Aspects of the Modelling of the Inception of Tip Vortex Cavitation

2008 ◽  
Author(s):  
S J P Watson ◽  
◽  
P W Bull ◽  
Keyword(s):  
Tip Vortex ◽  
Tip Vortex Cavitation

Noise due to extreme bubble deformation near inception of tip vortex cavitation

2004 ◽  
Vol 16 (7) ◽  
pp. 2411-2418 ◽  
Author(s):  
Jin-Keun Choi ◽  
Georges L. Chahine
Keyword(s):  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Bubble Deformation

Application of a Boundary Element Method in the Prediction of Unsteady Blade Sheet and Developed Tip Vortex Cavitation on Marine Propellers

2004 ◽  
Vol 48 (01) ◽  
pp. 15-30
Author(s):  
Hanseong Lee ◽  
Spyros A. Kinnas
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Pressure Fluctuations ◽  
Ship Hull ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Marine Propellers ◽  
Sheet Cavitation ◽  
Numerical Predictions ◽  
Element Method

Most marine propellers operate in nonaxisymmetric inflows, and thus their blades are often subject to an unsteady flow field. In recent years, due to increasing demands for faster and larger displacement ships, the presence of blade sheet and tip vortex cavitation has become very common. Developed tip vortex cavitation, which often appears together with blade sheet cavitation, is known to be one of the main sources of propeller-induced pressure fluctuations on the ship hull. The prediction of developed tip vortex cavity as well as blade sheet cavity is thus quite important in the assessment of the propeller performance and the corresponding pressure fluctuations on the ship hull. A boundary element method is employed to model the fully unsteady blade sheet (partial or supercavitating) and developed tip vortex cavitation on propeller blades. The extent and size of the cavity is determined by satisfying both the dynamic and the kinematic boundary conditions on the cavity surface. The numerical behavior of the method is investigated for a two-dimensional tip vortex cavity, a three-dimensional hydrofoil, and a marine propeller subjected to nonaxisymmetric inflow. Comparisons of numerical predictions with experimental measurements are presented.

Observation and Scaling of Tip Vortex Cavitation on Elliptical Hydrofoils

2011 ◽  
Author(s):  
Shigeki Nagaya ◽  
Risa Kimoto ◽  
Kenji Naganuma ◽  
Takayuki Mori
Keyword(s):  
Water Quality ◽  
Reynolds Number ◽  
High Speed ◽  
Tip Vortex ◽  
Video Observation ◽  
Tip Vortex Cavitation ◽  
Air Content ◽  
Sheet Cavitation ◽  
High Speed Video ◽  
Systems Research

Experimental study on tip vortex cavitation (TVC) was carried out for elliptical hydrofoils with various chord lengths. The purpose of the experiment was to clarify the influences of Reynolds number and water quality on tip vortex cavitation. Experiments were made in a large cavitation tunnel of the Naval Systems Research Center, TRDI/Ministry of Defense Japan. The elliptical hydrofoils tested were NACA 0012 cross section with chord lengths of 500mm, 250mm and 50mm. Reynolds number based on hydrofoil chord length was 2×105 < ReC < 7.4×106. Water quality of the tunnel was characterized by air content and nuclei distribution. Air content of the tunnel was varied between 30% and 80%. Nuclei distribution was measured by a cavitation susceptibility meter (CSM) with center-body venturi. Cavitation inception was determined from high speed video observation. A standard formula, (σL/σS) = (ReL/ReS)n, was applied for the scaling. In the present study, exponent of the scaling law n was found to be 0.2 < n < 0.4. High speed video observation showed that the process of the TVC inception strongly depends on water quality. In the experiments, unsteady behaviors of TVC were also investigated. Strong interactions between sheet cavitation and TVC were observed.

scholarly journals Numerical Investigation of Tip-Vortex Cavitation Noise of an Elliptic Wing Using Coupled Eulerian-Lagrangian Approaches

2020 ◽  
Vol 10 (17) ◽  
pp. 5897 ◽  
Author(s):  
Garam Ku ◽  
Cheolung Cheong ◽  
Hanshin Seol
Keyword(s):  
Flow Field ◽  
Numerical Method ◽  
Vortex Flow ◽  
Acoustic Pressure ◽  
Tip Vortex ◽  
Experimental Result ◽  
Cavitation Noise ◽  
Navier Stokes Equation ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

In this study, a numerical methodology is developed to investigate the tip-vortex cavitation of NACA16-020 wings and their flow noise. The numerical method consists of a sequential one-way coupled application of Eulerian and Lagrangian approaches. First, the Eulerian method based on Reynolds-averaged Navier–Stokes equation is applied to predict the single-phase flow field around the wing, with particular emphasis on capturing high-resolution tip-vortex flow structures. Subsequently, the tip-vortex flow field is regenerated by applying the Scully vortex model. Secondly, the Lagrangian approach is applied to predict the tip-vortex cavitation inception and noise of the wing. The initial nuclei are distributed upstream of the wing. The subsequent time-varying size and position of each nucleus are traced by solving spherically symmetric bubble dynamics equations for the nuclei in combination with the flow field predicted from the Eulerian approach. The acoustic pressure at the observer position is computed by modelling each bubble as a point source. The numerical results of the acoustic pressure spectrum are best matched to the measured results when the nuclei number density of freshwater is used. Finally, the current numerical method is applied to the flows of various cavitation numbers. The results reveal that the cavitation inception determined by the predicted acoustic pressure spectrum well matched the experimental result.

Block-sparse compressive localization for incipient tip vortex cavitation noise

2019 ◽  
Vol 145 (3) ◽  
pp. 1936-1936
Author(s):  
MinSeuk Park ◽  
Woojae Seong ◽  
Youngmin Choo ◽  
Yongsung Park
Keyword(s):  
Tip Vortex ◽  
Cavitation Noise ◽  
Tip Vortex Cavitation

Suppressing tip vortex cavitation by winglets

2019 ◽  
Vol 60 (11) ◽  
Author(s):  
Ali Amini ◽  
Martino Reclari ◽  
Takeshi Sano ◽  
Masamichi Iino ◽  
Mohamed Farhat
Keyword(s):  
Tip Vortex ◽  
Tip Vortex Cavitation

Tip Vortex Cavitation Inception Scaling for High Reynolds Number Applications

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Young T. Shen ◽  
Scott Gowing ◽  
Stuart Jessup
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layer Thickness ◽  
Reynolds Numbers ◽  
Present Theory ◽  
Full Scale ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
High Reynolds

Tip vortices generated by marine lifting surfaces such as propeller blades, ship rudders, hydrofoil wings, and antiroll fins can lead to cavitation. Prediction of the onset of this cavitation depends on model tests at Reynolds numbers much lower than those for the corresponding full-scale flows. The effect of Reynolds number variations on the scaling of tip vortex cavitation inception is investigated using a theoretical flow similarity approach. The ratio of the circulations in the full-scale and model-scale trailing vortices is obtained by assuming that the spanwise distributions of the section lift coefficients are the same between the model-scale and the full-scale. The vortex pressure distributions and core sizes are derived using the Rankine vortex model and McCormick’s assumption about the dependence of the vortex core size on the boundary layer thickness at the tip region. Using a logarithmic law to describe the velocity profile in the boundary layer over a large range of Reynolds number, the boundary layer thickness becomes dependent on the Reynolds number to a varying power. In deriving the scaling of the cavitation inception index as the ratio of Reynolds numbers to an exponent m, the values of m are not constant and are dependent on the values of the model- and full-scale Reynolds numbers themselves. This contrasts traditional scaling for which m is treated as a fixed value that is independent of Reynolds numbers. At very high Reynolds numbers, the present theory predicts the value of m to approach zero, consistent with the trend of these flows to become inviscid. Comparison of the present theory with available experimental data shows promising results, especially with recent results from high Reynolds number tests. Numerical examples of the values of m are given for different model- to full-scale sizes and Reynolds numbers.

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