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1
Content available Experimental study on dynamic structure of propeller tip vortex
Li Guangnian, Chen Qingren, Liu Yue
Polish Maritime Research
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2020
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nr 2
11--18
EN
Propeller cavitation is a main source of fluctuating pressure and noise induced by propellers, and the tip vortex cavitation is the principal source. The present study measures the flow fields near the blade tip using the 2D-PIV technique. The experimental setup and scheme are introduced. We monitor the process of generation and shedding of the propeller tip vortex in real time and analyse the dynamic structure of the tip vortex by testing the propeller wake field under different phases of the axial plane. The distribution characteristics of radial and axial velocity are also analysed. The influence range and the vorticity of the tip vortex and trailing vortex are obtained. All of the measured quantitative data are useful for future propeller design.
2
Content available Effects of boundary layer control method on hydrodynamic characteristics and tip vortex creation of a hydrofoil
Ghadimi P., Araz-Tanha A., Nemati-Kourabbasloo N., Tavakoli S.
Polish Maritime Research
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2017
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nr 2
27--39
EN
There is currently a significant focus on using boundary layer control (BLC) approach for controlling the flow around bodies, especially the foil sections. In marine engineering this is done with the hope of increasing the lift – to – drag ratio and efficiency of the hydrofoils. In this paper, effects of the method on hydrodynamic characteristics and tip vortex formation of a hydrofoil are studied. Steady water injection at the tip of the hydrofoil is simulated in different conditions by using ANSYS-CFX commercial software. Validity of the proposed simulations is verified by comparing the obtained results against available experimental data. Effects of the injection on the lift, drag, and lift – to – drag ratio are studied and the ranges within which the injection has the most positive or negative effects, are determined. Furthermore, flow pattern and pressure variation are studied upon the water injection to determine the most positive and negative case and to ascertain the main reasons triggering these phenomena.
3
Content available remote Numerical analysis of the tip vortex in an air-conditioner's propeller fan
Wang J., Wu K.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2006
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Vol. 10, No 2
101-112
EN
A steady, incompressible, turbulent flow field inside a propeller fan used in an air conditioner has been analyzed numerically using the single-equation Spalart-Allmaras turbulence model. It has been found that the formation of tip vortex starts from the blade tip's suction side at about one third of the axial chord's length aft of the rotor's leading edge. It is due to the rolling-up of the intense shear layer flow between the main axial flow and the suck-in inward flow caused by the large pressure difference between the pressure and the suction sides. The tip vortex passes through the blade passage in a curve reversed towards the direction of the blade's rotation. Its trace is partial to the tangential direction as it goes into the aft part of the blade passage covered by the shroud and, simultaneously, its trace in the radial direction is turned from the outward direction to the inward direction. The operating flow rates have an important effect on the axial position of the tip vor-tex's trace, while its effect on the radial position is negligible. At law flow rates, the vortex disappears at a location closer to the leading edge. The effect of the shroud's width on the tip vortex's trajectory is notable. For a fan with a wide shroud, the trace of the tip vortex moves upstream with a smaller radial influence region than that of a fan with a narrower shroud.
4
Content available remote Effect of background flow on helical jet characteristics.
Wojciechowski Jan, Szumowski Andrzej
Archive of Mechanical Engineering
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2001
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Vol. 48, nr 4
319-327
EN
Helical jet in moving air was used to simulate the flow downstream of a helicopter blade tip or a wing tip. The jet was generated by means of an opened pipe supplied tangentially (tangential nozzle) and placed in a wind tunnel. Flow properties were investigated in several cross-sections downstream of the nozzle. The flow direction and the total pressure were measured in function of the azimuthal angle and the distance from the axis of the system. The flow was visualized using the planar laser scatering technique. The decay of swirl intensity was measured by means of a probe with a rotating plate fixed to a miniature voltage generator.
PL
Przedmiotem badań jest strumień wirowy o niesymetrycznym (helicalnym) rozkładzie prędkości poruszający sie w jednorodnym polu przepływu. Strumień wytwarzany jest w dyszy zasilanej stycznie do jej obwodu; umieszczony w przestrzeni pomiarowej tunelu aerodynamicznego. Wypływający z dyszy strumień helikalny jest rozpatrywany jako model wiru krawędziowego generowanego na zakończeniu płata nośnego, np. łopaty helikoptera lub skrzydła samolotu. W pracy badane są struktury przepływu w wybranych przekrojach strumienia poprzez pomiary kierunków prędkości, ciśnienia całkowitego oraz wizualizację metodą noża świetlnego. Zanikanie wirowości strumienia w miarę jego rozprzestrzeniania się badane jest przy użyciu płytki napędzającej miniaturowy generator napięcia.
5
Content available remote Active control of tip vortex sheeding.
Szumowski Andrzej, Litwińczyk Mieczysław
Archive of Mechanical Engineering
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2001
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Vol. 48, nr 3
265-275
EN
A helicopter blade tip vortex generates impulsive noise of high intensity when it impinges upon the following blade. In the present work, the vortex is attenuated by coaxial swirling jet rotating in the opposite direction. The jet issues from a nozzle located at the blade tip. The nozzle was supplied with compressed air transported in the blade channel. The decrement of vortex strength is measured as a function of the compressed air pressure related to the dynamic pressure of the flow in the wind tunnel. It was found that the jet, even and relatively low intensity, considerably effects the blade tip vortex formation.
PL
Wir krawędziowy spływający z końcówk łopaty helikoptera w pewnych fazach jego lotu oddziaływuje z kolejną łopatą. W wyniku generowany jest intensywny hałas o charakterze impulsowym. W pracy, do tłumienia wiru zastosowano współosiowy strumień zawirowany o przeciwnym niż wir kierunku rotacji. Strumień wytwarzany jest w dyszy umieszczonej na końcu łopaty zasilanej sprężonym powietrzem przesyłanym kanałem we wnętrzu dźwigara łopaty. W wyniku badań wyznaczono zależność względnego natężenia wiru mierzonego w odległości jednej cięciwy od krawędzi opływu, w funkcji stosunku ciśnienia zasilania dyszy do ciśnienia dynamicznego w przestrzeni pomiarowej tunelu aerodynamicznego. Stwierdzono, że nawet względnie słaby strumień zawirowany wdmuchiwany do rdzenia wiru krawędziowego powoduje istotne osłabienie tego wiru.
6
Content available remote Theoretical and experimental investigation of the generation mechanism of tip vortex and vortex cavitation
Koronowicz T., Tuszkowska T., Wilczyński L.
Polish Maritime Research
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2000
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Vol. 7, nr 2
3-7
EN
The paper presents the problem of tip vortex cavitation inception in the flow around a screw propeller. The most recent experimental and theoretical results concerning mechanisms of tip vortex generation and vortex cavitation inception are reported.
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