Periodic Reporting for period 2 - WINGPULSE (Develop and test power efficient actuator concepts for separation flow control at large aerodynamic areas requiring very low actuation energy)
Reporting period: 2022-01-01 to 2023-08-31
Clean Sky 2 (CS2) Large Passenger Aircraft Programme has been dedicated to addressing slat cutbacks at the juncture of the engine pylon by developing active flow control (AFC) strategies. Among the various AFC techniques proposed in the literature, the pulsed jet actuator (PJA) control has been regarded as a particularly promising one as it suppression separation effectively and with much lower mass flow than the continuous blowing actuation. WINGPULSE is specifically designed to unlock the potential of the PJA technique by combining the expertise of UNOTT in wind tunnel experiments, high-fidelity simulations and control design and the cutting-edge infrastructure and expertise of large-scale flow control testing at ILOT. The overarching aim of WINGPULSE is to develop and demonstrate PJA concepts for flow separation control with efficiency beyond the state-of-the-art (reducing the net mass flow by a factor of 3-5).
The specific objectives and the associated work packages to achieve this aim are:
• To build a wind tunnel (WT) model consisting of a main element and flap with a system of PJAs integrated into the leading edge of the WT model.
• To characterise maximum lift and stall characteristics, namely position of separation line, for no AFC case and thereafter the baseline PJ actuation pattern. The control effect of the PJAs will be verified by both wind tunnel experiments and CFD on high-performance computing facilities.
• To investigate advanced PJ actuation patterns on the small-scale WT model, namely by variation of jet pulse sequence in the spanwise direction, variations of duty cycle for each jet, and variation of spacing between pair of adjacent blowing slots.
• To investigate advanced PJA patterns on a WT model at representative aircraft scale by applying the results for most promising actuation patterns.
• To analyse results of the advanced actuation methods from numerical simulations and to deliver a final report of recommendations and outlook for PJA application in real aircraft conditions.
In summary, PJA for flow separation control with efficiency beyond the state-of-the-art was achieved in the WINGPULSE project – net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing.
The specific objectives and the associated work packages to achieve this aim are:
• To build a wind tunnel (WT) model consisting of a main element and flap with a system of PJAs integrated into the leading edge of the WT model.
• To characterise maximum lift and stall characteristics, namely position of separation line, for no AFC case and thereafter the baseline PJ actuation pattern. The control effect of the PJAs will be verified by both wind tunnel experiments and CFD on high-performance computing facilities.
• To investigate advanced PJ actuation patterns on the small-scale WT model, namely by variation of jet pulse sequence in the spanwise direction, variations of duty cycle for each jet, and variation of spacing between pair of adjacent blowing slots.
• To investigate advanced PJA patterns on a WT model at representative aircraft scale by applying the results for most promising actuation patterns.
• To analyse results of the advanced actuation methods from numerical simulations and to deliver a final report of recommendations and outlook for PJA application in real aircraft conditions.
In summary, PJA for flow separation control with efficiency beyond the state-of-the-art was achieved in the WINGPULSE project – net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing.
WP1 - A small scale WT model, which includes the integration of PJA system with a control cabinet was completed and delivered.
WP2 - Numerical simulations of the baseline geometry with & without control is completed. Both experimental and simulation results indicate that active flow control via pulsed jet actuators is able to increase the maximum lift by more than 15% as well as delay the corresponding maximum angle of attack by around 4°. The implementation of active flow control does not have an obvious penalty on the drag coefficients at various angles of attack compared with clean cases.
WP3 - Good agreement and validation of numerical simulation against experiment for reduced duty cycle cases. Difference in maximum lift coefficient between experiment and simulation is found to be less than 10% for all cases with comparable stall angle observed for all cases.
WP4 - the WT model design was carried out in accordance with best practices and international standards. The system matches the requirements in terms of maximum jest velocity and pulse shape. Low DC results present high efficiency in terms of achieving desired jet velocity with much lower averaged mass flow rate in comparison to continuous blowing.
WP5 - In advanced CFD simulations of flow effects caused by PJA system, it has been found:
•The "Continuous Blowing" scenario gave the best results in term of the growth in lift coefficient and the delay of the buffet onset.
•Both scenarios "Lower-Frequency Pulsate Blowing" and "Higher-Frequency Pulsate Blowing" gave also significant growth in lift coefficient compared to "Clean Wing" reference configuration.
• for three nozzle blow control scenarios, the maximum percentage increase in the lift coefficient compared to the "Clean Wing" configuration is presented.
WP6 -PJA for flow separation control with efficiency beyond the state-of-the-art was achieved – net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing.
WP7 -Effective Project Management has been executed, including reporting on progress, expenditure and risk register and management.
In the project, the small-scale wind tunnel test demonstrates developed PJA system that is able to perform actuation with very low DC. Designed a large-scale wind tunnel model incl. integration of PJA system. dvanced time-accurate CFD simulations were in very good agreement with the experiment. PJA for flow separation control with efficiency beyond the state-of-the-art was achieved– net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing. The project findings have been disseminated in several international conferences and published in 4 scientific papers.
WP2 - Numerical simulations of the baseline geometry with & without control is completed. Both experimental and simulation results indicate that active flow control via pulsed jet actuators is able to increase the maximum lift by more than 15% as well as delay the corresponding maximum angle of attack by around 4°. The implementation of active flow control does not have an obvious penalty on the drag coefficients at various angles of attack compared with clean cases.
WP3 - Good agreement and validation of numerical simulation against experiment for reduced duty cycle cases. Difference in maximum lift coefficient between experiment and simulation is found to be less than 10% for all cases with comparable stall angle observed for all cases.
WP4 - the WT model design was carried out in accordance with best practices and international standards. The system matches the requirements in terms of maximum jest velocity and pulse shape. Low DC results present high efficiency in terms of achieving desired jet velocity with much lower averaged mass flow rate in comparison to continuous blowing.
WP5 - In advanced CFD simulations of flow effects caused by PJA system, it has been found:
•The "Continuous Blowing" scenario gave the best results in term of the growth in lift coefficient and the delay of the buffet onset.
•Both scenarios "Lower-Frequency Pulsate Blowing" and "Higher-Frequency Pulsate Blowing" gave also significant growth in lift coefficient compared to "Clean Wing" reference configuration.
• for three nozzle blow control scenarios, the maximum percentage increase in the lift coefficient compared to the "Clean Wing" configuration is presented.
WP6 -PJA for flow separation control with efficiency beyond the state-of-the-art was achieved – net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing.
WP7 -Effective Project Management has been executed, including reporting on progress, expenditure and risk register and management.
In the project, the small-scale wind tunnel test demonstrates developed PJA system that is able to perform actuation with very low DC. Designed a large-scale wind tunnel model incl. integration of PJA system. dvanced time-accurate CFD simulations were in very good agreement with the experiment. PJA for flow separation control with efficiency beyond the state-of-the-art was achieved– net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high-DC pulsed blowing. The project findings have been disseminated in several international conferences and published in 4 scientific papers.
Novel development of the small-scale wind tunnel model included incorporation of fast-switching valves (300 Hz) capable of operating at low duty cycles (down to 20%), additive manufacture of valve connectors and pulsed jet actuator (PJA) nozzles, with a valve connected to every two nozzles to achieve real-time, quasi-independent control of PJAs along the slat cut-out region via a FPGA-based NI cRIO controller.
Ground test of large-scale PJA system components in silent conditions showed that the system matches the requirements in terms of maximum jet velocity and pulse shape, with fine control over the latter achieved for various duty cycles. Furthermore, low pulsed jet duty cycle demonstrated high efficiency in terms of achieving the desired jet velocity with a much lower averaged mass flow rate in comparison to continuous blowing.
Novel combination of large eddy simulation (LES) and the hybrid RANS-LES stress-blended eddy simulation (LES-SBES) model was employed for the mid-wing (slat cut-out) and wing ends (with slats) respectively, to balance computational accuracy and expense.
Good agreement and validation of numerical simulation against experiment for reduced pulsed jet duty cycle cases. Difference in maximum lift coefficient between experiment and simulation is found to be less than 10% with comparable stall angle observed for all cases.
Pulsed jet actuation for flow separation control with efficiency beyond the state-of-the-art was achieved via the implementation of advanced actuation patterns, including reduced duty cycle, reduced operating area and travelling wave actuation. Net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high duty cycle blowing, with maximum lift coefficient increase shown to be most power efficient at the lowest duty cycle. In summary, the overarching aim of WINGPULSE was fulfilled – to develop and demonstrate concepts for flow separation control with efficiency beyond the state-of-the-art (reducing the net mass flow by a factor of 3-5).
The research has reached TRL5 since the advanced PJA control on the small-scale model has been tested in a wind tunnel as a relevant environment.
Ground test of large-scale PJA system components in silent conditions showed that the system matches the requirements in terms of maximum jet velocity and pulse shape, with fine control over the latter achieved for various duty cycles. Furthermore, low pulsed jet duty cycle demonstrated high efficiency in terms of achieving the desired jet velocity with a much lower averaged mass flow rate in comparison to continuous blowing.
Novel combination of large eddy simulation (LES) and the hybrid RANS-LES stress-blended eddy simulation (LES-SBES) model was employed for the mid-wing (slat cut-out) and wing ends (with slats) respectively, to balance computational accuracy and expense.
Good agreement and validation of numerical simulation against experiment for reduced pulsed jet duty cycle cases. Difference in maximum lift coefficient between experiment and simulation is found to be less than 10% with comparable stall angle observed for all cases.
Pulsed jet actuation for flow separation control with efficiency beyond the state-of-the-art was achieved via the implementation of advanced actuation patterns, including reduced duty cycle, reduced operating area and travelling wave actuation. Net mass flow was reduced by a factor of 3.5 compared with continuous blowing, and by a factor of 3 compared with high duty cycle blowing, with maximum lift coefficient increase shown to be most power efficient at the lowest duty cycle. In summary, the overarching aim of WINGPULSE was fulfilled – to develop and demonstrate concepts for flow separation control with efficiency beyond the state-of-the-art (reducing the net mass flow by a factor of 3-5).
The research has reached TRL5 since the advanced PJA control on the small-scale model has been tested in a wind tunnel as a relevant environment.