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A detailed numerical investigation was conducted to explore various flow-control strategies for restraining the serious laminar separation which commonly occurs on the LPT blades when operating under low Reynolds number conditions. The simulations were carried out at a Reynolds number of 25,000 with a free-stream turbulence intensity of 0.01. A novel approach of oscillatory blowing using fluidic oscillators (FOs) was developed to manage the separation. Steady and pulsed bowing were also investigated. The results show remarkable reductions in losses, with decreases of 45.7%, 36.1% and 50.7% achieved through oscillatory blowing, steady blowing and pulsed blowing, respectively. Particularly, the laminar separation was suppressed more significantly when emolying oscillatory and pulsed blowing under conditions of low blowing ratios. This is mainly attributed to the pronounced unsteadiness induced by the unsteady blowing method. A comprehensive analysis of flow control efficiency demonstrated that unsteady blowing delivered an energy gain exceeding 20 times the power cost of flow control, whereas only 72 percent of injection costs were recovered at the test plane with steady blowing. As the blowing ratio increases, the control advantages offered by unsteady control diminish, and the effects of steady and unsteady blowing tend to be consistent. Notably, the fluidic oscillator-based actuator has the ability to induce pulsations in the boundary layer without any moving parts, thus eliminating reliability concerns and making it an attractive choice for adoption in practical turbomachinery manufacturing. This research holds significant importance in the development of more advanced and reliable active blowing techniques. [ABSTRACT FROM AUTHOR]

Active technology for oscillatory blowing in the flap gap has been tested at INCAS subsonic wind tunnel in order to evaluate this technology for usage in high lift systems with active flow control. The main goal for this investigation was to validate TRL level 4 for this technology and to extend towards flight testing. CFD analysis was performed in order to identify local correlations with experimental data and to better formulate a design criteria so that a maximum increase in lift is possible under given geometrical constraints. Reference to a proposed metric for noise evaluation is also given. This includes basic 2D flow cases and also 2.5D configurations. In 2.5D test cases this work has been extended so that the proposed system may be selected as a mature technology in the JTI Clean Sky, Smart Fixed Wing Aircraft ITD. Complex post-processing of the experimental and CFD data was mainly oriented towards system efficiency and TRL evaluation for this active technology.

Following the successful results of the test campaign on 2D configuration of the oscillatoryblowing system in the flap gap of the INCAS F15 wind tunnel model, extensive evaluation of the 2.5Deffects have been initiated in order to enable solid understanding of the fluidic integrationsmechanisms and to validate this technology at a higher TRL level. Initial experiments on 2Dconfiguration were based on work performed in AVERT EU FP6 project where the oscillatory flapgap blowing system was designed and tested on a INCAS F15 2D wing model. In 2.5D test cases thiswork has been extended so that the proposed system may be selected as a mature technology in theJTI Clean Sky, Smart Fixed Wing Aircraft ITD. New experimental setup was used and also updatedelectronics for the blowing system have been introduces. This was complemented by a new extensionfor the data acquisition system and visualization tools. Complex post-processing of the experimentaldata was mainly oriented towards system efficiency and TRL evaluation for this active technology.

Fluidic oscillators and ejectors were combined to create an effective flow control device, proved effective but have not been optimized yet. In the current study, mostly steady RANS simulations were used to optimize 11 geometric parameters of a generic-simplified suction and oscillatory blowing actuator (SaOB). Selected unsteady simulations and experiments validated the numerical optimization procedure findings. In the parameter optimization process, multiple input and output parameters are chosen to identify the strongest correlations between them. Non- or weakly- correlated parameters are eliminated from further study and others are combined to obtain a reduced set of correlated parameters. It was found that the Throat ratio (ejector to oscillator) parameter predicts the Entrainment ratio , while the cross-flow pressure gradient ratio can predict the ability of the SaOB actuator to produce effective oscillation. The optimized device performs significantly better than the starting point device. While the approach is appealing, open questions remain concerning the comparison of 2D simulations and the actual 3D geometry and compressibility effects. [ABSTRACT FROM AUTHOR]