Estimation and Analysis of Hybrid Laminar Flow Control on a Transonic Experiment

This paper investigates the e^N method for predicting the laminar-to-turbulent transition in the context of hybrid laminar flow control. Transonic wind tunnel experiments are used to support our study. The relation between the discrete hole velocity in wind tunnel tests and the continuous surface velocity used in the simulation is established. With the calibrated relation, the e^N method, consisting of a boundary-layer code and linear stability theory framework, has successfully predicted the transition location at various conditions, within 4% chord error compared with the experimental results. Additionally, the simulation profile drag by the integration of momentum loss method matches the results of the experimental wake rake, and the difference is within 1.85 counts. The simulation results show that the microsized wall suctioning reduces the amplitude of cross-flow velocity and lowers the inflection point in the boundary layer, hence suppressing the cross-flow vortices. Hence, the laminar-to-turbulent transition is pushed aft significantly. Meanwhile, the experimental and simulation results show that the wall blowing degrades the HLFC benefit, and it needs to be avoided in applications. This paper concludes that the e^N method can be applied in the hybrid laminar flow control transition prediction with the given perforated panel properties.