Unbaffled plate acoustic radiation

Applications
1

Dear Bempp users,

I would to simulate the radiation of an unbaffled rectangular thin plate under motion below 1Khz. To do so, I defined a velocity field on both rectangle faces, as follow:

 plate = bempp.api.shapes.cuboid(length=(Lx, Ly, Lz), origin=(0, 0, 0), h=0.05)
       
@bem.complex_callable
def calc(r, n, domain_index, result):
    xs, ys, zs = r
    if n[2]:
        result[0] = VelocityField(xs, ys)
        if n[2]<0 :
            result[0] *= -1
    else : 
        result[0] = 0

The plate lies parallel in the xy plane, so when the z-normal is negative, then the velocity field is multiplied by -1 to shift the phase of the plate face underneath.

Then, the Helmotz integral equation is solved.

I am wondering if this the proper way to define an unbaffled plate and its velocity field.

Regards,
Mathieu

2

Did you have success with this?
I would like to solve the same problem, but Ive read that BEM methods can be unstable when used on thin objects. DId you have this problem? Ideally would be able to build a plate as 2D, but I suppose that’s not possible.

Also, do you know how to construct an infinite baffle with bempp, or do you just build a large box?

Paul

3

Affecting a velocity fied on one face and the same field multiplied by -1 seemed to be right.

I haven’t encountered any unstability.

I don’t know how to build an infinite baffled in bempp. To test the baffled case, I created a plate mesh with a finite baffle in blender and affected zero velocity to the baffle.

Mathieu

4

Thanks, Im going to try something similar with gmsh from Python.