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Numerical Study of Green Water Loads on a Fixed Structure with Various Gate Release Velocities by the MPS Method
Wu, Mengmeng (Shanghai Jiao Tong University, Shanghai) | Zhao, Weiwen (Shanghai Jiao Tong University, Shanghai) | Wan, Decheng (Shanghai Jiao Tong University, Shanghai) | Wang, Jifei (Shanghai Aerospace System Engineering Institute, Shanghai)
_ In rough sea conditions, a large mass of water will exceed the freeboard and cause violent slamming on the deck, which is known as green water. Many scholars have devoted themselves to the study of green water because of its strong destructiveness. Upon considering the complexity of green water, different simplified methods have been used to study its mechanism and loads. This paper investigates green water loads and patterns on a fixed structure using the meshless particle solver MLParticle-SJTU, which is based on the moving particle semi-implicit (MPS) method. A serial rapid flowstructure interaction was generated by the wet dam-break method. The experimental study by Hernández-Fontes et al. in 2020 investigated vertical loads of green water, and the numerical work by Areu-Rangel et al. in 2021 continued to study horizontal loads. In this paper, the study was extended by analyzing the effects of different gate release velocities on the generated wave patterns and green water loads. The results obtained in this paper were in good agreement with the existing results. Moreover, the influence of different gate release speeds on the green water simulation was analyzed.
Numerical Study of Cavitation Noise Around NACA66 (MOD) Hydrofoil with Direct Volume Integration
Yu, Lianjie (Shanghai Jiao Tong University, Shanghai) | Zhou, Fuchang (Wuhan Second Ship Design and Research Institute, Wuhan) | Zhao, Weiwen (Shanghai Jiao Tong University, Shanghai) | Wan, Decheng (Shanghai Jiao Tong University, Shanghai)
_ Underwater noise (URN) is the focus of academic research, and cavitation is an important source of underwater noise. This paper takes NACA66 (mod) two-dimensional hydrofoil as the research object and uses the open-source software OpenFOAM to simulate the sheet cavitation and sound field. The turbulence model is DDES, and the cavitation model is the Schnerr-Sauer model. The sound field is predicted by the FW-H formulation. Unlike the traditional method, this paper solves the quadrupole term (nonlinear term) by direct volume integration, so the nonlinear term can be predicted more accurately. At the same time, a new method of changing sound wave velocity is proposed considering the two-phase medium problem caused by cavitation. Four methods are compared, including two-phase volume integration, direct volume fraction, object surface integration, and penetrable formulation. It is found that the influence of two-phase flow is greater near the closure area of the cavity, which needs to be considered separately. The linear sound shows dipole directivity and the nonlinear component exhibits quadrupole characteristics. Introduction Underwater noise not only causes harm to marine life, but also affects the stealth of military equipment. The International Maritime Organization (IMO) issued non-mandatory noise standards for commercial ships (IMO, 2014). More and more attention has been paid to the acoustic environment. At this stage, the prediction of such noise becomes a hot topic (Deane and Stokes, 2010; Ianniello et al., 2013; Bensow and Liefvendahl, 2016).
- North America > United States (0.46)
- Asia > China (0.30)
- Transportation > Marine (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Numerical Study of the Effects of Yaw Error on the Wind Farm Performances
Wang, Nina (Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province, Huadong Engineering Corporation Limited) | Wei, Dezhi (Computational Marine Hydrodynamic Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamic Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT Wind turbine is the most frequently used device to extract the wind energy. Arising from the influences of various factors such as the high-frequency variation of incoming wind direction, it is difficult for the wind turbines to track the incoming wind timely. As a result of which, wind turbines inside the wind farm are commonly operated in a yaw state, known as yaw error, which can affect the wind farm performance. In the present work, taking a wind farm array with 12 NREL 5MW wind turbines as the research object, we conducted a series of large-eddy simulations under different incoming wind directions and surface roughness heights. The results reveal that yaw error can either increase the total power production or cause power loss of the wind farm array, depending on the change of wake effect. More seriously, the change in wind farm power caused by yaw error is not a small value, it can reach as much as 41.5% for the particular case considered here. This indicates that the influence of yaw error should be taken in wind farm power prediction in the real-world engineering. INTRODUCTION Wind energy is one of the promising renewable resources with the advantages of pollution-free and low development cost. Horizontal axis wind turbine is the most frequently used device to absorb the wind energy (Chehouri et al, 2014). It is quite common that the wind turbine inside the wind farm operates in a yaw state, i.e., the rotor plane is not aligned with the incoming flow direction, arising from the following reasons: (1) The randomness of natural wind, which leads to a high-frequency change in inflow wind direction. (2) The lack of wind measuring instruments, which makes it impossible to provide accurate real-time wind monitoring data for all wind turbines inside the wind farm. (3) Wake effect and instantaneous turbulent structures in the atmospheric flow field, which can affect the wind measurement accuracy. (4) In order to ensure the stable operation of wind turbine, the yaw error threshold is commonly set in the real-world engineering, indicating that the yaw control action has a certain hysteresis.
Numerical Investigation of Horizontal Thermal Buoyancy Jet in Linearly Stratified Fluid
Gao, Gang (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Cao, Liushuai (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Shen, Zhiben (Wuhan Second Ship Design and Research Institute) | Wang, Yun (Wuhan Second Ship Design and Research Institute) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT In general, the thermal jet flow generated by cooling water discharge from submarine is modeled as the horizontal thermal buoyancy jet. Most of the previous experimental researches do not take the influence of density gradient into account, only a few computational investigations considered the effect of jet temperature. In this paper, a temperature-driven density stratification (TDDS) method is proposed to achieve the continuously density stratified fluid, and then implemented in the commercial software Simcenter STAR-CCM+ framework. The linear temperature distribution in the background is specified, and the relationship between density and temperature is then provided explicitly. The detached eddy simulation (DES) method based on the shear stress transport (SST) k-ω turbulence model is adopted to resolve the turbulence. Results show that stratified flow gradients affect jet trajectories. With different discharge velocity of the thermal jet, the trajectory centerlines experience two stages: the horizontal stage and the ascending stage. The jet has a larger horizonal distance with the higher Froude number. The temperature of jets decreases significantly after flowing into open water domain. As the rising height increases, the temperature of jet decay becomes very slow. INTRODUCTION Underwater vehicles occupy an important position in the military field because of their strong concealment and surprise, among which submarines are the most representative. In recent years, benefiting from the rapid development of photoelectric technology, the resolution, accuracy and anti-interference ability of infrared detection equipment have been greatly improved. It has attracted extensive attention due to its advantages such as detection. During the voyage of the underwater vehicle, the waste heat generated by its power system will be absorbed by the cooling water and discharged into the seawater along with the cooling water. The temperature of these cooling waters is significantly higher than that of the surrounding water body. Driven by the density difference, they float upwards, which may form an abnormal infrared feature on the sea surface.
- Research Report > New Finding (0.88)
- Research Report > Experimental Study (0.70)
- Water & Waste Management > Water Management (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Comparison of Porous and Direct Volumetric Integration FW-H Formulation for Acoustic Prediction
Zhuang, Yuan (Computational Marine Hydrodynamic Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Yang, Luchun (Wuhan Second Ship Design and Research Institute) | Zhao, Weiwen (Computational Marine Hydrodynamic Lab, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamic Lab, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT In the present work, two integration methods of FW-H formulation for hydroacoustic prediction are adopted and compared. One of the methods uses porous surface integration method, the other is direct volumetric integration with a dual mesh technique. The numerical model is the flow past a circular cylinder. The setup of simulation case of the two methods keeps the same. The near-field and far-field sound pressure level are compared between these two methods. It is shown that peak value frequency of sound pressure level of both methods is around the shedding frequency of the cylinder. The near-field sound pressure level of those two methods has small differences while the far-field sound pressure levels are large. At last, the efficiency and disk storage of these two methods are also compared. With the dual mesh technique, the volumetric integration method shows small time cost in the simulation. INTRODUCTION Nowadays, the sound problem in hydrodynamics became essential. Many numerical methods have been done to solve these kinds of problems. A popular numerical method to predict fluid noise is coupled Computational Fluid Method (CFD) with acoustic analogies. One of the widely used numerical approach to simulate acoustic analogy is the Ffowcs Williams-Hawkings (FW-H) analogy. The contribution of Lighthill stress tensor which is a quadruple source term can be directly calculated with volumetric integration, or it can be calculated on a porous surface. These two methods both have their own advantages and disadvantages. For example, the porous surface integration method is sensitive to the choice of porous surface as well as the fluid data on the porous surface. Rahier et al (2015) pointed out that a spurious noise would be generated when the turbulent flow crossed through the porous surface. They thought the spurious noise generated due to the lack of volumetric terms. Cianferra et al (2019) compared porous surface integration method with volumetric integration method, and found out that under the low frequency, the accuracy of porous surface integration method is lower than both volumetric integration and linear Curle method. If only considered far-field noise, the nonlinear term of the sound decreased rapidly.
Hull Resistance Performance Optimization Based on Fitting Surface Deformation
Liu, Zhiqiang (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering Shanghai Jiao Tong University) | Wu, Linna (Shanghai Institute of Aerospace System Engineering) | Wei, Yabo (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering Shanghai Jiao Tong University)
ABSTRACT The resistance performance of ship is important for sailing and economy. For obtaining a less consumption of fuel, number of measures are taken. The deformation of marine structures is the basis for marine structure hydrodynamic performance optimization. In this paper, a barycentric coordinates called fitting body deformation is introduced based on maximum entropy theory. This method is used to deform the DTMB hull form to create different hull forms. Then, the in-house solver naoe-FOAM-SJTU is applied to calculated the resistance of different hull forms under Fr=0.18 in calm water. The Kriging theory is selected as the surrogate model. the single-objective genetic algorithm is applied to get the lowest total drag hull based on the Kriging surrogate model. The results show that the fitting body deformation has the capacity of deformation the hull forms and can be used to optimization the hydrodynamic performances in reality. INTRODUCTION Ship hydrodynamic performance is an essential aspect for ship building. For hull form optimization, modify the hull form is a important measure to optimize the hull hydrodynamic. With the development of computational ability and the computational fluid dynamic techniques, simulation-based design optimization (SBDO) is the main technique for the design optimization for the ship and ocean structure (Lin, 2018; Liu, 2018a; Nazemian, 2021) in recent years, such as the ship maneuver, seakeeping, resistance, and so on(Miao et al., 2020; Tahara et al., 2011). For the hull form deformation, the deformation is the first stage in the optimization process. Deformation refers to the twisting and deforming of geometry in order to obtain the shape desired by the user. In this process, the topological relationship of the geometry remains unchanged. For this purpose, a lot of hull form modified methods are proposed, the Free Form Deformation (FFD) is a quite basic and important deformation method, which is introduced in 1986 (Sederberg, 1986). This method changes the geometry shape by editing the grid embedded in the geometry. In 1990, the Extended Free Form Deformation Method (FFD) was introduced, which is an extended version of FFD and allows for the design of more flexible grids to control geometric deformation(Coquillart, 1990). And a generalized method is proposed, which can deform the hull form shape by arbitrary lattice shape (MacCracken, 1996). In 2003, the T-FFD (Triangular Free Form Deformation) is created based on the initial FFD (Kobayashi, 2003). Beside these method, some other deformation method are also proposed such as shifting deformation method (Kim, 2013), radial basis function deformation method (De Boer, 2007) and Leckenby method (Lackenby, 1950).
- North America (0.46)
- Asia > China (0.16)
- Energy > Oil & Gas > Upstream (0.50)
- Transportation (0.47)
- Shipbuilding (0.34)
Hull Form Optimization Using Bayesian Optimization Framework
Wei, Yabo (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering Shanghai Jiao Tong University) | Sun, Guocang (Wuhan Second Ship Design and Research Institute) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering Shanghai Jiao Tong University)
ABSTRACT In this paper, a data-driven shape optimization approach is proposed for ship hull form optimization. To avoid the time-consuming evaluation of ships via a viscous flow solver, we developed a Machine-Learning (ML) based model that predicts the hull's hydrodynamic performance. For this purpose, a Bayesian optimization framework is developed and applied to OPTShip-SJTU, an existing ship optimization solver. Among them, the CFD method is used to calculate ship performance, and the Radial Basis Function (RBF) method is adopted for hull surface deformation. To improve the efficiency of hull form optimization, the surrogate model is used to approximate the CFD simulation. Unlike the traditional static approximation models used in the process of hull form optimization, a dynamic approximation model based on expected improvement is proposed. The adaptive balance parameter is taken in the parallel efficient optimization (PEGO) algorithm to make a tradeoff between exploitation and exploration. The Optimal Latin hypercube algorithm is used as the method of design of experiments. The Kriging model is employed as the surrogate model. Wigley ship is used to demonstrate the proposed optimization framework. Lines of the ship are determined and optimization results of the resistance show the effectiveness of the proposed method. INTRODUCTION Ship is a significant tool for humans to explore and exploit the ocean. Design of a ship is so complex that multiple performances should be considered, especially hydrodynamic performance which includes maneuverability, rapidity, and seakeeping. In the process of ship design, rapidity is the main concern. Besides, the resistance of ship is an essential aspect that reflects the ship's rapidity performance. Reducing the resistance of ships becomes more and more challenging, which can be achieved by optimizing the ship hull lines. Changes in hull lines can also affect other ship properties, such as seakeeping performance and maneuverability. Noteworthy, how to obtain the best hull form is the main concern in the design stage. With the development of computer technology, Computer Fluid Dynamics (CFD) based on viscous theory has been widely applied to hydrodynamic problems. As a result, simulation-based design (SBD) technology has been widely applied to hull form optimization in the past decades.
- Transportation > Marine (1.00)
- Energy > Oil & Gas > Upstream (0.66)
Numerical Study of Spring Response of 20000TEU Containership in Waves
He, Fan (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wang, Jianhua (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT With the trend of increasing dimensions of large ships, especially for the ultra large container ship, the hydroelasticity of ship in waves become more and more important. The hydroelastic responses, such as springing and whipping, happen more frequently even in sea states that were not regarded as severe before. It is of great importance to estimate the wave and vibration induced loads of ships accurately. In the present work, a fluid-structure interaction (FSI) method is developed based on CFD-FEM method to predict the hydroelastic response of a 20000TEU container ship in waves. Fluid field is solved by RANS method with OpenFOAM. Structural vibration is represented by Timoshenko beam model and solved by Newmark-beta method. The springing response of container ships in different regular waves are calculated. The predicted results, including ship motions, vertical bending moment, are compared with the experimental results. and the present CFD-FEM solver is proved to be reliable in predicting hydroelastic response for ultra large container ship in waves. INTRODUCTION With the trend of increasing dimensions of large ships, particularly ultra large container ships with their length reaching approximately 400m, the ships become more flexible. The hydroelastic responses, such as springing and whipping, happen more frequently even in sea states that were not regarded as severe before. In recent years, a few critical ship accidents due to fatigue cracks and structure failure caused by hydroelastic responses took place unexpectedly. Two severe accidents involving large container ships occurred: MSC NAPOLI in 2007 and MOL COMFORT in 2013 (Hirdaris et al., 2023), as shown in Fig. 1. Both vessels were reported to have failed in a hogging condition due to the collapse of the hull girder. These accidents have drawn attention from the governmental organization (IMO), classification association (IACS) and international technical committees, such as ITTC and ISSC. Now, a joint work group between ISSC and ITTC is also carrying out research on this important issue of springing and whipping responses of ultra large container ship.
- Transportation > Marine (1.00)
- Transportation > Freight & Logistics Services > Shipping > Container Ship (1.00)
Two-Way Coupled CFD-FEM Method for High-Speed Water Entry of Elastic Wedge
Xiao, Jiawei (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Liu, Cong (Marine Design and Research Institute of China) | Wang, Jianhua (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT In this paper, a two-way coupling method of CFD-FEM is constructed based on preCICE, which is an open-source coupling library for partitioned multi-physics simulations. The flow field is solved by RANS method with OpenFOAM and the structural part is solved by one-step theta method with deal.ii. In order to verify the CFD-FEM method, this study simulates the slamming of a two-dimensional wedge-shaped body with a base angle of 10° at high speed into the water. Both slamming pressure and structural deformation are compared with the test results. Afterwards, a comparative study was carried out on wedge-shaped bodies with different falling speeds to explore the velocity effects on the evolution of slamming pressure, structural deformation, and flow field of wedge-shaped bodies. The results show that slamming pressure is highly nonlinear and has a strong relationship with entry velocities, where hydroelasticity should be considered. INTRODUCTION When a ship is sailing in rough waves, the bow of the ship will have a slamming phenomenon due to the interaction with encountering waves. The huge slamming load has a significant influence on the local structural strength. In order to make a reasonable safety assessment of the local structure of the ship, it is very important to accurately predict the slamming pressure. Generally, a simplified wedge-shaped body model is used for the research. Since the deformation response of the structure cannot be ignored, it is necessary to adopt the FSI method to study this phenomenon. Many researchers have done research on slamming problem, which can be divided into theoretical research, experimental research and numerical simulation. In the early theoretical research, Von Karman (1929) and Wagner (1932) made a preliminary exploration. The former initially proposed a theoretical method to calculate slamming pressure based on momentum theorem and additional mass assumption. On the basis of the former, the latter considers the jet and the rise of free surface, which improves the accuracy of this method in calculating the slamming pressure of wedge with small static rise angle. Scolan (2004) coupled the Wagner model and the linear model to simulate the hydroelastic effects of thin shells, and applied them to the cone falling on the incompressible plane free surface. Both the hydrodynamic model of liquid and the structural model were linearized on the basis of the plate approximation.
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (1.00)
CFD Prediction of Slamming Loads on KCS in Oblique Waves
Wang, Ao (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Guo, Hao (Marine Design and Research Institute of China) | Wang, Jianhua (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University) | Wan, Decheng (Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University)
ABSTRACT The slamming loads of the KCS model were studied in different wave directions. Angles between wave and ship heading are 0 deg, 30 deg and 60 deg when Fr = 0.26. Numerical simulations were studied by inhouse CFD solver naoe-FOAM-SJTU, where dynamic overset grid technology was used to deal with the large vertical movement of the hull. Ship motions and the characteristics of slamming loads were investigated in different wave directions. Both temporal and spatial characteristics of pressure in bow region were illustrated. Flow visualizations, such as pressure distribution on hull surface, wave pattern, etc. were presented and analyzed. The results showed that the slamming loads in small heading angle were higher than that in head wave while it is opposite for large heading angle. INTRODUCTION Ships sailing in waves often encounter slamming phenomena. The transient and huge impact force threatens the safety of ship structure, passenger, device, etc. Therefore, it is necessary to predict the slamming load. There are two types of ship slamming: symmetric slamming and asymmetric slamming. The former often occurs in head wave while the latter occurs in oblique wave. Compared with symmetric slamming, the prediction of asymmetric slamming load is more challenging due to the influence of ship roll and wave direction. Some studies on the asymmetric slamming problem have been done. Iafrati (2000) directly solved the velocity potential and its derivative in the water entry problem of asymmetric wedges through the boundary element method, and discussed the free surface form and pressure distribution under different heel angles. Judge et al. (2004) studied the water entry problem of wedge with both horizontal and vertical velocities through the vortex distribution model. The comparison between the experiment showed that the theoretical method cannot completely explain some fluid characteristics in the experiment. Aarsne (1996) carried out a falling body experiment on an asymmetric ship section. In the experiment, the slamming loads and slamming force were measured, but the latter had severe oscillation. Russo et al. (2018) conducted an oblique water entry experiment on a wedge with 37°deadrise angle, and measured the displacement, velocity and acceleration of the falling body. The results showed that with the heel angle increasing, the wedge decelerated faster and the side of lower deadrise angle was submersed faster. However, the water entry speed had little effect on the slamming pressure, free surface pile-up, etc.
- Information Technology > Mathematics of Computing (0.49)
- Information Technology > Grid (0.35)
- Information Technology > Architecture > Distributed Systems (0.35)