Full-scale resistance prediction in finite waters: A study using computational fluid dynamics simulations, model test experiments and sea trial measurements

Abstract

The development of large medium-speed catamarans aims increasing economic viability and reducing the possible negative influence on the environment of fast sea transportation. These vessels are likely to operate at hump speed where wave-making can be the dominating component of the total resistance. Shallow water may considerably amplify the wave-making and hence the overall drag force. Computational fluid dynamics (CFD) is used to predict the drag force of medium-speed catamarans at model and full scale in infinite and restricted water to study the impact on the resistance. Steady and unsteady shallow water effects that occur in model testing or full-scale operation are taken into account using CFD as they are inherently included in the mathematical formulations. Unsteady effects in the ship model response were recorded in model test experiments, CFD simulations and full-scale measurements and found to agree with each other. For a medium-speed catamaran in water that is restricted in width and depth, it was found that CFD is capable of accurately predicting the drag with a maximum deviation of no more than 6% when comparing to experimental results in model scale. The influences of restricted depth and width were studied using CFD where steady finite width effects in shallow water and finite depth effects at finite width were quantified. Full-scale drag from CFD predictions in shallow water (h/L = 0.12 − 0.17) were found to be between full-scale measurements and extrapolated model test results. Finally, it is shown that current extrapolation procedures for shallow water model tests over-estimate residuary resistance by up to 12% and underestimate frictional forces by up to 35% when compared to validated CFD results. This study concludes that CFD is a versatile tool to predict the full-scale ship resistance to a more accurate extent than extrapolation model test data and can also be utilised to estimate model sizes that keep finite water effects to an agreed minimum.

Scale effects and full-scale ship hydrodynamics: A review

“…They demonstrated that a good agreement with full-scale trials can be achieved in this way. Haase et al (2016a) subsequently performed a similar assessment for a catamaran in finite waters. This approach, which satisfies 𝐹 𝑛 and 𝑅𝑒 similarity simultaneously, makes use of the previously stated fact that theoretically, ship resistance depends on only two-dimensional groups.…”

“…The approach of Haase et al (2016bHaase et al ( , 2016a allows unique insight into the physics of scale effects without the need for resorting to high cell numbers, making such investigations much easier to handle. However, the benefits of using this approach have been contested.…”

Modelling heat transfer and fluid flow in a ship engine room using CFD analysis to evaluate and improve ventilation

“…10 There are a significant number of applications for CFD simulation of ventilation systems, including optimising the ventilation method for a subway station by inspecting the velocity and temperature field, 11 windinduced ventilation in apartments, 12 natural ventilation in buildings, 13 or the airflow field and aerosol pollutant dispersal in aircraft cabins. 14 There are also plenty of applications for CFD simulation in maritime fields, such as computing drag, lift and fin coefficients, 15,16 investigating internal wave propagation, 17 predicting wave resistance 18 and estimating interference effects on resistance component interaction of catamarans. 19 Numerical modelling of the ship's engine room is a productive instrument for investigating and enhancing the ship's ventilation system.…”