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Hydroelastic Response of Marine Structures to Impact-induced Vibrations
01 Oct 2011-
About: The article was published on 2011-10-01 and is currently open access. It has received 5 citations till now. The article focuses on the topics: Naval architecture.
Citations
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01 Dec 2012
TL;DR: In this article, a dry and wet dynamic analysis of vibration of a square Kirchhoff s plate is presented, where the elastic response of marine structures to intense, localized, transient, hydrodynamic impact loads is important in the design of marine vessels.
Abstract: The dynamic analysis of the elastic response of marine structures to intense, localized, transient, hydrodynamic impact loads is important in the design of marine vessels. A dry and wet dynamic analysis of vibration of a square Kirchhoff’ s plate is presented. The dry and wet natural frequencies and modeshapes of the plate have been evaluated by Galerkin’s method. The transient loads are of two kinds: a uniform stretching load and a hydrodynamic impact load (at different deadrise angles). The stretching load sets the plate into small-amplitude high-frequency vibrations. The computationally efficient normal mode analysis has been used to evaluate the dynamic deflections. Three different boundary conditions of the plate have been used. The response of the plate to these loads has been investigated for a wide range of impact speeds and material properties. The response characteristics have been established, namely (a) maximum deflection, (b) maximum dynamic overshoot relative to the static deflection, (c) quasi-static and dynamic zones of the response over the range of time-scales. The dependency of these characteristics on parameters like the deadrise angles, damping ratios, boundary conditions and forcing configurations have also been studied, to aid the designer. A separate study of the modal participation factor is used to establish modal truncation limits for the analysis, with subsequent increases in the computational efficiency.
10 citations
TL;DR: A semi-analytical approach to understand the manifestation of plate modeshapes associated with twin frequencies has been presented in this article, which highlights the importance of efficacy of the beam-wise trial functions in an energy-based plate vibration analysis method, in terms of accuracy, orthogonality, sense (plus/minus) and interference.
8 citations
01 Jan 2017
Abstract: The concept of using aluminum as the primary construction material for high speed ships and the hydroelastic behavior of the structure is widely gaining importance as a significant research topic in naval architecture. Aluminum is lighter than steel and hence can be predominantly used in high speed crafts which experiences significant slamming. This thesis work is focused on wedge shaped models. Free fall wedge impact is studied and a FORTRAN 90 computer program is developed to estimate the structural response of the wedge experiencing slamming by the use of matrix methods, finite element techniques and Newmark-Beta numerical time integration methods. The numerical solution is validated by comparison with the static solution. The theoretical hydrodynamic pressures which are used as input for this work was originally developed by using a flat cylinder theory [26]. The wedge drop at 0.6096 m (24 inch) drop height with an impact velocity of v=3.05 m/s is based as the premise and the experimental pressure distributions measured by the pressure-transducers and the theoretical pressure predictions are used as inputs and the structural response is derived. Additionally, the response is compared for three different plate thicknesses and the results are compared against each other. The maximum deflection is comparable to the deflection evaluated from the experiment and tends to attain convergence as well. As the plate thickness reduces there tends to be a significant rise in the deflection values for the wedge plate, in the manner that when the plate thickness is halved there is a deviation of more than 75% in the deflection values as such.
3 citations
01 Jan 2016
Abstract: The diverse applications of advanced marine craft ascribed to their high speed and technological advancements has led to the use of stronger and lighter metals in such crafts. High speed, in effect also increases slamming loads as higher speed increases frequency of wave encounter while operating in waves. The present study is limited to wedge impact models. Fundamentally, the study is thus about two-dimensional (2D) wedge impact in water. In an attempt to predict the structural response to impact hydrodynamic force, a beam element based finite element (FE) computer program is written and the results of the code are presented in the thesis. A computational tool is developed to predict the transient elastic response of a 2D wedge under impact force using two different numerical methods. Both explicit and implicit numerical schemes have also been studied in order to apply to the present work. Explicit forth order Runge-Kutta (RK4) method and implicit Newmark-β (NB) method have been used in the present work. Coupling effects between excitation and response are ignored in the present numerical computations. Both the numerical schemes are validated using simple static solution and also modal expansion technique. The hydrodynamic pressure distribution along the bottom of a 20◦ deadrise wedge is computed using a flat cylinder theory (Vorus, 1996). An impact velocity of 9.51 ft/sec is used and two different structural boundary conditions are considered in the present analysis. In addition, three different plate thicknesses have been used in the analysis and the results are compared against each other. Stability of the results is tested using node variation test. The results have shown that maximum deflection is around 8 times more for a pinned-pinned beam when compared to clamped-clamped beam. Also, lower plate thickness yielded very significant deflections in both the boundary conditions.
2 citations
01 Mar 2019
TL;DR: In this paper, a dynamic analysis of axially loaded Timoshenko beams with intermediate fixities is presented, where the underwater part of a craft is modeled as a flexible beam, which rises out and slams against the water at a large vertical velocity, causing highly localized hydrodynamic impact pressure moving at high velocities across the beam.
Abstract: A dynamic analysis of axially loaded Timoshenko beams with intermediate fixities is presented. The underwater part of a craft is modeled as a flexible beam, which rises out and slams against the water at a large vertical velocity, causing highly localized hydrodynamic impact pressure moving at high velocities across the beam, setting it into high-frequency vibrations. The beam natural frequencies depend on the slenderness ratio, axial load, end fixities, and structural damping. The natural frequencies and modeshapes (for total deflection and pure bending slope) are generated through Eigen analysis. Next, normal mode summation is used to analyze the impact-induced vibration response, which is generated for various impact speeds, deadrise angles, end fixities, and axial loads, of the beam. A parametric study is done to predict the maximum dynamic stresses on the structure. The sensitivity of the dynamic load factor (DLF) is studied with respect to the above parameter space. Conclusions are drawn leading to insights into sound structural designs.
1 citations
References
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05 Feb 2001
TL;DR: In this article, a modern treatment of the subject, both the theory of inviscid, incompressible, and irrotational aerodynamics and the computational techniques now available to solve complex problems is presented.
Abstract: Low-speed aerodynamics is important in the design and operation of aircraft flying at low Mach number, and ground and marine vehicles. This 2001 book offers a modern treatment of the subject, both the theory of inviscid, incompressible, and irrotational aerodynamics and the computational techniques now available to solve complex problems. A unique feature of the text is that the computational approach (from a single vortex element to a three-dimensional panel formulation) is interwoven throughout. Thus, the reader can learn about classical methods of the past, while also learning how to use numerical methods to solve real-world aerodynamic problems. This second edition has a new chapter on the laminar boundary layer (emphasis on the viscous-inviscid coupling), the latest versions of computational techniques, and additional coverage of interaction problems. It includes a systematic treatment of two-dimensional panel methods and a detailed presentation of computational techniques for three-dimensional and unsteady flows. With extensive illustrations and examples, this book will be useful for senior and beginning graduate-level courses, as well as a helpful reference tool for practising engineers.
1,810 citations
06 Sep 2017
TL;DR: In this paper, the first two parts -the foundations of solid mechanics and variational methods and the third part -explore the applicability of the finite element method to structural mechanics.
Abstract: The first two parts - ''Foundations of Solid Mechanics and Variational Methods'' and ''Structural Mechanics'' - develop a foundation in variational calculus and energy methods before progressing to the third section, which examines the finite element method and its application to stress, plate, torsion, stability, and dynamics problems. Throughout, the book makes finite elements more understandable in terms of fundamentals; provides the background needed to extrapolate the finite element method to areas of study other than solid mechanics; and shows how to derive working equations of structural mechanics through variational principles and to understand the limits of validity of these equations. New to the Second Edition are chapters on matrix methods for trusses, finite element methods for plane stress problems, and finite element methods for plates and elastic stability.
417 citations
381 citations
Book•
29 Feb 1980
TL;DR: In this article, the authors present a survey of ship response to wave excitation in the context of dry hulls and other marine structures to waves, including the characteristics of practical hulls.
Abstract: Preface 1. Ship response 2. The dry hull 3. More accurate analysis of hull dynamics 4. The characteristics of practical hulls 5. Ship distortion in still water 6. Wave theory 7. Symmetric generalised fluid forces 8. Symmetric response 9. Transient loading 10. Antisymmetric response to wave excitation 11. Statistical analysis of ship response 12. Responses of other marine structures to waves Bibliography Index.
338 citations
TL;DR: In this article, a model for a class of water-entry problems characterized by the geometrical property that the impacting body is nearly parallel to the undisturbed water surface and that the impact is so rapid that gravity can be neglected is presented.
Abstract: This paper summarizes and extends some mathematical results for a model for a class of water-entry problems characterized by the geometrical property that the impacting body is nearly parallel to the undisturbed water surface and that the impact is so rapid that gravity can be neglected. Explicit solutions for the pressure distributions are given in the case of two-dimensional flow and a variational formulation is described which provides a simple numerical algorithm for three-dimensional flows. We also pose some open questions concerning the well-posedness and physical relevance of the model for exit problems or when there is an air gap between the impacting body and the water.
295 citations