Tham khảo tài liệu 'cavitation and bubble dynamics part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 3 - Cavitation and Bubble Dynamics - Christopher E. Brennen Figure Typical spectra of noise from bubble cavitation for various cavitation numbers. From Ceccio and Brennen 1991 . The next step is to consider the synthesis of cavitation noise from the noise produced by individual cavitation bubbles or events. This is a fairly simple matter provided the events can be considered to occur randomly in time. At low nuclei population densities the evidence suggests that this is indeed the case see for example Morozov 1969 . Baiter Gruneis and Tilmann 1982 have explored the consequences of the departures from randomness that could occur at larger bubble population densities. Here we limit the analysis to the case of random events. Then if the impulse produced by each event is denoted by I and the number of events per unit time is denoted by xỵ the sound pressure level ps will be given by pS ỈNE Consider the scaling of cavitation noise that is implicit in this construct. We shall omit some factors of proportionality for the sake of clarity so the results are only intended as a qualitative guide. Both the experimental results and the analysis based on the Rayleigh-Plesset equation indicate that the nondimensional impulse produced by a single cavitation event is strongly correlated with the maximum volume of the bubble prior to collapse and is almost independent of the other flow parameters. It follows from Equations and that and the values of dV dt at the moments t t1 t2 when d2V dt2 0 may be obtained from the Rayleigh-Plesset equation. If the bubble radius at the time t1 is denoted by Rx and the coefficient of pressure in the liquid at that moment is denoted by Cpx then http archive 00000001 00 22 of 29 7 8 2003 3 54 22 AM Chapter 3 - Cavitation and Bubble Dynamics - Christopher E. Brennen Numerical integrations of the Rayleigh-Plesset equation for a range of typical circumstances indicate that .
