Computational challenges in high angle of attack flow prediction

Cummings, Russell M.; Forsythe, James R.; Morton, Scott A.; Squires, Kyle D.

doi:10.1016/s0376-0421(03)00041-1

Cited by 94 publications

(39 citation statements)

References 44 publications

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“…The reason may be the limitation of RANS method for the largely separated flow. 21 For the Modified-S foil (Figure 4(b)), the decline in lift coefficient occurs earlier at around 15°, but the tendency is much gentler. The drag coefficients are close to those of the baseline except for the stall-in-advance region (15°-21°).…”

Section: Resultsmentioning

confidence: 93%

“…Figure 9 shows the results at two angles of attack. At 6°, the highest amplitude occurs at the spatial frequency 0.02 mm 21 , which means one wavelength of the protuberance plays a dominant role in the lift distribution. Several higher order characteristic frequencies can be observed for the Modified-L foil, which may be due to larger difference between the 2D foil sections along the span.…”

Section: Resultsmentioning

confidence: 98%

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Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Cai

Zuo

Liu

et al. 2015

Advances in Mechanical Engineering

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Leading-edge protuberances on airfoils or hydrofoils have been considered as a viable passive method for flow separation control recently. In this article, the hydrodynamic performance of a NACA 63 4 -021 (baseline) foil and two modified foils with leading-edge protuberances was numerically investigated using the Spalart-Allmaras turbulence model. It was found that modified foils performed worse than the baseline foil at pre-stall angles, while the lift coefficients at high angles of attack of the modified foils were increased. Both the deterioration of pre-stall and the improvement of post-stall performance were enhanced with larger amplitude of protuberance. Near-wall flow visualizations showed that the leading-edge protuberances worked in pairs at high angles of attack, producing different forms of streamwise vortices. An attached flow along some valley sections was observed, leading to a higher local lift coefficient at post-stall angles. The leadingedge protuberances were considered as sharing a similar mechanism as delta wings, increasing nonlinear lift at large angles of attack. The specific stall characteristics of this leading-edge modification could provide some guidelines for the design of some special hydrofoils or airfoils.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 98%

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Cai

Zuo

Liu

et al. 2015

Advances in Mechanical Engineering

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show abstract

“…The deviation direction for different meshes shows the random feature of this bifurcation, which indicates that the appearance of this bifurcation is due to the inherent nonlinear property of JICF. This nonlinear property can be explained by analogizing it roughly to the well-known bifurcation of the bypass flow over a slender body, which has been subject to extensive investigations (Cummings et al, 2003;Zhang et al, 2007). With the increase of the angle of attack, the stability of the symmetric stable vortex system behind a slender body becomes unstable and sensitive to small disturbances.…”

Section: Stability Of Flow Structurementioning

confidence: 95%

Numerical Simulations of Imperfect Bifurcation of Jet in Crossflow

Wang

Liang

et al. 2012

Engineering Applications of Computational Fluid Mechanics

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This paper investigates the flow structure nearby a rectangular cooling hole on a flat plate by numerical simulations and topological analysis. The velocity ratio ranges from 0.5 to 1.5. Steady Reynolds-averaged NavierStokes simulations and unsteady detached eddy simulations are performed based on the Spalart-Allmaras turbulence model. The time-averaged velocity profiles in the central plane are verified by grid convergence study and comparison with the experimental data. The discussions mainly focus on the effect of the velocity ratio on the vortex structure and the stability of the jet-in-crossflow (JICF) system. The simulation results show that a bifurcation of the vortex system exists with respect to the velocity ratio. The averaged flow goes from a symmetric structure to an asymmetric structure on this bifurcation. The detached eddy simulation results show that both the symmetric vortex system and the asymmetric vortex system with different velocity ratios are stable.

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“…The difference between the CFD predictions and the experimental data in the poststall regime is also found in many other similar researches. In general, it is fair to say that the prediction of separated flow in the poststall region still remains a challenging frontier in CFD [24]. In addition, the pitch angle of the blade element applied in this paper is fixed at 37.73˚.…”

Section: Turbulence Model Validation Mesh Sensitivity and Time Stepmentioning

confidence: 99%

Two-Dimensional Moving Blade Row Interactions in a Stratospheric Airship Contra-Rotating Open Propeller Configuration

Tang¹,

Liu²,

Guo³

et al. 2015

International Journal of Aeronautical and Space Sciences

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The numerical simulation of two-dimensional moving blade row interactions is conducted by CFD means to investigate the interactions between the front and rear propeller in a stratospheric airship contra-rotating open propeller configuration caused by different rotational speeds. The rotational speed is a main factor to affect the propeller Reynolds number which impact the aerodynamic performance of blade rows significantly. This effect works until the Reynolds number reaches a high enough value beyond which the coefficients become independent. Additionally, the interference on the blade row has been revealed by the investigation. The front blade row moves in the induced-velocity field generated by the rear blade row and the aerodynamic coefficients are influenced when the rear blade row has fast RPMs. The rear blade row moving behind the front one is affected directly by the wake and eddies generated by the front blade row. The aerodynamic coefficients reduce when the front blade row has slow RPMs while increase when the front blade row moves faster than itself. But overall, the interference on the front blade row due to the rear blade row is slight and the interference on the rear blade row due to the front blade row is much more significant.

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Computational challenges in high angle of attack flow prediction

Cited by 94 publications

References 44 publications

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Numerical investigations of hydrodynamic performance of hydrofoils with leading-edge protuberances

Numerical Simulations of Imperfect Bifurcation of Jet in Crossflow

Two-Dimensional Moving Blade Row Interactions in a Stratospheric Airship Contra-Rotating Open Propeller Configuration

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