Fig. 7
From: On the accuracy of macroscopic equations for linearized rarefied gas flows
Spectra of the spontaneous (top row) and coherent (bottom row) RBS. The horizontal and vertical axis are the normalized frequency and spectrum, respectively. Form the left to right, the Knudsen number in each column are 0.04, 0.06, 0.08, and 0.1, respectively. Solid, dashed, and dotted lines are the results from G13, R13, and R26 moment equations, respectively, while triangles are results from Eu’s generalized hydrodynamic equations