Periodic Reporting for period 3 - UHURA (Unsteady High-Lift Aerodynamics – Unsteady RANS Validation)
Okres sprawozdawczy: 2021-09-01 do 2022-08-31
Laminar wing technology is seen as a major source for drag reduction of a transport aircraft. It is a key technology to achieve the targets for emission reduction. The Krueger flap leading edge device was found to be the most promising concept of a dual-functional leading-edge device for laminar wings. While previous studies focused on the general performance and integration, the behavior of the system during its deployment or retraction proves to be a major issue due to the very different kind of motion compared to conventional leading edge high-lift devices. The risks of this concept are identified in the areas of load estimates, handling qualities and asymmetric failure cases.
During the deployment, the Krueger device is deflected from the lower side against the flow, passing critical stations when perpendicular to the flow, forming large scale separated flow on the lower side when moved around the leading edge. Current conservative estimations require the installation of many independently driven Krueger flap elements to prevent examination of critical situations along the whole wing span. The multiplication of drive stations leads to increasing complexity, weight and maintenance costs.
Despite the great progress in numerical simulation methods in the past years, there have up to now been no investigations on the validity of the current methods for predicting the aerodynamics during movement of high-lift devices in detail.
With the project UHURA we address the following objectives:
> Validation of numerical simulation methods for prediction of the unsteady aerodynamics and dynamic loads during the deployment of high-lift systems - We expect to obtain an accuracy comparable to steady state calculations (less than 1% error in lift, drag and pitching moment).
> Quantification of the completely unknown aerodynamic characteristics of a slotted Krueger device during deployment - We aim to improve the load estimation and eliminate a current 10% uncertainty in comparison to state-of-the-art approaches.
> Accuracy improvement for the load determination for the sizing of structure and kinematics - We expect to achieve a system complexity reduction of about 70%. Further on, we expect a resulting 10% weight reduction due to the higher accuracy of load calculations.
> Qualification of impact on handling qualities and certification - We expect to save the above mentioned 70% of system complexity without any impact on the reliability of the system, handling qualities and certification issues.
During the deployment, the Krueger device is deflected from the lower side against the flow, passing critical stations when perpendicular to the flow, forming large scale separated flow on the lower side when moved around the leading edge. Current conservative estimations require the installation of many independently driven Krueger flap elements to prevent examination of critical situations along the whole wing span. The multiplication of drive stations leads to increasing complexity, weight and maintenance costs.
Despite the great progress in numerical simulation methods in the past years, there have up to now been no investigations on the validity of the current methods for predicting the aerodynamics during movement of high-lift devices in detail.
With the project UHURA we address the following objectives:
> Validation of numerical simulation methods for prediction of the unsteady aerodynamics and dynamic loads during the deployment of high-lift systems - We expect to obtain an accuracy comparable to steady state calculations (less than 1% error in lift, drag and pitching moment).
> Quantification of the completely unknown aerodynamic characteristics of a slotted Krueger device during deployment - We aim to improve the load estimation and eliminate a current 10% uncertainty in comparison to state-of-the-art approaches.
> Accuracy improvement for the load determination for the sizing of structure and kinematics - We expect to achieve a system complexity reduction of about 70%. Further on, we expect a resulting 10% weight reduction due to the higher accuracy of load calculations.
> Qualification of impact on handling qualities and certification - We expect to save the above mentioned 70% of system complexity without any impact on the reliability of the system, handling qualities and certification issues.
A Krueger flap and corresponding kinematics has been designed for the DLR-F15-LLE airfoil. Realistic design requirements from aircraft level have been specified and respected. The design has been performed in a loop where side constraints on kinematics have been developed and included in the aerodynamic design. The Kreuger flap and the kinematics have been implemented in the wind tunnel model design. Further on, the speed of deployment and retraction of the Krueger device have been established. These numbers reflect the manufacturer knowledge on handling quality and certification criteria for Krueger devices.
The simulation methods have been setup for designated simulation type. On grid generation side, a robust implementation of local reconnection algorithm for unstructured meshes was obtained. Further, a demonstration of local-grid refinement in conjunction with Chimera capability on structured meshes has been established. Beside this, Immersed Boundary Methods and full re-meshing has been successfully applied. With regard to flow solver technologies, most of the partners have demonstrated their capabilities of simulating the deployment of the Krueger device. Methods in use range from uRANS methods via different turbulence-resolving methods (hybrid RANS/LES) up to particle based Lattice Boltzmann Methods.
The modifications for both wind tunnel models have been designed and manufactured. Finite Element Analysis has been used to complete corresponding stress reports. The models are equipped with a significant number of unsteady pressure sensors for dynamic measurements. The PIV methodology to be used to monitor the dynamic flow field has been selected and the implementation in terms of measurement window as well as hardware setup in the tunnel has been achieved. As there are a number of different measurement systems, a synchronisation approach has been established, including trigger, automation and communication approaches.
In total, five wind tunnel tests have been conducted in three different wind tunnel facilities. A first exploratory test entry in ONERA-L1 provided experience on the model behaviour, revealed critical areas in routing sensor connections and proved at first the baseline conditions in first glance comparison of CFD and PIV data based on steady flow conditions. The wind tunnel test in DNW-NWB with a straight and swept cantilever wing arrangements were fully completed. A first entry has finally been conducted in DNW-LLF for the pressure and deformation measurements. Completing the high quality data base, detailed PIV measurements have been conducted in a second entry within both, the ONERA-L1 and the DNW-LLF facility.
In order to compare numerical and experimental data, guidelines for validation have been compiled. By specifying common formats and templates, a common ground for comparison was established. Specific simulations of the different wind tunnel setups were performed, especially using real-time recorded data of the drive system to closely match the real deflection process. Validation of the simulation methods has been achieved and the combination of both data sources has been used to derive important flow features of the Krueger flap for aircraft application.
The simulation methods have been setup for designated simulation type. On grid generation side, a robust implementation of local reconnection algorithm for unstructured meshes was obtained. Further, a demonstration of local-grid refinement in conjunction with Chimera capability on structured meshes has been established. Beside this, Immersed Boundary Methods and full re-meshing has been successfully applied. With regard to flow solver technologies, most of the partners have demonstrated their capabilities of simulating the deployment of the Krueger device. Methods in use range from uRANS methods via different turbulence-resolving methods (hybrid RANS/LES) up to particle based Lattice Boltzmann Methods.
The modifications for both wind tunnel models have been designed and manufactured. Finite Element Analysis has been used to complete corresponding stress reports. The models are equipped with a significant number of unsteady pressure sensors for dynamic measurements. The PIV methodology to be used to monitor the dynamic flow field has been selected and the implementation in terms of measurement window as well as hardware setup in the tunnel has been achieved. As there are a number of different measurement systems, a synchronisation approach has been established, including trigger, automation and communication approaches.
In total, five wind tunnel tests have been conducted in three different wind tunnel facilities. A first exploratory test entry in ONERA-L1 provided experience on the model behaviour, revealed critical areas in routing sensor connections and proved at first the baseline conditions in first glance comparison of CFD and PIV data based on steady flow conditions. The wind tunnel test in DNW-NWB with a straight and swept cantilever wing arrangements were fully completed. A first entry has finally been conducted in DNW-LLF for the pressure and deformation measurements. Completing the high quality data base, detailed PIV measurements have been conducted in a second entry within both, the ONERA-L1 and the DNW-LLF facility.
In order to compare numerical and experimental data, guidelines for validation have been compiled. By specifying common formats and templates, a common ground for comparison was established. Specific simulations of the different wind tunnel setups were performed, especially using real-time recorded data of the drive system to closely match the real deflection process. Validation of the simulation methods has been achieved and the combination of both data sources has been used to derive important flow features of the Krueger flap for aircraft application.
UHURA aimed to validate simulation solutions for key industrial problems to facilitate the introduction of innovative products and services. By creating high quality data with a series of detailed wind tunnel tests, a unique data base was used to compare with simulation results obtained by established and emerging simulation methods. These are assumed to become backbone for any future aircraft development as they now reliable deliver aerodynamic characterization and loads information used for structural sizing while reducing the overall development times.
UHURA aimed to qualify the Krueger flap as enabler of laminar wing technology. Detailed information explored from wind tunnel test and simulation provided further insight on integrating the high-lift system into the laminar wing, this further qualify the Krueger as enabler for the laminar wing. Moreover, by answering open topics on system architecture requirements and handling qualities, UHURA significantly contributes to increased system reliability and safety, reduced Recurring Costs (RC) in production and assembly as well as COC benefits through reduced maintenance efforts, overhaul and repair.
UHURA aimed to contribute towards maintaining the leadership of the European aeronautics industry. The close integration of major European aircraft manufacturers into the project guarantees the future application of the experience gained in the project. By rolling out simulation capabilities enables those to fully exploit the gained experience into the processes needed for new aircraft types. The current design closely matches the needs of industry and reflect the current expectations on potential improvements.
UHURA aimed to qualify the Krueger flap as enabler of laminar wing technology. Detailed information explored from wind tunnel test and simulation provided further insight on integrating the high-lift system into the laminar wing, this further qualify the Krueger as enabler for the laminar wing. Moreover, by answering open topics on system architecture requirements and handling qualities, UHURA significantly contributes to increased system reliability and safety, reduced Recurring Costs (RC) in production and assembly as well as COC benefits through reduced maintenance efforts, overhaul and repair.
UHURA aimed to contribute towards maintaining the leadership of the European aeronautics industry. The close integration of major European aircraft manufacturers into the project guarantees the future application of the experience gained in the project. By rolling out simulation capabilities enables those to fully exploit the gained experience into the processes needed for new aircraft types. The current design closely matches the needs of industry and reflect the current expectations on potential improvements.