Finite Element Contact/Impact Modeling Capability of Complex Surface Effect Ship Dynamics: Preliminary Assessment

2013 ◽  
Author(s):  
Ravi Challa ◽  
David Newborn ◽  
Solomon Yim
Keyword(s):  
Finite Element ◽  
Free Surface ◽  
Numerical Simulations ◽  
Water Surface ◽  
Large Scale ◽  
Surface Effect ◽  
Numerical Models ◽  
Channel Water ◽  
Surface Effect Ship ◽  
Air Cushion

Experimental tests were conducted on a large scale captive Surface Effect Ship (SES) specimen at the US Navy’s Large Cavitation Channel (LCC) to primarily determine the mechanics of bow finger seal motions. In this paper, preliminary qualitative comparisons between the experimental and numerical simulations comprised of test dependent variables such as spatially distributed channel water elevation, channel water speed and air-cushion pressure are presented. A surface effect ship is an air-cushion supported vessel with two side hulls and fore and aft flexible seals. The side hulls of the SES along with the wet deck, seals and the fluid-water surface constitute the boundary of the air-cushion. An evaluation of the predictive capabilities of the existing technology of a state-of-the-art nonlinear multi-physics finite element code (LS-DYNA) with its arbitrary Lagrangian Eulerian (ALE) technique in modeling the coupled fluid-structure interaction (FSI) behavior of the boundary of a SES with the water surface is studied. The predictive capability of the code to model a single stern seal deployment, a single seal impacting a rigid flat surface, multiple seals impacting a water free surface and the centerline profile of multiple stern seal deployment between two rigid surfaces were verified. Simple numerical models for a five-finger bow seal with partial submergence in uniform current have been developed. Additional features including the mechanism to pressurize the air cushion chamber were included. Preliminary finite element (FE) simulation results show that the robust contact and impact algorithm is shown to capture the physics of the complex flexible body FSI problem well. In view of the good qualitative comparison between the experimental and numerical simulations, the ALE feature is being employed for studying the complex flexible structural mechanics including bow and stern seal motions interacting with air cushion and free-surface hydrodynamics.

Radiation Hydrodynamics of a Surface Effect Ship

2013 ◽  
Author(s):  
Palaniswamy Ananthakrishnan
Keyword(s):  
Free Surface ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Stokes Equations ◽  
Surface Effect ◽  
Wave Radiation ◽  
Absolute Pressure ◽  
Radiation Hydrodynamics ◽  
Surface Effect Ship ◽  
Air Cushion

The radiation hydrodynamics of a heaving surface effect ship (SES) is examined including the effect of air compressibility on the hydrodynamic forces and surface waves. Of particular focus of the study has been on determining the nonlinear viscous and air compressibility effects at natural frequencies corresponding to the piston and sloshing wave modes between the hulls and at the natural frequency corresponding to the heave motion of a surface effect ship with the restoring force dominated by the compressibility of the air cushion. In the present paper, the air cushion pressure is assumed to be uniform with its variation due to change of volume modeled using the adiabatic gas law pVγ = constant, where p denotes the absolute pressure of the air, V the air volume bounded by the side hulls, the free surface and the wet deck, and γ the ratio of specific heats Cp/Cv which is about 1.4 for air. The incompressible Navier-Stokes equations governing the nonlinear viscous wave-air-body interaction problem is solved in the time domain using a finite-difference method based on boundary fitted coordinates. New results presented in this paper show that air cushion compressibility affects the generation of waves and wave radiation forces significantly even at small amplitude of hull motion. As already well known, the free surface nonlinearity due to hull motion is significant for large amplitude of oscillation. At small amplitude of body oscillation, significant nonlinearity can be caused by air compressibility resulting in the generation of higher harmonic waves and forces. The results also highlight the significance of viscosity and flow separation, in conjunction with air compressibility, in the case of large amplitude hull motion with a small draft.

Comparison of Single and Overset Grid Techniques for CFD Simulations of a Surface Effect Ship

2014 ◽  
Author(s):  
Colton G. Clark ◽  
David G. Lyons ◽  
Wayne L. Neu
Keyword(s):  
Free Surface ◽  
Surface Effect ◽  
The Body ◽  
Computational Domain ◽  
Overset Grid ◽  
Hexahedral Mesh ◽  
Surface Effect Ship ◽  
Mesh Resolution ◽  
Refined Meshes ◽  
Air Cushion

Overset, or Chimera meshes are used to discretize the governing equations within a computational domain using multiple meshes that overlap in an arbitrary manner. The overset mesh technique is most applicable to problems dealing with multiple or moving bodies. In order to extend existing full craft CFD (RANS) simulations of a surface effect ship (SES) into shallow water and maneuvering cases, an overset mesh is needed. Deep water simulations were carried out using both single and overset grid techniques for evaluation of the overset grid application. The single grid technique applies a hexahedral mesh to the fluid domain and SES geometry. An adequate mesh resolution was determined by performing a grid convergence study on a series of systematically refined meshes. An overset mesh of the same resolution was then constructed and was fixed to the body. Drag and pitch results are compared among the two simulations. Free surface elevations around the craft and under the air cushion for simulations with the single and overset meshes are compared. Steady-state simulations using the overset mesh and the single mesh show general similarities in drag, pitch, and free surface elevations.

Development of a Large-scale Surface Effect Ship Bow Seal Testing Platform

2013 ◽  
Vol 29 (04) ◽  
pp. 191-198
Author(s):  
Andrew D. Wiggins ◽  
Steven F. Zalek ◽  
Marc Perlin ◽  
Steven L. Ceccio ◽  
Lawrence J. Doctors ◽  
...  
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Surface Effect ◽  
Water Channel ◽  
Data Set ◽  
Testing Platform ◽  
Test Platform ◽  
Surface Effect Ship ◽  
Scale Surface ◽  
The U.S

A large-scale surface effect ship (SES) bow seal testing platform was constructed by the University of Michigan and is presently being commissioned at the U.S. Navy's Large Cavitation Channel (LCC) in Memphis, TN. Using a recently installed (2008) free-surface forming gate, the test platform is capable of investigating the physics of the two-dimensional planing seal and three-dimensional finger-type bow seal in calm water conditions and at scales relevant to SES designers and numerical modelers. The LCC environment permits extended run times at high Reynolds number and provides unfettered optical access to the seal geometry and flow field. This article describes the development of the testing platform and presents some preliminary results. The test platform is nominally 7.9 m long, 1.52 m wide, and 2.0 m tall and of welded and bolted steel construction. The seals are nominally sized similar to those currently used by the U.S. Navy's Landing Craft Air Cushion class. An extensive measurement suite was integrated with the test platform. The goal was to provide numerical modelers a data set with sufficient spatial and temporal resolution to validate their models of the experiment and, where appropriate, to develop new analytic models. The results of this effort demonstrate a feasible system for investigating surface effect ship seal physics within a large free surface water channel.

scholarly journals Combined numerical and experimental study of microstructure and permeability in porous granular media

2020 ◽  
Author(s):  
Philipp Eichheimer ◽  
Marcel Thielmann ◽  
Wakana Fujita ◽  
Gregor J. Golabek ◽  
Michihiko Nakamura ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Numerical Simulations ◽  
Granular Media ◽  
Large Scale ◽  
Earth Science ◽  
Numerical Models ◽  
Effective Porosity ◽  
Flow Properties ◽  
Wide Range ◽  
Flow Through

Abstract. Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with various porosities. The microstructure, namely effective porosity and effective specific surface, is investigated using image processing. We determine flow properties like hydraulic tortuosity and permeability using both experimental measurements and numerical simulations. By fitting microstructural and flow properties to porosity, we obtain a modified Kozeny-Carman equation for isotropic low-porosity media, that can be used to simulate permeability in large-scale numerical models. To verify the modified Kozeny-Carman equation we compare it to the computed and measured permeability values.

Static and Dynamic Analyses of the LSES Hull Structure

1978 ◽  
Vol 22 (02) ◽  
pp. 110-122
Author(s):  
A. S. Hananel ◽  
E. J. Dent ◽  
E. J. Philips ◽  
S. H. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Surface Effect ◽  
Three Dimensional ◽  
Element Model ◽  
Finite Element Program ◽  
Hull Structure ◽  
Surface Effect Ship ◽  
Hull Design ◽  
Element Program

To avoid the conservativeness in the large surface-effect ship hull design which results from simplifying assumptions in the stress analysis, the hull structure was analyzed as a three-dimensional elastic body. The NASTRAN finite-element program, level 15.0, was selected for use in this analysis as the most suitable program available. A finite-element model representing the true hull stiffness was used in obtaining the internal load and displacement distributions. The inertia effect of the ship masses was included with each set of static loads. This was done by using the Static Analysis with Inertia Relief solution included in NASTRAN. The stress redistribution around cutouts in the hull was treated in a separate study. The interaction between hull and deckhouse was investigated by attaching a model of the deckhouse onto the hull model, and then solving for the appropriate load conditions. The natural frequencies were obtained using a reduced finite-element model of both the hull and hull/deckhouse combination. A new technique was developed for determining the dynamic stresses and their proper superposition on the static stresses.

An Analysis of Heave Added Mass and Damping of a Surface-Effect Ship

1981 ◽  
Vol 25 (01) ◽  
pp. 44-61
Author(s):  
C. H. Kim ◽  
S. Tsakonas
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Surface Effect ◽  
Practical Method ◽  
Added Mass ◽  
Damping Coefficients ◽  
Calm Water ◽  
Surface Effect Ship ◽  
Long Time ◽  
Computational Procedures

The analysis presents a practical method for evaluating the added-mass and damping coefficients of a heaving surface-effect ship in uniform translation. The theoretical added-mass and damping coefficients and the heave response show fair agreement with the corresponding experimental values. Comparisons of the coupled aero-hydrodynamic and uncoupled analytical results with the experimental data prove that the uncoupled theory, dominant for a long time, that neglects the free-surface effects is an oversimplified procedure. The analysis also provides means of estimating the wave elevation of the free surface, the escape area at the stern and the volume which are induced by a heaving surface-effect ship in uniform translation in otherwise calm water. Computational procedures have been programmed in the FORTRAN IV language and adapted to the PDP-10 high-speed digital computer.

scholarly journals Roll damping of a surface effect ship with split air cushion

2018 ◽  
Vol 51 (29) ◽  
pp. 450-456
Author(s):  
Jonas Tønnessen ◽  
Håkon E. Bryn ◽  
Jan T. Gravdahl ◽  
Vahid Hassani ◽  
Øyvind F. Auestad
Keyword(s):  
Surface Effect ◽  
Roll Damping ◽  
Surface Effect Ship ◽  
Air Cushion

Air Cushion Vehicles and Surface Effect Ships for Great Lakes and Great Rivers Transportation

1990 ◽  
Vol 27 (06) ◽  
pp. 337-355
Author(s):  
John L. Allison
Keyword(s):  
Great Lakes ◽  
Surface Effect ◽  
Coast Guard ◽  
Rapid Expansion ◽  
Short Paper ◽  
Surface Effect Ship ◽  
Present Design ◽  
Air Cushion ◽  
Hull Forms ◽  
The U.S

A brief introduction to air cushion vehicle (ACV) and surface effect ship (SES) technology is presented, with past and present examples, to show that this technology may now be considered mature. Applicability of ACVs and SESs to transportation on the Great Lakes and rivers of Canada and the U.S. is discussed, with some emphasis on year-round service in the regions affected by ice. An indication of present design capabilities is provided with some examples of application to typical sets of requirements. Future developments are outlined in the light of the rapid expansion of air-supported ferry operation in other parts of the world, and military and Coast Guard applications in the U.S. and Canada. Some data on acquisition and operating costs are presented in comparison with those for other hull forms, with information on the type of technical and port support required for ACV and SES operation. Numerous references are provided to enable the reader to pursue the topics discussed in greater detail than is possible in a short paper.

Characterisation of the Shear Stud-Concrete Connection Using Finite Element Analysis

2014 ◽  
Vol 553 ◽  
pp. 570-575
Author(s):  
Daniel John Lowe ◽  
Raj Das ◽  
George Charles Clifton ◽  
Namasivayam Navaranjan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Large Scale ◽  
Numerical Models ◽  
Experimental Testing ◽  
Element Model ◽  
Cement Matrix ◽  
Element Analysis ◽  
Mesoscopic Model ◽  
Concrete Interface

The degradation of the connection between shear studs and concrete is a complicated phenomenon that depends on many factors, including; interfacial properties, concrete crushing and steel yielding. The purpose of this paper is to outline the scope and methodology of the research project being undertaken to characterise the shear stud-concrete interface of a composite beam using finite element analysis. A mesoscopic model will be created for a section of the interface. With the use of a multi-scale approach, the mesoscopic model will be incorporated into a global model. The influence of steel roughness and mechanical properties will be included. Concrete is to be modelled as heterogeneous, comprising discrete regions of aggregate, cement matrix, and an interfacial transition zone (ITZ). The effect of the ITZ will be taken into account using a zero thickness cohesive element. Experimental testing using a push-up rig is to be conducted to verify the numerical models. The ultimate aim is to develop a simplified representation of the shear stud-concrete interface that can be used in a large scale finite element model of a composite member to correctly capture the behaviour of the shear stud-concrete interface in the elastic and inelastic state.

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