Correlation-Based Riblet Model for Turbomachinery Applications

An empirical riblet model for manufactured V-shaped and trapezoidal riblets which is suitable for turbomachinery application is presented. The implementation of the riblet effect employs a correlation-based correction for the damping of the specific dissipation rate omega in the vicinity of the wall which has been previously presented by other researchers. In the current paper the correlations are extended into the drag-increasing regime and are extended to account for the effect of misalignment of the riblets relative to the flow and for the effect of adverse pressure gradients. In order to account for the latter in modern, massive parallel CFD-codes, a local Clauser-Parameter has been newly derived. The model is implemented in the 3D turbomachinery design code TRACE and validated with flat plate measurement data and a NACA6510 compressor cascade. The predictions of the experimental values are in very good agreement with the experimental data, showing the capability of the model for designing riblet structured turbomachinery blading.