• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.23-30
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• 2001

The cavitation noise of high-speed propellers was experimentally studied using new measurement device in KRISO cavitation tunnel. A series of cavitation noise tests were carried out for 6 propellers with various sections, loading distributions, and a different area ratio. From the experimental results, the noise characteristics for various cavitation patterns and the noise performance for a series of propellers were analyzed. These can be used for full-scale prediction study of the noise and optimum design of high-speed propellers.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.12-19
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• 2021

An experimental study was performed for a cavitating venturi supplying a constant rate of flow independent of downstream pressure fluctuations when providing liquid propellant. The venturi was designed and manufactured in order to figure out the performance of the cavitating venturi. Effects of the rear-end shape, upstream pressure, and back pressure on the ratio of downstream to upstream pressure of the venturi as well as the flow-rate were observed. As a result, critical pressure ratio of the venturi, which generally depends only on the configuration of the venturi, was kept at 0.74 regardless of the rear-end shape and the upstream pressure of the venturi.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.52-68
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• 1991

A new propeller series is developed using the newly developed blade section(KH18 section) which behaves better cavitation characteristics and higher lift-drag ratio at wide range of angle-of-attack. The pitch and camber distributions are disigned in order to have the same radial and chordwise loading distribution with the selected circumferentially averaged wake input. Since the geometries of the series propeller, such as chord length, thickness, skew and rate distribations, are selected by regression of the recent full scale propeller geometric data, the performance prediction of a propeller at preliminary design stage can be mure realistic. Number of blades of the series propellers is 4 and the expanded blade area ratios are 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are selected as 0.5, 0.65, 0.8, 0.75 and 1.1 for each expanded area ratio. The new propeller series is composed of 20 propellers and is named as KD(KRISO-DAEWOO) propeller series. Propeller open water tests are performed at the experimental towing tank, and the cavitation observation tests and fluctuating pressure measurements are carried out at the cavitation tunnel of KRISO. $B_{P}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller often water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The caviy extent of a propeller can be predicted more accurately by using the KD-cavitation chart at a preliminary design stage, since it is derived from the results of the cavitation observation tests in the selected ship's wake, whereas the existing cavitation charts, such as the Burrill's cavitation chart, are derived from the test results in uniform flow.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.60-66
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• 2000

In order to improve cavitation characteristics for a high-speed propeller, leading edge shape of a 2-D hydrofoil is investigated numerically and experimentally. For flowfield analysis around the leading edge, the incompressible Reynolds Averaged Navier-Stokes(RANS) equation is solved using the standard $k-\varepsilon$ turbulence model and a finite volume method(FVM). The cavitation thickness, which is occurred on hydrofoil surface, is predicted using the panel code. It is shown that the calculation codes predict the experimental trend fairly well. From these results, new hydrofoils are designed

• Journal of the Society of Naval Architects of Korea
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• v.37 no.2
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• pp.22-29
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• 2000

The cavitation noised of high-speed propellers was experimentally studied in KRISO cavitation tunnel. In this paper, a series of cavitation noise tests were carried out for five propellers with various sections and loading distributions. From the experimental results, the noise characteristics of various cavitation pattern and the noise performance of the propellers were analyzed. There can be used for optimum design for high-speed propellers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.50-55
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• 2015

This study examined the relationship between the shape of the inside of the PRV and the cavitation of the water supply system of an apartment house. In this paper, nine types of PRV with different gaps and shapes were analyzed numerically using a 3D model embedded in the commercial code, ANSYS-CFX. The lowest pressure and the maximum velocity occurred at the narrow gap, which is located at the between the stem and the disk. When the gap size was increased, the vapor volume fraction was always greater than 0, but the vapor volume fraction of the type of expansion pipe approached 0. These results indicate that the cavitation of PRV can be reduced by a shape change to the type of expansion pipe.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1170-1174
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• 2014

If cavitation occurs in propeller, it generates vibration and noise accordingly which results in low efficiency of propeller. It's important to increase cavitation inception speed(CIS) since the noise of cavitation increases significantly from the beginning of cavitation. This paper describes the result of actual observation and measurement onboard ship with controllable pitch propeller(CPP), so as to verify the first occurrence phenomenon of cavitation. The research suggests new type of controllable pitch propeller with improved CIS at the bolt as it started with bolt cavitation as result of observation. It's not found bolt cavitation on the CPP proposed in this paper, furthermore its CIS is increased approximately by 4.5 knots than the existing CPP. The result of the research can be used for development of low-noise CPP and improving performance of CIS.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.84-93
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• 1994

The purpose of present study is to investigate the surface roughness on tip-vortex cavitation and its induced noise, emanating from an elliptic wing of NACA 0012 section. Roughness elements of $200{\mu}m$ are applied to the 10% portion of wing tip, and then, the wing tip as well as the leading edge. It is shown from cavitation observation that the cavitation inception is first visible at about half chord downstream of wing tip for most experimental conditions, and developed into the tip-vortex cavitation and finally the fully developed cavitation as cavitation number is decreased. Acoustic noise generated by a tip-vortex cavitation has its frequency range of 3 kHz to 50 kHz, while the fully-developed cavitation at lower cavitation number induces a broad band spectrum. It is also shown that, when the roughness elements are applied to the wing tip and the leading edge, the cavitation characteristics and its induced noise are improved. Moreover, it is appeared that the condition at which the rough surface is at pressure side gives a better result. although its lift-drag ratio is reduced.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.243-249
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• 2023

The occurrence of cavitation on the propeller is directly linked to the naval ship's survivability, and it is necessary to design a propeller shape that delays the cavitation inception. However, the propeller cavitation can occur under various operating conditions, thus it is important to identify whether the propeller cavitation exists during operation as well as in the design phase. To this end, it is necessary to use noise or vibration signals on board to monitor the cavitation inception. In this study, a hydrophone and an accelerometer were installed on the ship hull right above the propeller to compare the performance of analyzing cavitation inception between acoustic and vibration signals. Also, a high speed camera was used to visually observe the occurrence of cavitation through an observation window. The measured results showed that the spectral shapes between acoustic and vibration signals were different, but the level increases at each frequency band and the overall level of the frequency band from 1 kHz to 10 kHz showed a similar tendency. The Detection of Envelope Modulation On Noise (DEMON) analysis also showed similar results for both acoustic and vibration signals, confirming that both hydrophones and accelerometers can be utilized in the analysis of cavitation inception.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.72-75
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• 2003

In this research, we focused on the effects of the orifice internal flow such as cavitation and hydraulic flip. The breakup characteristics such as the breakup length and trajectory were measured by changing the orifice diameter (d), the orifice length/orifice diameter (L/d), the injection pressure and the shapes (sharp and round) of orifice entrance to provide a lot of conditions of the orifice internal flow. It is found that cavitation bubbles that occur inside the sharp-edged orifice make the liquid jet ejecting from the orifice turbulent. In the orifices (L/d = 5), the hydraulic flip phenomenon is shown when the injection pressure is high. In case cavitation occurs it breaks up more earlier than that in case of non-cavitation. In case hydraulic flip occurs, since the area of the liquid jet becomes small, the breakup length is also small as that in case of cavitation. But the liquid column trajectories have a similar tendency irrespective of cavitation.