Model Verification and Experimental Study of the Turbomachinery Wake Flow Field Reconstruction

Abstract A clear understanding of the turbomachinery wake flow field is one of the key problems in developing turbomachinery aerodynamics. The theoretical model of helical vortices is established in cylindrical coordinates (r,θ,z), and the model corresponds to the experimental scheme, which verifies the feasibility of reconstructing flow field by interpolation in r–z plane under different θ. This model shows that theta should not exceed 20 deg in order to reconstruct the flow field more accurately. Taking rotors as the representative of the turbomachinery, particle image velocimetry (PIV) is used to measure the velocity field in the rotor wake. Interpolating reconstruction of spacing between different measurement planes, the reconstruction results are relative to the theory, in which plane spacing should be less than 20 deg. Using the vorticity-weighted average method to calculate the central position of the vortex core, the wandering motion of the tip vortex is obtained. Through the analysis method of the circulation, it is proved that the point where the second derivative of the circulation with respect to the radius is 0 corresponds to the radius of the vortex core, and the evolution trend of the growth of the vortex core radius is proportional to the square root of the vortex ages. The results provide a reliable experimental method for the quantitative study of the spatio-temporal evolution of complex vortex structures in the three-dimensional flow of turbomachinery wakes.