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

2005 ◽  
Vol 127 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Size Distribution ◽  
Bubble Dynamics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Simultaneous Increase ◽  
Pressure Amplitude ◽  
Scaling Effects ◽  
Dynamics Model ◽  
Cavitation Inception ◽  
Reference Number

The acoustic pressure generated by cavitation inception in a tip vortex flow was simulated in water containing a realistic bubble nuclei size distribution using a surface-averaged pressure (SAP) spherical bubble dynamics model. The flow field was obtained by the Reynolds-averaged Navier–Stokes computations for three geometrically similar scales of a finite-span elliptic hydrofoil. An “acoustic” criterion, which defines cavitation inception as the flow condition at which the number of acoustical “peaks” above a pre-selected pressure level exceeds a reference number per unit time, was applied to the three scales. It was found that the scaling of cavitation inception depended on the reference values (pressure amplitude and number of peaks) selected. Scaling effects (i.e., deviation from the classical σi∝Re0.4) increase as the reference inception criteria become more stringent (lower threshold pressures and less number of peaks). Larger scales tend to detect more cavitation inception events per unit time than obtained by classical scaling because a relatively larger number of nuclei are excited by the tip vortex at the larger scale due to simultaneous increase of the nuclei capture area and of the size of the vortex core. The average nuclei size in the nuclei distribution was also found to have an important impact on cavitation inception number. Scaling effects (i.e., deviation from classical expressions) become more important as the average nuclei size decreases.

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.

Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model

1999 ◽  
Vol 121 (1) ◽  
pp. 198-204 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Vortex Core ◽  
Bubble Dynamics ◽  
Three Dimensional ◽  
Window Size ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Cavitation Inception ◽  
Flow Effects ◽  
Bubble Sizes ◽  
Real Flow

The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.

Scaling Effect on Prediction of Cavitation Inception in a Line Vortex Flow

2003 ◽  
Vol 125 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine ◽  
Han-Lieh Liu
Keyword(s):  
Flow Field ◽  
Bubble Size ◽  
Bubble Dynamics ◽  
Spherical Model ◽  
Tip Vortex ◽  
Bubble Motion ◽  
Scaling Effects ◽  
Fundamental Physics ◽  
Cavitation Inception ◽  
Viscous Core

The current study considers the prediction of tip vortex cavitation inception at a fundamental physics based level. Starting form the observation that cavitation inception detection is based on the “monitoring” of the interaction between bubble nuclei and the flow field, the bubble dynamics is investigated in detail. A spherical model coupled with a bubble motion equation is used to study numerically the dynamics of a nucleus in an imposed flow field. The code provides bubble size and position versus time as well as the resulting pressure at any selected monitoring position. This model is used to conduct a parametric study. Bubble size and emitted sound versus time are presented for various nuclei sizes and flow field scales in the case of an ideal Rankine vortex to which a longitudinal viscous core size diffusion model is imposed. Based on the results, one can deduce cavitation inception with the help of either an “optical inception criterion” (maximum bubble size larger than a given value) or an “acoustical inception criterion” (maximum detected noise higher than a given background value). We use here such criteria and conclude that scaling effects can be inherent to the way in which these criteria are exercised if the bubble dynamics knowledge is not taken into account.

scholarly journals Numerical Investigation of Viscous Flow Velocity Field around a Marine Cavitating Propeller

2014 ◽  
Vol 6 ◽  
pp. 272316 ◽  
Author(s):  
Zhifeng Zhu
Keyword(s):  
Velocity Field ◽  
Bubble Dynamics ◽  
Volume Fraction ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Back Side ◽  
Propeller Blade ◽  
Propeller Wake ◽  
Numerical Predictions ◽  
Hybrid Grid

Velocity field around a ship cavitating propeller is investigated based on the viscous multiphase flow theory. Using a hybrid grid, the unsteady Navier-stokes (N-S) and the bubble dynamics equations are solved in this paper to predict the velocity in a propeller wake and the vapor volume fraction on the back side of propeller blade for a uniform inflow. Compared with experimental results, the numerical predictions of cavitation and axial velocity coincide with the measured data. The evolution of tip vortex is shown, and the interaction between the tip vortex of the current blade and the wake of the next one occurs in the far propeller wake. The frequency of velocity signals changes from shaft rate to blade rate. The phenomena reflect the instability of propeller wake.

Bubble Dynamics and Cavitation Inception in Cavitation Susceptibility Meters

1986 ◽  
Vol 108 (4) ◽  
pp. 444-452 ◽  
Author(s):  
G. L. Chahine ◽  
Y. T. Shen
Keyword(s):  
Bubble Dynamics ◽  
Scaling Effects ◽  
Mean Flow ◽  
Cavitation Inception ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
Tentative Explanation ◽  
Bursting Events ◽  
Acoustic Device ◽  
The Relationship

To improve the understanding of the scaling effects of nuclei on cavitation inception, bubble dynamics, multibubble interaction effects, and bubble-mean flow interaction in a venturi Cavitation Susceptibility Meter are considered theoretically. The results are compared with classical bubble static equilibrium predictions. In a parallel effort, cavitation susceptibility measurements of ocean and laboratory water were carried out using a venturi device. The measured cavitation inception indices were found to relate to the measured microbubble concentration. The relationship between the measured cavitation inception and bubble concentration and distribution can be explained by using the theoretical predictions. A tentative explanation is given for the observation that the number of cavitation bursting events measured by an acoustic device is sometimes an order of magnitude lower than the number of microbubbles measured by the light scattering detector. The questions addressed here add to the fundamental knowledge needed if the cavitation susceptibility meter is to be used effectively for the measurement of microbubble size distributions.

Numerical Study of the Effect of Propellers Skew on Cavitation Performance

2013 ◽  
Vol 705 ◽  
pp. 405-409
Author(s):  
Zhi Feng Zhu
Keyword(s):  
Bubble Dynamics ◽  
Volume Fraction ◽  
Numerical Study ◽  
Tip Vortex ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Skew Angle ◽  
Cavitation Performance ◽  
Numerical Predictions ◽  
Hybrid Grid

The effect of propeller skew on cavitation distribution, thrust and the torque is studied numerically. With the hybrid grid strategy and the sliding mesh, the Unsteady Navier-Stokes (N-S) and the Bubble Dynamics equations were solved to predict the vapor volume fraction around ships propellers blades. The numerical predictions of the sheet and the tip vortex cavitation of the propeller E779A are in agreement with the results in other literature in general. For propeller models DTMB, the proper increase of the propeller skew angle may enhance the hydrodynamic performance.

Numerical Computation of Tip Vortex Flow Generated by a Marine Propeller

1999 ◽  
Vol 121 (3) ◽  
pp. 638-645 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Cross Section ◽  
Vortex Flow ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Marine Propeller ◽  
Mean Velocity ◽  
Cavitation Inception ◽  
Section Design ◽  
The Mean ◽  
Propeller Performance

The uniform flow past a rotating marine propeller was studied using incompressible Reynolds-averaged Navier-Stokes computations with the Baldwin-Barth turbulence model. Extensive comparison with the experimental data was made to validate the numerical results. The general characteristics of the propeller flow were well predicted. The current numerical method, however, produced an overly diffusive and dissipative tip vortex core. Modification of the Baldwin-Barth model to better predict the Reynolds stress measurements also improved the prediction of the mean velocity field. A modified tip geometry was also tested to show that an appropriate cross section design can delay cavitation inception in the tip vortex without reducing the propeller performance.

Numerical investigation into effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wing

2021 ◽  
Vol 263 (5) ◽  
pp. 1813-1817
Author(s):  
Garam Ku ◽  
Cheolung Cheong ◽  
Hanshin Seol ◽  
Hongseok Jeong
Keyword(s):  
Bubble Dynamics ◽  
Lagrangian Method ◽  
Tip Vortex ◽  
Bubble Collapse ◽  
Acoustic Analogy ◽  
Dynamics Model ◽  
Cavitation Noise ◽  
Tip Vortex Cavitation ◽  
Gas Concentration ◽  
Vortex Pattern

In this study, the effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wings are investigated using coupled Eulerian-Lagrangian method based on sequential application of Reynolds averaged Navier-Stokes (RANS) solver, bubble dynamics model and acoustic analogy. The bubble dynamics model used in the preceding study (Ku et al., 2020) is modified by including the gas pressure terms and the bubble collapse model, which depends on the timing and threshold of bubble collapse, the number, initial radius and location of divided bubbles. The validity of the modified bubble dynamics model is confirmed through its application to a benchmark problem where single bubble is triggered by laser. Then, the coupled Eulerian-Lagrangian method based on the modified bubble dynamic model is applied for the prediction of tip-vortex cavitation noise of NACA16-020 wing. The predicted results of the tip vortex pattern and acoustic pressure spectrum are compared with the measured results, which shows closer agreements between two results than those in the previous study.

Establishment of cavitation inception speed judgment criteria by cavitation noise analysis for underwater vehicles

2020 ◽  
pp. 147509022096751
Author(s):  
Seung-Jin Jeong ◽  
Suk-Yoon Hong ◽  
Jee-Hun Song ◽  
Hyun-Wung Kwon ◽  
Han-Shin Seol
Keyword(s):  
Bubble Dynamics ◽  
Noise Analysis ◽  
Tip Vortex ◽  
Ocean Engineering ◽  
Cavitation Noise ◽  
Cavitation Inception ◽  
Propulsion Performance ◽  
Before And After ◽  
Random Placement ◽  
Cavitation Nuclei

Cavitation occurs on objects that move underwater at high speeds, and it is accompanied by an increase in hull vibrations, a reduction in propulsion performance, and an increase in noise that is important for warships and submarines. Of the various types of cavitations, tip vortex cavitations (TVC) are the earliest occurring and are considered the most important in terms of cavitation inception speed (CIS). This study predicts the cavitation inception speed by conducting cavitation noise analyses. The trend of the noise according to the cavitation numbers before and after CIS was analysed, and the quantitative criteria to determine the CIS were presented through established procedures. The CIS value obtained through the analysis was verified by comparing it against the value obtained experimentally. The methods used to analyse the cavitation inception speed are developed using bubble dynamics for cavitation noises. First, flow-field information was obtained downstream of the wing to estimate the external force acting on the bubbles, and this was used to calculate the behaviour of the cavitation bubbles. The bubble dynamics analyses were performed for each cavitation nuclei by Lagrange approach to calculate the behaviour of the bubbles. The number of cavitation nuclei was calculated based on the density function with random placement upstream of the wing. The cavitation noise was analysed for various cavitation numbers, and the tendency of the noise generated for each case was investigated. The noise analysis results and the CIS predictions were compared and verified with the measured values in the Large Cavitation Tunnel (LCT) of the Korea Research Institute of Ship & Ocean Engineering (KRISO). Using these results, the effect of the tip vortex cavitation on the total flow noise was analysed, and CIS determination criteria using noise values was validated and established.

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.

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