Experimental study of the up-pitching blade effect with a PIV application

In this paper, we are interested in the experimental study of the hydrodynamic structure of the flow in a stirred vessel generated by the up-pitched blade turbines (PBT). Particularly, our studies focused on three PBT turbines with different blade inclinations equal to 45°, 60° and 75°. Particle image velocimetry (PIV) technique was used in this work. The field of interest is obtained by a double pulsed Nd:YAG laser producing a green beam at 532 nm wavelength. The images are recorded trough a 1600×1200 pixels2 of CCD camera resolution. The impeller speed was fixed to generate a Reynolds number equals to Re=26010. In these conditions, we have investigated the velocity field, the vortices, the shear strain, the turbulent kinetic energy, the dissipation rate of the turbulent kinetic energy, the turbulent viscosity, the Kolmogorov length scale and the Taylor micro-scale. Based on these results, the highest and the lowest local values were found at the impeller level. Also, it has been clearly noticed that the velocity vector is directly affected by the turbine type. In fact, within the PBT 75° the radial flow is very important.