Periodic Reporting for period 2 - PERSEUS (Pulsed jEt actuatoRs for SEparation control of tUrbulent flowS)
Periodo di rendicontazione: 2021-12-01 al 2023-02-28
Context of the project:
Flow separation occurring during the take off and/or landing phases of flight or at wing/nacelle junction is a critical phenomenon which may lead to strong degradations of aircraft performances. Active flow control is an attractive way to mitigate the detrimental effects induced by flow separation. While current flow control applications are mostly based on trial-and-error procedures, which are time and resources consuming, the methodology developed in the PERSEUS project will pave the way to a new approach to control system optimization.
Objectives of the project:
Within the PERSEUS project, the ultimate goal is to develop advanced and more efficient active flow control in comparison to currently available technology. To this end, two main outcomes are expected:
1/ Develop a new generation of pulsed jet actuators for of flow control capable to cover a wide range of actuation frequencies.
2/ Develop a new methodology based on sophisticated numerical tools to optimize the actuator performances.
By coupling these approaches, the objective is to design an optimized active flow control device that will combine performance and energy sobriety.
Impact of the project:
The development of outperforming flow control device, which is at the core of the PERSEUS project, will enable to improve the overall efficiency of aircrafts. During the project, a proof of feasibility will be carried out on a wing prototype. If successful, this project will lead to sustainable and safer aircrafts, which is a goal targeted by the CleanSky program of Horizon 2020.
Flow separation occurring during the take off and/or landing phases of flight or at wing/nacelle junction is a critical phenomenon which may lead to strong degradations of aircraft performances. Active flow control is an attractive way to mitigate the detrimental effects induced by flow separation. While current flow control applications are mostly based on trial-and-error procedures, which are time and resources consuming, the methodology developed in the PERSEUS project will pave the way to a new approach to control system optimization.
Objectives of the project:
Within the PERSEUS project, the ultimate goal is to develop advanced and more efficient active flow control in comparison to currently available technology. To this end, two main outcomes are expected:
1/ Develop a new generation of pulsed jet actuators for of flow control capable to cover a wide range of actuation frequencies.
2/ Develop a new methodology based on sophisticated numerical tools to optimize the actuator performances.
By coupling these approaches, the objective is to design an optimized active flow control device that will combine performance and energy sobriety.
Impact of the project:
The development of outperforming flow control device, which is at the core of the PERSEUS project, will enable to improve the overall efficiency of aircrafts. During the project, a proof of feasibility will be carried out on a wing prototype. If successful, this project will lead to sustainable and safer aircrafts, which is a goal targeted by the CleanSky program of Horizon 2020.
During the project, the work has been focused on the development of the tools required to carry out the optimization process. To this end, five main actions have been performed:
1/ two swept-wing mock-ups were made. One of these models has been designed in such a way that it can accommodate different types of fluidic actuators.
2/ an extensive dataset has been generated using wind-tunnel experiments in which a wing prototypes have been installed. A wide range of physical parameters have been varied (wind velocity, angle of attack ...). Active flow control has been incorporated and the wing performances have been measured.
3/ a first generation of actuators has been designed, manufactured and integrated into the wing model, which is used in the wind-tunnel experiments. Following this first phase of tests, a second generation of actuators was designed with performances greatly exceeding those of the first generation. For a very low amount of mass flowrate, this new generation of actuators has made it possible to achieve net aerodynamic gains of around 15%.
4/ Using high-fidelity simulations, the physical mechanisms driving the operation of the internal flow of the actuators have been identified and modelled.
5/ optimization tools have been developed and assessed against the data generated from the wind-tunnel experiments. First developed at low Reynolds number, these optimization tools have been extended to higher Reynolds number range. These tools have evidenced several regions where the flow seems to be highly sensitive to external perturbations. These insights have been incorporated in the design of the actuator.
The PERSEUS project led to several outputs at the dissemination level. The main outputs are:
● 1 paper published in Journal of Fluid Mechanics about the sensitivity methodology.
● 1 paper under review in AIAA Journal about the high-fidelity simulation (LES) of the PJAs and the physical analysis of the switching mechanism.
● 6 oral communications in international conferences/workshops (AIAA SciTech, EFMC, 3AF, ERCOFTAC).
● 2 oral communications at the French academic and industrial network dedicated to flow separation control GDR 2502 “Control of separated flows”.
1/ two swept-wing mock-ups were made. One of these models has been designed in such a way that it can accommodate different types of fluidic actuators.
2/ an extensive dataset has been generated using wind-tunnel experiments in which a wing prototypes have been installed. A wide range of physical parameters have been varied (wind velocity, angle of attack ...). Active flow control has been incorporated and the wing performances have been measured.
3/ a first generation of actuators has been designed, manufactured and integrated into the wing model, which is used in the wind-tunnel experiments. Following this first phase of tests, a second generation of actuators was designed with performances greatly exceeding those of the first generation. For a very low amount of mass flowrate, this new generation of actuators has made it possible to achieve net aerodynamic gains of around 15%.
4/ Using high-fidelity simulations, the physical mechanisms driving the operation of the internal flow of the actuators have been identified and modelled.
5/ optimization tools have been developed and assessed against the data generated from the wind-tunnel experiments. First developed at low Reynolds number, these optimization tools have been extended to higher Reynolds number range. These tools have evidenced several regions where the flow seems to be highly sensitive to external perturbations. These insights have been incorporated in the design of the actuator.
The PERSEUS project led to several outputs at the dissemination level. The main outputs are:
● 1 paper published in Journal of Fluid Mechanics about the sensitivity methodology.
● 1 paper under review in AIAA Journal about the high-fidelity simulation (LES) of the PJAs and the physical analysis of the switching mechanism.
● 6 oral communications in international conferences/workshops (AIAA SciTech, EFMC, 3AF, ERCOFTAC).
● 2 oral communications at the French academic and industrial network dedicated to flow separation control GDR 2502 “Control of separated flows”.
The actuator technology developed in the PERSEUS project is based on bi-stable fluidic oscillators. To match the frequency range which is targeted to control the separated flow at high angle of attack, a new design of the feedback loops has been defined. This design has been guided by high-fidelity numerical simulations, which have revealed new physical mechanisms of the internal flow. A new model has been proposed in order to link the different parameters of the actuator to the phenomenon of switching between the branches of the oscillator. This model allows for predicting faithfully the excitation frequency of the actuator over a broad range of operating conditions.
Another progress is the development of optimization tools based on sensitivity analysis at high Reynolds number and for 3D separated flows. First, this method was validated at low Reynolds number. In a second phase, the tools were extrapolated to a large Reynolds number. Comparison with large Reynolds wind tunnel tests reveals very good agreement with the predictions from the sensitivity method.
In the end, an experimental demonstrator was built to validate the proof of feasibility of the PERSEUS project. The results obtained with the optimized actuators put forward a very high efficiency of the control strategy for a low operating cost.
The project produced high quality data and results that open up prospects for the development of optimization tools to guide the design of more efficient and sustainable aircraft. Even if the heart of the PERSEUS project was focused on a wing-type demonstrator, the benefits of the project are much broader. Indeed, the optimization and control tools developed during the project can be extended to many other areas such as transport in general and thermal regulation systems. Moreover, these new optimization techniques are tools on which future engineers will have to be trained. The PERSEUS project provides the first elementary bricks to build these new skills to be incorporated in university courses.
Another progress is the development of optimization tools based on sensitivity analysis at high Reynolds number and for 3D separated flows. First, this method was validated at low Reynolds number. In a second phase, the tools were extrapolated to a large Reynolds number. Comparison with large Reynolds wind tunnel tests reveals very good agreement with the predictions from the sensitivity method.
In the end, an experimental demonstrator was built to validate the proof of feasibility of the PERSEUS project. The results obtained with the optimized actuators put forward a very high efficiency of the control strategy for a low operating cost.
The project produced high quality data and results that open up prospects for the development of optimization tools to guide the design of more efficient and sustainable aircraft. Even if the heart of the PERSEUS project was focused on a wing-type demonstrator, the benefits of the project are much broader. Indeed, the optimization and control tools developed during the project can be extended to many other areas such as transport in general and thermal regulation systems. Moreover, these new optimization techniques are tools on which future engineers will have to be trained. The PERSEUS project provides the first elementary bricks to build these new skills to be incorporated in university courses.