Turbulent flow of quadrangle mode in interdisk midplane between two shrouded co-rotating disks

Particle image velocimetry (PIV) was employed to study the flow patterns, time-averaged velocity field, and turbulence properties of the flow in the interdisk midplane between two shrouded co-rotating disks at the interdisk spacing to disk radius ratio S = 0.1 and rotating Reynolds number Re = 2.25 × 10⁵. A quadrangle core flow structure rotating at a frequency 75% of the disks’ rotating frequency was observed. The flow in the region outside the quadrangle core flow structure consisted of four cellular flow structures. Five characteristic flow regions—the hub-influenced region, solid-body rotation region, buffer region, vortex region, and shroud-influenced region—were identified in the flow field. Circumferential and radial turbulence intensities, Reynolds stresses, turbulence kinetic energy, correlation coefficients, as well as the Lagrangian integral time and length scales of turbulent fluctuations were analyzed and presented. Features of the turbulence properties were found to be closely related to the rotation motion of the inner and outer characteristic flow structures. The circumferential components of the turbulence properties exhibited local minima in the buffer region and maxima in the solid-body rotation and vortex regions, while the radial components of the turbulence intensity, turbulent normal stress, and Lagrangian integral turbulence time scale exhibited maximum values in the buffer region and relatively low values in the regions near the hub and the shroud.