Noise Due to Extreme Bubble Deformation Near Inception of Tip Vortex Cavitation

2003 ◽  
Author(s):  
Jin-Keun Choi ◽  
Georges L. Chahine
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Vortex Flow ◽  
Jet Noise ◽  
Video Camera ◽  
Tip Vortex ◽  
Bubble Behavior ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Bubble Deformation

A study on the tip vortex cavitation inception based on extreme bubble deformation and jet noise is presented. First, two preliminary experiments are performed to provide a correlation between the numerically computed splitting/jet noise and the measured noise. The bubble behavior and pressure signal predicted by the axisymmetric method are compared with those recorded simultaneously by using a high-speed video camera and hydrophone. Then, numerical studies on the bubble behavior in the tip vortex flow field are conducted. The tip vortex flow near a hydrofoil is provided by a viscous flow computation, and the bubble behavior is simulated by an axisymmetric boundary element method based on the provided vortex flow field. The characteristics of the bubble behavior and jet noise over a range of cavitation numbers are investigated. The effect of initial bubble nucleus size and the Reynolds number effect of the tip vortex flow on the tip vortex cavitation inception, the bubble behavior including its splitting, and jet noise are also discussed.

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.

Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nucleus Size Distribution

2003 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Size Distribution ◽  
Vortex Flow ◽  
Bubble Dynamics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Nucleus Size ◽  
Scaling Effects ◽  
Dynamics Model ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

A Surface-Averaged Pressure (SAP) spherical bubble dynamics model accounting for a statistical nuclei size distribution was used to model the acoustic signals generated by cavitating bubbles near inception in a tip vortex flow. The flow field generated by finite-span elliptic hydrofoils is obtained by Reynolds-Averaged Navier-Stokes computations. An “acoustic” criterion which defines the cavitation inception by counting the number of acoustical signal peaks that exceed a certain level per unit time was applied to deduce the cavitation inception number for different scales. It was found that the larger scale results in more cavitation inception events per unite time because more nuclei are excited by the tip vortex at the larger scale. The nuclei size was seen to have an important effect on cavitation inception number with scaling effects due to nuclei increasing as nuclei sizes decreases.

Tip-Vortex Induced Cavitation on a Ducted Propulsor

2003 ◽  
Author(s):  
Christopher J. Chesnakas ◽  
Stuart D. Jessup
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Three Dimensional ◽  
Tip Vortex ◽  
Number Range ◽  
Vortical Structures ◽  
Tip Vortices ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Ducted Rotor

An extensive experimental investigation was carried out to examine tip-vortex induced cavitation on a ducted propulsor. The flowfield about a 3-bladed, ducted rotor operating in uniform inflow was measured in detail with three-dimensional LDV; cavitation inception was measured; and a correlated hydrophone/high-speed video system was used to identify and characterize the early, sub-visual cavitation events. Two geometrically-similar, ducted rotors were tested over a Reynolds number range from 1.4×106 to 9×106 in order to determine how the tip-vortex cavitation scales with Reynolds number. Analysis of the data shows that exponent for scaling tip-vortex cavitation with Reynolds number is smaller than for open rotors. It is shown that the parameters which are commonly accepted to control tip-vortex cavitation, vortex circulation and vortex core size, do not directly control cavitation inception on this ducted rotor. Rather it appears that cavitation is initiated by the stretching and deformation of secondary vortical structures resulting from the merger of the leakage and tip vortices.

Experimental Study of Scale Effects on the Scaling Law for Tip Vortex Cavitation Noise

2014 ◽  
Author(s):  
Jisoo Park ◽  
Cheolsoo Park ◽  
Youngmin Choo ◽  
Woojae Seong
Keyword(s):  
High Speed ◽  
Scale Effects ◽  
Scaling Law ◽  
Size Variation ◽  
Tip Vortex ◽  
Cavitation Noise ◽  
Scaling Exponents ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Vortex Model

Novel scaling law for the tip vortex cavitation (TVC) noise is derived from the physical basis of TVC, employing the Rankine vortex model, the Rayleigh-Plesset equation, the lifting surface theory, and the number of bubbles generated per unit time (N0). All terms appearing in the scaling law have physical or mathematical grounds except for N0. Therefore, to experimentally validate the N0 term, experiments are designed to keep the same TVC patterns as velocities and dimensions vary. Optimal shooting conditions with a velocity and size variation are determined from the scaling exponents, cavitation numbers and Reynolds numbers at each condition. To avoid wall effects and flow field interaction, two hydrofoils are optimally arranged by using computational fluid dynamics (CFD) for size variation. Images taken by a high speed camera are used to count N0, considering similitude of the spectra of nuclei. Scaling exponents curve fitted from five velocities and cavitation inception numbers have an exponent value of 0.371, which is closely placed on scaling exponents curve deduced from Schlichting’s friction coefficients fitting with Reynolds number. The tendency that N0 is proportional to a velocity and inversely proportional to a size can be confirmed by this study.

Numerical Analysis of Tip Vortex Cavitation Behavior and Noise on Hydrofoil

2006 ◽  
Author(s):  
Kwangkun Park ◽  
Hanshin Seol ◽  
Soogab Lee
Keyword(s):  
Flow Field ◽  
Cavitation Bubble ◽  
Vortex Flow ◽  
High Amplitude ◽  
Point Of View ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Amplitude Noise ◽  
Radius Variation ◽  
Cavitation Behavior

In this study, tip vortex cavitation behavior and noise are numerically analyzed. Eulerian-Lagrangian approach is used to simulate the tip vortex cavitation on the hydrofoil. In this approach, the flow field and cavitation behavior are computed by Eulerian and Lagrangian point of view, respectively. The vortex flow field is simulated by combining Moore and Saffman’s vortex core radius variation equation with Sculley vortex model. The tip vortex cavitation behavior is analyzed by coupled Rayleigh-Plesset equation and trajectory equation based on Newton’s 2nd law. Kamiirisa’s experimental nuclei data are adopted to produce computational cavitation nuclei population and the nuclei are released in the vortex flow field. The tip vortex cavitation trajectories and radius variations of the nuclei are calculated according to the initial sizes of the nuclei. Noise is analyzed using time dependent cavitation bubble position and radius variation data. When the acting pressure on the nucleus goes down below the vapor pressure, the nucleus grows into a cavitation bubble. And, the cavitation bubble emits very high amplitude noise during collapse stage. This study may become a foundation of the vortex cavitation study.

scholarly journals Numerical Investigation of Tip Vortex Cavitation Inception and Noise of Underwater Propellers of Submarine Using Sequential Eulerian–Lagrangian Approaches

2020 ◽  
Vol 10 (23) ◽  
pp. 8721
Author(s):  
Garam Ku ◽  
Cheolung Cheong ◽  
Ilryong Park ◽  
Hanshin Seol
Keyword(s):  
Numerical Methods ◽  
Flow Field ◽  
Bubble Dynamics ◽  
Swirling Flow ◽  
Tip Vortex ◽  
Entire Body ◽  
Cavitation Noise ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Vortex Model

In this study, the high-fidelity numerical methods are developed to investigate the tip vortex cavitation (TVC) inception and noise of underwater propellers, namely, Model-A and Model-B, which are designed to investigate the effects of sweep angle on cavitation inception and noise. In addition, the entire body of the DARPA Suboff submarine is included to consider the effects of the inflow distortion originating from the boundary layer flow of the submarine body on the cavitating flow of the propellers. The Eulerian approach consisting of Reynolds-averaged Navier–Stokes (RANS) solver and the vortex model is coupled with the Lagrangian approach using the bubble dynamics equations and the acoustic analogy for nuclei initially distributed in inlet flow. First, three-dimensional incompressible unsteady RANS simulations are performed to predict the hydrodynamic flow field driven by underwater propellers installed on a DARPA Suboff submarine body. The Scully vortex model and dissipation vortex model (DVM) are used to regenerate the tip vortex dissipated by artificial numerical damping and low grid resolution around the vortex core center, which is identified by using minimum λ2-criterion in the swirling flow field originating from the propeller blade tip. Then, tip vortex cavitation inception is simulated by applying the bubble dynamics equations to nuclei initially distributed in the inflow region. The volume and location of each nucleus are obtained by solving the bubble dynamics equations on the flow field obtained using the Eulerian method. Finally, the cavitation noise is predicted by modeling each bubble with a point monopole source whose strength is proportional to its volume acceleration. The validity of the present numerical methods is confirmed by comparing the predicted acoustic pressure spectrum with the measured ones.

Studies of Scaling of Tip Vortex Cavitation Inception on Marine Lifting Surfaces

1991 ◽  
Vol 113 (3) ◽  
pp. 504-508 ◽  
Author(s):  
C. C. Hsu
Keyword(s):  
Vortex Flow ◽  
Vortex Sheet ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Early Stages ◽  
Lifting Surface ◽  
Viscous Core ◽  
Lifting Surfaces ◽  
Good Agreement

The roll up of vortex sheet on a lifting surface in early stages is studied. The structures of tip vortex flow, both in the outer inviscid and inner viscous regions, are examined. The velocity in the viscous core is determined and used as basis for the prediction of tip vortex cavitation. Some comparisons between the calculated and measured tip vortex cavitation inception numbers are made, and the results are generally in good agreement.

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

Subcooled Boiling of Surfactant Solutions

2000 ◽  
Author(s):  
G. Hetsroni ◽  
M. Gurevich ◽  
A. Mosyak ◽  
R. Rozenblit ◽  
L. P. Yarin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Heated Surface ◽  
Pure Water ◽  
Video Camera ◽  
Subcooled Boiling ◽  
Bubble Behavior ◽  
Boiling Hysteresis

Abstract During subcooled boiling of pure water and water with cationic surfactants, the motion of bubbles and the temperature of the heated surface were recorded by both a high-speed video camera and an infrared radiometer. The results show that the bubble behavior and the heat transfer mechanism for the surfactant are quite different from those of clear water. Bubbles formed in Habon G solutions were much smaller man those in water and the surface was covered with them faster. Boiling hysteresis is found for degraded solutions. Dependencies of heat transfer coefficient for various solutions were obtained and compared. The boiling curves of surfactant are quite different from the boiling curve of pure water. Experimental results demonstrate that the heat transfer coefficient of the boiling process can be enhanced considerably by the addition of a small amount of Habon G. The experiments show that the limitations of the ER technique with respect to frequency response are outweighed by its unique capacity to measure wall temperature distribution with high spatial resolution over an area encompassing many nucleation sites and over long periods.

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.

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