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Brodogradnja : An International Journal of Naval Architecture and Ocean Engineering for Research and Development, Vol. 69 No. 1, 2018.

Original scientific paper

PROBING INTO THE EFFECTS OF CAVITATION ON HYDRODYNAMIC CHARACTERISTICS OF SURFACE PIERCING PROPELLERS THROUGH NUMERICAL MODELING OF OBLIQUE WATER ENTRY OF A THIN WEDGE

Nasrin Javanmardi ; Dept. of Marine Technology, Amirkabir University of Technology, Tehran, Iran
Parviz Ghadimi orcid id orcid.org/0000-0002-9315-5428 ; Dept. of Marine Technology, Amirkabir University of Technology, Tehran, Iran
Sasan Tavakoli orcid id orcid.org/0000-0003-3155-2628 ; Dept. of Marine Technology, Amirkabir University of Technology, Tehran, Iran

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Abstract

The current paper investigates flow around a blade section of a surface piercing hydrofoil. To this end, a thin wedge section is numerically modelled through an oblique water entry. The flow is numerically studied using a multiphase approach. The proposed numerical approach is validated in two steps. First, pressure and free surface around a wedge entering water are simulated and compared against previously published analytical results. Subsequently, cavitation phenomenon around a submerged supercavitating hydrofoil is modelled and analyzed. It is observed that cavity length, pressure, and lift force are accurately predicted. Subsequently, the main problem has been studied for two different cavitation numbers for a range of advanced ratios equivalent to fully, transition and partially ventilated conditions in order to investigate the effect of ambient pressure on hydrodynamics of the water entry of the foil. The numerical findings reveal that, when the cavitation number decreases, the start of transition mode is postponed and this mode is expanded for the larger range of velocity ratios. This implies that fully ventilated velocity ratio modes are expanded, too. However, in the transition mode, the cavitation number plays an essential role and may lead to a decrease in the pressure difference across the surface piercing hydrofoil which yields a decrease in the resultant force.

Keywords

Surface piercing propeller; oblique water entry; thin wedge; Cavitation number; Numerical modelling

Hrčak ID:

190223

URI

https://hrcak.srce.hr/190223

Publication date:

31.3.2018.

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