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Local water slamming impact on sandwich composite hulls

kaushik das's picture

Recently we analyzed water-slamming impacts on sandwich composite hulls. Water slamming impact problems are very interesting problems involving fluid-structure interactions.  A link to our paper and the abstract are given below. I hope that you will find the paper interesting. Please feel free to write your comments below.      

Kaushik Das and Romesh C. Batra, Local water slamming impact on sandwich composite hulls, Journal of Fluids and Structures, Volume 27, Issue 4, May 2011, Pages 523-551

http://www.esm.vt.edu/~rbatra/pdfpapers/Fluids2011%28523-551%29.pdf

Abstract

The local water slamming refers to the impact of a part of a ship hull on stationary water for a short duration during which high local pressures occur on the hull. We simulate slamming impact of rigid and deformable hull bottom panels by using the coupled Lagrangian and Eulerian formulation included in the commercial software LS-DYNA. We use the Lagrangian formulation to describe plane-strain deformations of the hull panel and consider geometric nonlinearities. The Eulerian formulation is used to analyze deformations of the water. Deformations of the hull panel and of the water are coupled through the hydrodynamic pressure exerted by water on the hull, and the velocity of particles on the hull wetted surface affecting deformations of the water. The continuity of surface tractions and the inter-penetrability of water into the hull are satisfied by using a penalty method. The computer code is verified by showing that the computed pressure distributions for water slamming on rigid panels agree well with those reported in the literature. The pressure distributions computed for deformable panels are found to differ from those obtained by using a plate theory and Wagner's slamming impact theory. We have also delineated jet flows near the edges of the wetted hull, and studied delamination induced in a sandwich composite panel due to the hydroelastic pressure.

Comments

You can contact Mark Battley at the University of Auckland for experimental data on slamming (sandwich hulls).  Our company has a slamming rig where Mark and his students perform their experiments.

-- Biswajit

kaushik das's picture

We work in collaboration with Dr. Battley. We comparied results of our simulations with those from his experiments. I hope that those results will be publised soon. Are you interested in simular problems?

Your paper would have been more interesting if some of those comparisons had been given, but I'm willing to wait.  I had written a proposal for ONR funding for a similar problem in 2005, hence the interest.  I would have used MPM-ICE to solve it.

-- Biswajit

kaushik das's picture

Our paper reports comparisons of numerical results with
those found from experiments. Please refer to figures 13 to 19 of the paper.
Here, we compared pressure distributions on rigid hulls with experimental
results for three different experiments. Currently, we are working on comparing
our results for deformable hulls with those from Dr. Battley's group.

Dr. Batra's group is also working on solving the
equations for the fluid using BEM and for the structure using FEA. I hope those
results will also be published soon

Thanks Kaushik, I'd skipped over those sections to the sandwich simulations.  The paper contains a lot of information and I haven't read the paper in its enitirety yet.

Based on the experimental data you've plotted in Figure 19, do you think that the rigid hull approximation is better than using an elastic hull?  How confident are you of the experimental data presented by Yettou et al.?

-- Biswajit

kaushik das's picture

Sorry for the late reply.

In figure 19, we have compared pressure profiles on a rigid hull with those   found experimentally by Yettou et. al. (2007, Journal of Fluids and Structures, 23(3),501–522). In their experiments, they used solid blocks of wood as the hull. In this case, I believe the assumption that the hull is rigid is acceptable. However, as you can see the pressure profiles did not match well with those reported from experiments. The total force and the acceleration of the hull found numerically compared well with those from experiments.  The reason for this discrepency in pressure distribution is not known to me. It could be due to some error in how the pressure (force per unit area or force per unit length of the block) and the mass of the block (total mass or mass per unit width) are reported in by Yettou et. al. or some wrong unit conversion. We could not be certain about these from information available in the literature. 

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