As I already tried to explain, v_induced and v_slipstream are only formal parameters for the integral2 function. They cannot transport values that you gave to them in a preceding calculation.
The functions bl_induced and q2_induced are called from integral2 with certain values for v_induced and z resp. ke_out_induced and z in the intervals [0,delta99] and [0,2*pi] to approximate the integrals. Thus you get the same result as in the first part of the code ; only the names of the independent variables in your integral functions have changed, but this doesn't influence the values of the integrals.
Maybe you have a matrix of values for bl_induced and ke_out_induced over a 2d-grid for v_induced and z resp. v_slipstream and z. If this is the case, use trapz twice instead of integral2 and take a look at the example "Multiple Numerical Integrations" under
But before, you will have to explain the z-dependency of your functions to be integrated. If they don't depend on z, you have a 1d-integration and you can multiply the result by 2*pi.
