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Application of IITM-RANS3D to free-fall water entry of prismatic and non-prismatic finite wedges

水动力学研究与进展B辑:英文版 2023年第3期35卷 417-430页

作者： Shaswat Saincher Kshitij Srivastava R.Vijayakumar V.Sriram Center for Maritime Experiments to Maritime Experience(ME2ME) Indian Institute of Technology MadrasChennaiIndia Department of Ocean Engineering Indian Institute of Technology MadrasChennaiIndia

High-speed watercraft and ships undergo coupled motions which make the front portion of the hull exit and violently re-enter *** induces short-term slamming loads that may compromise the structural integrity of the *** slamming of the bow can be modeled as straight wedges of different deadrise angles(DRAs)falling into water from different *** advent of computational fluid dynamics has allowed the problem of wedge-slamming to be simulated using the full Navier-Stokes equations thus complementing the pioneering studies based on ***,most researchers are opting to use commercial software to simulate the wedge-impact problem as it allows access to overset meshing algorithms which are robust in modeling the wedge as a moving *** boundary methods(EBMs)offer some advantages over overset meshing in that the mesh only needs to be generated once and Cartesian mesh-based solvers can be ***,the application of EBMs to wedge-impact has been limited in the literature and merits further *** this context,we investigate the applicability of the fast-fictitious-domain(FFD)based embedded boundary treatment to simulate the violent water-entry of *** extend our in-house Navier-Stokes model IITM-RANS3D to handle floating bodies through integration of a rigid-body dynamics solver and an algorithm to embed three-dimensional stereolithography(STL)geometries as solids over a Cartesian *** proposed algorithm is extensively benchmarked against variable DRA wedge-slamming experiments reported in the literature as well as constant DRA wedge-slamming experiments performed *** good agreement is reported in terms of the time-history of hydrodynamic impact pressures measured at various locations on the hull as well as the wedge motion responses thus demonstrating the suitability of FFD for simulating the coupled hydrodynamics of slamming for simplified hull geometries.

关键词： Wedge water entry slamming fast-fictitious-domain IITM-RANS3D experiments

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Experimental observation on water entry of a sphere in regular wave

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Theoretical & Applied Mechanics Letters 2023年第5期13卷 367-374页

作者： Qian Wang Changze Zhao Haocheng Lu Hua Liu Department of Engineering Mechanics MOE Key Laboratory of HydrodynamicsShanghai Jiao Tong UniversityShanghai 200240China

This paper presents a novel experiment to observe the whole water entry process of a free-falling sphere into a regular wave.A time-accurate synchronizing system modulates the moment elaborately to ensure the sphere impacting onto the water surface at the desirable wave *** high-speed cameras focus locally to measure the high-precision size of the cavity ***,the aggregated field view of the camera array covers both the splash above the free surface and the entire cavity in the *** detailed methodologies are described and verified for the hardware set-up and the image *** theoretical maximum deviation is 1.7%on the space *** integral morphology of the cavity is captured precisely in the coordinate system during the sphere penetrates through the water at four representative wave phases and the still *** result shows that the horizontal velocity of the fluid particle in the wave impels the cavity and changes the shape ***,the wave motion causes the cavity to pinch offearlier at the wave trough phase and later at the wave crest phase than in the still *** wave motion influences the falling process of the sphere slightly in the present parameters.

关键词： Physical experiment water entry Free-falling sphere Regular wave

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water entry OF A WEDGE BASED ON SPH MODEL WITH AN IMPROVED BOUNDARY TREATMENT

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Journal of Hydrodynamics 2009年第6期21卷 750-757页

作者： GONG Kai LIU Hua WANG Ben-long Department of Engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai 200240 China

The hydrodynamic problem of a two-dimensional wedge entering water is studied based on Smoothed Particle Hydrodynamics （SPH） model. A non-reflection boundary treatment for SPH method is proposed to reduce the reflection of sound waves. The boundary pressure is obtained using an improved coupling boundary treatment approach, which is validated by comparing the simulation results with experimental and analytical results in literature. A series of cases with different initial entering velocities are simulated. The maximum force on the wedge and the corresponding time required to reach it for the different cases of initial entering velocities of the wedge are obained and fitted into formulas against the initial entering velocity of the wedge. The maximum drag coefficients of the wedge for the different cases with Froude number greater than 2 are all near the value of 0.91.

关键词： water entry Smoothed Particle Hydrodynamics (SPH) non-reflection boundary

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water entry of decelerating spheres simulations using improved ISPH method

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Journal of Hydrodynamics 2018年第6期30卷 1120-1133页

作者： Abdelraheem M.Aly Mitsuteru Asai Department of Mathematics Faculty of Science King Khalid University Department of Mathematics Faculty of Science South Valley University Department of Civil Engineering Kyushu University

In this paper, we simulated the vertical impact of spheres on a water surface using three-dimensional incompressible smoothed particle hydrodynamics(3-D ISPH) method. The sphere motion is taken to be a rigid body motion and it is modeled by ISPH method. The governing equations are discretized and solved numerically using ISPH method. A stabilized incompressible SPH method by relaxing the density invariance condition is adopted. Here, we computed the motions of a rigid body by direct integration of the fluid pressure at the position of each particle on the body surface. The equations of translational and rotational motion were integrated in time domain to update the position of the rigid body at each time step. In this study, we improved the boundary treatment between fluid and fixed solid boundary by using virtual marker technique. In addition, an improved algorithm based on the virtual marker technique for the boundary particles is proposed to treat the moving boundary of the rigid body motion. The force exerted on the moving rigid boundary particles by the surrounding particles, is calculated by the SPH approximation at the virtual marker points. The applicability and efficiency of the current ISPH method are tested by comparison with reference experimental results.

关键词： Incompressible smoothed particle hydrodynamics(ISPH) free surface flow sphere rigid body water entry

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water entry and exit of axisymmetric bodies by CFD approach

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Journal of Ocean Engineering and Science 2018年第2期3卷 156-174页

作者： Vinod V.Nair S.K.Bhattacharyya Department of Ocean Engineering Indian Institute of Technology MadrasChennai 600036India

The water impact and subsequent entry of three rigid axisymmetric bodies,a sphere and two cones,in the early phase are simulated using CFD utilizing a VOF scheme to track the free surface and the results compared with the recent experimental results available in the *** penetration depth,vertical velocity and vertical acceleration time histories have been reproduced well by CFD with a wide choice of mesh density,whereas the peak pressure on impact required a much finer mesh and appropriate choice of the time *** an interaction region around the trajectory of the body with fine mesh and an adaptive time stepping strategy has worked well to capture the peak impact pressure accurately with reasonable computational ***‘full’motion of the sphere,which is buoyant,has also been simulated using CFD allowing its 6-dof motion for several cycles of entry and exit *** features of the behavior,especially the loss of symmetry of the trajectory,are discussed.

关键词： CFD Cone Sphere water entry water impact

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Numerical Simulation of water entry of Wedges in Waves Using A CIPBased Model

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China Ocean Engineering 2021年第1期35卷 48-60页

作者： HU Zi-jun ZHAO Xi-zeng LI Meng-yu ZHAO Xin YAO Wen-wei SHAO Jie Zhejiang Institute of Hydraulic and Estuary Hangzhou 310020China Ocean College Zhejiang UniversityZhoushan 316021China

In this study,the water entry of wedges in regular waves is numerically investigated by a two-dimensional in-house numerical *** numerical model based on the viscous Navier−Stokes(N−S)equations employs a high-order different method—the constrained interpolation profile(CIP)method to discretize the convection term.A Volume of Fluid(VOF)-type method,the tangent of hyperbola for interface capturing/slope weighting(THINC/SW)is employed to capture the free surface/interface,and an immersed boundary method is adopted to treat the motion of *** momentum source function derived from the Boussinesq equation is applied as an internal wavemaker to generate regular *** accuracy of the numerical model is validated in comparison with experimental results in the *** results of water entry in waves are provided in terms of the impact force of wedge,velocity and pressure distributions of *** attention is paid to the effects of wave parameters and the position of wedge impacting the water *** is found that the existence of waves significantly influences the velocity and pressure field of fluid and impact force on the wedges.

关键词： water entry water wave wedge internal wave maker CIP method VOF method

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Numerical study on the dynamic characteristics of water entry of cavity body using two-phase SPH method

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Acta Mechanica Sinica 2021年第7期37卷 1072-1089,I0002页

作者： Qiuzu Yang Fei Xu Yang Yang Jingyu Wang Anwen Wang Chunhao Ma School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Department of Mechanical Engineering Technical University of Munich85748 GarchingGermany ASN Technology Group Co.Ltd Xi’an 710065China

The air usually has a major influence on the water entry of a typical cavity body(cavity body is a hollow,cylindrical,semiclosed structure),which not only lowers the slamming load but also affects the dynamic characteristics of water *** this paper,a two-phase smoothed particle hydrodynamics(SPH)model for simulating the water entry of cavity body is *** SPH model combined with Riemann solver is improved to deal with the two-phase flows with the discontinuous quantities across the ***-sided Riemann problem is used to impose the fluid–structure interaction and a switchfunction-based Riemann solver dissipation is formulated to improve the interfacial instability owing to the strong *** motion equations of rigid body are incorporated into two-phase SPH model to describe the motion of cavity *** proposed model is validated by research on the test cases in the published ***,this work presents a study of water entry of cavity body by experiment and this two-phase SPH *** dynamics phenomena in the coupling process between cavity body and two-phase flow are *** the effects of air,mass,the sizes and incline angles of cavity body on the dynamic characteristics of cavity body and two-phase flows are shown.

关键词： water entry Cavity body Dynamic characteristics Multi-phase flow Smoothed particle hydrodynamics(SPH)

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HYDRODYNAMIC BEHAVIOR OF AN UNDERwater MOVING BODY AFTER water entry

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Acta Mechanica Sinica 2001年第1期17卷 35-44页

作者：施红辉高见卓也 Department of Mechanical Engineering Nagoya Institute of Technology Gokiso-cho Showa-kuNagoya 466-8555 Japan Space Engineering Division Space Engineering Development Co. Ltd. Issei Build. Takezono 2-3-12 Tsukuba 305-0032 Japan

An experimental study was conducted to investigate the water entry phenomenon. A facility was designed to carry out the tests with the entry veloci- ties of around 352 m/s. Visualization, pressure ineasurement, velocity measurement and underwater impact test were performed to investigate the hydroballistic behav- ior of the underwater moving body, the underwater flow field, the supercavitation, etc.. This study shows that the motion of a high-speed underwater body is strongly three-dimensional and chaotic. Furthermore, it is found that the distribution of the trajectory deflection of the underwater projectile depends on the depth of water. It is also found by measuring the deformation on a witness plate submerged in water, that the impact energy of an underwater projectile is reduced as it penetrates deeper into water.

关键词： water entry supercavitation underwater acoustic wave underwater projectile trajectory projectile velocity

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UNDERwater ACOUSTICS AND CAVITATING FLOW OF water entry

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Acta Mechanica Sinica 2004年第4期20卷 374-382页

作者：施红辉 KUME Makoto State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China College of Mechanical Engineering and Automatic ControlZhejiang University of SciencesXiasha Higher Education ZoneHangzhou 310018China Department of Mechanical Engineering Nagoya Institute of TechnologyGokiso-choShowa-kuNagoya 466-8555Japan

The fluid mechanics of water entry is studied through investigating the underwater acoustics and the *** acoustic signals in water entry are extensively measured at about 30 different positions by using a PVDF needle *** the measurements we obtain (1)the primary shock wave caused by the impact of the blunt body on free surface;(2)the vapor pressure inside the cavity;(3)the secondary shock wave caused by pulling away of the cavity from free surface;and so *** supercavitation induced by the blunt body is observed by using a digital high-speed video camera as well as the single shot *** periodic and 3 dimensional motion of the supercavitation is *** experiment is carried out at room temperature.

关键词： water entry underwater acoustics supercavitation PVDF hydrophone high-speed photography

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Effects of Froude number and geometry on water entry of a 2-D ellipse

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Journal of Hydrodynamics 2018年第4期30卷 738-749页

作者：张旭刘沛清屈秋林王睿 Ramesh K.Agarwal School of Aeronautic Science and Engineering Beihang University School of Engineering and Applied Science Washington University in St.Louis

By using the finite volume method with volume of fluid model and global dynamic mesh technique, the effects of Froude number and geometry on the water entry process of a 2-D ellipse are investigated numerically. For the time history of the vertical force, the computational fluid dynamics（CFD） results match the experimental data much better than the classical potential-flow theories due to the consideration of the viscosity, turbulence, surface tension, gravity, and compressibility. The results show that the position of peak pressure on ellipse shifts from the spray root to the bottom of ellipse at a critical time. The critical time changes with the geometry and Froude number. By studying the vertical force, the ellipse water entry process can be divided into the initial and late stages based on the critical dimensionless time of about 0.1. The geometry of the ellipse plays a dominant role in the initial stage, while the Froude number is more important in the late stage of entry. The classical Wagner theory is extended to the ellipse water entry, and the predicted maximum value of vertical force coefficient in the initial stage is 4？a/b that matches the CFD results very well, where a and b are the horizontal axis and vertical axis of the ellipse parallel and perpendicular to the initial calm water surface, respectively.

关键词： water impact water entry fluid-structure interaction Froude number

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