Fully turbulent flows of viscoplastic fluids in a rectangular duct

Turbulent flows of viscoplastic fluids at high Reynolds numbers have been investigated recently with direct numerical simulations (DNS) but experimental results limited. For this reason, we carry out an study fully turbulent a yield stress fluid in rectangular aspect ratio channel high-resolution laser doppler velocimetry (LDA) setup. We employ aqueous Carbopol solutions, often considered to be simple fluid. formulate different concentrations address the effect rheology on turbulence statistics approximately constant number. Additionally, also perform experiments single formulation its effect. The flow analysis is performed via measurements, and power spectral densities velocity fluctuations. addition increases anisotropy, enhancement streamwise fluctuations decrease wall normal comparison water same mean velocity. This change reflected fluctuations, where observe large increase energy scale structures. Conversely, smaller scales decreased water, drops steeper than Newtonian law $k_x^{-5/3}$. As number solution, stresses approach values core, which suggests diminishing effects shear-thinning. reveal that content larger decreases slightly However, shear thinning do not disappear even as approaches 50000.