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.

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.

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.

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

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.

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.

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