Dear k-Wave team,
I’m currently running a 2D simulation using kspaceFirstOrder2DG to model ultrasound propagation of a plane wave at 0° from a linear array source in water (L11-5), and I’m observing a strong “chevron-like” interference pattern in the reference medium (homogeneous water).
This pattern looks like crossed diagonal bands, even though the medium is fully homogeneous.I define the sources using karraysources class. My grid size is 1/15 of the wavelengt
The same simulation were also conducted in 3D considering probe elevation of 5 mm and using kwave_transducer.
If the simulatios are run with a kerf (both 2D and 3D) of some grid points, the issue is amplificated and the artifacts become stronger. At lower frequencies, these artifacts are still present but at a smaller scale.
Here are the main parameters of my setup:
fc = 7.6e6; % Central frequency
c_water = 1540; % Sound speed in water
rho_water = 1000; % Density
ppw = 15; % Points per wavelength
dx = floor((c_water/fc/ppw)*1e5)*1e-5;
dy = dx;
N_elements = 64;
pitch_m = 300e-6;
elem_width_m = pitch_m;
ix_probe = round(1e-3/dx)+1;
tone_burst_cycles=3;
win = hanning(N_elements);
source_signal = toneBurst(1/kgrid.dt, fc, tone_burst_cycles);
PML_size = 30;
PML_alpha =4; % higher values were also used but no change
cfl = 0.15;
`
The transducer and sensor are both linear arrays located at ix_probe (which is 1mm away from the boundary).
I’m running two simulations (one with scatterers, one reference), then subtracting their pressure fields.
However, even in the reference case (homogeneous water), I see this strong interference pattern (see attached figure).
My questions are:
Is this interference pattern expected given my pitch (300 µm) and frequency (7.6 MHz)?
Could it be a spatial aliasing or grating-lobe effect related to the array discretization?
Are there recommended values for pitch, element_width, or PML parameters to avoid these artifacts in k-Wave 2D simulations?
Would reducing the pitch below λ/2 or adjusting the apodization help mitigate this?
Any insight or guidance on proper transducer discretization or grid setup to avoid this pattern would be greatly appreciated.
Best regards,
Amadou