Modeling of steady motion and vertical-plane dynamics of a tunnel hull

International Journal of Naval Architecture and Ocean Engineering.
2014.
Jun,
6(2):
323-332

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

- Published : June 30, 2014

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INTRODUCTION

Ultra-fast boats and wing-in-ground craft utilize aerodynamic lift to either partially or completely support the vehicle’s weight at sufficiently high speeds. This usually results in increased lift-drag ratio. However, such marine vehicles can also become less stable and respond more dramatically to wind gusts and surface waves (
Matveev and Kornev, 2013
).
The main subject of this paper is the modeling of the vertical-plane dynamics of a tunnel hull (
Fig. 1
), which is one of the most common configurations of fast boats with aerodynamic unloading. Side planning hulls on this boat remain in contact with water most of the time, whereas the above-water platform generates aerodynamic support. Linear stability of a tunnel hull was analyzed by
Kornev et al. (2010)
. Some aspects of aero-hydrodynamics, stability and dynamics of other aerodynamically assisted marine craft were considered by
Nangia (1987)
,
Collu et al. (2010)
,
Gu et al. (2011)
, and Matveev (2012).
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- Mathematical model

A schematic of a tunnel hull with simplified geometry is given in
Fig. 2
. Since only vertical-plane motions of this craft at relatively small pitch angles τ are considered here, the vehicle dynamics is governed by the following equations,
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RESULTS AND DISCUSSION

The configuration of the boat modeled in this paper is selected to resemble off-shore racing tunnel hulls. Simplified geometry is chosen to avoid unnecessary complexity in modeling and result presentation. Side hulls have single deadrise, as is typically used in such boats to reduce spray in the tunnel. Hull cross-sections are uniform and do not incorporate steps. The platform has a chord of 10
Main parameters of the considered tunnel hull.

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CONCLUDING REMARKS

A simplified mathematical model developed in this work can be used for producing quick simulations of vertical-plane dynamics of tunnel hull boats in wind gusts and waves, as well as for determining their equilibrium states in calm conditions. When fully validated, the current method can be applied for design optimization of marine craft with aerodynamically supported surfaces operating in pronounced ground effect. Results presented in this study illustrate calculated vertical-plane responses of a selected boat configuration to head or following wind gusts and regular waves, acting separately. Since wind gusts and waves are often present simultaneously, the current method can be also used in the future to identify dangerous regimes in such conditions and suggest operational actions for reducing extreme motions and loads on aerodynamically unloaded boats.
Future development of the mathematical model can include more degrees of freedom, addition of control surfaces, and large-amplitude motions that may possibly lead to accidents, such as boat flipping and slamming. Application of Computational Fluid Dynamics (CFD) methods can improve accuracy of the model’s components, although complete unsteady CFD simulations for an entire air-assisted boat would be very costly, especially in a broad range of system conditions. While the present model’s expressions for the different forces have been previously validated, experimental validation of the combined dynamic model for a tunnel hull requires complete test information for boats of this type, which is currently unavailable in the open literature. Hence, the applicability of the present method for design of actual boats is rather limited. Calculation results obtained with this model will need further experimental verification.
Acknowledgements

This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1026264.

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,
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Modeling of vertical-plane motions of a tunnel hull boat
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Citing 'Modeling of steady motion and vertical-plane dynamics of a tunnel hull
'

@article{ E1JSE6_2014_v6n2_323}
,title={Modeling of steady motion and vertical-plane dynamics of a tunnel hull}
,volume={2}
, url={http://dx.doi.org/10.2478/IJNAOE-2013-0182}, DOI={10.2478/IJNAOE-2013-0182}
, number= {2}
, journal={International Journal of Naval Architecture and Ocean Engineering}
, publisher={The Society of Naval Architects of Korea}
, author={Chaney, Christopher S.
and
Matveev, Konstantin I.}
, year={2014}
, month={Jun}