Modeling of Hydrodynamic Cavitation Reactors: Reflections on Present Status and Path Forward

Abstract

Hydrodynamic cavitation (HC) is finding ever increasing applications in water, energy, chemicals, and materials sectors. HC generates intense shear, localized hot spots, and hydroxyl radicals, which are harnessed for realizing desired physicochemical transformations. Despite identification of HC as one of the most promising technology platforms, its potential is not yet adequately translated in practice. Lack of appropriate models for design, optimization, and scale-up of HC reactors is one of the primary reasons for this. In this work, the current status of modeling of HC reactors is presented. Various prevailing approaches covering empirical, phenomenological, and multiscale models are critically reviewed in light of personal experience of their application. Use of these approaches for different applications such as biomass pretreatment and wastewater treatment is briefly discussed. Some comments on extending these models for other applications like emulsions and crystallization are included. The presented models and discussion will be useful for practicing engineers and scientists interested in applying HC for a variety of applications. Some thoughts on further advances in modeling of HC reactors and outlook are shared, which may stimulate further research on improving the fidelity of computational models of HC reactors.

ANN based surrogate model for key Physico-chemical effects of cavitation

“…Such availability of surrogate models has a potential to significantly enhance fidelity of representing physico-chemical effects of cavity collapse into device/ reactor scale models as discussed in Sarvothaman et al [20] or Ranade [10] . The Equation (3) and corresponding matrices in the supplementary information provide the algebraic equations to estimate jet velocity, •OH generation and localised energy dissipation rates by cavity collapse and can be incorporated in any higher level models for simulating particle/ drop breakage, reactions of hydroxyl radicals for degradation of pollutants or any other cavitation based process applications.…”

“…Recently Pandit et al [4] have critically reviewed different variants of Rayleigh-Plasset type of equations used for simulating cavity dynamics and have presented simulated results on jet velocity, hammer pressure, hydroxyl radicals and local energy dissipation rates over the wide parameter space covering ambient temperature, pressure, amplitude and frequency of pressure fluctuations and initial cavity radius. These estimated physico-chemical effects of cavitation can be used for developing a device scale model for simulating performance of cavitation based reactor/ process (see recent perspective by Ranade [10] ). However, incorporation of complex cavity dynamics model requiring very fine spatio-temporal resolution in the macroscopic model is not straight forward and is extremely compute intensive.…”

Degradation of methyl orange using hydrodynamic Cavitation, H2O2, and photo-catalysis with TiO2-Coated glass Fibers: Key operating parameters and synergistic effects

“…In light of this, we have used the per-pass degradation factor (Φ), which is dependent on the reactor design and operating conditions but not on volume of the holding tank used in the experiments. The approach is particularly useful to comprehend and interpret how pollutants degrade and optimize key operating parameters for the best HC effect [48] . However, for comparing the performance of the HC system with other hybrid options and for quantifying synergistic effects, we have used the pseudo kinetics approach following the accepted trend in most of the published studies using hybrid AOPs.…”

“…Turbulence fluctuations in such a low-pressure region generate cavities. When such cavities travel to high pressure regions and are exposed to turbulence pressure fluctuations, they collapse and under certain circumstances lead to local hot spots and highly oxidizing radicals [18] . HC has proven its effectiveness in the elimination of POPs present in synthetic and real wastewater (industrial scale) [19] sourced from diverse sectors including the agricultural [20] , packaged food [21] , textile [22] , and pharmaceutical [23] .…”

Simulation of Water Flow in a Cavitation Reactor

“…The calculation was carried out with account for the turbulent nature of the flow based on the k-ε turbulence model (Ranade, 2022). The cavitation process was calculated with the use of the Rayleigh-Plesset cavitation model (Hilgenfeldt et al, 1998).…”