Fig. 3: FEM simulation on the effect of measurement depth.
From: Elastic orbital angular momentum transfer from an elastic pipe to a fluid
Fourier analysed time domain simulation with a Intensity (hue) and phase (colour) showing typical “doughnut” acoustic beam indicative of OAM at a plane close to the pipe end (1 mm below). b Normalised acoustic Intensity along x−z plane (y = 0): data extracted along the dashed yellow line is used in a and the dash-dotted line in Fig. 2a, b (20 mm below the pipe). The acoustic vortex is obscured at the lower plane due to interaction with other modes present in the pipe, the cross-section of which is shown by the grey rectangles.
