Influence of Different Parameters on the Cavitation Process

The different processes occurring during cavitation (i.e. nucleation, bubble growth and collapse) can be affected by parameters such as liquid medium, intensity and hydrostatic pressure, which are among the most important.

Thus, the formation of cavitation bubbles decreases on increasing ultrasonic frequency. This is due to insufficient time for the rarefaction cycle to allow the growth of the bubble so that disruption of the liquid can be produced.

As expected, cavitation is decreased in viscous media as a result of the increased negative pressure in the rarefaction region needed for disruption of the liquid.

The number of nuclei for cavitation depends on temperature. An increase of temperature from — 10 to + 50°C causes an increase in sonochemical effects as a result of the increased cavitation. Nevertheless, when temperature exceeds 50°C the decrease in surface tension and increase in vapour pressure within the cavity will result in a lower Pmax and, consequently, sonochemical effects will diminish.

The increase in gas content within the liquid leads to a lower cavitation threshold and intensity of the shock wave released on the collapse of the bubble. It has been observed that the use of monoatomic gases (He, Ar, Ne) provides more effective cavitation than diatomic gases (N2, O2, air).

External pressure also influences the cavitation process. Thus, when the external pressure is increased (Ph), a lower cavitation threshold and intensity of cavitational collapse are observed. When Ph — Pa > 0, it means that the negative phase of the sound will no longer exist, hence eliminating cavitation.

Finally, another factor that can influence cavitation is intensity, which enhances cavitation.

!n the cavity

(High pressures and temperatures generated during collapsel

!n the cavity

(High pressures and temperatures generated during collapsel

In The bulk media At the interface

(Shock wave on collapse (Less forcing conditions plus induces shear forces) shock wave on collapse)

Figure 3 Cavitation effects in a homogeneous liquid.

In The bulk media At the interface

(Shock wave on collapse (Less forcing conditions plus induces shear forces) shock wave on collapse)

Figure 3 Cavitation effects in a homogeneous liquid.

Solar Panel Basics

Solar Panel Basics

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