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.

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.

Assessment of Hydrodynamic Tools for R/V Athena Model 5365 in Calm Water

2017 ◽  
Author(s):  
Anne Fullerton ◽  
Charles Weil ◽  
Evan Lee ◽  
Minyee Jiang ◽  
Fredrick Stern ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Structural Design ◽  
High Speed ◽  
Irregular Waves ◽  
Impact Loads ◽  
Empirical Methods ◽  
Regular Waves ◽  
Hull Form ◽  
Calm Water ◽  
Naval Surface Warfare

Current structural design methods for high speed naval craft rely heavily on empirical methods. Though these methods have been employed reliably for a number of years, it is likely that an unknown level of conservatism exists in the prediction of impact loads. A better physical understanding of the dynamic response of high speed craft in seas would allow for increased structural optimization. The publicly releasable hull form Naval Surface Warfare Center Carderock Division (NSWCCD) Model 5365 (R/V Athena) was chosen to facilitate release of results to various computational teams. Model 5365 was tested in calm water, regular waves, and irregular waves. After reviewing data from the first test in 2014, it was determined that the model should be modified to enable towing from the longitudinal center of gravity. Model 5365 was then modified and re-tested using with added calm water speeds, and additional wave conditions. Calm water results from this test are presented with uncertainty analysis for resistance, heave, and trim.

Comparative Investigation of an Automated Oceanic Wave Surface Glider Robot Influence on Resistance Prediction Using CFD Method

2015 ◽  
Vol 710 ◽  
pp. 91-97
Author(s):  
Aladdin Elhadad ◽  
Wen Yang Duan ◽  
Rui Deng
Keyword(s):  
High Speed ◽  
Water Resistance ◽  
Comparative Investigation ◽  
Numerical Predictions ◽  
Calm Water ◽  
Oceanic Wave ◽  
Computational Fluid Dynamics Cfd ◽  
Wave Glider ◽  
Cfd Method ◽  
Solution Parameters

Thewave glideris composed of two parts: the float is roughly the size and shape of a surfboard that contains all the instrumentation needed for scientific experiments; the sub has wings and hangs 6 meters below on an umbilical tether. This difference allows wave energy to be harvested to produce forward thrust. According to the lake of design information and data for thewave glider, the main aim of the study is usingcomputational fluid dynamics (CFD)to present a method to predict calm water resistance for the floating part of thewave glider(the hull).Wigley parabolic hulland high speed round bilge form (NPL)have been investigated in order to estimate the hydrodynamic performances of the hull usingCFDsoftware fluent.Wave glideris designed with slender hull shapes in order to decrease the wave making resistance of the ship.In this paper a method is evaluated by comparing the numerical predictions forwigleyandNPLforms (2m) using the same mesh generation method under the same conditions to design the hull. Calculations fortotal calm water resistanceare carried out using three different mesh sizes for Froude numbers in the range of 0.10 to 0.40 and compared for accuracy of the solution parameters. The close agreement between the numerical predictions shows the importance ofCFDapplications in estimating the hydrodynamics performance to design the floating hull and the numerical method is useful in glider design. This means that the method discussed in this paper can be used for the resistance calculation of some hulls like the float of the glider.

Comparative Performance of Optimum High Speed SWATH and Semi-SWATH in Calm Water and in Waves

2015 ◽  
Author(s):  
S. Brizzolara ◽  
G. Vernengo ◽  
L. Bonfiglio ◽  
D. Bruzzone
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Forward Speed ◽  
Comparative Performance ◽  
Hull Form ◽  
High Speeds ◽  
Head Waves ◽  
Calm Water ◽  
Minimization Algorithms ◽  
Ranse Solver

The hydrodynamic performance of unconventional SWATH and Semi-SWATH for high speed applications are analyzed and compared in this paper. Bare hull resistance in calm water is estimated by an inviscid boundary element method with viscous corrections and verified by a fully turbulent, multiphase unsteady RANSE solver. Motions response in head waves, calculated by a frequency domain 3D panel method with forward speed effects are also evaluated and compared. Both considered hulls are the best designs coming from full parametric hull form optimization procedures, based on CFD solvers for the estimation of their hydrodynamic performance and driven by evolutionary minimization algorithms. The SWATH has twin parabolic struts and an unconventional underwater shape, the semi-SWATH has a slender triangular waterline, a bulbous shape in the entrance body which gradually morph into a U-section with a shallow transom in the run body. In general, as expected, the Semi-SWATH hull shows a lower drag at high speeds while the single strut SWATH is superior at lower speeds. As regards seakeeping, the SWATH shows unbeatable lower pitch and heave motions in shorter waves, where the Semi-SWATH evidences a double peaked RAO. More detailed analysis and conclusion are drawn in the paper.

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.

scholarly journals Experimental Study on Motion Behavior and Longitudinal Stability Assessment of a Trimaran Planing Hull Model in Calm Water

2021 ◽  
Vol 9 (2) ◽  
pp. 164
Author(s):  
Jin Zou ◽  
Shijie Lu ◽  
Hanbing Sun ◽  
Liru Zan ◽  
Jiuyang Cang
Keyword(s):  
High Speed ◽  
Longitudinal Direction ◽  
Longitudinal Stability ◽  
Hull Form ◽  
Average Mass ◽  
Calm Water ◽  
Special Vehicle ◽  
Lift Enhancement ◽  
Resistance Decrease ◽  
Relationship Of

In this study, a high-speed planing trimaran hull form is designed, and the effects of different displacements and gravity longitudinal layouts on the performance of the trimaran planing hull in calm water are experimentally investigated in the towing tank of the China Special Vehicle Research Institute. Based on previous work, an innovative inner tunnel appendage hydroflap is mounted in the inner aft tunnel, located 1/8 L from the transom in the longitudinal direction with attack angles of 0° and 4°, respectively. Furthermore, a regular stern flap is mounted on the transom close to the chine. The towing test results show that, as the gravity center moves forward, the high-speed region resistance of the planing trimaran increases and the longitudinal stability is also strengthened. Further, the total resistance of the planing trimaran with a heavier displacement is larger while the average mass resistance declines; i.e., the resistance efficiency is improved. The results also indicate that the inner tunnel hydroflap and stern flap enhance the aft hull hydrodynamic lift and tunnel aerodynamic lift. As a result, mounting aft hull lift enhancement appendages can affect the bottom and inner tunnel pressure distribution and then cause a slight resistance decrease in the low-speed region. The value relationship of resistance between groups of appendages for the attached hull and bare hull is reversed at a speed of about Froude number 3.0. Although the aft hull lift enhancement appendages result in a higher resistance cost in the high-speed region, the longitudinal stability is effectively promoted and the occurrence speed of porpoising results in a delay of 1 to 2 m/s.

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.

Design Aspects of a High Speed Monohull RoPax Ferry

2015 ◽  
Author(s):  
Florian Kluwe ◽  
Kay Martinsen ◽  
Stefan Krüger ◽  
Adele Lübcke ◽  
Johannes Will
Keyword(s):  
Froude Number ◽  
Design Process ◽  
Life Cycle Cost ◽  
High Speed ◽  
Steel Structure ◽  
Hull Form ◽  
Numerical Predictions ◽  
The Stability ◽  
Weather Criterion ◽  
Engine Power

This paper describes the design process of a high speed mono hull RoPax ferry which operates at a Froude number of 0.4. The design task was quite challenging, as two possible transport concepts were in principle possible: Two ships were needed with a total speed of 50knots, which could result in a combination of a 30kn high speed Catamaran plus a conventional 20kn RoPax Ferry or alternatively in two identical sister vessels of 25kn each. The solution with the high speed catamaran plus the conventional RoPax-Ferry defined the total cost budget, which must not be exceeded by the design of the two sister vessels. This resulted in a tough boundary condition and made life cycle cost evaluations necessary. Due to harbor restrictions, the length of the ships was limited by abt. 110m, resulting in a Froude number of abt. 0.4. This resulted in high costs for the propulsion system. The ferries should initially have open RoRo-Cargo spaces for cost reasons, which made the stability requirements (weather criterion plus Stockholm Agreement) quite challenging. This also strongly influenced the design of the final hull form. As the ship is very sensitive to weight, detailed steel structure optimizations had to be carried out to optimize the main grillage systems of the vehicle decks. The hull form and the appendage design required careful optimization to guarantee the required service speed with the engine power which was available in the price budget. As no vessel of comparison was available, the speed power estimation as well as all design tasks had fully to rely on numerical predictions. As the ship had further demanding requirements for course keeping and comfort in waves, the optimization of the hull form must include also these issues. The paper shows that the design of complex ships is actually a holistic task which includes many engineering disciplines. The paper also shows that 1st principle based design methods can support the design process of specialized vessels significantly.

Preliminary Evaluation of a Semi-Submerged Ship for High-Speed Operation in Rough Seas

1960 ◽  
Vol 4 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Edward V. Lewis ◽  
Clayton Odenbrett
Keyword(s):  
High Speed ◽  
Structure Design ◽  
Preliminary Evaluation ◽  
Wave Impact ◽  
Hull Form ◽  
High Speeds ◽  
Sufficient Power ◽  
Calm Water ◽  
Rough Water ◽  
Large Peak

This paper describes the evaluation by means of model tests of an unusual hull form intended for high-speed operation in rough seas. The form can be described as a surfaced submarine, made longer and more slender in order to attain high calm-water speed. A long natural pitching period is obtained by fine, hollow waterline endings and use of large peak ballast tanks for rough-water operation. It was considered best not to attempt to keep water off the deck, and therefore comparatively low freeboard and tumblehome were adopted. Tests in regular head seas of model length and twice model length confirmed the expectation that at high speeds the semi-submerged ship could exceed the speeds at which the peaks of synchronous pitching and heaving motions occur. Consequently, in irregular head seas corresponding to a storm of Beaufort force 6, motions decreased as speed increased. Heaving was more pronounced than pitching, but accelerations were not prohibitively high even at a speed of 40 knots. It is concluded that a semi-submerged ship of the type tested shows promise of attaining much higher rough-water speeds than conventional destroyers, provided sufficient power can be installed. It is recommended that further research be directed toward providing a super-structure design that will reduce wave-impact effects and a hull form which will require less power at high speed in rough water.

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