Effect of Injection Slot Size on the Performance of Coflow Jet Airfoil

Zha, Gecheng; Paxton, Craig D.; Conley, Clark A.; Wells, Adam P.; Carroll, Brace F.

doi:10.2514/1.16999

Cited by 117 publications

(69 citation statements)

References 9 publications

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“…The CFJ0025-033-065 airfoil also experiences a small separation at the trailing edge because the jet momentum is not strong enough. Both the CFJ0025-065-196 and CFJ0025-131-196 airfoils do not have any separation at AOA 20 deg due to the stronger CFJ, which is also the same as demonstrated in the wind-tunnel tests [8,12]. It is interesting to note that even though the CFJ0025-033-065 airfoil has the separation at AOA 20 deg, the airfoil stall does not occur until AOA 50 deg, as shown in Fig.…”

Section: Resultssupporting

confidence: 67%

“…(6)(7)(8), (42), (17), and (18), the repeated subscripts i or k represent the coordinates x, y, and z following Einstein summation convention. Equations (17) and (18) are transformed to the generalized coordinate system in computation.…”

Section: A Governing Equationsmentioning

confidence: 99%

“…Flow control is the most promising route to bring significant performance improvement to aircraft [1][2][3][4][5][6][7]. Recently, Zha et al [8][9][10][11] developed a promising airfoil flow control technique using a coflow jet, which significantly increases lift, stall margin, and drag reduction.…”

mentioning

confidence: 99%

“…In [8,12], the CFJ airfoils with two different slot sizes are tested to compare the performance. It is observed that the larger slot size is more effective to reduce drag.…”

mentioning

confidence: 99%

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Numerical Investigations of Injection-Slot-Size Effect on the Performance of Coflow Jet Airfoils

Wang

Haddoukessouni

Levy

et al. 2008

Journal of Aircraft

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100

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Three coflow jet airfoils with twice-doubled injection-slot sizes are calculated using a Reynolds-averaged NavierStokes computational fluid dynamics solver with the one-equation Spalart-Allmaras model. At the same angle of attack, the twice-larger injection-slot-size airfoil passes the (about twice-greater) jet mass flow rate, with the momentum coefficients also nearly doubled. The coflow jet airfoil with the largest slot size has the least stall angle of attack. When the injection-slot size is reduced from the maximum by half, the stall angle of attack and the maximum lift coefficient are increased. When the injection-slot size is further reduced by half, the stall angle of attack is still increased, but the maximum lift coefficient is lower due to the smaller momentum coefficient. The trends of the stall angle of attack and maximum lift coefficient agree with the experiment. At low angles of attack, both the computed lift and drag coefficients agree fairly well with the experiment. At high angles of attack, the lift and drag are underpredicted. The reason may be that the Reynolds-averaged Navier-Stokes model cannot handle the turbulence mixing at high angles of attack. Nomenclatureof the field point to the trip location e = total energy per unit mass F = reactionary force J = Jacobian of transformation L = lift l, m, n = normal vectors on , , and surfaces with their magnitudes equal to the elemental surface areas and pointing to the directions of increasing , , and l t , m t , n t = grid moving velocities _ m = mass flow rate Pr = Prandtl number Pr t = turbulent Prandtl number p = pressure q k = total heat flux in Cartesian coordinates R = gas constant Re = Reynolds number R 0 = force from the airfoil surface integral S = magnitude of vorticity in Cartesian coordinates T = temperature t = time U, V, W = contravariant velocities in the , , and directions u, v, w = velocity components in the x, y, and z directions V = velocity vector x, y, z = Cartesian coordinates = angle of attack = ratio of specific heats U = difference of the velocities between the field point and the trip location x t = grid spacing along the wall at the trip location = angle between slot surface and the line normal to the airfoil chord = molecular viscosity t = turbulent viscosity = kinematic viscosity , , = generalized coordinates = density ik = shear stress in Cartesian coordinates ! t = wall vorticity at the wall boundary-layer trip location Subscripts i, j, k = indices L, R = left-and right-hand sides of the interface

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Section: Resultssupporting

confidence: 67%

Section: A Governing Equationsmentioning

confidence: 99%

mentioning

confidence: 99%

“…In [8,12], the CFJ airfoils with two different slot sizes are tested to compare the performance. It is observed that the larger slot size is more effective to reduce drag.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Numerical Investigations of Injection-Slot-Size Effect on the Performance of Coflow Jet Airfoils

Wang

Haddoukessouni

Levy

et al. 2008

Journal of Aircraft

Self Cite

100

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“…Zha et al [14][15][16][17][18][19][20] have developed a novel flow control technique by implementing a Co-Flow Jet (CFJ) on the suction surface, which has an attractive ability to significantly increase lift, stall margin, and drag reduction. In the present study, this concept is implemented on the NREL S809 airfoil, and the effect of the co-flow jet on enhancing wind turbine performance will be numerically investigated in detail.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the S809 airfoil aerodynamic performance using a co-flow jet active control concept

Xing

2015

Journal of Renewable and Sustainable Energy

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A Co-Flow Jet (CFJ) active flow control concept is implemented on the S809 airfoil and numerically investigated by using an in-house code based on Reynoldsaveraged Navier-Stokes equations and the Spalart-Allmaras turbulence model, aiming to systematically study the jet effect on the airfoil aerodynamic performance. The solver is validated by comparing the computed results with the baseline experiment measurement. The calculated aerodynamic force and moment coefficients agree fairly well with the experimental data, demonstrating the present solver can predict the attached as well as separated flows around the S809 airfoil with an acceptable precision. The CFJ jet-off geometry of S809 airfoil is simulated to study the jet channel effect on the baseline aerodynamic characteristic, showing that the jet channel could reduce the lift, increase the drag and cause an earlier abrupt stall at angle of attack (AoA) 16.24 . The CFJ jet-on geometry is elaborately studied at three jet momentum coefficient levels, showing that co-flow jet has a significantly positive effect in increasing lift, stall margin, and drag reduction. For the cases with jet momentum coefficients 0.12 and 0.18, the total drag even becomes negative. It is found that the drag from pressure and shear stress of CFJ airfoil is larger than that of baseline, and it is the negative mass-flow-produced drag that significantly reduces the total drag to be below zero. For cases in which AoA are below a critical value (e.g., 20.15 for the case with jet momentum coefficient 0.18), the power required to drive the jet flow decreases when AoA increases, demonstrating that the CFJ concept has an attractive advantage of minimum energy consuming. The present CFJ concept is proved to be a promising and effective active flow control method in the wind turbine application. V C 2015 AIP Publishing LLC.

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