CFD, potential flow and system-based simulations of fully appended free running 5415M in calm water and waves

Abstract

The seakeeping ability of ships is one of the aspects that needs to be assessed during the design phase of ships. Traditionally, potential flow calculations and model tests are employed to investigate whether the ship performs according to specified criteria. With the increase of computational power nowadays, advanced computational tools such as Computational Fluid Dynamics (CFD) become within reach of application during the assessment of ship designs. In the present paper, a detailed validation study of several computational methods for ship dynamics is presented. These methods range from low-fidelity system-based methods, to potential flow methods, to high-fidelity CFD tools. The ability of the methods to predict motions in calm water as well as in waves is investigated. In calm water, the roll decay behavior of a fully appended self-propelled free running 5415M model is investigated first. Subsequently, forced roll motions simulated by oscillating the rudders or stabilizer fins are studied. Lastly, the paper discusses comparisons between experiments and simulations in waves with varying levels of complexity, i.e. regular head waves, regular beam waves and bi-chromatic waves. The predictions for all methods are validated with an extensive experimental data set for ship motions and loads on appendages such as rudders, fins and bilge keels. Comparisons between the different methods and with the experiments are made for the relevant motions and the high fidelity CFD results are used to explain some of the complex physics. The course keeping and seakeeping of the model, the reduction rate of the roll motion, the effectiveness of the fin stabilizers as roll reduction device and the interaction of the roll motion with other motions are investigated as well. The paper shows that only high-fidelity CFD is able to accurately predict all the relevant physics during roll decay, forced oscillation and sailing in waves.

Assessment of percent-time-operable of surface combatants with conventional and wave-piercing hulls

“…Therefore, the time history of the roll, pitch, and heave motions, which are indirect to the mooring system, were mainly investigated to find out the period and magnitude of the wave-induced motions before reflected waves. In addition, the seakeeping test results of 5415M in beam and head seas by Toxopeus et al 17 were also compared to the present numerical analysis.…”

“…“Aqwa_Set” and “Aqwa_Des.” mean numerical analysis results with the weight setting of “model (set)” and “model (design)” in Table 4 respectively. The study of Toxopeus et al 17 corresponds to “Aqwa_Des.” Because of the difference in GM T between the two weight distribution conditions, the roll motion difference was recognizable. The roll damping of the numerical analysis of 5415M was adjusted to fit with the seakeeping experiments, and the magnitude was 0.011 Nms/°.…”

“…16 5415M is a variation of DTMB5415 by adding bilge keels and stabilizers for research on the suppression of roll damping. 17 ONR Tumblehome (hereafter ONRT) is a study design of Zumwalt-class destroyers. In Bishop et al 18 seakeeping performance by varying superstructure shapes, that is, flared, tumblehome, and wall-sided hulls, were compared in the same transverse metacentric height (GM T ) conditions.…”

“…mean numerical analysis results with the weight setting of ''model (set)'' and ''model (design)'' in Table 4 respectively. The study of Toxopeus et al 17 corresponds to ''Aqwa_Des.'' Because of the difference in GM T between the two weight distribution conditions, the roll motion difference was recognizable.…”

An Investigation on the Vortex Effect of a CALM Buoy under Water Waves Using Computational Fluid Dynamics (CFD)

“…They concluded that the WIM of the buoy is dominated by inertial and viscous effects of the hull, and that the results of coupled study on free-decay and wave-induced motions match well with model testing. In a similar study, Toxopeus et al [36] conducted some CFD simulations under waves and calm water using a self-propelled free running 5415M ship model and presented some motion response distributions. Bandringa et al [37] presented a CFD investigation which was validated using a linked CFD-dynamic mooring model for simulating the behaviour of a shallow water CALM buoy in extreme waves.…”