Effects of microvortex generators on cavitation erosion by changing periodic shedding into new structures

Abstract

Cavitation erosion is a common phenomenon and continues to be a primary concern in the fields of hydraulic machinery. It is important to develop effective methods to avoid adverse effects. In the previous studies, the microvortex generators (VGs) were arranged parallel to the leading edge on the surface of the NACA0015 hydrofoil and, thus, changed the feature of the attached cavity. However, the effect on cavitation erosion has not been studied. The current work aims at understanding the aggressiveness of cavitation structures and the intensity of impact changed by microvortex generators. This study presents findings of experimental investigation of impulsive loading on the hydrofoil surface from collapsing cavities. Attempts to predict the cavitation erosion aggressiveness and the relationship with cavitation structures were based on visual observations. Under certain cavitation conditions, the periodic shedding disappears after the micro-VGs are installed. By dispersing the collapse in time and space, the maximum pressure fluctuation is reduced by 32% and the acoustic power is reduced by 10.8 dB at about 20 kHz. The maximum impact energy appears to be concentrated around the cavity closure. The maximum impact energy of a hydrofoil with VGs is 48% of that of a smooth hydrofoil. When the attack angle is lower, the erosion at the leading edge is more obvious on the smooth hydrofoil. Thus, the effect of VGs on alleviating the erosion at the leading edge is more prominent. The characteristic feature of vortex generators is their strong swirling motion that allows them to promote large-scale mixing of fluids with different momentum and energy. The unsteadiness is alleviated by VGs because of the interaction with the reverse flow.

Prediction of Cavitation Evolution and Cavitation Erosion on Centrifugal Pump Blades by the DCM-RNG Method

“…Pressure waves can be generated by the collapse. Based on the hypothesis of Qiu et al [23,[28][29][30][31][32], the potential energy of the cavity structure is defined as…”

“…Li et al [22] conducted a comparative analysis of the erodible area on the NACA0015 hydrofoil based on the first-order deviation of pressure versus time and proved that this method can better match the erodible area on the hydrofoil. Through experiments, Qiu et al [23] compared the cavitation erosion of NACA0015 hydrofoils with different leading-edge structures and conducted a quantitative analysis of the cavitation impact energy. Usta et al [24] compared the differences between the Intensity Function Method, Gray level Method, and Erosive Power Method.…”

Intelligent Fault Diagnosis of Hydraulic Piston Pump Based on Wavelet Analysis and Improved AlexNet

“…The vibration signal of the hydraulic piston pump is a typical non-stationary signal [ 1 , 36 ]. The short-time Fourier transform, Wigner transform, and wavelet transform are widely utilized in the analysis of non-stationary signals [ 37 , 38 , 39 ]. Short-time Fourier transform has a defect of low resolution [ 40 ].…”

Assessment of Cavitation Erosion in a Water-Jet Pump Based on the Erosive Power Method

“…Cavitation erosion is a hot research currently [25]. Traditionally, cavitation erosion risk is assessed by experimental methods [26][27][28][29][30].…”

“…Peter et al [32,33] proposed a new method considering the microjet mechanism and applied the method to predict cavitation erosion around a hydrofoil. Pereira et al [25,[34][35][36] used a macroscopic cavitation theory to assess the cavitation erosion risk in experiment and simulation. Usta et al [37] compared the applicability of intensity function method, Gary level method, and erosive power method and predicted the erosible areas on a ship propeller.…”