Numerical calculation of the resistance of catamarans at different distances between two hulls

For the design of high-speed catamarans, different distances between slices have obvious interference with the total resistance of the catamaran. In order to accurately predict the hydrodynamic characteristics of the catamaran and explore the interference of the chip spacing on the resistance prediction, this paper uses a combination of CFD calculations and empirical formulas to predict the ship model resistance under different chip spacings and calculate them. The result is compared with the empirical formula. The results of the ship model test and the results calculated by the empirical formula were used to verify the numerical calculation results. The results show that the resistance change trend is consistent, and the numerical calculation method is effective and feasible. Finally, the numerical calculation method is compared with the ship model test method, and the result is within the error range, which has certain reference value for the design and optimization of the catamaran model parameters.

Ship Maneuvering Prediction Using Grey Box Framework via Adaptive RM-SVM with Minor Rudder

A grey box framework is applied to model ship maneuvering by using a reference model (RM) and a support vector machine (SVM) (RM-SVM). First, the nonlinear characteristics of the target ship are determined using the RM and the similarity rule. Then, the linear SVM adaptively fits the errors between acceleration variables of RM and target ship. Finally, the accelerations of the target ship are predicted using RM and linear SVM. The parameters of the RM are known and conveniently acquired, thus avoiding the modeling process. The SVM has the advantages of fast training, quick simulation, and no overfitting. Testing and validation are conducted using the ship model test data. The test case reveals the practicability of the RF-SVM based modeling method, while the validation cases confirm the generalization ability of the grey box framework.

Evaluation of a Practical Approach for Numerical Propulsion Tests

Prediction of resistance and propulsion characteristics for a ship is among the most important steps in a ship design process. Traditionally, model tests are used for these predictions and the results are extrapolated to the full-scale ship. Model test techniques can provide reasonably accurate results, but the cost and time they require — and the unavoidable scaling issues — have lead Naval Architects to look for other alternatives. With the increasing computer power and the increasing experience with numerical simulation of fluid flow, Computational Fluid Dynamics (CFD) have become an appealing alternative to model tests. Numerical computations will always be a trade-off between computational efforts and numerical accuracy. Typically, increased accuracy requirements will cause the mesh to be very fine, and hence the computational time will increase. At a Workshop on numerical simulation of full-scale ships in Southampton in November 2016, a practical approach for predicting the propulsion characteristics of a full-scale ship was introduced by participants from Becker Marine Systems. The pragmatic CFD approach reduced the computational efforts without scarifying the level of accuracy! In the present work, the alternative practical CFD approach is evaluated in a model scale case to study its benefits and possible short-comings compared to conventional CFD simulations of the self-propulsion case.

Analisa Ketidakpastian Pengujian Resistance Model Kapal LCT 1000 DWT

Uji tahanan yang dilakukan di tangki tarik memiliki kesalahan (ketidakpastian) pada hasil. Analisa ketidakpastian dapat digunakan untuk mengevaluasi kualitas data percobaan dan menyediakan perkiraan kuantitatif kesalahan percobaan. Metodologi analisa ketidakpastian, prosedur, dan hasil disajikan untuk uji tahanan model kapal LCT 1000 DWT skala (λ) 15 dengan ukuran model kapal L = 3,997 M, B = 1000 M, T = 0,167 M, WSA = 4,089 M2, Prosedur dirangkum dan mengikuti International Towing Tank Conference (ITTC) Kualitas Manual Prosedur. Hasil penelitian menunjukkan nilai ketidakpastian sebesar 1,27% dari kecepatan 1,3271 m/s dan nilai ketidakpastian sebesar 4,79% dari tahanan 1,2771 kg.Keywords : Uncertainty analysis, Procedures, Ship model test.

Measurement and Analysis of Coastal Waves Along The North Sea Area of China

Taking advantage of coastal wave environment to carry out scaled ship model test is an effective testing technology for ship performance. In this paper, the method of spectral analysis is adopted to calculate the significant wave height, period, wave spectrum and some other parameters of some places along the North Sea area of China. The measured wave spectrum and the ocean spectrum are handled into non-dimensional form to evaluate their similarity. The influence of wind direction and tide on coastal waves was analyzed. And the results indicate that the coastal wave spectrum is similar to the ocean spectrum under some specific conditions.

Research on Navigable Ship Model Test in Curved Waterway

The flow of bend reach is complicated, which is difficulty for intersection of ship,and is accident prone. According to the lower reaches of the Hanjiang River MaKou reach of ship model test results, the relationship between channel width and flow are summarized when ship navigation sail in bend reach, which indicated that at approximately the same speed, navigation width of sailing through the bend upward are much smaller than down. As velocity or flow angle increases, the ship track width is broader, and channel width is also broader. the ship control and peer safety management points are forwarded in the lower reaches of Hanjiang river bend, which can provide reference for similar engineering designand research of waterway.

System Identification of Unmanned Planning Boat Rolling Motion Mode

In this paper, the author took an unmanned planning boat as the object of study and carried out a series of rolling decay ship model test by changing the draft. The author established nine kinds of mathematical model of rolling decay motion model system identification by using different damping and righting moment and established the optimization calculation of the objective function based on the principle of system identification. Then the author adapted the genetic algorithm of system identification program which is based on the Visual Basic 6.0 and got 15 kinds of identification programs. By doing research on the first three cycles of the series of rolling angular velocity curve and identifying respectively the resulting 15 kinds of identification programs, the author confirmed the feasibility of the adapted program. Comparing different drafts and the initial roll angle identification results, the author found a reasonable hydrostatic roll motion equation of the unmanned planning boat in the case of different drafts and the initial roll angle, and made a preliminary analysis.

Ice Resistance Model Test Technology for 110K Tanker Adopting FSICR Ice Class IA

Ship model test in ice towing tank is one of the key technologies for the design of ice-strengthened ship, and is the primary measure of determining the ship required minimum engine output power in ice navigation and checking whether satisfies the requirements of ice class rules. Researched the relevant requirements of 1A ice-strengthened ship based on the Finnish-Swedish ice class rules (FSICR), which is minimum engine output power according to the forward form of hull line and according to standard formulas. Studied the technical requirements of ice model test. Determined the minimum engine output power for 110k oil tanker with ice class 1A based on ice model test.

Diversion Scheme for Yuliang Hydro-Junction Project of Youjiang River in Construction Period

Determination of construction diversion scheme is the most important part in the hydro-junction engineering design of inland waterway, which will influence the general layout, construction time and total cost. Based on the method of combining remote-controlled self-propelled ship model test with physical model test, the velocity and flow pattern of diversion channel in the first construction period, navigation flow condition of temporary channel, the velocity and flow pattern of release sluice and the navigation flow condition during the second construction period were analyzed in this paper. The problems in the construction diversion scheme were studied, and the improve measures which could meet the requirement for navigation and diversion were proposed.