Cd 0.7 Discharge coefficient
Znonlin rho0*sqrt(0.5*U*conj(U))*1/(2*Cd^2)/(rho0*c0) Nonlinear contribution to the impedance
U intop_mid(w)/intop_mid(1) Average velocity in orifice
U2 sqrt(2)*w_rms Average velocity in orifice
Sr 2*pi*freq*2*ac/abs(U) Strouhal number (frequency)
Sr2 omega0*2*ac/abs(U2) Strouhal number (transient)
Sh 2*ac*sqrt(2*pi*freq*rho0/(4*mu0)) Shear number (frequency)
Sh2 2*ac*sqrt(omega0*rho0/(4*mu0)) Shear number (transient)
FC 1/(1+2*Sr*(1+0.06*exp(3.74/Sh))) Help variable
GC if(Sr>1,GC2,GC1) Help variable
GC1 0.2-0.5/Sr*(1-0.42/Sh^2)+0.05/Sr^2*(1-0.68/Sh^2) Help variable
GC2 -0.05*(1/Sr*(1-1/Sh))-0.6*(1/Sr*(1-1/Sh))^2 Help variable
Rnonlin real(Zlin)+FC*U*rho0/(2*Cd^2)/(rho0*c0) Nonlinear resistance (Temiz at al.)
Dnonlin imag(Zlin)+GC*2*pi*freq*rho0*2*a/(2*rho0*c0) Nonlinear reactance (Temiz at al.)