Tuning of bound states in the continuum by waveguide rotation
We consider acoustic wave transmission in non axisymmetric waveguide which consists of cylindrical resonator and two semi-infinite cylindrical waveguides whose axes are shifted relative to the resonator axis and each other by azimuthal angle $Δϕ$. We show that for rotation of one of attached waveguides the coupling matrix elements of the eigenmodes of resonator classified by the integer $m$ and propagating mode of the waveguide acquire phase factor $e^{imΔϕ}$. That crucially effect Fano resonances and creates an analog of faucet opening and closing wave flux under rotation of the waveguide. We show that under the rotation of the waveguide and variation of the length of resonator numerous bound states in the continuum occur complimenting by the Fano resonance collapse.