Comparison of amplitudes (column 1) and slowly varying phases (column 2) through a uniform (Eq. (8)) and a laminar (Eq. (4)) flow velocity profile along the no-flow acoustic axis (x = y = 0) up to z = d = 0.5 m, for frequencies of 150 kHz (ka = 23.6, row 1) and 500 kHz (ka = 78.5, row 2). The red dot indicates the reception point at z = d. The Rayleigh distances R ₁ (for 150 kHz) and R ₂ (for 500 kHz) is indicated by the pink vertical dashed line. The minimal distances L ₁ (for 150 kHz) and L ₂ (for 500 kHz) are indicated by the red vertical dashed line. Flow velocity of v _avg = 40 m/s is applied.