Numerical Study of Hydrodynamic Cavitation Pretreatment of Food Waste: Effect of Pressure Drop on the Cavitation Behavior

Abstract

Hydrodynamic cavitation (HC) has a wide range of application scenarios. However, there are few studies on the HC treatment of food waste (FW). A Venturi device is designed and operated and plays a clear role in changing the characteristics of FW. The medium viscosity is often neglected when studying cavitation behavior by numerical simulations. We use the Herschel–Bulkley model to describe the viscosity curves of artificial FW samples obtained experimentally. RANS numerical simulation is carried out with a simplified 2D axisymmetric CFD-based model considering the non-Newtonian fluid properties. A numerical simulation study is carried out for FW (TS = 10.0 wt%) at pressure drop (ΔP = 0.05–0.4 MPa). The numerical simulation results show the variation of flow characteristics, viscosity, vapor volume, turbulent viscosity ratio, cavitation number, and pressure loss coefficient. With the increase in ΔP, the flow rate in the Venturi throat increases, and the average viscosity decreases. It reduces the inhibition effect of viscosity on cavitation. The position of incipient vacuoles at the moment of cavitation is constant and unrelated to the variation of ΔP. Under the effect of increasing ΔP, the average vapor volume fraction is increased, and the cavitation effect is enhanced; the cavitation number (σ) is decreased, and the cavitation potential is improved. A larger ΔP should be selected to increase the cavitation efficiency E of the device.