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Research Papers: Ocean Engineering

Rigid-Object Water-Entry Impact Dynamics: Finite-Element/Smoothed Particle Hydrodynamics Modeling and Experimental Validation

[+] Author and Article Information
Ravi Challa

School of Civil and Construction Engineering,
Oregon State University,
Corvallis, OR 97331

Solomon C. Yim

Professor
Coastal and Ocean Engineering Program,
School of Civil and Construction Engineering,
Oregon State University,
Corvallis, OR 97331

V. G. Idichandy, C. P. Vendhan

Professor
Department of Ocean Engineering,
Indian Institute of Technology Madras,
Chennai, 600036, Tamilnadu, India

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received January 21, 2014; final manuscript received April 10, 2014; published online June 12, 2014. Assoc. Editor: Ron Riggs.

J. Offshore Mech. Arct. Eng 136(3), 031102 (Jun 12, 2014) (12 pages) Paper No: OMAE-14-1002; doi: 10.1115/1.4027454 History: Received January 21, 2014; Revised April 10, 2014

A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project to determine the maximum force for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element (FE) arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle, and object weight. The numerical results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered, and the impact acceleration varies practically linearly with increase in drop height. In view of the good comparison between the experimental and numerical simulations, both models can readily be employed for parametric studies and for studying the prototype splashdown under more realistic field conditions in the oceans.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Overall configuration of WLO prototype (all dimensions are in mm)

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Fig. 2

(a) and (b) Elevation and top view of the FE-ALE computational mesh (top part is the air domain; bottom part is the water domain; and the rigid body in the air domain is the WLO model)

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Fig. 3

Animation images at various time steps for vertical impact

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Fig. 4

Numerical simulation response of a 5 m drop test: (a) acceleration time history

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Fig. 5

Numerical simulation response of a 5 m drop test: (b) pressure time history

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Fig. 6

Height of drop versus depth of Immersion for case-I

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Fig. 14

Number of particles (SPH nodes) versus maximum impact acceleration

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Fig. 13

Mesh size variation versus maximum impact acceleration

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Fig. 12

Comparison of results for maximum acceleration with ALE and SPH [weight of WLO = 3.5 kg (case-II: electromagnetic release)] (vertical entry/entry angle = 0 deg)

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Fig. 11

Comparison of peak impact acceleration for pitch tests using ALE and SPH methods

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Fig. 10

Comparison of results for maximum acceleration with ALE and SPH [weight of WLO = 2.03 kg (case-I: mechanical release)] (vertical entry/entry angle = 0 deg)

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Fig. 9

SPH acceleration time history for a 5 m drop height

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Fig. 8

SPH animation images of the particle impingement at various time steps

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Fig. 7

Plan of the SPH water domain and the WLO (number of SPH nodes: 712,000)

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Fig. 15

Number of CPUs versus estimated clock time for ALE and SPH test models

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Fig. 16

Clock-time ratios of SPH/ALE versus number of CPUs

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Fig. 17

Speed scaling of the performance of ALE and SPH (N1/Np)

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