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"Floating bodies."
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Does it sink or float?
\"Vibrant photographs and accessible text introduce young scientists to the concept of density. Readers are encouraged to explore what makes some objects float and others sink.\"--Provided by publisher.
Book
Hydroinformatic tools and their potential in the search for missing persons in rivers
This research proposes a methodological approach to search floating bodies or floating body parts in rivers using hydroinformatic tools. These tools may allow possible search locations and potential release sites to be determined. The approach draws from hydrometric field information, two-dimensional (2D) hydrodynamic modeling, particle tracking (PT) models, and large-scale particle image velocimetry (LSPIV). This methodology was applied to a case study of the La Miel river in Colombia, where existing reports of deceased persons are available. A series of hydraulic accidents have been defined to represent the hydrodynamic and transport processes that occur in such situations. The results indicate that potential search locations, namely places where human floating bodies or floating body parts may be found, are principally on the left and right shores of recirculation systems.
Journal Article
What floats in a moat?
While trying to cross a moat, Archimedes the Goat and Skinny the Hen learn why objects sink or float.
Book
Novel three-dimensional stacked capacitorless DRAM architecture using partially etched nanosheets for high-density memory applications
This study presents a novel three-dimensional stacked capacitorless dynamic random access memory (1T-DRAM) architecture, designed using a partially etched nanosheet (PE NS) to overcome the scaling limitations of traditional DRAM designs. By leveraging the floating body effect, this architecture eliminates the need for capacitors, thereby improving integration density and memory performance. Through Sentaurus technology computer-aided design simulations, we compare the PE NS 1T-DRAM device with a conventional NS 1T-DRAM device to evaluate its effectiveness. The results reveal superior retention time (RT) and sensing margin (SM) performance of the proposed PE NS 1T-DRAM device, surpassing the memory criteria outlined by the International Roadmap for Devices and Systems, which requires an RT exceeding 64 ms at 358 K. This enhanced performance of the proposed device is attributed to its extension region, which functions as a potential well for efficient hole storage, as well as the suppression of Shockley‒Read‒Hall recombination. The PE NS 1T-DRAM device also demonstrates robustness to disturbances, maintaining over 89% of its SM and RT under diverse conditions. This superiority is again attributed to its extension region, which minimizes the effects of current flow and electrostatic potential rise. These results highlight the potential of the PE NS 1T-DRAM design for future high-density memory applications.
Journal Article
Wave Radiation by a Floating Body in Water of Finite Depth Using an Exact DtN Boundary Condition
The present paper focuses on the wave radiation by an oscillating body with six degrees of freedom by using the DtN artificial boundary condition. The artificial boundary is usually selected as a circle or spherical surface to solve various types of fields, such as sound waves or electromagnetic waves, provided that the considered domain is infinite or unbounded in all directions. However, the substantial wave motion is considered in water of finite depth, that is, the fluid domain is bounded vertically but unbounded horizontally. Thus, the DtN boundary condition is given on an artificial cylindrical surface, which divides the water domain into an interior and exterior region. The boundary integral equation is adopted to implement the present model. In the case of a floating cylinder, the results of hydrodynamic coefficients of a chamfer box are discussed.
Journal Article
Stereo Reconstruction Method for 3D Surface Wave Fields around a Floating Body Using a Marker Net in a Wave Tank
Spatial wave fields around floating bodies are important for the understanding of hydrodynamics, and particularly the wave drift forces, of floating bodies in waves; however, experimental measurement of these fields is challenging. This paper presents a stereo reconstruction method for three-dimensional (3D) surface wave fields around floating bodies in a wave tank. Styrofoam markers were attached to a flexible net in a regular grid, called a marker net, and were placed on the water surface to be used as targets for stereo cameras (SCs). A thin plate spline was applied to the markers detected by the SCs to reconstruct the 3D surface wave profile around a floating body model. The proposed method was validated by measuring the wave field around a cylindrical floating body with a footing at its bottom. These experiments were conducted under regular wave incidence conditions. A wave elevation time series measured using a servo-controlled wave gauge was used as the benchmark data. The 3D surface wave field reconstruction method was applied under three different conditions: without the model, with a fixed model, and with a freely oscillating model. The results showed reliable reconstructions of the scattering and radiation waves. The marker net’s effects on the floating body’s motion and the surrounding wave fields were shown to be negligible by comparing the results acquired with and without the marker net.
Journal Article
Coupled Effects of Incident Waves Forcing and Internal Tank Sloshing on the Dynamics of Twin Floating Bodies
The growing demand for ocean space has generated significant interest in multi-body floating systems, where gap resonance in confined regions plays a critical role in ensuring the safety of offshore operations. This study develops a numerical tank model using the Smoothed Particle Hydrodynamics (SPH) method, implemented through the open-source code DualSPHysics, to investigate hydrodynamic resonance in a twin-floater system and to examine the influence of internal tank sloshing on its hydrodynamic characteristics. The hydrodynamic behavior of the gap flow between a fixed twin-floater system in the numerical tank is validated through systematic comparison with experimental data. Subsequently, the wave-induced motions and forces on a twin-floater system are compared with those on a single floater. Furthermore, the effects of internal tank sloshing on the hydrodynamic response of the twin-floater system are explored. A parametric study is conducted to analyze the influence of incident wave frequency on floater motion and tank sloshing dynamics. The results show that the presence of an internal tank can significantly reduce pitch motion and vertical forces on the floating body, while exerting minimal influence on heave motion and horizontal forces. The findings provide new insights into the hydrodynamic performance of twin-floater systems and their interaction with internal sloshing phenomena.
Journal Article
A robust algorithm for computational floating body dynamics
We present a non-iterative algorithm, FloatStepper, for coupling the motion of a rigid body and an incompressible fluid in computational fluid dynamics (CFD) simulations. The purpose of the algorithm is to remove the so-called added mass instability problem, which may arise when a light, floating body interacts with a heavy fluid. The idea underlying the presented coupling method is to precede every computational time step by a series of prescribed probe body motions in which the fluid response is determined, thus revealing the decomposition of the net force and torque into two components: (i) an added mass contribution proportional to the instantaneous body acceleration and (ii) all other forces and torques. The algorithm is implemented and released as an open-source extension module to the widely used CFD toolbox, OpenFOAM, as an alternative to the existing body motion solvers. The accuracy of the algorithm is investigated with several single-phase and two-phase flow benchmark cases. The benchmarks demonstrate excellent stability properties, allowing simulations even with massless bodies. They also highlight aspects of the implementation, such as the mesh motion method, where it can be improved to further enhance the flexibility and predictive capabilities of the code.
Journal Article
Numerical Analysis and Validation of Horizontal and Vertical Displacements of a Floating Body for Different Wave Periods
This study concentrates on numerically evaluating the behavior of a floating body with a box format. Although research on floating objects has been conducted, the numerical modeling of Wave Energy Converter (WEC) devices, considering the effects of fluctuations, remains underexplored. Therefore, this research intends to facilitate the analysis of floating devices. First, the experimental data served as a benchmark for evaluating the motion paths of the floating box’s centroid. Second, the effects of various wave periods and heights on the floating body’s movement were analyzed. The Volume of Fluid (VOF) multiphase model was applied to simulate the interactions between phases. The computational model involved solving governing equations of mass conservation, volumetric fraction transport, and momentum, employing the Finite Volume Method (FVM). The validation demonstrated that the Normalized Root Mean Square Error (NRMSE) for the x/h ratio was 3.3% for a wave height of 0.04 m and 4.4% for a wave height of 0.1 m. Moreover, the NRMSE for the z-coordinate to the depth of water (z/h) was higher, at 5% for a wave height of 0.04 m and 5.8% for a wave height of 0.1 m. The overall NRMSE remained within acceptable ranges, indicating the reliability of the numerical solutions. Additionally, the analysis of horizontal and vertical velocities at different wave periods and heights showed that for H = 0.04 m, the wave periods had a minimal impact on the amplitude, but the oscillation frequency varied. At H = 0.1 m, both velocities exhibited significantly larger amplitudes, especially for T = 1.2 s and T = 2.0 s, indicating stronger motion with higher wave heights.
Journal Article
Mooring Failure Analysis of Semisubmersible Floating Offshore Wind Turbines Considering Mooring Redundancy at Each Azimuth Angle
Semisubmersible floating structures are becoming the predominant understructure type for floating offshore wind turbines (FOWTs) worldwide. As FOWTs are erected far away from land and in deep seas, they inevitably suffer violent and complicated sea conditions, including extreme waves and winds. Mooring lines are the representative flexible members of the whole structure and are likely to incur damage due to years of impact, corrosion, or fatigue. To improve mooring redundancy at each azimuth angle around a wind turbine, a group of mooring lines are configured in the same direction instead of just one mooring line. This study focuses on the mooring failure problems that would probably occur in a realistic redundant mooring system of a semisubmersible FOWT, and the worst residual mooring layout is considered. An FOWT numerical model with a 3 × 3 mooring system is established in terms of 3D potential flow and BEM (blade element momentum) theories, and aero-hydro floating-body mooring coupled analyses are performed to discuss the subsequent time histories of dynamic responses after different types of mooring failure. As under extreme failure conditions, the final horizontal offsets of the structure and the layout of the residual mooring system are evaluated under still water, design, and extreme environmental conditions. The results show that the transient tension in up-wave mooring lines can reach more than 12,000 kN under extreme environmental conditions, inducing further failure of the whole chain group. Then, a deflection angle of 60° may occur on the residual laid chain, which may bring about dangerous anchor dragging.
Journal Article