Computational Studies on Topological Properties of Vortex Core Lines in Separated Flow Field Around High-Angle-of-Attack Cone-Cylinders

Energy components in the flow field at high angle of attack were analyzed by the dynamic measurement. The effect of the unsteadiness induced by these components on the flow was analyzed as well. The results showed that the flow itself at high angle of attack is a kind of "vortices behavior" and the effect of unsteadiness on the asymmetry of flow is relatively weak. The key factor that can essentially affect the flow at high angle of attack is the response of the dynamic unsteadiness of the vortices to the unpredictable micro-disturbance coming from near the nose of the model.

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Fan-Intake Coupling With Conventional and Short Intakes

10.1115/gt2021-58829 ◽

2021 ◽

Author(s):

E. J. Gunn ◽

T. Brandvik ◽

M. J. Wilson

Keyword(s):

Flow Field ◽

Potential Flow ◽

Pressure Ratio ◽

Current Trend ◽

Angle Of Attack ◽

High Angle ◽

High Angle Of Attack ◽

Field Distortion ◽

Intake Flow ◽

The Impact

Abstract The current trend in civil engine fans towards lower pressure ratio and larger diameter is accompanied by a need to shorten the engine intake length to reduce weight and drag. This paper uses full-annulus, unsteady CFD simulations of two coupled fan-intake configurations to explain the impact of flow field coupling and intake length on fan and intake performance. On-design and off-design operating points are considered at cruise and high angle of attack, respectively. The fan efficiency at cruise is shown to be determined by a trade-off between two effects. Cruise efficiency is reduced by 0.11% with a short intake due to increased potential flow field distortion, which alters the incidence and diffusion of the rotor. This is partially offset by a reduction in casing boundary layer thickness due to lower intake wetted area. At high angle of attack conditions, a short intake leads to increased potential flow field distortion and an earlier onset of intake flow separation due to a higher adverse pressure gradient approaching the fan. Both effects combine to reduce the fan thrust at such conditions, although the fan is shown to remain stable at attack angles up to 35°. The reduction in performance is shown to be dominated by flow separations in the rotor, which increase in size and severity for a given attack angle as the intake length is decreased. The fan is also shown to have a stronger influence on the form of the intake flow field in a short intake, suggesting that it is necessary to model the fan in the intake design process for a successful design.

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High Angle of Attack Missile Aerodynamics

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1243/pime_proc_1993_207_241_02 ◽

1993 ◽

Vol 207 (1) ◽

pp. 15-19

Author(s):

P C Dexter

Keyword(s):

Angle Of Attack ◽

Separated Flow ◽

The Body ◽

Major Influence ◽

Control Problems ◽

High Angle ◽

High Angle Of Attack ◽

Wing Stall ◽

High Angles Of Attack

A major influence in the aerodynamics of missiles is the significant amount of separated flow encountered for most flight conditions. This flow may be of an ordered nature, forming vortices, or random, such as encountered in wing stall. At high angles of attack the vortices of the body leeside flow may become unpredictably asymmetric, even on geometrically symmetric configurations, and their interactions with wing and tail panels can result in possible control problems. The modelling of such flows both accurately and easily is beyond present capabilities.

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Detached Eddy Simulation of Complex Separation Flows Over a Modern Fighter Model at High Angle of Attack

Communications in Computational Physics ◽

10.4208/cicp.oa-2016-0132 ◽

2017 ◽

Vol 22 (5) ◽

pp. 1309-1332 ◽

Cited By ~ 3

Author(s):

Yang Zhang ◽

Laiping Zhang ◽

Xin He ◽

Xiaogang Deng ◽

Haisheng Sun

Keyword(s):

Flow Field ◽

Angle Of Attack ◽

Vortical Flow ◽

Leeward Side ◽

Detached Eddy Simulation ◽

High Angle ◽

Flow Topology ◽

High Angle Of Attack ◽

Eddy Simulation ◽

Separation Flows

AbstractThis paper presents the simulation of complex separation flows over a modern fighter model at high angle of attack by using an unstructured/hybrid grid based Detached Eddy Simulation (DES) solver with an adaptive dissipation second-order hybrid scheme. Simulation results, including the complex vortex structures, as well as vortex breakdown phenomenon and the overall aerodynamic performance, are analyzed and compared with experimental data and unsteady Reynolds-Averaged Navier-Stokes (URANS) results, which indicates that with the DES solver, clearer vortical flow structures are captured and more accurate aerodynamic coefficients are obtained. The unsteady properties of DES flow field are investigated in detail by correlation coefficient analysis, power spectral density (PSD) analysis and proper orthogonal decomposition (POD) analysis, which indicates that the spiral motion of the primary vortex on the leeward side of the aircraft model is highly nonlinear and dominates the flow field. Through the comparisons of flow topology and pressure distributions with URANS results, the reason why higher and more accurate lift can be obtained by DES is discussed. Overall, these results show the potential capability of present DES solver in industrial applications.

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