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Author : J. A. Keuning
Results 1 - 5 of 17
Hydrodynamics of Wind-Assisted Ship Propulsion Validation of RANS-CFD Methodology
A Reynolds-Averaged Navier Stokes computational fluid dynamics (RANS-CFD) package will be one of the primary tools used during the development of a performance prediction program for Wind- Assisted commercial ships. The modelling challenge presented by large separated flow structures in the wake of the sailing ship points to a conscientious validation study. A validation data set, consisting of hydrodynamic forces acting on the ship sailing with a leeway angle, was collected at the Delft University of Technology towing tank facility, for bare-hull and appended cases. Four hull geometries were selected to represent of the Delft Wind-Assist Systematic Series. Appended cases were designed to represent a broad range of appendage topologies: Rudder, Bilge-keels, Skeg, and Barkeel. The direct validation exercise for the bare-hull case was successful, with the validation level for the sideforce equal to 9.5% (fine mesh: 9M cells). An extended validation statement is made for simulations for the entire series. This exercise was successful for leeway angles equal to = [3 , 6 ]. The validation level (base mesh, 3M cells) for each force component is: ′=12%, ′=17%, ′=10%. The validation for appended geometries was not regarded as successful, with the exception of the Rudder case. The numerical uncertainty is the dominant contribution for the validation level, motivating a proportionate refinement of the grid. Here, it is sufficient to achieve parity with other contributions to the uncertainty within the larger context of the project.
The Influence of Heel on the Bare Hull Resistance of a Sailing Yacht
For the useful prediction of the performance of a sailing yacht using a generic Velocity Prediction Program (VPP) an accurate assessment of the hydrodynamic and aerodynamic forces and moments involved is essential...
A new Method for the Prediction of the Side Force on Keel and Rudder of a Sailing Yacht based on the Results of the Delft Systematic Yacht Hull Series
Since the first introduction of an expression for the assessment of the side force production of a sailing yacht as function of leeway and heel, based on the results of the Delft Systematic Yacht Hull Series, in 1981, considerable changes in appendage layouts and planforms have taken place. The side force production as function of the leeway and heel played only a very limited role in the present VPP calculations and remained therefore for many years somewhat undervalued. The last years more attention has been paid to the subject in particular caused by the necessity to asses the yaw balance of (large) sailing yachts and the introduction of maneuvering models for yachts under sail. This report shows the developments and presents a new assessment model which yields far better results for a large variety of appendages. The results of this study are presented in the present paper.
A Bare Hull Resistance Prediction Method Derived from the Results of the Delft Systematic Yacht Hull Series Extended to Higher Speeds
Since 1975 several regression based polynomial
expressions have been presented to enable the assessment
of the (bare hull) residuary resistance of a sailing yacht
all using the database obtained from the results of the
Delft Systematic Yacht Hull Series (DSYHS)...
Further Analysis of the Forces on Keel and Rudder of a Sailing Yacht
In order to be able to calculate the forces on the keel and rudder of a sailing yacht more is to be known
about their interaction. Both for determining the yaw balance of a sailing yacht as for the maneuvering it is
of importance to have a good assessment on these forces because they determine the yaw moment to a large
extent.
Therefore a research project was set up in the Delft Shiphydromechanics Department to investigate the
influence of the keel on the rudder. Aim was to improve on the side force prediction of keel and rudder and
to assess the wake of the keel and the downwash on the rudder in various conditions. Based on the
measured results the the previous developped formulation within the DSYHS for the keel residuary
resistance is validated and a new formulation for the downwash behind the keel is presented. In addition
the expression within the DSYHS for the sideforce on the yacht is improved for higher aspect ratios.