Frequency response of an electrochemical probe to the wall shear stress fluctuations of a turbulent channel flow

We analyzed numerically the frequency response of the mass transfer rates produced at the surface of an electrochemical probe to the fluctuations of the wall shear stress obtained from a direct numerical simulation of a turbulent plane channel flow at Re-tau = 150. At low and high frequencies the response to the turbulent wall shear stress is in accordance with the existing relations between the amplitudes of the wall shear stress and the mass transfer rates obtained for harmonic perturbations. At intermediate frequencies the turbulent wall shear stress fluctuations produce a larger damping in comparison with the harmonic perturbations. The phase angle of the response of mass transfer rates with respect to the wall shear stress shows important deviations in comparison with the phase angle obtained with harmonic perturbations, specially at high frequencies. (c) 2008 Elsevier Ltd. All rights reserved.