The Systematic Variation of Step Configuration and Displacement for a Double-step Planing Craft

2014 ◽  
Vol 30 (02) ◽  
pp. 89-97 ◽  
Author(s):  
Evan Lee ◽  
Mark Pavkov ◽  
Mark Pavkov
Keyword(s):  
Model Test ◽  
Systematic Variation ◽  
Step Height ◽  
Double Step ◽  
Planing Craft ◽  
Speed Range ◽  
Calm Water ◽  
Systematic Understanding

A model test was conducted to provide a systematic understanding of the effects that displacement and step location have on the performance of a stepped planing hull. Seven different step configurations were tested at three different displacements and over a range of four different speeds in calm water. Of all the configurations tested, the stepped hull configurations showed reduced resistance compared with the unstepped hull. The configuration with the smallest step height forward and the largest step height aft showed the least amount of drag over the speed range tested. The increased displacements had the same effect on craft performance for both the stepped and unstepped hulls.

A Simple Method for Predicting the Maximum Squat of a High-Speed Displacement Ship

2006 ◽  
Vol 43 (03) ◽  
pp. 146-151
Author(s):  
Tim Gourlay
Keyword(s):  
Satisfactory Agreement ◽  
Model Test ◽  
High Speed ◽  
Simple Formula ◽  
Test Results ◽  
Simple Method ◽  
Wide Range ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

Numerical Modelling of a Planing Craft with a V-Shaped Spray Interceptor Arrangement in Calm Water

2020 ◽  
Author(s):  
Mikloš Lakatoš ◽  
Kristjan Tabri ◽  
Abbas Dashtimanesh ◽  
Henrik Andreasson
Keyword(s):  
Reaction Force ◽  
The Other ◽  
Numerical Comparison ◽  
Total Resistance ◽  
Stagnation Line ◽  
Planing Craft ◽  
Water Conditions ◽  
Calm Water ◽  
Wetted Surface Area ◽  
Novel Concept

V-shaped spray interceptors are a novel concept of spray deflection on planing craft. Conventional spray rails are positioned longitudinally on the bottom of the hull and detach the spray from hull deflecting it towards the sides or slightly down and aftward. The V-shaped spray interceptors, on the other hand, are located in the spray area forward of the stagnation line such that they would deflect the oncoming spray down and aftward, thereby producing a reaction force that reduces the total resistance. An experimental study reported that the V-shaped spray interceptors to reduce the total resistance at low planing speed by up to 4%. This paper features a numerical comparison of two planing craft, one equipped with a conventional setup of longitudinal spray rails and the other with a V-shaped spray interceptor. Both configurations were simulated in calm water conditions and were free to pitch and heave in a speed range of Fr∇ = 1.776 to 3.108. The numerical model was analyzed for grid sensitivity and numerical results were compared with experimental results. The two concepts were compared in terms of total resistance, lift, running position and wetted surface area. Conventional spray rails were shown to account for up to 5.6% of total lift and up to 6.5% of total resistance. The V-shaped spray interceptor was shown to reduce the total resistance by up to 8%. Since the V-shaped spray interceptor was located in the spray area forward of the stagnation line, it deflected the oncoming spray thereby producing a horizontal reaction force (-1.5% of RTM) in the direction of the craft’s motion. The rest of differences in the total resistance of the hulls equipped with the conventional spray rails and the V-shaped spray rails was due to absence of the resistance of the absent spray rails.

Experimental appraisal of hydrodynamic performance and motion of a single-stepped high-speed vessel in calm water and regular waves

2020 ◽  
pp. 095440622096812
Author(s):  
Sayyed Mahdi Sajedi ◽  
Parviz Ghadimi ◽  
Aliakbar Ghadimi ◽  
Mohammad Sheikholeslami
Keyword(s):  
High Speed ◽  
Single Step ◽  
Hydrodynamic Performance ◽  
Sea Waves ◽  
Regular Waves ◽  
Height Range ◽  
Step Model ◽  
Speed Range ◽  
Calm Water ◽  
Laboratory Models

High-speed vessels exhibit various motions and accelerations in calm water and sea waves. For examining the behavior of high-speed vessels, it is possible to examine these movements in laboratory models. In this paper, a single-step model in calm water is experimentally tested and compared with a model of no step. The speed range of these vessels is 1 m/s to 9 m/s equivalent to Beam Froude numbers of 0.43 to 3.87. During these experiments, the resistance parameters, trim, bow, and stern rise-up as well as the center of the gravity are measured. The non-step model has longitudinal instability at a speed of 8 m/s. This instability is avoided when the vessel is equipped by a transversal step. The vessel's trim and resistance are also reduced in the planing mode in calm water. Subsequently, hydrodynamic performance and its seakeeping condition in the planing regime are investigated for both vessels in regular waves. The single-step and non-step vessels are tested in the wavelength range of [Formula: see text], and the wave height range of 6 to 18 centimeters. It is observed that stepped vessel experiences lower motions and bow accelerations and less added resistance in comparison to the non-stepped vessel.

Icebreaking Model Tests: Systematic Variation of Bow Lines and Main Dimensions of Hull Forms Suitable for the Great Lakes

1973 ◽  
Vol 10 (03) ◽  
pp. 236-243
Author(s):  
Bengt M. Johansson ◽  
Eero Makinen
Keyword(s):  
Great Lakes ◽  
Power Level ◽  
The Other ◽  
Systematic Variation ◽  
Bulk Carrier ◽  
Basic Form ◽  
Speed Range ◽  
Level Ice ◽  
Hull Forms ◽  
Ice Resistance

Nine bulk carrier models were tested in the Wartsila Icebreaking Model Basin (WIMB) in Helsinki, Finland. Eight of the models form a series with systematically varying parameters. This test series was the first one in which the influence of bow form, ship length and, ship beam on ice resistance was investigated systematically. The basic form was that of the existing Great Laker SS Ryerson, which was not originally designed for navigating in ice. The other models were modified in order to improve their icebreaking capability. The main objective was to study the icebreaking resistance in level ice, but in addition some tests were made for determining the ice resistance in a broken channel and for determining the steering ability of the models. All models were tested in level ice of 1, 2 and 3 ft thickness and at a speed range of 0–12 knots. Finally, a method for the calculation of the ice resistance and necessary power level of the Great Lakers is presented.

Comparisons Between Prediction and Experiment for Lift Force and Heel Moment for a Planing Hull

2013 ◽  
Vol 29 (01) ◽  
pp. 36-46
Author(s):  
Carolyn Q. Judge
Keyword(s):  
High Speed ◽  
Lift Force ◽  
Forward Speed ◽  
Dynamic Effects ◽  
Planing Craft ◽  
Underwater Photography ◽  
Calm Water ◽  
Transverse Stability ◽  
The Relationship ◽  
Righting Moment

Even in calm water, high-speed vessels can display unstable behaviors such chine walking, sudden large heel, and porpoising. Large heel results from the loss of transverse stability at high forward speed. When a planing craft begins to plane, the hydrodynamic lift forces raise the hull out of the water. The available righting moment resulting from the hydrostatic buoyancy is, therefore, reduced. As the righting moment resulting from hydrostatic buoyancy is reduced, the righting moment resulting from dynamic effects becomes important. These hydrodynamic righting effects are related to the hydrodynamic lift. This article explores the relationship between the hydrostatic lift and righting moment, the hydrodynamic lift and righting moment, and the total lift and heel-restoring moment of a planing craft operating at planing speeds. A series of tow tests using a prismatic hull with a constant deadrise of 20 measured the lift force and righting moment at various angles of heel and at various model velocities. The model was completely constrained in surge, sway, heave, roll, pitch, and yaw. The underwater volume is determined from the known hull configuration and the underwater photography of the keel and chine wetted lengths. The results presented include the total lift and righting moment with the hydrostatic and hydrodynamic contributions for various model speeds at two model displacements.

Hydrodynamics of High-Speed Planing Craft: Savitsky Method and 2D+t Approach

2021 ◽  
Author(s):  
M. Javad Javaherian ◽  
Richard Royce ◽  
Raju Datla ◽  
Christine M. Gilbert
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Hydrodynamic Force ◽  
Prediction Method ◽  
Water Entry ◽  
Planing Craft ◽  
Towing Tank ◽  
Entry Model ◽  
Calm Water

The progressive interest in high-speed planing craft has made it crucial to conduct more accurate assessments of the behavior of these vessels in motion. In this paper, a 2D+t approach is employed to predict the resistance, trim and wetted length of a prismatic planing craft cruising in calm water. Although this approach is based on original Zarnick 2D+t model, the hydrodynamic force is estimated using experimental wedge drop experiments in conjunction with the Logvinovich wedge water entry model. The analysis is repeated employing Savitsky prediction method and results are compared with that of towing tank measurements of Naples series. The comparison shows that the Savitsky prediction results match very well with the experimental data. The 2D+t approach also shows reasonable outcomes for the trim and wetted length. However, this approach slightly underestimates the resistance of the craft at very low Froude numbers.

scholarly journals Manoeuvrability of a Large Cruise Ship after Damage for Safe Return to Port

2020 ◽  
Vol 8 (5) ◽  
pp. 378
Author(s):  
Tetsuhiro Yuura ◽  
Hirotada Hashimoto ◽  
Akihiko Matsuda
Keyword(s):  
Simulation Model ◽  
Model Test ◽  
Model Experiment ◽  
Cruise Ship ◽  
Scaled Model ◽  
Cruise Ships ◽  
Head Waves ◽  
Calm Water ◽  
Free Running ◽  
Captive Model Test

Free-running model tests were conducted using a scaled model of a large cruise ship with a damaged compartment, to investigate the effects of damage opening and floodwater on the manoeuvring performance in calm water and regular and irregular head waves. Drifting tests in regular beam waves were also performed. The experimental results indicated that the course-keeping ability in waves and turning ability became worse in the damaged condition. However, the target ship retained its manoeuvrability for safe return to the port, on its own, even in a damaged state. As it is time- and cost-consuming to conduct a free-running model experiment, a captive model test was also carried out to develop a system-based simulation model for evaluating the manoeuvrability of large cruise ships after damage.

First Step Towards the Co-Design of Planing Craft and Active Control Systems

2015 ◽  
Author(s):  
Esteban L. Castro-Feliciano ◽  
Jing Sun ◽  
Armin W. Troesch
Keyword(s):  
Control Systems ◽  
Active Control ◽  
Traditional Approach ◽  
Linear Quadratic Regulator ◽  
Vertical Acceleration ◽  
Linear Quadratic ◽  
Planing Craft ◽  
Novel Approach ◽  
Calm Water ◽  
The Stability

This paper takes a novel approach to the design of planing craft with active control systems (ACS) by co-designing the longitudinal center of gravity (lcg) and ACS, and compares its performance with a vessel where the lcg and ACS are designed sequentially (traditional approach). The vessels investigated are prismatic in shape. The ACS are modeled as forces on the vessel. The ACS controller is a Linear Quadratic Regulator designed using a reduced order model of the vessel. In the design, only the calm water drag is optimized. The simulated co-designed vessel had 10% lower calm water and mean seaway drag than the sequentially designed vessel. However, the co-designed vessel’s seakeeping was poorer — vertical acceleration doses 25% higher. Results indicate that the traditional sequential design approach does not fully exploit the synergy between a planing craft and its ACS; as a first step, the stability constraints should be relaxed in the design exploration.

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