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Modeling of planing craft in waves
KTH, Superseded Departments, Aeronautical and Vehicle Engineering.ORCID iD: 0000-0002-9110-9401
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Simulation of the planing hull in waves has been addressed during the last 25 years and basically been approached by strip methods. This work follows that tradition and describes a time-domain strip model for simulation of the planing hull in waves. The actual fluid mechanical problem is simplified through the strip approach. The load distribution acting on the hull is approximated by determining the section load at a number of hull sections, strips. The section-wise 2-dimensional calculations are expressed in terms of added mass coefficients and used in the formulations of both inertia and excitation forces in the equations of motions. The modeling approach starts from the hypothetic assumption that the transient conditions can be modeled based on those section-wise calculations. The equation of motion is solved in the time-domain. The equation is up-dated at each time step and every iteration step with respect to the momentary distribution of section draught and relative incident velocity between the hull and water and catches the characteristic non-linear behavior of the planing craft in waves.

The model follows the principles of the pioneering work of E. E. Zarnick differing on model structure and in details such as the modeling of the lift in the transom area. A major part of the work is concerned with experiments and evaluation of simulations with respect to performed model tests and to published experiment data. Simulations of model tests have been performed and comparisons have been made between measured and simulated time series. The link between simulation and experiment is a wave model which is based on a wave height measurement signal. It is developed and evaluated in the thesis.

The conclusions are in favor of the 2-dimensional approach to modeling the conditions for the planing hull in waves and among further studies is evaluation of simulated loads and motions to full-scale trial measurement data.

Place, publisher, year, edition, pages
Stockholm: Farkost och flyg , 2004.
Series
Trita-AVE, ISSN 1651-7660 ; 2004:34
Keyword [en]
Hydraulic engineering, marine, ocean, Planing craft, time-domain simulation, design loads
Keyword [sv]
Vattenteknik
National Category
Water Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14ISBN: 91-7283-861-2 (print)OAI: oai:DiVA.org:kth-14DiVA: diva2:7256
Public defence
2004-10-14, Kollegiesalen, KTH, Valhallavägen 79, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2012-03-20
List of papers
1. A method to analyse seakeeping model measurements in time domain
Open this publication in new window or tab >>A method to analyse seakeeping model measurements in time domain
1999 (English)In: Proceedings of the 1999 Ninth International Offshore and Polar Engineering Conference (Volume 3), 1999, 629-634 p.Conference paper, Published paper (Refereed)
Abstract [en]

The paper introduces a method to determine a wave equation from a measured wave system. The method is applied to wave measurements recorded in a seakeeping experiment. The obtained wave equations accurately repeat the wave gauge signals. The wave equation provides a link between a numerical and physical model test. This is verified for heave and pitch motions of the ship model in regular and irregular waves. Time domain simulation with the wave equation and initial conditions from the model test, gives motion time series in good agreement with the measurements.

Keyword
Seakeeping, Ship motion, Wave equation, Wave measurement
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4963 (URN)1880653427 (ISBN)
Conference
Ninth International Offshore and Polar Engineering Conference; Brest; 30 May 1999 through 4 June 1999
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2011-09-02Bibliographically approved
2. Time-domain simulations and full-scale trials on planing craft in waves
Open this publication in new window or tab >>Time-domain simulations and full-scale trials on planing craft in waves
2003 (English)In: International Shipbuilding Progress, ISSN 0020-868X, E-ISSN 1566-2829, Vol. 50, no 3, 177-208 p.Article in journal (Refereed) Published
Abstract [en]

A time-domain simulation model for prediction of global response of planing craft in waves is presented. The simulation model is based on 2-dimensional potential theory, and by updating the hydrodynamic coefficients at each time step, taking the momentary section draught into account, the solution is non-linear. For evaluation captive model tests and full-scale trials that have been performed. Characteristic results from the full-scale trials are reviewed and discussed. The simulations are also validated with published model experiments. The agreement between simulations and experiments is generally good except for discrepancies in pitch moment and motion. The 2-dimensional approach is attractive from a computational cost point of view and it is believed that an adequate simulation model could be developed from the presented model by better modelling of the pressure at transom.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4964 (URN)
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2017-12-05Bibliographically approved
3. Model Experiment Addressing the Impact Pressure Distribution on Planing Craft in Waves
Open this publication in new window or tab >>Model Experiment Addressing the Impact Pressure Distribution on Planing Craft in Waves
2004 (English)In: International Journal of Small Craft Technology, ISSN 1740-0694, Vol. 146Article in journal (Refereed) Published
Abstract [en]

The aim of the experiment was time-domain monitoring and analysis of the pressure distribution on planing craft inwaves. A model was instrumented with pressure transducers and towed in calm water, head and oblique regular andirregular waves. The transducers were concentrated to a fore matrix to capture the impact loads and an aft matrix tofollow the pressure in the transom area. In waves, the propagation of the pressure enabled a reconstruction of the impactpressure distribution time history from the transducer signals. The impact loads determined as the integratedreconstructed pressure were compared with inertia forces determined from accelerometer signals. Correlation was clearand verified the reconstruction method and the instrumentation in terms of transducer matrix position, size and density.Besides pressure and accelerations, rigid body motions, speed, wave height and resistance were measured. The paper describes the set-up, discusses difficulties concerning model hull rigidity, sampling frequencies and signal analysis, and shows on characteristic results. The paper concludes that detailed time-domain studies of the impact pressure distribution are accessible from the set-up and the suggested analysis methods.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-4965 (URN)10.3940/rina.ijsct.2004.b1.15041 (DOI)
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2011-09-20Bibliographically approved
4. Improved Time-Domain Simulation of Planing Hulls in Waves by Correction of the Near-Transom Lift
Open this publication in new window or tab >>Improved Time-Domain Simulation of Planing Hulls in Waves by Correction of the Near-Transom Lift
2005 (English)In: International Shipbuilding Progress, ISSN 0020-868X, E-ISSN 1566-2829, Vol. 52, no 3, 201-230 p.Article in journal (Refereed) Published
Abstract [en]

Time-domain simulation, based on 2-dimensional high-frequency added mass formulation of the sectional forces, is a computationally attractive approach to the non-linear behaviour of the planing craft in waves. Nevertheless, the 2-dimensional strip approach, demands for corrections of the lift distribution in order to correctly model the running attitude which is significant for the loads and motions for planing craft in waves. This has traditionally been made by a reduction of the hydrostatic lift and moment with reference to the geometrical fact that the transom stern is dry. This action improves the simulation of the running attitude in calm water but not necessarily of the dynamic behaviour in waves. The paper proposes a correction operating on both the hydrostatic and the hydrodynamic terms of the load distribution. A reduction function is chosen on the basis of model test measurements of the near-transom pressure, and on published model data on running attitude. The approach is satisfactory validated in calm water, regular and irregular waves. Simulations of model experiments and comparison with measurement time series are presented. The correction improves the simulation in both calm water and in waves for a wider speed range compared to a correction limited to the hydrostatic terms.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-4966 (URN)2-s2.0-24944492239 (Scopus ID)
Available from: 2004-10-08 Created: 2004-10-08 Last updated: 2017-12-05Bibliographically approved

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