A REAL TIME SPEED MODULATION SYSTEM TO IMPROVE OPERATIONAL ABILITY OF AUTONOMOUS PLANING CRAFT IN A SEAWAY

This study focuses on developing a control system to enhance the seaworthiness of Autonomous high-speed Planing Crafts (APCs). APCs operating at high-speed in a seaway encounter very high vertical accelerations which pose a hazard to payload and crafts' structural integrity. Therefore, for safety operation of APCs in a seaway it is proposed to employ a system termed vision-aided speed modulation system (VSMS). The proposed VSMS employs an embedded analytical tool termed Motion Assessment of Planing Craft in a Seaway (MAPCS) for the prediction of vertical accelerations and angular velocities, the APC might encounter in the incoming waves. As a response to the MAPCS predicted values the VSMS speed setting module modulates the craft's forward speed. All modules of the VSMS are presented together with their validation and system's preliminary operational results. It is concluded that VSMS might be an essential tool to considerably enhance the operational ability of APCs.

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

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.

OpenPlaning: Open-Source Framework for the Hydrodynamic Design of Planing Hulls

The use of Dr. Savitsky's empirical methods for the hydrodynamic design of planing hulls is widespread in industry and academia. In spite of their common use, their implementations are frequently inconsistent among their users. This makes it difficult to share and replicate exact results, and apply those results to a reader's desired case study. This paper presents an open-source Python-based framework of the Savitsky '64 and Savitksy & Brown '76 papers that is suitable for industry and research purposes, named OpenPlaning. The original Savitsky method implementation required the use of charts and results interpolation to find the boat's equilibrium. OpenPlaning instead uses a root-finding algorithm to determine the equilibrium attitude, automating the process and assuring consistent use of the Savitsky method. This formulaic approach allows the users to change and explore variations among any desired hull characteristic (beam, deadrise, weight, flap size/deflection, etc.), and use Python packages to optimize these parameters. OpenPlaning includes Faltinsen's 2010 planing hull porpoising inception work, which expanded upon the Savitsky method to estimate the vessel's mass, damping, and restoring coefficients. Consequently, control engineers can also use OpenPlaning to obtain a linear system in the heave and pitch degree of freedoms, and obtain initial tuning parameters for control systems. To illustrate the use of OpenPlaning, an example planing craft is designed, explored and optimized with real-world constraints.

Modeling Vertical Planing Boat Motions using a Neural-Corrector Method

The dynamics of high-speed planing craft are complex and nonlinear. Standard analysis methods, such as linear potential theory, while convenient and computationally efficient, are often not suitable for use in predicting the dynamics of such craft because physical realities or design requirements invalidate the inherent assumptions. High-fidelity methods, such as state-of-the-art CFD simulations, can offer accurate solutions, but these methods are limited by computational cost and numerical sensitivity. In addition, these methods are not efficient enough to provide rapid evaluation of operability, i.e. simulations over a wide range of operating conditions and environments. This leaves few practical analysis options for small, high-speed craft designers who need to perform such predictions. In this paper, the authors present a neural-corrector method that shows promise in providing efficient predictions of vertical planing craft motions. The method retains higher-order terms typically truncated in the classical coupled 2-DOF system of ordinary differential equations using Long Short-Term Memory (LSTM) recurrent neural networks. In this manner, the robust solution provided by the linear model is retained, and the LSTM networks act as higher-order correctors. The correctors primarily regress on the solution, affording familiar numerical integration techniques for systems of nonlinear differential equations. Training and validation results from the method are compared to nonlinear simulations of 2-DOF motion of a Generic Prismatic Planing Hull (GPPH) at forward speed in head seas, with time histories given for both regular and irregular waves.

Investigation of planing craft maneuverability using full-scale tests

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.

Validation of Forced Heave Simulations on a Planing Hull

Advances in nonlinear modeling techniques have created opportunities for more robust modeling of planing hull dynamics than previous techniques relying on linear assumptions. These techniques rely on the imposition of complex, coupled forced motions on a hull. RANSE CFD provides a distinct advantage over experimentation when imposing complicated forced motions because mechanical limitations of the forced motion mechanism and uncertainty in the prescribed motion are eliminated, though the accuracy of the simulations needs to be validated. In this work, a series of sinusoidal forced heave experiments on a planing craft are used to validate the force response predicted by simulation for the same forced motion. The accuracy of the predicted force response is evaluated relative to the experiments with the experimental setup uncertainty considered. Within the experimental setup uncertainty, the force response is predicted well by RANSE CFD and is found to be reasonably accurate. The dynamic trim angle is found to have a major impact on the dynamic force response with variations on the order of half a degree having substantial impacts on the measured forces.

A Combined Method to Predict Impact Pressure on Planing Craft

Prediction of the pressure distribution on a planing craft in waves deeply affects its structural design and safe operation. In this paper, the possibility of pressure prediction for the planing craft in waves is studied. A combined method is formulated by which craft motions in waves are computed using a 2.5D method, and the impact pressure is anticipated by the equivalent wedge method. Experiments are conducted to record the vertical acceleration and pressure time trends on a model. Comparing the results of the combined method with the experiments indicates that this approach successfully predicts the heave and pitch motions and the time evolution of the acceleration and pressure. The method presents good estimations for the peaks of the acceleration and pressure. Using the combined method, a parametric study on maximum peak acceleration and pressure is also conducted for various forward velocities and wave heights. It has been shown that the combined method is a fast and reliable tool for maximum peak pressure prediction. The method may be employed for structural design and optimization.