Abstract
Predicting the cavitation impact loads on a propeller surface using numerical tools is becoming essential, as the demand for more efficient designs, stretched to the limit, is increasing. One of the possible design limits is governed by cavitation erosion. The accuracy of estimating such loads, using a URANS approach, has been investigated. We follow the energy balance approach by (Schenke and van Terwisga, 2019), (Schenke et al., 2019), where we take account of the focusing of the potential energy into the collapse center before it is radiated as shock wave energy in the domain. In complex flows, satisfying the total energy balance, when reconstructing the radiated energy, has always been an issue in the past. Therefore, in this study, we investigate different considerations for the vapor reduction rate, in order to minimize the numerical errors, when estimating the local surface impact power. We show that when the vapor volume reduction rate is estimated using the mass transfer source term, then all the energy is conserved and the total energy balance is satisfied. The model is verified on a single cavitating bubble collapse, and it is further validated on a model propeller test case. The obtained surface impact distribution agrees well with the experimental paint test results, illustrating the potential for practical use of our fully conservative method to predict cavitation implosion loads on propeller blades.
Highlights
Cavitation is the formation of vapor bubbles of a flowing liquid in regions where the liquid accelerates such that the local pressure of the liquid drops below its vapor pressure
We show that when the vapor volume reduction rate is estimated using the mass transfer source term, all the energy is conserved and the total energy balance is satisfied
The increased demand for the prediction of cavitation erosion has paved the way for the development of computational tools that can give a numerical estimation of high erosion risk areas
Summary
Cavitation is the formation of vapor bubbles of a flowing liquid in regions where the liquid accelerates such that the local pressure of the liquid drops below its vapor pressure. None of the attempts was able to ensure energy conservation, while they all ignore the spatial and temporal focusing of the potential energy, which takes place during a cavity collapse Another philosophy applies the microjet erosion model [12,13], as elaborated by Peters et al [14], considering only collapses of single bubbles near the blade surface. A collapse shock wave can plastify almost 800 times larger volume, and the erosion rate will be higher Considering that both the collapse shock and the microjet impact are eventually fed by the initial potential energy content, and the fact that reliable prediction of a microjet formation and its water hammer would require extremely high resolution in time and space, an energy balance consideration, based on the initial potential energy contained in cavitating structures, is believed to be more successful on a macroscopic scale. It is imminent to investigate different possible approaches to reconstruct the radiated energy in such a way that all the initial potential energy is conserved
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