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STAtic and DYnamic piezo-driven streamWIse vortex generators for active flow COntrol

Final Report Summary - STA-DY-WI-CO (STAtic and DYnamic piezo-driven streamWIse vortex generators for active flow COntrol)

STAtic and DYnamic piezo-driven StreamWIse vortex generators for active flow Control (STA-DY-WI-CO) was Marie Curie IAPP transfer of knowledge programme involving two partners, Institute of Fluid Flow Machinery Polish Academy Of Sciences and LMS International Belgium.

STA-DY-WI-CO developed an innovative approach for coupled multi physics co-simulation, testing and optimization of piezoelectric driven static and dynamic active flow control systems applied in the aerospace and wind turbine industry. Numerical simulation and experimental validation approach encompassed by optimization loop with maximizing the positive impact on environment was applied.

Research work has been active within all three Work Packages. In Work Package 1, Fluid dynamics Synthetic Jet Actuator and Retractable Vortex Generator were investigated.

Initial numerical models of the system was developed in tight cooperation of Fluid Dynamic (WP1), Structural Mechanics (WP2) supported by fluid-structure interaction (WP3) code coupling. Based on the preliminary results two actuators were designed and manufactured for testing and numerical model improvement. Starting from the investigation of the isolated piezoelectric membrane towards fully encapsulated actuator numerous experimental campaigns has been conducted to develop different characteristics of the system. Input quantities were made variable to observe and understand their influence on the output in the parametric study. Control signal frequency, voltage and electrical current powering entire system, material properties and geometry of the membrane were measured as inputs towards output mechanical (vibration amplitude velocity, geometry, temperature) and flow (fluid velocity in jet) parameters of the system. This allowed to learn energy consumption, temperature gain and efficiency of the system performance.

In conjunction to the investigation focused on the isolated actuator development of the wind tunnel test stand was running. Several profile configurations were accounted with the criteria being prone to separation. Profile for the wind tunnel tests was made adjustable in purpose of the smooth regulation of the separation intensity for the given inflow velocity in the tunnel. The final configuration of the actuators for wind tunnel tests was adopted in form of multi-actuator stack and integrated into the profile. Numerous tests were made and comprehensive test matrix was defined to cover different test stand configurations representative for the different realistic flow cases. Outcomes of the experimental campaign are very promising. The preliminary research assumption that the vortex generators have a potential to reduce separation has been confirmed. This reduction of separation causes a reduction in helicopter drag and hence the fuel consumption. How much? It is dependent on the flight scenario. Piezo-driven actuators are very light and consume very little energy thus their potential to reduce the overall fuel consumption of the helicopter is high.

In parallel to the experimental activity two numerical analyses of possible scenarios of the flow separation control system application were investigated. In particular acoustics and flutter analysis has been performed.

The former was looking into noise quality assessment of rotorcraft noise. In this study, a comprehensive and interactive noise quality evaluation tool was developed which goes one step further and links the metrics to the underlying sound components (such as loudness and sharpness) as resulting from time- and frequency-domain analysis studies. This approach allow to identify critical sound features, time structures and frequency ranges and obtain a better understanding of sound quality differences among various aircraft types and rotorcraft designs. Acoustic signature was a subject of numerical simulations performed on the industrial car shape. The method of the quantification of the main aerodynamic sources of noise generated by the flow of air around the industrial car shape has been developed. It has been proven that using a sufficiently detailed surface model of the vehicle and simplified Euler modelling of the flow on hybrid grids designed to capture the near-field sound waves propagation it is possible to locate major contributors to noise level. It is also evident that the methodology is very efficient and could be easily extended to allow for more complex, turbulent flow modelling (URANS, DES or LES). Thanks to a constant increase of an available computing power it is possible to refine the spatial and temporal resolution of the combined CFD – CAA simulation to a point when the additional acoustic modelling is no longer necessary – the acoustic pressure fluctuations are part of the flow-field solution.

The latter done within Advanced CFD flutter analysis to complement possible scenarios. The invalid flow control can cause increased vibration level of the blades eventually leading to the unstable flutter. Increased vibration level causes the shortening of the blade lifetime Additional objectives formulated studied the durability analysis of the composite material blade and flutter analysis in structural domain.

Dynamic behavior of complex coupled fluid-structure systems is often of non-linear nature. Comprehensive numerical and experimental studies of the nonlinear systems structural dynamics was investigated based on the rotating machinery test stand. Numerical study encompassing sophisticated model of the hydrodynamic bearings was performed with the application of the commercial and in-house software tools. Experimental setup under investigation was modelled and analyzed. Measurement campaign of the rotor system delivered data sets used for the numerical models verification and validation. As the outcome the nonlinear damping and stiffness characteristics were identified.

Yet another building block of the overall system was being investigated in view of integration of the above-described subcomponents a numerical platform for the coupled multi-physics phenomena analysis was implemented. It was decided to set-up a research partnership with Fraunhofer SCAI developer of the MpCCI CouplingEnvironment – The Standard Interface for Multiphysics Code Coupling. It provides an application independent interface for the coupling of different simulation codes: Nastran (FEM), Fluent (CFD) and Matlab (control). Moreover this platform was launched on the Supercomputer Resources. The platform runs at the CI TASK on cluster 'Galera' - 1344 Intel Xeon QuadCore processors (5376 cores), 25 TB total system memory, 100 TB disk storage. Its computing power of 50 TFlops is exploited in parallel computations and simulations of coupled structural and fluid dynamics in the STA-DY-WI-CO project.

The project outcomes will both serve the designers of the next-generation aircrafts and wind turbine blades and at the same time strengthen the human potential in R&D in Europe.