Distributions of the x speed at t = 340b/v_Ae along the y cut through the left tube center for a number of grid spacings as labeled. All computations pertain to the S​_x motion for a fixed combination of physical parameters, [ρ_i/ρ_e = 5, ℓ/ℛ = 0.4, d/ℛ = 2.5, kb = π/30]. The computational domain size is fixed at [x_M = 12b, y_M = 10b]. Only the lower half (y ≤ 0) is shown for any y profile, the other half being symmetric about y = 0. The vertical dash-dotted lines delineate the borders of the nonuniform layer.