Control of Massive Separation over Thick-Airfoil Wing: A Computational and Experimental Study

Arad, Eran; Martin, Preston B.; Wilson, Jacob; Tung, Chee; Directorate, Aeroflightdynamics

doi:10.2514/6.2006-322

Cited by 8 publications

(7 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the prediction using v 2 −f model did not improve the agreement in this region. As was found in other separated-flow simulation [5], a more accurate temporal model, at the DES level or higher, is a minimal requirement for proper simulation of massively separated flow. …”

Section: Baseline (Uncontrolled) Flowmentioning

confidence: 99%

See 1 more Smart Citation

Generic Transport Aft-body Drag Reduction using Active Flow Control

Ben-Hamou

Arad

Seifert

2007

Flow Turbulence Combust

Self Cite

View full text Add to dashboard Cite

Active flow-separation control is an effective and efficient mean for drag reduction and unsteady load alleviation resulting from locally or massively separated flow. Such a situation occurs in configurations where the aerodynamic performance is of secondary importance to functionality. The performance of heavy transport helicopters and aeroplanes, having a large, and almost flat, aft loading ramp suffer from the poor aerodynamics of the aft body. Hence, a combined experimental and numerical investigation was undertaken on a generic transport aeroplane/helicopter configuration. The experimental study provided surface pressures, direct drag measurements, surface and smoke flow visualization. The baseline flow was numerically analyzed, using finite volume solutions of the RANS equations. The baseline flow around the model was insensitive to the Reynolds number in the range it was tested. The flow separating from the aft body was characterized by two main sources of drag and unsteadiness. The first is a separation bubble residing at the lower ramp corner and the second is a pair of vortex systems developing and separating from the sides of the ramp. As the model incidence is decreased, the pair of vortex systems also penetrates deeper towards the centerline of the ramp, decreasing the pressure and increasing the drag. As expected, the ramp lower corner bubble was highly receptive to periodic excitation introduced from four addressable piezo-fluidic actuators situated at the ramp lower corner. Total drag was reduced by 3-11%, depending on the model incidence. There are indications that the flow in the wake of the model is also significantly steadier when the bubble at the lower ramp corner is eliminated. The vortex system is tighter and steadier when the ramp-corner bubble is eliminated.

show abstract

Section: Baseline (Uncontrolled) Flowmentioning

confidence: 99%

“…In the next phase, LES and DES simulations, which have already been applied for flow-separation analysis [3,5], will be used to provide better representation of the temporal flow mechanism.…”

Section: Introductionmentioning

confidence: 99%

Generic Transport Aft-body Drag Reduction using Active Flow Control

Ben-Hamou

Arad

Seifert

2007

Flow Turbulence Combust

Self Cite

View full text Add to dashboard Cite

show abstract

“…Thus, a computational paradigm must be able to account for these complexities. Nearly a decade ago, Arad et al 11 showed that Detached Eddy Simulation (DES) technique was required to account for the base and controlled separated flow over a thick airfoil, while conventional CFD techniques (like RANS/URANS) missed the whole phenomena. Recently, Arad et al 8 utilized advanced Large Eddy Simulation (LES) formulation to reproduce the flow in a synthetic jet actuator.…”

Section: A Computational Approachmentioning

confidence: 99%

Suction and Oscillatory Blowing Interaction with Boundary Layers

Schatzman

Wilson

Marom

et al. 2015

53rd AIAA Aerospace Sciences Meeting

Self Cite

View full text Add to dashboard Cite

This work presents ongoing experiments toward developing fundamental understanding of suction and oscillatory blowing (SaOB) flow control mechanisms along with development of accurate and practical CFD simulation methodologies for complex unsteady active flow control systems. Experimental and computational studies were conducted on SaOB actuators' internal flow and external interaction with two zero pressure gradient boundary layers. The experimental work incorporates detailed multi component hot-wire measurements of both laminar and turbulent boundary layers with steady suction and pulsed blowing for a single actuator and an array configuration. Large eddy simulation was employed for the computational model. Simulations were carried out on the actuator internal flow, and the resulting oscillatory blowing jet exit velocity profiles are characterized and fit with a functional form, in order to create simplified boundary conditions for future flow control simulations. Both experimental and computational results show that the suction hole geometry and configuration is an important factor in determining the structure and stability of the downstream laminar as well as turbulent boundary layer flow-fields. Measurements of oscillatory blowing jets interacting with a turbulent boundary layer demonstrate this flow control produces unsteady spanwise and streamwise vorticity components that can be interpreted as counter-rotating streamwise vortex patterns. NomenclatureA = area of suction holes A i = phase-locked coefficients C i = coefficients for functional fit jet velocity C f = skin friction coefficient d = suction hole diameter f = actuator oscillation frequency H = boundary layer shape factor 2 L FB = length of feedback tube L n = nozzle width P in = air supply pressure at actuator inlet P suc = static pressure in suction chamber Q = volume flow rate of suction Re x = Reynolds number based on streamwise distance Re L = Reynolds number based on nozzle width S ij = strain rate tensor s = suction hole spanwise spacing U e = local external velocity U j = jet velocity U r = reference supply jet velocity at converging nozzle U s = suction velocity U ∞ = freestream velocity u',v',w' = turbulent velocity fluctuations w , ṽ , ũ = coherent velocity fluctuations x, y, z = coordinates distance in turbulent boundary layer X, Y, Z = coordinates distance in laminar boundary layer  = linear phase-lock function δ = boundary layer thickness δ * = boundary layer displacement thickness  = non-dimensional spanwise nozzle coordinate θ = boundary layer momentum thickness λ 2 = second negative eigenvalue of the matrix S ij S ij + Ω ij Ω ij  = suction loss factor ρ = air density ν = kinematic viscosity  = phase angle ω x = streamwise vorticity component ω z = spanwise vorticity component Ω ij = vorticity tensor = denotes phase-averaging

show abstract

“…The lift to drag ratio is vastly improved as the Gurney flap size is increased, an effect usually not observed with Gurney flaps. Normally, Gurney flaps decrease the lift to drag ratio after 0.005-0.02c 4 . In drag and L/D, the positive effect of the Gurney flap is rapidly diminished as angle of attack is increased.…”

Section: Figure 26 Effect Of Gurney Flaps On An Untripped Naca 0036mentioning

confidence: 99%

“…In order to determine how the error propagates through this equation, one can say, in general, for some ( ) with uncertainties of the uncertainty can be stated as [4][5][6][7] However, this might overstate the error. If each variable"s error is random and independent, the probability of all error maximizing at one time is statistically unlikely.…”

Section: Observable Error Analysismentioning

confidence: 99%

An Investigative Study of Gurney Flaps on a NACA 0036 Airfoil

Altmann¹

View full text Add to dashboard Cite

This project examined the effect of Gurney flaps on a 2D, 2-ft chord NACA 0036 airfoil in the Cal Poly 3"x4" low speed wind tunnel at 25 m/s. It also covered the numerical simulation of the experiment in computational fluid dynamics (CFD). During the study, problems with the wind tunnel data were seen. After a careful diagnosis, the problem was traced to dirty flow conditioners which were subsequently replaced.Five Gurney flaps at 1, 2, 3, 4, and 5% of the chord were tested. The Gurney flaps had the effect of eliminating the lift reversal effect and lowering the profile drag at low angles of attack, ranging from 4-27%. The optimal Gurney flap appeared to be 2% of the chord. CFD modeling of the problem had limited success, with the best results coming from Mentor"s k-w SST turbulence model. This model reproduced the non-linear lift curve, and captured the trend in rising drag fairly well, but failed to predict the correct point of separation. Attempts to model the Gurney flap in CFD were unsuccessful. v ACKNOWLEDGEMENTS

show abstract

Control of Massive Separation over Thick-Airfoil Wing: A Computational and Experimental Study

Cited by 8 publications

References 14 publications

Generic Transport Aft-body Drag Reduction using Active Flow Control

Generic Transport Aft-body Drag Reduction using Active Flow Control

Suction and Oscillatory Blowing Interaction with Boundary Layers

An Investigative Study of Gurney Flaps on a NACA 0036 Airfoil

Contact Info

Product

Resources

About