredged sludge for protection of submarine pipelines was carried out in Bohai Bay, China, which demonstrated the feasibility of mixing dredged sludge with cement on board and solidifying in seawater environment. Compared to the traditional subsea pipeline protection solutions, the cost of using solidified sludge to protect subsea pipelines is 25 % and 39 % less than the cost of using sandbags and concrete mats, respectively. This study provides a more economic and environmentally friendly idea for dredged sludge treatment and subsea pipeline protection than the conventional methods, which provides a new source of green ocean building materials, reduces the pollution of the marine environment by the discharge of dredged sludge, turns waste into treasure and has wide applications in ocean engineering.
全球每年因航道疏浚产生数亿吨疏浚污泥。传统的疏浚污泥处置方式,如就地堆放、近海倾倒等,无法避免对土地资源的浪费和海洋环境的污染。目前采用的污泥稳定化/固化处理方法可以实现疏浚污泥的再利用,但需要大量的投资和时间。因此,如何有效、环保、廉价地变废为宝是一个值得注意的问题。本研究通过无侧限压缩试验研究了在空气中固化的固化污泥强度随水灰比、含水率和固化时间的变化,并通过 XRD 试验揭示了强度受水灰比和含水率影响的内在机理,为其提供了最佳工作条件。同时,将最佳工况下强度最大的固化污泥浸入不同时间的海水中,结果表明,混合完成后浸入海水中 8 小时后的 7d 强度可达 20.60 MPa(是空气中强度的 1.37 倍),并建立了考虑上述所有参数的预测公式。最后,在中国渤海湾进行了固化疏浚淤泥用于海底管道保护的现场试验,证明了将疏浚淤泥与水泥在船上混合并在海水环境中固化的可行性。与传统的海底管道保护方案相比,使用固化污泥保护海底管道的成本分别比使用沙袋和混凝土垫的成本低 25% 和 39%。这项研究为疏浚淤泥处理和海底管道保护提供了一种比传统方法更经济、更环保的思路,为绿色海洋建材提供了新的来源,减少了疏浚淤泥排放对海洋环境的污染,变废为宝,在海洋工程中具有广泛的应用前景。
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引用次数: 0
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Applied Ocean Research
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