Rigid-Body Water–Surface Impact Dynamics: Experiment and Semianalytical Approximation

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Ravi Challa ◽  
Solomon C. Yim ◽  
V. G. Idichandy ◽  
C. P. Vendhan
Keyword(s):  
Rigid Body ◽  
Closed Form ◽  
Experimental Results ◽  
Scale Model ◽  
Water Impact ◽  
Equivalent Radius ◽  
Closed Form Solutions ◽  
Von Karman ◽  
Von Kármán ◽  
The Impact

An experimental study of the dynamics of a generic rigid body during water impact and an equivalent-radius approximate analytical procedure is developed and calibrated in this study. The experimental tests in a wave basin covered a range of drop heights using a 1/6th-scale model of a practical water-landing object prototype for two drop mechanisms to determine the water impact and contact effects. The first mechanism involved a rope and pulley arrangement, while the second mechanism employed an electromagnetic release to drop the rigid body. Hydrodynamic parameters including peak acceleration and touchdown pressure were measured and the maximum impact/contact force was estimated for various entry speeds (corresponding to various drop heights) and weights of the rigid body. Results from the tests show that the impact acceleration and touchdown pressure increases approximately linearly with increasing drop height and the data provides conditions that keep impact accelerations under specified limits for the rigid-body prototype. The experimentally measured maximum accelerations were compared with classical von Karman and Wagner approximate closed-form solutions. In this study, an improved approximate solution procedure using an equivalent radius concept integrating experimental results with the von Karman and Wagner closed-form solutions is proposed and developed in detail. The resulting semianalytical estimates are calibrated against experimental results and found to provide close matching.

An Experimental Study on Rigid-Object Water-Entry Impact and Contact Dynamics

2010 ◽  
Author(s):  
Ravi Challa ◽  
V. G. Idichandy ◽  
C. P. Vendhan ◽  
Solomon Yim
Keyword(s):  
Contact Dynamics ◽  
Experimental Results ◽  
Scale Model ◽  
Water Impact ◽  
Major Purpose ◽  
Closed Form Solutions ◽  
Numerical Studies ◽  
Wave Basin ◽  
Drop Tests ◽  
The Impact

The dynamics of a generic rigid water-landing object (WLO) during water impact is presented in this paper. Tests from a range of drop heights were performed in a wave basin using a 1/6th-Froude scale model of a practical prototype using different drop mechanisms to determine the water impact and contact effects. The first experimental case involved dropping the WLO by using a rope and pulley arrangement, while the second case employed an electromagnetic release to drop the object. Hydrodynamic parameters including peak acceleration, touchdown pressure and maximum impact/contact force were measured using the two different drop mechanisms. The WLO was assumed as rigid, so the experimental results could be correlated with von Karman and Wagner closed form solutions and the maximum accelerations predicted are bounded by these classical analytical solutions. The major purpose of this study are to use the experiments to determine trends that occur when the object is dropped from successive heights using different drop mechanisms by varying the entry speed, angle of impact and the weight of the object. The predictions from the experimental results were used for subsequent numerical studies. Results from the drop tests show that the impact acceleration and touchdown pressure increases practically linearly with the increase in the height of the drop and the data provides conditions of drop mechanism that keep impact accelerations under specified limits for the WLO prototype.

scholarly journals Elastohydrodynamics of a pre-stretched finite elastic sheet lubricated by a thin viscous film with application to microfluidic soft actuators

2019 ◽  
Vol 862 ◽  
pp. 732-752 ◽  
Author(s):  
Evgeniy Boyko ◽  
Ran Eshel ◽  
Khaled Gommed ◽  
Amir D. Gat ◽  
Moran Bercovici
Keyword(s):  
Closed Form ◽  
Closed Form Solution ◽  
Finite Domain ◽  
Viscous Film ◽  
Elastic Sheet ◽  
Von Karman ◽  
Von Kármán Equations ◽  
Wide Range ◽  
Soft Actuators ◽  
Von Kármán

The interaction of a thin viscous film with an elastic sheet results in coupling of pressure and deformation, which can be utilized as an actuation mechanism for surface deformations in a wide range of applications, including microfluidics, optics and soft robotics. Implementation of such configurations inherently takes place over finite domains and often requires some pre-stretching of the sheet. Under the assumptions of strong pre-stretching and small deformations of the lubricated elastic sheet, we use the linearized Reynolds and Föppl–von Kármán equations to derive closed-form analytical solutions describing the deformation in a finite domain due to external forces, accounting for both bending and tension effects. We provide a closed-form solution for the case of a square-shaped actuation region and present the effect of pre-stretching on the dynamics of the deformation. We further present the dependence of the deformation magnitude and time scale on the spatial wavenumber, as well as the transition between stretching- and bending-dominant regimes. We also demonstrate the effect of spatial discretization of the forcing (representing practical actuation elements) on the achievable resolution of the deformation. Extending the problem to an axisymmetric domain, we investigate the effects arising from nonlinearity of the Reynolds and Föppl–von Kármán equations and present the deformation behaviour as it becomes comparable to the initial film thickness and dependent on the induced tension. These results set the theoretical foundation for implementation of microfluidic soft actuators based on elastohydrodynanmics.

Liquid Container Filling and Charging

1976 ◽  
Vol 98 (2) ◽  
pp. 730-732
Author(s):  
R. H. Nunn ◽  
E. J. Gibson
Keyword(s):  
Closed Form ◽  
Dynamic Behavior ◽  
Analytical Model ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Liquid Slug ◽  
Analytical Formulation ◽  
Closed Form Solutions

A simple analytical model has been developed to describe the dynamic behavior of a liquid slug as it is rapidly and suddenly rammed into a receiving chamber. Useful closed-form solutions are obtained from approximate versions of the governing relationships. Experimental results indicate the essential correctness of the analytical formulation.

Power Allocation-Aided Enhanced SM-OFDM: Closed-form Solutions and Experimental Results

2021 ◽  
pp. 1-1
Author(s):  
Ke Jiang ◽  
Ping Yang ◽  
Yue Xiao ◽  
Zilong Liu ◽  
Yong LIANG Guan ◽  
...  
Keyword(s):  
Closed Form ◽  
Power Allocation ◽  
Experimental Results ◽  
Closed Form Solutions

Faraday instability threshold in large-aspect-ratio containers

2002 ◽  
Vol 467 ◽  
pp. 307-330 ◽  
Author(s):  
FRANCISCO J. MANCEBO ◽  
JOSÉ M. VEGA
Keyword(s):  
Aspect Ratio ◽  
Numerical Solution ◽  
Closed Form ◽  
Ad Hoc ◽  
Linear Problem ◽  
Experimental Results ◽  
Large Aspect Ratio ◽  
Faraday Waves ◽  
Closed Form Solutions ◽  
Faraday Instability

We consider the Floquet linear problem giving the threshold acceleration for the appearance of Faraday waves in large-aspect-ratio containers, without further restrictions on the values of the parameters. We classify all distinguished limits for varying values of the various parameters and simplify the exact problem in each limit. The resulting simplified problems either admit closed-form solutions or are solved numerically by the well-known method introduced by Kumar & Tuckerman (1994). Some comparisons are made with (a) the numerical solution of the original exact problem, (b) some ad hoc approximations in the literature, and (c) some experimental results.

The Closed-Form Solutions For The Breakdown Voltages Of 6H-SiC Reachthrough Diodes

1998 ◽  
Vol 512 ◽  
Author(s):  
You-Sang Lee ◽  
D.-S. Byeon ◽  
Y.-I. Choi ◽  
I.-Y. Park ◽  
Min-Koo Han
Keyword(s):  
Closed Form ◽  
Breakdown Voltage ◽  
Epitaxial Layer ◽  
Doping Concentration ◽  
Impact Ionization ◽  
Analytic Solutions ◽  
Ionization Coefficient ◽  
Closed Form Solutions ◽  
The Impact ◽  
Effective Ionization

ABSTRACTThe closed-form analytic solutions for the breakdown voltage of 6H-SiC RTD, reachthrough diode, having the structure of p+-n-n+, are successfully derived by solving the impact ionization integral using effective ionization coefficient in the reachthrough condition. In the region of the lowly doped epitaxial layer, the breakdown voltages of 6H-SiC RTD nearly constant with the increased doping concentration. Also the breakdown voltages of 6H-SiC RTD decrease, in the region of the highly doped epitaxial layer, which coincides with Baliga'seq. [1].

scholarly journals A novel-iterative simulation method for performance analysis of non-coherent FSK/ASK systems over Rice/Rayleigh channels using the wolfram language

2016 ◽  
Vol 13 (2) ◽  
pp. 157-174 ◽  
Author(s):  
Vladimir Mladenovic ◽  
Danijela Milosevic
Keyword(s):  
Closed Form ◽  
Communication Systems ◽  
Rayleigh Fading ◽  
Simulation Method ◽  
Rician Fading ◽  
New Approach ◽  
Closed Form Solutions ◽  
Numerical Tools ◽  
The Impact ◽  
Insight Into

In this paper, a new approach in solving and analysing the performances of the digital telecommunication non-coherent FSK/ASK system in the presence of noise is derived, by using a computer algebra system. So far, most previous solutions cannot be obtained in closed form, which can be a problem for detailed analysis of complex communication systems. In this case, there is no insight into the influence of certain parameters on the performance of the system. The analysis, modelling and design can be time-consuming. One of the main reasons is that these solutions are obtained by utilising traditional numerical tools in the shape of closed-form expressions. Our results were obtained in closed-form solutions. They are resolved by the introduction of an iteration-based simulation method. The Wolfram language is used for describing applied symbolic tools, and SchematicSolver application package has been used for designing. In a new way, the probability density function and the impact of the newly introduced parameter of iteration are performed when errors are calculated. Analyses of the new method are applied to several scenarios: without fading, in the presence of Rayleigh fading, Rician fading, and in cases when the signals are correlated and uncorrelated.

Experimental and Theoretical Study of Three-Dimensional Effects on Vertical Wave-in-Deck Forces

2009 ◽  
Author(s):  
Rolf Baarholm
Keyword(s):  
Model Test ◽  
Three Dimensional ◽  
Water Entry ◽  
Scale Model ◽  
Two Dimensional ◽  
Wave Impact ◽  
Dimensional Effects ◽  
Von Karman ◽  
Von Kármán ◽  
Water Exit

In order to validate theory for computing wave-in-deck loads of offshore platforms, a small scale model test campaign of wave impact on an idealized platform deck is performed at Towing Tank no. II at MARINTEK. The main objectives of the tests were to assess three-dimensional effects and to better understand the effect transverse and longitudinal structural members have on the fluid flow. The emphasis in the present paper is to demonstrate the three-dimensional effects. Model tests of the same structure were performed for both two-dimensional and three-dimensional flow conditions. The model test results show that three-dimensional effects significantly reduce the wave-in-deck loads. In particular, for the water exit phase, the vertical force is almost halved due to three-dimensional effects. Two different two-dimensional methods are used to study water impact on the deck: one method is based on a generalization of Wagner’s impact theory while the latter is a simple von Karman approach. Moreover, a three-dimensional correction is introduced. Comparisons show that the Wagner based method yields good results for the water entry phase, but it overestimates the water exit force and underestimates the duration of the wave-in-deck event. The von Karman type approach underestimates the water entry force.

The Impact of Arbitrary Oriented Ellipsoidal Shell With a Barrier: Analytical Study

2015 ◽  
Vol 82 (4) ◽  
Author(s):  
Shahab Mansoor-Baghaei ◽  
Ali M. Sadegh
Keyword(s):  
Closed Form ◽  
Numerical Solutions ◽  
Closed Form Solution ◽  
Linearization Method ◽  
Form Solution ◽  
Ellipsoidal Shell ◽  
Explicit Finite Element ◽  
Closed Form Solutions ◽  
Transmitted Force ◽  
The Impact

In this paper, a closed form solution of an arbitrary oriented hollow elastic ellipsoidal shell impacting with an elastic flat barrier is presented. It is assumed that the shell is thin under the low speed impact. Due to the arbitrary orientation of the shell, while the pre-impact having a linear speed, the postimpact involves rotational and translational speed. Analytical solution for this problem is based on Hertzian theory (Johnson, W., 1972, Impact Strength of Materials, University of Manchester Institute of Science and Technology, Edward Arnold Publication, London) and the Vella’s analysis (Vella et al., 2012, “Indentation of Ellipsoidal and Cylindrical Elastic Shells,” Phys. Rev. Lett., 109, p. 144302) in conjunction with Newtonian method. Due to the nonlinearity and complexity of the impact equation, classical numerical solutions cannot be employed. Therefore, a linearization method is proposed and a closed form solution for this problem is accomplished. The closed form solution facilitates a parametric study of this type of problems. The closed form solution was validated by an explicit finite element method (FEM). Good agreement between the closed form solution and the FE results is observed. Based on the analytical method the maximum total deformation of the shell, the maximum transmitted force, the duration of the contact, and the rotation of the shell after the impact were determined. Finally, it was concluded that the closed form solutions were trustworthy and appropriate to investigate the impact of inclined elastic ellipsoidal shells with an elastic barrier.

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