Reynolds Number Scalability for Separation Control on a Laminar Airfoil

31st AIAA Applied Aerodynamics Conference

et al. 2013

A wing glove for active flow control free-flight experiments using a one-fifth dynamically scaled Aeromot 200S Super Ximango motor glider was developed. The wing glove has a modified NACA 643 − 618 airfoil and is instrumented with off-the-shelf pressure transducers and amplitude-modulated synthetic jet actuators. Before the flight-testing was commenced the wing glove and the instrumentation were tested in two open return low-speed wind tunnels. Due to the low-aspect ratio of the glove, particular attention was paid to the two-dimensionality of the flow field over the wing glove. Several flight experiments were carried out and free-flight data with and without actuation were recorded. Unexpected challenges that were encountered during the flight-testing are discussed and an analysis of the wall pressure data in the frequency domain is provided.

Section: Introductionmentioning

confidence: 89%

Wind Tunnel and Free-Flight Testing of Active Flow Control for Modified NACA 613-618 Airfoil

Dianics

Balthazar

31st AIAA Applied Aerodynamics Conference

et al. 2013

“…11,12 The full size cruise Reynolds number is 3.2million. Thake et al 7 investigated separation control by steady vortex generator jets for the original NACA 64 3 -618 airfoil. Four different Reynolds numbers, Re=64,200, 180,000, 1 Million, and 4 Million were considered.…”

Section: Introductionmentioning

confidence: 99%

“…Examples are separation control for low-pressure turbine blades 1-3 and laminar airfoils. [4][5][6][7] In this paper the question is addressed if harmonic blowing through a slot is also effective at higher Reynolds numbers. The Reynolds number scalability of a flow control strategy can be investigated by keeping an appropriate dimensionless parameter (such as the momentum coefficient) constant and then determining how dimensionless performance parameters (such as the lift and drag coefficient) change when the Reynolds number is altered (e.g.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Separation Control for Wing Sections

6th AIAA Flow Control Conference

Fasel

2012

Numerical simulations of the unsteady separated flow over wing sections at flight Reynolds numbers are challenging. Direct numerical simulations which resolve all scales of the fluid motion promise the highest degree of fidelity but are computationally very expensive. Even large-eddy simulations can be prohibitively expensive because of the high grid resolution required near the walls. Hybrid turbulence models employ Reynolds-averaged NavierStokes near the walls and adjust the turbulence model contribution away from the walls according to the local physical grid resolution. In this paper hybrid simulations based on a one-equation renormalization group model are presented for a modified NACA643-618 airfoil at a chord Reynolds number of 1 million and for 10, 20, and 30 degrees angle of attack. For these conditions a short laminar separation bubble develops near the leading edge and the flow separates turbulent from the suction side downstream of the leading edge bubble. For 10 degrees angle of attack the lift and drag data obtained from the simulations are in good agreement with XFoil predictions and active flow control by harmonic blowing through a spanwise slot upstream of the turbulent separation is investigated.

“…Separation control strategies such as pulsed vortex generator jets and harmonic blowing and suction through slots were successfully employed for controlling laminar separation at low Reynolds number conditions. Examples are separation control for low-pressure turbine blades [1][2][3] and laminar airfoils [4][5][6][7]. In this paper the question is addressed if harmonic blowing through a slot is also effective at higher Reynolds numbers.…”

Section: Introductionmentioning

confidence: 99%

“…The Reynolds number scalability of a flow control strategy can be investigated by keeping an appropriate dimensionless parameter (such as the momentum coefficient) constant and then determining how dimensionless performance parameters (such as the lift and drag coefficient) change when the Reynolds number is altered (e.g. Thake et al [7]). Of particular interest is also the question if similar physical mechanisms can be exploited for an efficient flow control when the Reynolds number is varied.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Separation Control for Wing Sections

International Journal of Flow Control

Fasel²

2013

For Reynolds numbers that are typical for general aviation aircraft separation is typically turbulent. In this paper the question is addressed if flow control strategies that are successful at low-Reynolds number conditions remain effective at higher Reynolds numbers. Towards this end hybrid simulations based on a one-equation renormalization group model were carried out for a modified NACA643-618 airfoil at a chord Reynolds number of one million. For ten degrees angle of attack a short laminar separation bubble develops near the leading edge and the flow separates turbulent from the suction side downstream of the leading edge bubble. Active flow control by harmonic blowing through a spanwise slot was investigated. The control was found to be only mildly effective or even counterproductive. In particular, the disturbances that were introduced by the control were only weakly amplified or even dampened. The unresolved eddy viscosity in the separated boundary layer lowers the effective Reynolds number and makes the flow less unstable or even stable with respect to two-dimensional disturbances. As a consequence of this, higher blowing ratios are required compared to flow control at low-Reynolds number conditions where the shear-layer instability is stronger. *