Fig. 13

Convergence test of moment equations: sound amplitude at the receiver as function of the dimensionless length \(\sqrt \pi \varpi {L}/v_{m}\). Solid lines represent the accurate results from the Shakhov model (44) solved by the discrete velocity method [69]. Symbols are approximate solutions of the Shakhov model when the molecular velocity space v is discretized according to Gauss-Hermite quadrature of order N; these solutions are equivalent to those of Grad moment equations (having (N+1)(N+2)(N+3)/6 moments) that are accurate up to the order of Kn^N−2