Development and Optimization of Mathematical Model of High Speed Planing Dynamics

2015 ◽  
Author(s):  
Prin Kanyoo ◽  
Dominic J. Taunton ◽  
James I. R. Blake
Keyword(s):  
Relative Velocity ◽  
High Speed ◽  
Lift Force ◽  
Hydrodynamic Pressure ◽  
Physical Nature ◽  
Ship Motions ◽  
Additional Contribution ◽  
Forward Speed ◽  
Planing Craft ◽  
Hydrostatic Force

The primary difference between a planing craft and a displacement ship is that the predominant force to support the conventional or displacement craft is hydrostatic force or buoyancy. While in the case of planing craft, the buoyancy cedes this role to hydrodynamic lift force caused by flow and pressure characteristics occurring when it is travelling at high forward speed. However, the magnitude of hydrostatic force is still significant that cannot be completely neglected. Due to the high forward speed and trim angle, the flow around and under the planing hull experiences change of momentum and leads to the appearance of lift force according to the 2ndlaw of Newton. In other words, there is a relative velocity between the craft hull and the wave orbital motion that causes hydrodynamic pressure generating hydrodynamic lift force act on the hull surface. Then, in case of behaviors in waves, an additional contribution of ship motions is necessary to be considered in the relative velocity, resulting in nonlinear characteristic of its physical nature.

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.

Empirical Methods for Predicting Lift and Heel Moment for a Heeled Planing Hull

2014 ◽  
Vol 30 (04) ◽  
pp. 175-183
Author(s):  
Carolyn Q. Judge
Keyword(s):  
High Speed ◽  
Experimental Program ◽  
Naval Academy ◽  
Forward Speed ◽  
Empirical Methods ◽  
Empirical Relationships ◽  
Planing Craft ◽  
Underwater Photography ◽  
Calm Water ◽  
Transverse Stability

Even in calm water, high-speed vessels can display unstable behaviors such as chine walking, sudden large heel, and porpoising. Large heel angle can result in 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, reducing the underwater geometry. An experimental program at the U.S. Naval Academy has been designed to investigate the transverse stability of planing hulls. An experimental mechanism to force a planing hull model in heave and roll motion was designed and built. The first model tested was a wooden prismatic planing hull model with a constant deadrise of 20, a beam of 1.48 ft (0.45 m), and a total length of 5 ft (1.52 m). The model was held at various heel and running draft positions while fixed in pitch, yaw, and sway. The tests were done at two model speeds, for one model displacement, five fixed heel angles, and five fixed running heave positions. The lift and sway forces, along with the heel moment, were measured and underwater photography was taken of the wetted surface. This article presents a set of equations based on empirical relationships for calculating the lift and heel moment for a prismatic planing hull at nonzero heel angles.

Numerical Study on the Hydrodynamic Performance of Integrated Interceptor-Flap Fitted to the Transom of a Planing Vessel

2018 ◽  
Author(s):  
Suneela Jangam ◽  
Parameswaran Krishnankutty ◽  
Anantha Subramanian V.
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Frictional Resistance ◽  
Hydrodynamic Pressure ◽  
Power Input ◽  
Hydrodynamic Performance ◽  
Planing Craft ◽  
Displacement Mode ◽  
Hydrodynamic Behaviour ◽  
Flap Design

Depending on the type of support, vessels are classified as displacement, semi-displacement and planing. But all types of vessels are in the displacement mode when they operate at low speed. In planing, due to the supportive hydrodynamic pressure, the hull wetted surface area reduces leading to low frictional resistance and consequent increase in speed for the same power input. Planing vessels are used for different purposes such as for fast patrol, sport activities, service, ambulance, rescue and recreation. The use of stern flaps, both fixed or controllable, interceptors and integrated interceptor-flap in high speed boats has become an acceptable option to control the running trim of the vessel to enhance its speed and powering performance. The interceptor-flap changes the pressure distribution underneath the hull which in turn causes reduced resistance acting on ships aftbody. The integrated stern interceptor-flap effect on planing craft performance depends on its parameters and also on those of the craft. So, an in depth study on the hydrodynamic behaviour of integrated interceptor-flap is essential, before it is adapted to a vessel, to get the best performance during the craft operation. In recent years, the computational fluid dynamics (CFD) technique has proved to be accurate and robust for hydrodynamic calculation of high-speed planing hulls. The aim of this paper is to study numerically on the performance of planing hull fitted with integrated stern interceptor-flap configuration. These studies help in understanding the flow field and other parameters on resistance of planing hulls with different flap angles. The study shows that the interceptor-flap performs well compared to bare hull. The guidelines that could be derived from these studies help in improving the interceptor-flap design for a high speed planing craft.

Slamming Kinematics, Impulse and Energy Transfer for Wave-Piercing Catamarans

2015 ◽  
Vol 59 (03) ◽  
pp. 145-161
Author(s):  
Jason Lavroff ◽  
Michael Richard Davis
Keyword(s):  
Cross Section ◽  
Relative Velocity ◽  
High Speed ◽  
Peak Load ◽  
Structural Response ◽  
Model Tests ◽  
Structural Deformation ◽  
Forward Speed ◽  
Regular Waves ◽  
High Froude Number

Wave slam on high-speed wave-piercing catamarans involves interaction between unsteady hydrodynamics and structural response. For this class of vessel, the period of whipping and the duration of slam loading are similar, and hydroelastic simulation in model testing is important. The high Froude number results in relatively large heave and pitch motions that influence slamming. The model tests carried out were intended to identify the most severe slams possible. Slam loads increase with wave height and forward speed, and peak slam loading was related most clearly to the maximum relative velocity between bow and water surface. The peak load mostly occurred after the time at which the center bow arched cross section would fill with displaced water when calculated on the basis of the hull cross-section movement relative to the encountered wave and before the top of the arch reached the undisturbed surface of the encountered wave. For a 112-m vessel with 2500 tonnes displacement slams in 5.4 m height, regular waves would reach a maximum force of 2115 tonnes weight with a duration of 1.14 seconds and an impulse of 918 tonne seconds. The energy imparted to structural deformation would reach 3.9 MJ at full scale, of which approximately 1.0 MJ would be transferred into structural whipping. The results obtained in these model tests are broadly consistent with the most severe slam loads observed during sea trials.

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

Investigation of planing craft maneuverability using full-scale tests

2021 ◽  
pp. 147509022110303
Author(s):  
Kazem Sadati ◽  
Hamid Zeraatgar ◽  
Aliasghar Moghaddas
Keyword(s):  
Full Scale ◽  
Performance Characteristics ◽  
Forward Speed ◽  
Speed Reduction ◽  
Planing Craft ◽  
Full Scale Tests ◽  
Turning Maneuver

Maneuverability of planing craft is a complicated hydrodynamic subject that needs more studies to comprehend its characteristics. Planing craft drivers follow a common practice for maneuver of the craft that is fundamentally different from ship’s standards. In situ full-scale tests are normally necessary to understand the maneuverability characteristics of planing craft. In this paper, a study has been conducted to illustrate maneuverability characteristics of planing craft by full-scale tests. Accelerating and turning maneuver tests are conducted on two cases at different forward speeds and rudder angles. In each test, dynamic trim, trajectory, speed, roll of the craft are recorded. The tests are performed in planing mode, semi-planing mode, and transition between planing mode to semi-planing mode to study the effects of the craft forward speed and consequently running attitude on the maneuverability. Analysis of the data reveals that the Steady Turning Diameter (STD) of the planing craft may be as large as 40 L, while it rarely goes beyond 5 L for ships. Results also show that a turning maneuver starting at planing mode might end in semi-planing mode. This transition can remarkably improve the performance characteristics of the planing craft’s maneuverability. Therefore, an alternative practice is proposed instead of the classic turning maneuver. In this practice, the craft traveling in the planing mode is transitioned to the semi-planing mode by forward speed reduction first, and then the turning maneuver is executed.

SHIP MOTIONS DURING REPLENISHMENT AT SEA OPERATIONS IN HEAD SEAS

2021 ◽  
Vol 152 (A4) ◽  
Author(s):  
G Thomas ◽  
T Turner ◽  
T Andrewartha ◽  
B Morris
Keyword(s):  
Experimental Study ◽  
Green Function ◽  
Prediction Method ◽  
Ship Motion ◽  
Motion Prediction ◽  
Ship Motions ◽  
Forward Speed ◽  
Theoretical Predictions ◽  
Relative Separation ◽  
Replenishment At Sea

During replenishment at sea operations the interaction between the two vessels travelling side by side can cause significant motions in the smaller vessel and affect the relative separation between their replenishment points. A study into these motions has been conducted including theoretical predictions and model experiments. The model tests investigated the influence of supply ship displacement and longitudinal separation on the ships’ motions. The data obtained from the experimental study has been used to validate a theoretical ship motion prediction method based on a 3-D zero-speed Green function with a forward speed correction in the frequency domain. The results were also used to estimate the expected extreme roll angle of the receiving vessel, and the relative motion between the vessels, during replenishment at sea operations in a typical irregular seaway. A significant increase in the frigate’s roll response was found to occur with an increase of the supply ship displacement, whilst a reduction in motion for the receiving vessel resulted from an increase in longitudinal separation between the vessels. It is proposed that to determine the optimal vessel separation it is vital that the motions of the vessels are not considered in isolation and all motions need to be considered for both vessels simultaneously.

Operation of Ride Control Systems to Minimise Slamming of Wave-Piercing Catamarans

2021 ◽  
Vol 163 (A1) ◽  
pp. 29-40
Author(s):  
M R Davis
Keyword(s):  
Control Systems ◽  
High Speed ◽  
Vertical Motion ◽  
Ship Motions ◽  
Wave Surface ◽  
Active Motion ◽  
Ride Control ◽  
Heave Motion ◽  
Control Feedback ◽  
Active Controls

Wave slam produces dynamic loads on the centre bow of wave piercing catamarans that are related to the relative vertical motion of the bow to the encountered wave surface. Rapid slam forces arise when the arch sections between centre bow and main hulls fill with rising water. In this paper time domain solutions for high speed ship motion in waves, including the action of active motion controls, are used to compute the slam forces. Slamming occurs at specific immersions of the bow whilst the peak slam force is characterised by the maximum relative vertical velocity of the bow during bow entry. Vertical motions of bow and encountered wave are in antiphase at encounter frequencies where slamming is most severe. The range of encounter frequencies where slamming occurs increases with wave height. Wave slam loads reduce ship motions, the heave motion being most reduced. Deployment of a fixed, inactive T-foil can reduce slamming loads by up to 65 %. With active controls peak slamming loads on the bow can be reduced by up to 73% and 79% in 4 m and 3 m seas, local control feedback being marginally the most effective mode of control for reduction of slamming.

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