Figure 6

Effect of fluid viscosity parameter on neutrally stable solution. The critical Mach number (red lines) and the phase speed (blue lines) are plotted as functions of the fluid viscosity parameter, S. Three cases are shown in each panel where ϱ = 1, β = 1,$\alpha =\sqrt{3}$, and L = 10² (solid lines); L = 10³ (broken line); and L = 10⁴ (dotted lines). (a, b) Symmetric solutions with δ = 0 and 0.5. (c, d) Antisymmetric solutions with δ = 0 and 0.5. The phase velocity of the antisymmetric solution does not vary significantly in this parameter range (|c| ≃ 0.9194).