Numerical Analysis of Planing Boats in Regular and Irregular Head Waves Using a 2D+t Method

2015 ◽  
Author(s):  
Hendrik Haase ◽  
Jan P. Soproni ◽  
Moustafa Abdel-Maksoud
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
The State ◽  
Operating Conditions ◽  
Head Waves ◽  
Calm Water ◽  
Rough Water ◽  
Small Craft ◽  
Vertical Accelerations ◽  
Hydrodynamic Evaluation

A large number of small craft with a demand of high speed are planing vessels (Faltinsen, 2005). Their hulls are designed to plane, a condition, in which the boat's weight is carried mainly by hydrodynamic rather than hydrostatic forces. In order to reach the state of stable planing, planing hulls usually have hard chines, a transom stern and a certain deadrise angle, which is often constant in the aft and becomes larger towards the bow. Smaller deadrise angles are associated with a higher dynamic lift, which is often beneficial for the calm water performance. However, smaller deadrise angles also lead to higher vertical accelerations the crew is exposed to when the boat travels in rough water. To ensure good performance in all operating conditions, a hydrodynamic evaluation of the boat's behaviour both in calm water and in waves is important.

Comparison between the Dynamic Behavior of the Non-stepped and Double-stepped Planing Hulls in Rough Water: A Numerical Study

2020 ◽  
Vol 36 (01) ◽  
pp. 52-66
Author(s):  
Arman Esfandiari ◽  
Sasan Tavakoli ◽  
Abbas Dashtimanesh
Keyword(s):  
Numerical Simulations ◽  
High Speed ◽  
Numerical Study ◽  
Vertical Plane ◽  
Recent Decade ◽  
Vertical Acceleration ◽  
Gravitational Acceleration ◽  
Head Waves ◽  
Calm Water ◽  
Rough Water

Reducing vertical motions of high-speed planing hulls in rough water is one of the most important factors that help a boat to become more operable, and will benefit the structure of the boat and the crew on board. In the recent decade, stepped planing hulls have been investigated with emphasis on their better performance in calm water than that of nonstepped planing hulls. However, there are still doubts about their performance in rough water. In this study, we investigate this problem by providing numerical simulations for motions of a double-stepped and a non-stepped planing hull in a vertical plane when they encounter head waves. The problem will be solved using the finite volume method and volume of fluid method. To this end, a numerical computational fluid dynamics code (STARCCM1) has been used. Accuracy of the numerical simulations is evaluated by comparing their outcome with available experimental data. The dynamic response of the investigated hulls has been numerically modeled for two different wave lengths, one of which is smaller than the boat length and the other which is larger than the boat length. Using the numerical simulations, heave and pitch motions as well as vertical acceleration are found. It has been found that at wave lengths larger than the boat length, heave amplitude decreases by 10–40%when two steps are added to the bottom of a vessel. It has also been observed that pitch of a planing hull is reduced by 18–32% in the presence of the two steps on its bottom. Finally, it has been observed that for wave lengths larger than the boat length, the maximum vertical acceleration decreases by a gravitational acceleration of about .2–.7.

A Proposal for Performance Criteria for Propulsion Losses Due to Ship Steering

1982 ◽  
Vol 104 (2) ◽  
pp. 158-165 ◽  
Author(s):  
R. E. Reid
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Relative Performance ◽  
Performance Criteria ◽  
Ship Steering ◽  
Calm Water ◽  
Simulation Results ◽  
Definition Of ◽  
Hydrodynamic Data

The problem of definition of propulsion loss related to ship steering is addressed. Performance criteria representative of propulsion losses due to steering over a range of operating conditions including operation in calm water and a seaway are considered. Criteria are derived from strict analytical considerations and from empirical assumptions based on experimentally derived hydrodynamic data. The applicability of these various criteria and the implications for both assessment of relative performance of existing ship autopilots and for the design of new steering controllers is discussed in relation to simulation results for a high-speed containership.

A study on vertical motions of high-speed planing boats with automatically controlled stern interceptors in calm water and head waves

2014 ◽  
Vol 10 (3) ◽  
pp. 335-348 ◽  
Author(s):  
Mohammad Hossein Karimi ◽  
Mohammad Saeed Seif ◽  
Majid Abbaspoor
Keyword(s):  
High Speed ◽  
Head Waves ◽  
Calm Water

A Life-cycle Cost Analysis of the Application of a Hull Vane to an Offshore Patrol Vessel

2015 ◽  
Author(s):  
Bruno Bouckaert ◽  
Kasper Uithof ◽  
Perry van Oossanen ◽  
Niels Moerke ◽  
Bart Nienhuis ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Life Cycle Cost ◽  
Point Of View ◽  
Life Cycle Cost Analysis ◽  
Speed Profile ◽  
Total Resistance ◽  
Head Waves ◽  
Small Craft ◽  
Total Fuel Consumption ◽  
Vertical Accelerations

The consequences of applying a Hull Vane to a Holland Class 108 m Oceangoing Patrol Vessel of the Royal Netherlands Navy were studied by means of a Computational Fluid Dynamics study using Fine/Marine. The effect on the annual fuel consumption was determined by linking the savings percentages at several speeds to the operational speed profile. This paper demonstrates that - from propulsion point of view - a reduction in total fuel consumption can be achieved of 12.5% if a Hull Vane is installed, along with a small modification to the ship’s hull. At the speed at which most fuel is consumed annually (17.5 knots), the total resistance is reduced by 15.3%. Further operational benefits were quantified, such as a reduction of the vertical accelerations at the helicopter deck when sailing in head waves (-13%), a reduction of the turbulent zone just behind the slipway enabling small craft launch and recovery (from 5 to 2.5 meters), an increased range (from 5,000 nautical miles to 5,850 nautical miles at 15 knots) and an increased top speed (from 21.5 knots to 22.1 knots).

Operation of T-Foils and Stern Tabs to Improve Passenger Comfort on High-Speed Ferries

2021 ◽  
pp. 1-20
Author(s):  
Michael R. Davis
Keyword(s):  
Time Domain ◽  
High Speed ◽  
Transfer Functions ◽  
Passenger Comfort ◽  
Strip Theory ◽  
Head Waves ◽  
Similar Range ◽  
Vertical Accelerations ◽  
The Time Domain ◽  
Passenger Discomfort

High-speed ferries of around 100 m length cruising at around 40 knots can cause significant passenger discomfort in head waves. This is due to the frequencies of encountering waves, of maximum hull response to encountered waves and of maximum passenger discomfort all falling within a similar range. In this paper, the benefit obtained by fitting active T-foils and stern tabs to control heave and pitch in head waves is considered. Ship motion responses are computed by numerical integration in the time domain including unsteady control actions using a time domain, high-speed strip theory. This obviates the need to identify transfer functions, the computed time responses including nonlinear hull immersion terms. The largest passenger vertical accelerations occur at forward locations and are best controlled by a forward located T-foil acting in combination with active stern tabs. Various feedback control algorithms have been considered and it is found that pitch damping control gives the greatest improvement in passenger comfort at forward positions. Operation in adaptive and nonlinear modes so that the control deflections are maximized under all conditions give the greatest benefit and can reduce passenger motion sickness incidence (MSI) by up to 25% in a 3-m head sea on the basis of International Organization for Standardization (ISO) recommendations for calculation of MSI for a 90-minute seaway passage.

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.

Pressure wave characteristics of a high-speed train in a tunnel according to the operating conditions

2017 ◽  
Vol 232 (3) ◽  
pp. 928-935 ◽  
Author(s):  
Joon-Hyung Kim ◽  
Joo-Hyun Rho
Keyword(s):  
Numerical Analysis ◽  
Pressure Wave ◽  
High Speed ◽  
High Reliability ◽  
Rate Of Change ◽  
Operating Conditions ◽  
Pressure Waves ◽  
High Speed Train ◽  
Wave Characteristics ◽  
Pressure Characteristics

The pressure waves of a high-speed train in a tunnel exhibit complicated variations in their characteristics because the waves propagate and reflect with superposition. Studies have been consistently carried out on the pressure waves of a single train since changes in the area of pressure is a key element that influences ride comfort. Recently, the frequency of the operation of coupled trains has increased in order to improve the efficiency of running a train. The cross-sectional area of a train entering a tunnel has a rate of change that greatly influences the pressure characteristics; therefore, a coupled train can have different pressure characteristics when compared to a single train. However, adequate research works have not been done to assess these characteristics. To this end, the pressure characteristics of a train according to the operating conditions are investigated in this study. A high-speed train operating in practice and a tunnel located in a service section were chosen for this study, and the pressure characteristics of a single train were assessed via numerical analysis and an experiment. The numerical analysis was carried out with high reliability by comparing and verifying each result. After the pressure wave characteristics caused by running a coupled train had been assessed by the established numerical analysis, an obvious pressure variation was confirmed to occur at the connecting point. In addition, the maximum pressure applied to a tunnel and a passenger car increased. Thus, the aerodynamic effect of a coupled train should be considered as an important parameter in the early design state of a new high-speed train.

Numerical Analysis of the Effect of Misaligned Guide Vanes on Improving S-Shaped Characteristics for a Pump-Turbine

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Xiao Yexiang ◽  
Zhu Wei ◽  
Wang Zhengwei ◽  
Zhang Jin ◽  
Ahn Soo-Hwang ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Flow Behavior ◽  
Internal Flow ◽  
Operating Conditions ◽  
Guide Vanes ◽  
Electrical Grid ◽  
Runner Blade ◽  
Discharge Rates ◽  
Unit Speed

The S-shaped characteristic curves in pump-turbines complicate synchronization with the electrical grid and affect system safety. Misaligned guide vanes (MGVs) are one of the most effective solutions to avoid S-shaped characteristics. The internal flow mechanism with the MGV for improving S-shaped characteristics was studied by numerical analysis. Six operating conditions were modeled in the S-shaped region. Four guide vanes were arranged as the MGVs to qualitatively and quantitatively analyze the flow behavior. The internal flow was quite complex at the four operating points without the MGV; here, the attack angle and the flow behavior had no obvious difference at each vane. For the similar conditions with MGVs, attack angles and internal flow fields varied clearly at each vane, especially in the vaneless region and in the runner blade passages. For the same discharge rates, total openings, and rotating speeds, the internal flows were quite different between with and without the MGVs. The MGVs disrupt the high-speed circumferential water ring (appreciably faster compared to the main flow) in the vaneless region and maintain operation with higher unit speeds. Consequently, the unit speed is larger at the same unit discharge in the S-shaped region. Therefore, the MGV method can reduce S-shaped characteristics.

Validation of CFD-MBD FSI for High-Fidelity Simulations of Full-Scale WAM-V Sea-Trials with Suspended Payload

2015 ◽  
Author(s):  
Maysam Mousaviraad ◽  
Michael Conger ◽  
Frederick Stern ◽  
Andrew Peterson ◽  
Mehdi Ahmadian
Keyword(s):  
Second Generation ◽  
Full Scale ◽  
Average Error ◽  
High Fidelity ◽  
Time Step ◽  
Single Wave ◽  
Head Waves ◽  
Calm Water ◽  
Rough Water ◽  
V Wave

High-fidelity CFD-MBD FSI (Computational Fluid Dynamics - Multi Body Dynamics Fluid-Structure Interaction) code development and validation by full-scale experiments is presented, for a novel hull form, WAM-V (Wave Adaptive Modular Vessel). FSI validation experiments include cylinder drop with suspended mass and 33-ft WAM-V sea-trials. Calm water and single-wave sea-trails were with the original suspension, while the rough-water testing was with a second generation suspension. CFD Ship-Iowa is used as CFD solver, and is coupled to Matlab Simulink MBD models for cylinder drop and second generation WAM-V suspension. For 1DOF cylinder drop, CFD verification and validation (V&V) studies are carried out including grid and time-step convergence. CFD-MBD results for 2DOF cylinder drop show that 2-way coupling is required to capture all important physics. Overall, 2-way results are validated with an overall average error value of E=5.6%DR for 2DOF cylinder drop. For WAM-V in calm water, CFD-MBD 2-way results for relative pod angle are validated with E=16.3%DR. For single-wave, CFD-MBD results show that 2-way coupling significantly improves the prediction of the peak amplitude in pontoon motions, while the trough amplitudes in suspension motions are under-predicted. The same under-prediction is observed in EFD-MBD (un-coupled MBD), likely due to using second generation suspension properties. The current CFD-MBD 2-way results for single-wave are validated with E=19.8%DR. For rough-water, simulations are carried out in regular head waves representative of the irregular seas. CFD-MBD 2-way results are validation with E=23%D for statistical values and the Fourier analysis results, which is reasonable given the differences between simulation waves and experiments.

Comments on the Structural Design of High Speed Craft

1995 ◽  
Vol 32 (02) ◽  
pp. 77-100
Author(s):  
Joseph G. Koelbel
Keyword(s):  
Structural Properties ◽  
Structural Design ◽  
High Speed ◽  
Structural Member ◽  
Calculation Methods ◽  
Rough Water ◽  
History Of ◽  
Vertical Accelerations ◽  
Materials Used

A brief discussion of materials used in the construction of small high speed craft is given along with a history of the calculation of hydrodynamic bottom loads. Calculation methods currently in use are reviewed, including those for added drag in waves, vertical accelerations in rough water, total bottom load, load on each structural member, and the required structural properties of the member. In particular, a discussion of the uncertainty inherent in these methods is presented, as well as a recommendation for a somewhat simpler approach which removes some of the uncertainty, and additional recommendations for the improvement of several details of the procedure.

Sign in / Sign up

Export Citation Format

Share Document