Trajectories for ONR Tumblehome maneuvering in calm water and waves

2013 ◽  
Vol 72 ◽  
pp. 45-65 ◽  
Author(s):  
Yugo Sanada ◽  
Kenji Tanimoto ◽  
Kanako Takagi ◽  
Lichuan Gui ◽  
Yasuyuki Toda ◽  
...  
Keyword(s):  
2018 ◽  
Vol 24 (3) ◽  
pp. 948-967 ◽  
Author(s):  
Yugo Sanada ◽  
Haitham Elshiekh ◽  
Yasuyuki Toda ◽  
Frederick Stern
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Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz

The hydrodynamic characteristics of the planing hulls in particular at the planing regime are completely different from the conventional hull forms and the determination of these characteristics is more complicated. In the present study, calm water hydrodynamic characteristics of planing hulls are investigated using a hybrid method. The hybrid method combines the dynamic trim and sinkage from the Zarnick approach with the Savitsky method in order to calculate the total resistance of the planing hull. Since the obtained dynamic trim and sinkage values by using the original Zarnick approach are not in good agreement with experimental data, an improvement is applied to the hybrid method using a reduction function proposed by Garme. The numerical results obtained by the hybrid and improved hybrid method are compared with each other and available experimental data. The results indicate that the improved hybrid method gives better results compared to the hybrid method, especially for the dynamic trim and resistance. Although the results have some discrepancies with experimental data in terms of resistance, trim and sinkage, the improved hybrid method becomes appealing particularly for the preliminary design stage of the planing hulls.


2021 ◽  
Vol 9 (6) ◽  
pp. 680
Author(s):  
Hui Li ◽  
Yan Feng ◽  
Muk Chen Ong ◽  
Xin Zhao ◽  
Li Zhou

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route.


2021 ◽  
Vol 9 (1) ◽  
pp. 59
Author(s):  
Mina Tadros ◽  
Roberto Vettor ◽  
Manuel Ventura ◽  
Carlos Guedes Soares

This study presents a practical optimization procedure that couples the NavCad power prediction tool and a nonlinear optimizer integrated into the Matlab environment. This developed model aims at selecting a propeller at the engine operating point with minimum fuel consumption for different ship speeds in calm water condition. The procedure takes into account both the efficiency of the propeller and the specific fuel consumption of the engine. It is focused on reducing fuel consumption for the expected operational profile of the ship, contributing to energy efficiency in a complementary way as ship routing does. This model assists the ship and propeller designers in selecting the main parameters of the geometry, the operating point of a fixed-pitch propeller from Wageningen B-series and to define the gearbox ratio by minimizing the fuel consumption of a container ship, rather than only maximizing the propeller efficiency. Optimized results of the performance of several marine propellers with different number of blades working at different cruising speeds are also presented for comparison, while verifying the strength, cavitation and noise issues for each simulated case.


2015 ◽  
Author(s):  
Mohammed Islam ◽  
Fatima Jahra ◽  
Michael Doucet

Mesh and domain optimization strategies for a RANS solver to accurately estimate the open water propulsive characteristics of fixed pitch propellers are proposed based on examining the effect of different mesh and computation domain parameters. The optimized mesh and domain size parameters were selected using Design of Experiments (DoE) methods enabling simulations to be carried out in a limited memory environment, and in a timely manner; without compromising the accuracy of results. A Reynolds-Averaged Navier Stokes solver is used to predict the propulsive performance of a fixed pitch propeller. The predicted thrust and torque for the propeller were compared to the corresponding measurements. A total of six meshing parameters were selected that could affect the computational results of propeller open water performance. A two-level fractional factorial design was used to screen out parameters that do not significantly contribute to explaining the dependent parameters: namely simulation time, propeller thrust and propeller torque. A total of 32 simulations were carried out only to find out that the selected six meshing parameters were significant in defining the response parameters. Optimum values of each of the input parameters were obtained for the DOE technique and additional simulations were run with those parameters. The simulation results were validated using open water experimental results of the same propeller. It was found that with the optimized meshing arrangement, the propeller opens simulation time was reduced by at least a factor of 6 as compared to the generally popular meshing arrangement. Also, the accuracy of propulsive characteristics was improved by up to 50% as compared to published simulation results. The methodologies presented in this paper can be similarly applied to other simulations such as calm water ship resistance, ship propulsion to systematically derive the optimized meshing arrangement for simulations with minimal simulation time and maximum accuracy. This investigation was carried out using STAR-CCM+, a commercial CFD package; however the findings can be applied to any RANS solver.


2021 ◽  
Vol 236 ◽  
pp. 109254
Author(s):  
Evan J. Lee ◽  
Maysam Mousaviraad ◽  
Charles R. Weil ◽  
Minyee J. Jiang ◽  
Anne M. Fullerton ◽  
...  
Keyword(s):  

Author(s):  
Sébastien Fouques ◽  
Ole Andreas Hermundstad

The paper is concerned with the launch of free-fall lifeboats (FFL). It proposes a method that complies with the DNV-OS-E406 standard in order to select characteristic launches from Monte Carlo simulations for further structural load assessment with CFD and FEM. Proxy variables derived from kinematic parameters and aiming at predicting pressure load indicators are computed with the VARUNA launch simulator developed by MARINTEK. The statistical distributions of the proxy variables obtained from the Monte Carlo simulations are used to identify critical scenarios, and characteristic launches can then be selected from a chosen probability level. The feasibility of the proposed method is documented in the paper for several types of pressure loads. Existing model test data from various FFL-launch campaigns in calm water and in waves are used to compute the proxy variables as it would be done in the VARUNA simulator. Scatter diagrams showing the correlation with actual measured pressure load indicators are then established to assess the quality of the chosen proxy variables.


1975 ◽  
Vol 95 ◽  
pp. 169-171 ◽  
Author(s):  
A. Trevor Hodge

In his reconstruction of the campaign of Marathon, Prof. N. G. L. Hammond postulates that the Persian fleet accomplished its hurried voyage from Marathon to Phaleron after the battle in a time of 9 hours, and in theory could perhaps have done it in 8 (JHS 1968, p. 43). This very fast time (9 hours for 58 sea miles = 6½ knots; 8 hours = 7), necessary if the fleet is to arrive in Phaleron in time to confront the Athenians on the same day as the battle (sic Plut. Aristeides, v, 5; but cf. Mor. 350 E), is justified by two arguments: (1) the wind blowing at the time was a north-easter, providing ‘the fastest conditions for sailing’; and (2), the Phoenician galleys in the Persian fleet were faster than Greeks, making figures based on Greek performance irrelevant.(1) A strong north-easter is indeed very probable. During the summer and until mid-September (i.e., there is a strong probability that Marathon is covered, whichever date one prefers for it) the etesian winds (nowadays known as the meltemi) are blowing in the Aegean. These winds are of great strength and regularity, blowing only by daytime, and more or less from the North (Dem. iv 31; viii 14; Arist. Meteo, ii 361–2; A. R. Burn, Persia and the Greeks, p. 388). But the conditions they offer are not favourable for fast sailing from Marathon to Phaleron. Off the east coast of Attica a very choppy sea builds up. The seas come rolling down from the North, and in the funnel-shaped Thorikos Channel, between Makronissi and the mainland, build up to some really heavy weather between Lavrion and Sounion, particularly in the afternoon. This would delay the war galleys. Little is known about Phoenician war vessels, but they appear to have been triremes of some sort—light craft that can make good speed only in calm water. Far from a ‘following sea’ being favourable, a trireme would not give of its best in a sea of any kind, coming from any direction.


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