Thin vs Full Navier-Stokes Computation for High-Angle-of-Attack Aerodynamics

AIAA Journal ◽  
10.2514/2.134 ◽  
1997 ◽  
Vol 35 (3) ◽  
pp. 565-567 ◽  
Author(s):  
D. Degani ◽  
S. W. Marcus
Keyword(s):  
Angle Of Attack ◽  
Navier Stokes ◽  
High Angle ◽  
High Angle Of Attack

scholarly journals Numerical Simulation on Aerodynamics of Multi-Element Airfoil with Drooped Spoiler in Ground Effect

2019 ◽  
Vol 37 (1) ◽  
pp. 167-176
Author(s):  
Jiang Liu ◽  
Junqiang Bai ◽  
Guozhu Gao ◽  
Min Chang ◽  
Nan Liu
Keyword(s):  
Lift Coefficient ◽  
Angle Of Attack ◽  
Ground Effect ◽  
Lower Surface ◽  
Navier Stokes ◽  
High Angle ◽  
High Angle Of Attack ◽  
Ride Height ◽  
Navier Stokes Equation ◽  
Sst Turbulence Model

By using the finite volume method and k-ω SST turbulence model to solve the Reynolds Average Navier-Stokes equation and using the slipping wall to simulate the relative movement of the ground, the ground effect on the aerodynamic characteristic of multi-element airfoil with drooped spoiler is investigated numerically, and the reason why the lift coefficient decreased in ground effect is analyzed. The results indicate that, with the reduction in ride height, the lift and the drag decrease and the lift-drag ratio increases for the multi-element airfoil; the amplitude of the reduction in the lift coefficient increases with the reduction in ride height and the increase in the angle of attack, the maximum of lift coefficient can be reduced by about 22%; with the effect of ground, the losses of suction at upper surface make the lift decrease, the increases of pressure at lower surface make the lift increase, the variation of the lift coefficient for the main wing caused by the former is more than three times that of the latter. Analyzing the reason why the lift coefficient decreases showed that:on the one hand, ground effect on the lift coefficient for clean airfoil is changed with the range of angle of attack. For the low-to-moderate angle of attack, the lift coefficient increases; for the high angle of attack, the lift coefficient decreases. But multi-element airfoil works in the takeoff and landing stage for the high angle of attack, which causes the reduction of the lift coefficient in ground effect. On the other hand, the increase of the lift coefficient caused by the deflection of spoiler decreases with the reduction in ride height and the maximum reduction can be about 50%, which illustrates that ground effect makes interaction of the front and back section for the multi-element airfoil weak, resulting in further decreasing the coefficient for the multi-element airfoil.

On the Vortex Breakdown Phenomenon in High Angle of Attack Flows Over Delta Wing Geometries

2014 ◽  
Author(s):  
Eric D. Robertson ◽  
Varun Chitta ◽  
D. Keith Walters ◽  
Shanti Bhushan
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
High Angle ◽  
High Angle Of Attack ◽  
Eddy Simulation ◽  
Wing Model

Using computational methods, an investigation was performed on the physical mechanisms leading to vortex breakdown in high angle of attack flows over delta wing geometries. For this purpose, the Second International Vortex Flow Experiment (VFE-2) 65° sweep delta wing model was studied at a root chord Reynolds number (Recr) of 6 × 106 at various angles of attack. The open-source computational fluid dynamics (CFD) solver OpenFOAM was used in parallel with the commercial CFD solver ANSYS® FLUENT. For breadth, a variety of classic closure models were applied, including unsteady Reynolds-averaged Navier-Stokes (URANS) and detached eddy simulation (DES). Results for all cases are analyzed and flow features are identified and discussed. The results show the inception of a pair of leading edge vortices originating at the apex for all models used, and a region of steady vortical structures downstream in the URANS results. However, DES results show regions of massively separated helical flow which manifests after vortex breakdown. Analysis of turbulence quantities in the breakdown region gives further insight into the mechanisms leading to such phenomena.

NUMERICAL STUDIES OF ASYMMETRIC VORTEX FLOWS AROUND A SLENDER BODY AT HIGH ANGLE OF ATTACK

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1463-1466
Author(s):  
TONGQING GUO ◽  
ZHILIANG LU
Keyword(s):  
Stokes Equations ◽  
Angle Of Attack ◽  
Navier Stokes ◽  
Finite Volume Scheme ◽  
Vortex Flows ◽  
High Angle ◽  
High Angle Of Attack ◽  
Asymmetric Vortex ◽  
Vortex Pattern ◽  
Asymmetric Shape

The asymmetric vortex flows about slender bodies at high angle of attack are investigated numerically. 3D O-O type multi-block structured grids are adopted for the computation, and a series of small spatial disturbances are imposed on the leeward body surface near the tip to trigger the asymmetry. The unsteady Navier-Stokes equations are solved using a dual-time method based on the cell-centered finite-volume scheme. Comparisons between numerical results and experimental data demonstrate that the asymmetric vortex pattern observed in the experiment is successfully simulated. In a certain small perturbation level, the magnitude of the side-force is independent of the size of the spatial perturbation, but its direction is dependent on the direction of the spatial perturbation, i.e. a counterclockwise or clockwise circumferential angle from the leeward meridian. When perturbation is removed, the flow field returns to its original asymmetric shape after a period of oscillation.

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