Wood, C.D., Hudson, Dominic A. and Tan, Mingyi
CFD simulation of orifice flow for the flooding of damaged ships
At NuTTS 2010: 13th Numerical Towing Tank Symposium, Germany.
10 - 12 Oct 2010.
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The aim of this research is to investigate parameters that affect the behaviour of a damaged ship and also to assess the ability of RANS codes to accurately model the physical processes occurring in the flooding of a damaged ship. Initially, the flooding of a damaged ship has been divided into smaller components to assess the accuracy of the predictions for these flow-fields when validated against experiment or other simulation methods.
Damage size affects the frequency and amplitude of floodwater oscillation compared to wave oscillation and for certain conditions this can lead to maximum floodwater being present as a wave trough passes amidships. When the ship length is equal to the wave length this can increase hull girder loads significantly. Full simulation of this condition requires accurate simulation of flooding rates into the ship.
Typical state of the art flooding models use Torricelli’s formula (equation 1) to calculate flooding rates using a constant coefficient of discharge (de Kat, et al., 2002).
Q=C_d A_0 ?2gh, (1)
where, Cd is the discharge coefficient, with typical values between 0.6-0.8, A0 is the area of the hole, g is gravitational acceleration and h is the height difference between the internal and external water levels. Based on Bernoulli’s theorem, turbulence and viscosity effects are included in this equation using a Cd which is independent of damage size or shape. It is believed this assumption could potentially over-simplify the problem to an extent where the calculated flooding rates are in error
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