Spectral dynamics in a channel flow with microbubbles

Measurements were carried out near the upper wall of a turbulent water channel flow at Reynolds number equal to 10256 (considering total height of the channel and the bulk velocity). Particle Image Velocimetry (PIV) measurement technique was used to record instantaneous velocity fields in the x-y plane. The evaluation of the one dimensional spectra for the fluctuating streamwise velocity was performed in the streamwise wavenumber direction (k₁) with and without microbubbles in the boundary layer. A redistribution of the energy from larger wavenumber to lower wavenumber was observed for the spectra close to the wall. However, the opposite trend was obtained in the outer region. The energy content with microbubbles was less than the energy without microbubbles in the near wall region of the boundary layer.