Experimental and Numerical Study of Cavitation Behavior During Hydrodynamic Cavitation Pretreatment of Food Waste with Varying Total Solids

Hydrodynamic cavitation (HC) is an energy-efficient pretreatment technology; however, few studies have directly applied it to food waste (FW). Most HC modeling approaches simplify the cavitating medium as water, whereas FW exhibits non-Newtonian rheology, which may introduce deviations in cavitation simulation. In this study, the rheological properties of FW with different total solids (TS) were measured, and a CFD model of FW-HC in a Venturi reactor was developed. Simplifying FW as water (TS = 0 wt%) underestimated viscosity within the Venturi tube and overestimated the low-pressure region. For FW at TS = 5, 10, and 20 wt%, the relative root means square error (RRMSE) in average vapor volume fraction, relative to TS = 0 wt%, was 31.8%, 36.1%, and 61.5%, respectively. This simplification also led to a lower model-predicted critical pressure for cavitation inception and produced different predictions of the turbulent viscosity ratio (TVR). When non-Newtonian rheology was incorporated, increasing TS significantly elevated FW viscosity and produced high-viscosity regions in the throat and diffuser. These regions restricted the development of the low-pressure zone, thereby suppressing cavitation. Analysis of vapor volume fraction and TVR indicated that high-TS FW required a higher critical pressure for cavitation, whereas moderate dilution or increased pressure drop enhanced HC in FW.