Azimuthal deviation of the pitch angle from the linear prediction. Top panel: azimuthal distance of the maximum (blue) and minimum (yellow) from the linear wake prediction for the M_p = 1.00 m_th case. We used this estimate to trace the pitch angle of the spiral wake. Solid lines represent the values obtained from the simulation, while dash dotted lines are obtained from the analytical model. Bottom panel: difference between the maximum (blue) and minimum (yellow) from the analytical model and the simulation as a function of the disc radius.