Vapor bubble instability could enhance the sonochemical activities and accelerate the reaction rate. In the present paper, vapor bubble instability in acoustic fields is investigated through combining both the spherical and stiffness stabilities within a wide range of parameter zone (consisting of bubble radius, acoustic frequency and pressure amplitude) in order to determine the stability states of vapor bubbles. The status of bubble oscillations are divided into four zones in terms of their stability characteristics. Influences of several paramount parameters on the bubble stability are demonstrated in detail. Different orders of spherical instability are quantitatively given together with cases in high-frequency and low-frequency limits. The practical applications of the present work are twofold: identification of the parameter zones with rapid sonochemical reactions; validity of the spherical bubble assumption for simplification of the numerical studies.
Keywords: Acoustic bubble; Cavitation; Spherical harmonics; Stability; Stiffness; Vapor bubbles.
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