Illustration of the scale separation assumption for the stochastic excitation. In the turbulent cascade, λ_i denotes the energy injection scale in the framework of the turbulent cascade, while λ_d is the dissipation scale. The size of the largest eddy in the inertial range is estimated by the mixing length λ_i. The size of an arbitrary eddy is denoted λ. All the eddies in the cascade contribute to the stochastic excitation.