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1. doguzaif
   

   Member
   Joined: Jul '20
   Posts: 6

   Hi all,

   I am running a 2D simulation where I'm modelling a unidirectional probe made up of a number of gridpoints stacked together horizontally, collectively representing the diameter of the probe surface. This acts as both the source and the sensor in my simulation. The probe is at the top of the 2D medium and is sending out a burst signal vertically downwards into the medium. I would like to know what the beam spread of my current settings are, yet I'm unsure how to check this. I have not set any beam spread value or angle specifically - I have only set the profile of the burst signal, and thats it. Many thanks in advance, any help with this would be much appreciated.

   Best wishes,
   Dogu
   PhD researcher in Mechanical Engineering
   MEng, University of Bath

   Posted 3 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Dogu,

   Do you mean an analytical formula, or something numerical? There are formula in 3D for disc sources, e.g., to compute the far-field divergence angle. I can't recall if equivalent ones have been derived in 2D (e.g., for a rectangular source that is infinite in one dimension).

   Brad.

   Posted 3 years ago #

3. doguzaif
   

   Member
   Joined: Jul '20
   Posts: 6

   Mr Treeby,

   Thank you for your response. So in my model, I have a unidirectional, unfocused transducer modelled in 2D. In real life, to estimate the beam spread of such a transducer, I would use the following formula:

   sin(theta) = 1.2*(V/D*F)

   where theta = beam divergence angle, V = speed of sound in medium, D = diameter of transducer and F = frequency of transducer. Is this also what the model would simulate? Can I confidently use this formula to predict simulation behaviour?

   Many thanks in advance.

   Dogu

   Posted 3 years ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Dogu,

   This formula is for the far-field divergence angle of a plane piston transducer in 3D (not 2D). Remember that a 2D model inherently assumes that everything in the out-of-plane direction is infinitely extended. Thus a line source in 2D is actually an infinite rectangle.

   Brad.

   Posted 3 years ago #

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