Numerical Calculation of the Near Field for Spherically Symmetric Nonlinear Acoustic Flows in an Unbounded Ideal Gas.

摘要

An implicit finite-difference method has been developed for calculating spherically symmetric nonlinear acoustic flows generated by a high-intensity periodic source. This method makes it possible to match the conditions prescribed at the source to a low-amplitude solution (in Blackstock's sense) valid at large distances from the source. Numerical computations have been made for piston-like and siren-like sources of three different periods and several source amplitudes. Extensive graphs of the results are presented in this report,together with estimates of the errors associated with the method of computation. The numerical results have also been used to show that,in some instances, a low-amplitude solution may be matched directly to a given source even though the conditions for validity of that solution are not satisfied near the source. (Author)