Assessment of Cavitation Erosion With a URANS Method

Abstract

An assessment of the cavitation erosion risk by using a contemporary unsteady Reynolds-averaged Navier–Stokes (URANS) method in conjunction with a newly developed postprocessing procedure is made for an NACA0015 hydrofoil and an NACA0018-45 hydrofoil, without the necessity to compute the details of the actual collapses. This procedure is developed from detailed investigations on the flow over a hydrofoil. It is observed that the large-scale structures and typical unsteady dynamics predicted by the URANS method with the modified shear stress transport (SST) k-ω turbulence model are in fair agreement with the experimental observations. An erosion intensity function for the assessment of the risk of cavitation erosion on the surface of hydrofoils by using unsteady RANS simulations as input is proposed, based on the mean value of the time derivative of the local pressure that exceeds a certain threshold. A good correlation is found between the locations with a computed high erosion risk and the damage area observed from paint tests.

An energy conservative method to predict the erosive aggressiveness of collapsing cavitating structures and cavitating flows from numerical simulations

“…Cord length and span of the foil are 0.06 m and 0.04 m, respectively. The dimensions of the tunnel cross section, the foil and its position and angle of attack are in line with an experimental set-up by Van Rijsbergen et al (2012) and a corresponding numerical set-up by Li et al (2014) . The tunnel width is w t = 0 .…”

“…The match improves in the sense that the power impact distribution in the first impact zone close to the leading edge gets less pronounced compared to the distribution in the second impact zone close to the trailing edge, and that the second impact zone stretches further towards the trailing edge as the intensity exponent n increases. Different from the approach presented in this study, Li et al (2014) assumed the local partial pressure time derivative ∂ p / ∂ t to be a measure for the impact aggressiveness.…”

“…From previous studies ( Schenke and van Terwigsa, 2017 ), the values C c = 50 0 0 kg ·c/m 5 and C v = C c / 2 for the mass transfer coefficients have been found to be large enough to obtain model parameter independent results for the cavity shedding frequency. Just as in the study by Li et al (2014) , the vapor pressure is p v = 1854 Pa and the densities of the vapor and the liquid phase are ρ v = 0 . 014 kg/m 3 and ρ l = 998 .…”

“…Common erosion risk indicators are obtained from the accumulation or integration of local impact events over time, where the individual event is only taken into account if it exceeds a certain threshold level. Examples are found in the work by Li et al (2014) and Leclercq et al (2017) . This means, however, that above the pre-defined threshold level, the collapse rapidness is not further taken into account.…”

“…Van Rijsbergen et al (2012) have identified locations of high erosion risk for this configuration from experimental paint tests. Numerical erosion risk assessment for this case has been carried out by Li et al (2014) .…”