An Optimization Study of TriSWACH Side-Hull Position for Minimum Resistance in Calm Water

2017 ◽  
Author(s):  
Yufei Ai ◽  
Yulin Zhao ◽  
Raju Datla
Keyword(s):  
Froude Number ◽  
Water Resistance ◽  
Hydrodynamic Characteristics ◽  
Hull Form ◽  
Optimization Study ◽  
Seakeeping Performance ◽  
Stevens Institute ◽  
Calm Water ◽  
Institute Of Technology ◽  
Minimum Resistance

TriSWACH is a promising novel hull form for its reduced resistance, larger deck area and good seakeeping performance. This paper aims to determine an optimal sidehull position for TriSWACH based on the minimum resistance in calm water. STAR-CCM+, a RANS-based commercial CFD tool and a potential flow code Michelet are compared in their calculations of resistance. Four different side-hull positions of the TriSWACH operated within Froude number from 0.1 to 0.5 with increment 0.05 are considered for the numerical simulations. The simulation results are further validated by the model tests performed in Stevens Institute of Technology Davidson Laboratory towing tank. The comparison shows that STAR-CCM+ RANS codes can predict TriSWACH’s hydrodynamic characteristics in calm water with high accuracy. Finally, TriSWACH's optimal side-hulls’ position was discussed based on calm water resistance within different Froude number ranges.

Experimental Analysis on Flow around Fin Assisted Semi SWATH

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
Arifah Ali ◽  
Adi Maimun ◽  
Yasser M. Ahmed ◽  
Rahimuddin Rahimuddin ◽  
Mohamad Pauzi A. Ghani
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Resistance ◽  
Wave Pattern ◽  
Resistance Test ◽  
Hull Form ◽  
Wave Interference ◽  
Calm Water ◽  
Water Test ◽  
Zero Degree

Demand on High Speed Craft (HSC) is increasing due to development of inland transportation. Therefore, many analysis have been conducted to evaluate performance of this modern ship. One of the important analysis is calm water resistance test. Resistance component of the hull and wave pattern around the hull are obtained from the calm water test. These criteria are important in analyzing flow around hull, especially on wave interference between the hulls. In this paper, flow around hull has been studied for one model of Semi SWATH hull form with fin stabilizers installation by performing calm water resistance test in deep water. The fore fin angle is fixed to zero degree while the aft fin angle is varied to 0, 5 and 15 degree. The effects of fin angle to resistance criteria and flow around hull are investigated. Wave height has been recorded using longitudinal wave probe during resistance test. For each configuration, the investigation is conducted with range of Length Froude Number from 0.34 to 0.69. From the analysis, it is found that flow around the hull of Semi SWATH is affected by fin angle and the effect is various depend on the Froude number.

scholarly journals Computational and experimental determination of waterjet aeration exposure in waves

2020 ◽  
Vol 4 (394) ◽  
pp. 21-30
Author(s):  
Tatyana A. Dyakova ◽  
Sergey O. Rozhdestvensky ◽  
Nikolai V. Marinich ◽  
Alexey A. Rudnichenko
Keyword(s):  
Numerical Simulation ◽  
Video Camera ◽  
Full Scale ◽  
Irregular Waves ◽  
Head Wave ◽  
Hydrodynamic Characteristics ◽  
Regular Waves ◽  
Seakeeping Performance ◽  
Calm Water ◽  
Air Penetration

Object and purpose of research. The object of research was a model of a fast seaworthy boat with discretevariable bottom deadrise and two waterjet propulsors. The purposes of research were to experimentally determine hydrodynamic characteristics of the model in calm water and head regular waves corresponding to the irregular waves of sea states 3 and 4, as well as to determine the possibility of air penetration to waterjet inlets for two variants of their arrangement on model bottom in head-wave conditions, numerical simulation of the full-scale boat movement in oblique irregular waves (sea state 4) for two variants of waterjet arrangement, with an assessment of waterjet duct aeration exposure. Materials and methods. Model hydrodynamics was estimated experimentally by means of towing tests in highspeed seakeeping basin in calm water and head regular waves using standard test equipment; air penetrations were recorded by a GO PRO digital video camera installed on the model above the water inlets. Numerical simulation of the full-scale boat movement was carried out in Star-CCM+ CFD package. Main results. The study yielded the curves of towing resistance, running trim and sinkage versus model speed in calm water and head regular waves of different length for two longitudinal CG positions, as well as the areas of air penetration to waterjet inlets on model bottom. Analysis of the experimental data enabled the estimation of attainable speed for the boat with displacement of 50 and 29 tf in waves for given delivered power. Numerical simulation of the full-scale boat movement in oblique irregular waves for two variants of waterjet arrangement has also been carried out. Conclusion. The results have shown that seakeeping performance of the boat is quite satisfactory and that the most obvious way to mitigate air penetrations is to reduce the speed. Other important factors were shifting the waterjet inlet towards the transom and to the CL, as well as shifting the longitudinal CG forward. The obtained results can be used to select the position of the waterjet inlets on boat bottom in order to increase waterjet efficiency. Using the methods of numerical hydrodynamics, the characteristics of the waterjets have been obtained, the probability and volumes of air penetrations to waterjet ducts (for different variants of waterjet arrangement) at several angles of oblique irregular waves have been estimated.

Seakeeping Evaluation of a Tri-SWACH Based on CFD Calculations and Model Tests

2021 ◽  
Author(s):  
Gong Xiang ◽  
Raju Datla ◽  
Xianbo Xiang
Keyword(s):  
Time Domain ◽  
High Speed ◽  
Three Dimensional ◽  
Primary Objective ◽  
Model Tests ◽  
Numerical Predictions ◽  
Seakeeping Performance ◽  
Stevens Institute ◽  
Transverse Stability ◽  
Institute Of Technology

AEGIR is a time-domain seakeeping CFD code that uses an advanced, high-order boundary element method (BEM) to solve the three-dimensional potential-flow and has been developed for several years. In this paper, the latest version of AEGIR is used to predict the seakeeping of the Tri-SWACH with and without side hulls in headsea regular waves respectively. The primary objective was to evaluate its accuracy of predicting seakeeping performance of the Tri-SWACH under regular headsea waves in AEGIR. A series of simulated time domain heave and pitch responses for Tri-SWACH with and without side hulls via AEGIR have been compared with corresponding model tests conducted in the high speed towing tank in Davidson Lab, Stevens Institute of Technology. A good agreement in terms of heave and pitch responses between AEGIR numerical predictions and experimental data shows the seakeeping prediction capability of AEGIR for Tri-SWACH Preliminary Design. Also, the simulated seakeeping of a Tri-SWACH is compared with a Tri-SWACH center hull. It is found that the effects of side hulls will increase the transverse stability of the Tri-SWACH without causing additional significant effect on the seakeeping performance of the Tri-SWACH.

scholarly journals Study on Hull Optimization Process Considering Operational Efficiency in Waves

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 898
Author(s):  
Beom-Soo Kim ◽  
Min-Jae Oh ◽  
Jae-Hoon Lee ◽  
Yong-hwan Kim ◽  
Myung-Il Roh
Keyword(s):  
Water Resistance ◽  
Operational Efficiency ◽  
Free Form ◽  
Total Resistance ◽  
Added Resistance ◽  
Deformation Method ◽  
Cross Sectional ◽  
Hull Form ◽  
Strip Theory ◽  
Calm Water

This study investigates the optimization of the hull form of a tanker, considering the operational efficiency in waves, in accordance with the recent Energy Efficiency Design Index regulation. For this purpose, the total resistance and speed loss of the ship under representative sea conditions were minimized simultaneously. The total resistance was divided into three components: calm water resistance, added resistance due to wind, and to waves. The first two components were calculated using regression formulas, and the last component was estimated using the strip theory, far-field method, and the short-wave correction formula. Next, prismatic coefficient, waterline length, waterplane area, and flare angle were selected as design variables from the perspective of operational efficiency. The hull form was described as a combination of cross-sectional curves. A combination of the method shifting these sections in the longitudinal direction and the Free-Form Deformation method was used to deform the hull. As a result of applying the non-dominated sorting genetic algorithm to a tanker, the hull was deformed thinner and longer, and it was determined that the total resistance and speed loss were reduced by 3.58 and 10.2%, respectively. In particular, the added resistance due to waves decreased significantly compared to the calm water resistance, which implies that the present tendency differs from conventional ship design that optimizes only the calm water resistance.

Hull Form Optimization for Hydrodynamic Performance

2004 ◽  
Vol 41 (04) ◽  
pp. 167-182
Author(s):  
Gregory J. Grigoropoulos
Keyword(s):  
Water Resistance ◽  
Optimization Procedure ◽  
Hydrodynamic Performance ◽  
Hull Form ◽  
Principal Characteristics ◽  
Calm Water ◽  
Rough Water ◽  
Hull Forms ◽  
Scaled Models ◽  
Formal Optimization

A method for optimizing hull forms with respect to their hydrodynamic performance in calm and rough water is presented. The method is based on an initial optimization of a parent hull form for seakeeping and the improvement of the resulting optimum hull form for calm water resistance. In the first part of the method, variant hull forms differing from a parent in the main dimensions and/or in one or more hull form parameters, such as CWP, LCF, CB, LCB, KB, CP, are automatically generated and their seakeeping qualities evaluated. When appropriate ranges for the principal characteristics and parameters of the hull form under investigation are prescribed, a formal optimization procedure is used to obtain the variant with the best seakeeping behavior. The weighted sum of the resonant values of selected ship responses for a number of ship speeds and headings in regular waves forms the objective function. The Hooke and Jeeves algorithm is used to accomplish the optimization. The procedure results in a set of trends regarding the proposed variations of the selected hull form parameters, within the specified constraints. These trends are then applied on the parent hull to derive an optimized hull form with fair lines. Subsequently, this hull form can be locally modified to improve its calm water resistance or, as it should be done, its propulsion characteristics. The applicability of the method is demonstrated in two cases: a conventional reefer ship and a naval destroyer. Scaled models of the parent and the optimized hull forms have been tested for calm water resistance and seakeeping. In both cases the validity of the methodology is demonstrated.

Numerical evaluation of hydrodynamic characteristics of planing hulls by using a hybrid method

2021 ◽  
pp. 147509022199024
Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Calm Water ◽  
Preliminary Design Stage ◽  
Reduction Function ◽  
Hull Forms ◽  
Good Agreement

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.

scholarly journals An Approach to Determine Optimal Bow Configuration of Polar Ships under Combined Ice and Calm-Water Conditions

2021 ◽  
Vol 9 (6) ◽  
pp. 680
Author(s):  
Hui Li ◽  
Yan Feng ◽  
Muk Chen Ong ◽  
Xin Zhao ◽  
Li Zhou
Keyword(s):  
Numerical Simulation ◽  
Water Resistance ◽  
Numerical Technique ◽  
Experimental Studies ◽  
Resistance Index ◽  
Simulation Method ◽  
Present Approach ◽  
Calm Water ◽  
Level Ice ◽  
Ice Resistance

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.

Some Guidance for Hull Form Selection for SWATH Ships

1988 ◽  
Vol 25 (04) ◽  
pp. 239-252
Author(s):  
G. Robed Lamb
Keyword(s):  
High Speed ◽  
Early Stage ◽  
The United States ◽  
Practical Application ◽  
Hull Form ◽  
Stage Design ◽  
Seakeeping Performance ◽  
The World ◽  
Selection For ◽  
Early Stage Design

Even though in 1987 there were only a dozen SWATH (smali-waterplane-area twin-hull) craft and ships afloat around the world, word of their markedly superior seakeeping performance is spreading rapidly. The number of SWATH vessels is likely to double within five years. As in many other areas of technology, the United States and Japan are the acknowledged leaders in the development and practical application of the SWATH concept. This paper reviews the characteristics of existing SWATH craft and ships from the standpoint of the stated seakeeping objective. Hull form differences between four SWATH craft and ships, including the Navy's SSP Kairnalino, are analyzed and interpreted. Important considerations for the early-stage design of a SWATH ship are discussed. Differences in the range of feasible hull form geometries for coastal areas and unrestricted ocean operations, and for low-speed versus moderately high-speed applications, are pointed out.

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