10:30
Ship hydromechanics resistance I
Chair: Tom van Terwisga
10:30
30 mins
|
VALIDATION OF A SIMPLE AERODYNAMIC MODEL CAPABLE TO PREDICT THE INTERACTION EFFECTS OCCURRING BETWEEN TWO GENERIC WIND PROPULSION SYSTEMS
Giovanni Bordogna, Jan Alexander Keuning, Rene' Herman Maria Huijsmans, Fabio Vittorio Fossati, Marco Belloli
Abstract: In recent years wind-assisted propulsion for commercial ships has gained an increasing interest as valuable alternative to reduce fuel pollutant emissions. However, the development of feasible and commercially viable wind propulsion systems to partially (or fully) propel a ship is nowadays hindered by the difficulties of modelling the complicated aerodynamic and hydrodynamic aspects involved. From an aerodynamic point of view, it appears that one of the main challenges of predicting the performance of a wind-assisted ship, is to properly evaluate the interaction effects that occur between the various wind propulsion systems mounted on the deck of the ship.
This research deals with the validation of a simple and quick-to-use aerodynamic model that is capable of evaluating such effects, i.e. upwash, downwash and wake, occurring between two generic propulsion systems placed at any given relative position on the ship's deck. The wind propulsion systems might assume any given angle of attack; the flow can be attached as well as separated. Such aerodynamic model, that was first presented in [1], consists of the horseshoe vortex method modified with semi-empirical formulas to take into account the effects of viscosity.
First, the results provided by the aerodynamic model were compared with results obtained by using more sophisticated tools, i.e. a CFD body force model and RANS CFD. Then, experimental validation was carried out by means of dedicated wind-tunnel tests.
It can be concluded that, despite the simplicity of the aerodynamic model employed, it proved to give reasonable results when compared to more sophisticated tools and to experimental data.
REFERENCES
[1] K. Roncin and J.M. Kobus, “Dynamic simulation of two sailing boats in match racing”, Sports Engineering , Vol. 7, pp. 139152, (2004).
|
11:00
30 mins
|
A STUDY ON THE PROPULSIVE PERFORMANCE OF HI-FIN
Soo-Yeong Park, Bum-Woo Han, Bong-Jun Chang
Abstract: With the increased interest in fuel saving technologies for ships, many kinds of energy saving devices (ESDs) have been developed and applied. Hi-Fin is a kind of energy saving device that has fin on the propeller boss cap which eliminates the hub vortex induced by propeller rotation as well as increases in propulsive efficiency. The aim of this study is to investigate the effects of Hi-Fin using computational fluid dynamics (CFD). To verify the results of numerical analysis, propeller wake fields were measured by stereoscopic particle image velocimetry (SPIV) and self-propulsion test has been performed in Hyundai Maritime Research Institute (HMRI). The result shows a good agreement between calculations and measurements in model scale.
|
11:30
30 mins
|
HYDRODYNAMICS OF WIND-ASSISTED SHIP PROPULSION VERIFICATION AND VALIDATION OF RANS METHODOLOGY
Nico van der Kolk, J.A. Keuning, R.H.M. Huijsmans
Abstract: Wind energy as an auxiliary form of propulsion for commercial ships has again become of great interest as a possible response to volatile fuel prices and increasingly stringent environmental regulations. A well-founded performance prediction tool is a key prerequisite for the further development of this promising technology, and with the support of the European Commission and others, a group of researchers at Delft University of Technology is developing a performance prediction program for these hybrid ships. Reynolds-Averaged Navier Stokes (RANS) packages will be one of the primary tools used during the study. The advent of the numerical towing tank brings possibilities but also new challenges. The predominance of large, separated flow structures in the wake of the sailing ship, and the particular interest in the transverse force component points to a conscientious grid verification and validation study. Here, it is sufficient to achieve parity for absolute uncertainty within the larger context of the project. The ‘drift sweep’ procedure is presented with validation levels alongside computational time to demonstrate the utility of this approach in support of the derivation of empirical formulations using systemic hull form variations. Finally, a moving mesh for the rudder may be implemented in an extended drift/rudder sweep. However for this case there is no validation data presently available.
|
|
