Vapor concentration and bimodal distributions of turbulent fluctuations in cavitating flow around a hydrofoil

Cavitation suppression and transformation of turbulence structure in the cross flow around a circular cylinder: Surface morphology and wettability effects

“…Ilyushin et al [31] also demonstrated that a two-peak histogram of the fluctuating velocity is typical of unsteady cloud cavitation over a hydrofoil. The relatively high coherence of vapor cloud detachments allowed the authors to collate certain phases of the quasi-periodic flow dynamic with each of the peaks of the bimodal distribution.…”

“…In order to calculate central moments of turbulent fluctuations of the flow field, the procedure of statistical filtration of velocity vectors [28] was applied to the entire PIV dataset separately for either regime from Table 2 . This validation method was previously demonstrated by Ilyushin et al [31] to be an effective tool to remove vector outliers from the ensemble of velocity fields, specifically in cavitating flow, thereby making calculation of higher-order statistical moments of turbulent fluctuations possible, which are known to be highly sensitive even to single incorrect measurements. The representativeness of the statistical ensembles of the flow velocity was checked comparing spatial distributions of the higher-order moments of turbulent fluctuations calculated over N = 1000 and 5000 realizations (i.e., single measurements of instantaneous velocity fields) as shown in Fig.…”

“…18 ). According to Ilyushin et al [31] , such a two-mode form of the histograms is associated with the process of periodic advection of large-scale vortices in the wake of the cylinder, with the peaks of the distributions corresponding to the utmost (opposite) phases of these flow oscillations.

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“…In this arrangement of the measurement system, the optical magnification and spatial resolution of the camera were 0.12 and 16.75 pixels/mm, respectively. The processing and validation procedures of PIV data are fully described in Ilyushin et al [31] . A detailed analysis of the measurement uncertainties is available in Nichik et al [49] .…”

Unsteady Cloud Cavitation on a 2D Hydrofoil: Quasi-Periodic Loads and Phase-Averaged Flow Characteristics

“…However, it is not enough for the precise evaluation of higher-order statistical moments. Nevertheless, the higher-order moments can be estimated with high confidence based on a statistic of 1700 realizations, provided that the procedure of statistical vector filtration is used (see details in reference [56]).…”