Simulation of active flow control on the flap of a 2D high-lift configuration

The numerical investigations described in the present paper deal with active flow control for a 2D, 2-element high-lift airfoil under low speed wind tunnel conditions. Here, the aim of the flow control application is the transport of fluid-momentum from the outer part of the boundary layer towards the wall to actively reduce or eliminate the large flow separation on the flap. The URANS simulations carried out in this study focus on the variation of the streamwise actuator-slot width and the actuation direction, and their potential to suppress or delay separation. Different slot-exit settings coupled with a constant frequency, duty cycle, and mass flow are discussed regarding their impact on the local flow

Assesment of blocking/mean flow effects in the Cepra19 w/t analyzed by means of CFD simulations

The report describes the CFD work performed at DLRs Institute of Aerodynamic and Flow Technology under contract to Airbus France. The study is assign to Task 1.1 of the LAGOON project on the assesment of the influence in aerodynamic performances for a simplified landing gear model located in two different wind tunnels. The flow around an identical model in the free jet Cepra19 WT and in the F2 closed test section tunnel is simulated, as well as the free stream setting.Due to the lack of previous free jet tunnel simulations some initial studies of the empty Cepra19 WT flow were performed

Parameter study for a slatless 2D high-lift airfoil with active separation control using a URANS approach

The numerical investigations described in the present paper deal with active flow separation control for a 2D, 2-element high-lift airfoil. Here, the aim of the flow control application is to actively reduce or eliminate a large flow separation on the flap by a periodic excitation mechanism, known as pulsed blowing. This study explores the resulting effects of the flow control application on the global aerodynamic coefficients and, beyond this, by the analysis of the resulting loads variation by specific actuation parameters. For enabling the extrapolation towards flight Reynolds numbers the URANS computations are addressed at both low speed atmospheric windtunnel conditions (Re≈2x10^6.) as well as for higher Reynolds number comparable to flight conditions (Re≈7x10^6)

Numerical Optimization of a Zero-Net-Mass-Flux Actuation for a High Lift Airfoil

A common research project (CRP) of ONERA and DLR, the CRP LEAFCO (2012-2015), tackles the application of zero-net-mass-flux (ZNMF) actuation on a laminar high-lift airfoil by means of wind tunnel experiments and simulations. Here only numerical results are discussed. The capability of modern numerical methods, unsteady Reynolds-averaged Navier-Stokes (uRANS), to predict the impact of the AFC application on the aerodynamic performance is here used to optimize the unsteady actuation parameters prior the manufacturing and testing of a high-lift airfoil DLR-F15LLE (Laminar Leading Edge). The main objective is to define geometrical parameters of the actuation slit, such as position, direction and width, which are to be considered for the extensive wind tunnel testing with ZNMF-actuators in large test facilities of ONERA and DLR

Active Separation Control on High-Lift Configurations using a URANS approach

This contribution discusses numerical investigations of active flow separation control for high-lift configurations under atmospheric low-speed wind tunnel conditions. A two dimensional (2D), 2-element airfoil and a three-dimensional (3D), 3-element, wing body setup are the configurations of interest. The slot-actuators are applied on the suction side of the trailing edge flap to prevent the local flow separation. The active flow control (AFC) method of choice is the pulsed blowing. This study explores the resulting effects of the flow control application on the global aerodynamic coefficients and, beyond this, by the analysis of the resulting loads variation by specific actuation parameters. The computational results highlight the ability of pulsed blowing at moderate blowing momentum coefficients to suppress the flow separation on the trailing edge flap and support the global aerodynamic enhancement

Active Flow Separation Control on a High-Lift Wing-Body Configuration. Part 2: The Pulsed Blowing Application.

This contribution discusses the implementation of active flow separation control for a 3D high-lift wing-body configuration under atmospheric low-speed wind tunnel conditions. The slot-actuators are applied on the suction side of the trailing edge flap to prevent local flow separation. It is the consequent progression of the work presented in Part 1 of this paper. The active flow control (AFC) method of choice is now the pulsed blowing. The experimental results indicate that this AFC technique is feasible for such applications with a global performance enhancement. Here, the wind tunnel findings are briefly discussed while the emphasis is given on the numerical investigations. The verification of the URANS approach points out that the global enhancement through AFC may easily be overestimated by insufficient numerical convergence. Thus, high computational requirements are needed for a consistent numerical evaluation. The computational results highlight the ability of pulsed blowing at moderate blowing momentum coefficients to suppress the flow separation on the trailing edge flap and support the global aerodynamic enhancement. The numerical results show an acceptable agreement with the experimental results for this AFC application

Active Flow Separation Control on a High-Lift Wing-Body Configuration - Part 1: Baseline Flow and Constant Blowing

This paper describes the influence of grid resolution and turbulence modeling for a 3D transport aircraft in high lift configuration with massive flap separation. The flap is equipped with spanwise slotted active flow control (AFC) devices to allow studies on active separation control. The effects of constant slotted blowing on the high lift performance are highlighted. Oil flow pictures from a mid-scale experiment in the low speed wind tunnel of Airbus in Bremen (B-LSWT) serve as a validation database for the baseline CFD results. RANS calculations are carried out with and without constant blowing boundary conditions. The baseline flow is also investigated with a time-accurate URANS approach. One of the major outcomes of the AFC study is the demonstration of the feasibility to simulate AFC concepts on a 3D configuration. Constant blowing shows the beneficial effect that separation can largely be suppressed because of the energy added to the flow on the suction side of the flap. This study serves as a preceding validation for the subsequent pulsed blowing approach treated in Part 2

A CFD process chain for simulating open windtunnel test sections

This paper discusses a CFD procedure for simulating open wind tunnel test sections based on the investigations of the DLR project ForMEx II. Within this project numerical simulations and the analysis of the wind tunnel (w/t) experiments are performed in order to study the potential of CFD to support and improve the w/t corrections. In this paper, the aerodynamic low speed w/t DNW-NWB and the aeroacoustic w/t AWB are investigated. First, computations for the empty test sections are conducted, for the evaluation of the CFD potential to simulate the open jet flow in each of the w/ts, and second, the open jet flow with the DLR F16 2D high-lift model installed, for the aeroacoustic AWB w/t. The overall good agreement of the numerical results compared to the experiments indicate a reliable capability to simulate and further support the development and adjustment of the tunnel corrections for open test sections

Active Flow Separation with the DLR F15 Configuration

A short overview on simulation and experiment with the DLR F15 configuration towards the posible challenge of a common workshop for active flow control