Physical Basis of Hydrodynamic Cavitation Generation

2.3 Device Families

Hydrodynamic cavitators may be classified by the mechanism that creates the low pressure region. Figure 2.2 summarizes representative static and dynamic configurations. Orifice plates generate high speed jets and separated shear layers. Venturi devices accelerate and decelerate the flow more gradually, which can reduce irreversible losses relative to a sharp restriction. Multihole plates divide the flow into multiple jets and increase the number of simultaneous cavities. Vortex devices use tangential momentum to produce a low pressure core. Rotor stator systems combine rotational shear with rapid pressure fluctuations, while multistage baffles impose repeated cycles of acceleration and recovery. Contemporary studies of vortex based devices, continuous emulsification, and rotary cavitation illustrate the influence of geometry, scale up, and scale out on device performance [4,5,6].

Figure 2.2. Common hydrodynamic cavitation device families. [7]

Table 2.1. Principal device characteristics and typical engineering implications.

Device	Cavitation zone	Strengths	Main limitations
Single orifice	Jet vena contracta and downstream shear layer	Simple, compact, inexpensive, easy to characterize	High pressure loss; clogging risk; wall collapse and erosion if poorly designed
Multihole plate	Multiple jets and interacting cavity clouds	High event density; distributes flow; geometry is easily varied	Hole fouling; unequal flow distribution; manufacturing tolerances matter
Venturi	Throat and diffuser	Smoother acceleration; potentially lower irreversible loss	Longer device; cavity position depends strongly on diffuser and backpressure
Vortex chamber	Low pressure vortex core	Cavitation can occur away from walls; open flow passage; scale out is practical	Swirl stability and outlet geometry are critical; pressure measurements may not represent core pressure
Rotor or rotor stator	Rotor tip, gap, and wake regions	High throughput and strong mixing; tunable rotational speed	Moving parts, seals, mechanical wear, and more complex scale up
Multistage baffles	Repeated local restrictions	Multiple treatment zones in one body; adjustable designs are possible	Cumulative pressure loss and potential solids deposition