Turbulence model effects on separated flow about a prolate spheroid

Gee, Ken; Cummings, Russell M.; Schiff, Lewis B.

doi:10.2514/3.10969

Cited by 36 publications

(4 citation statements)

References 17 publications

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“…This modifica tion has led to the ability to accurately simulate steady vortical flows with RANS computations. An example of the improvements to both zero-equation and oneequation turbulence models for predicting vortical flowfields was done by Gee et al [22]. Vortical flow modifications for the k À e turbulence model have also been suggested [23] and have been applied to flow over slender bodies at high incidence angles [24].…”

Section: Turbulence Modelingmentioning

confidence: 99%

Computational challenges in high angle of attack flow prediction

Cummings

Forsythe

Morton

et al. 2003

Progress in Aerospace Sciences

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Aircraft aerodynamics have been predicted using computational fluid dynamics for a number of years. While viscous flow computations for cruise conditions have become commonplace, the non-linear effects that take place at high angles of attack are much more difficult to predict. A variety of difficulties arise when performing these computations, including challenges in properly modeling turbulence and transition for vortical and massively separated flows, the need to use appropriate numerical algorithms if flow asymmetry is possible, and the difficulties in creating grids that allow for accurate simulation of the flowfield. These issues are addressed and recommendations are made for further improvements in high angle of attack flow prediction. Current predictive capabilities for high angle of attack flows are reviewed, and solutions based on hybrid turbulence models are presented. Contents

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Section: Turbulence Modelingmentioning

confidence: 99%

Computational challenges in high angle of attack flow prediction

Cummings

Forsythe

Morton

et al. 2003

Progress in Aerospace Sciences

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“…Here, U ∞ is the velocity of the model, L the length of the model, and ν the fluid viscosity. To validate turbulence models, the prolate spheroid has been investigated with a broad variety of experimental approaches over the last decades (Gee et al 1992;Choi and Kwon 2015). Fu et al (1994) used planar particle image velocimetry (PIV) to capture the instantaneous spanwise velocity and vorticity distributions.…”

Section: Introductionmentioning

confidence: 99%

Vortex-wake formation and evolution on a prolate spheroid at subcritical Reynolds numbers

Guo

Kaiser

Rival

2023

Preprint

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Three-dimensional (3D) flow reconstruction over a 6:1 prolate spheroid using scanning stereoscopic particle image velocimetry has been conducted in a towing-tank facility. Forces, moments, surface pressure and reconstructed 3D vortical-flow structures are acquired in order to characterize the separated flow within the subcritical regime at three Reynolds numbers (Re = 0.5 × 106, 1.0 × 106 and 1.5 × 106), and at four incidence angles (α = 5◦, 10◦, 15◦ and 20◦). Key flow features are evaluated through the reconstructed 3D flowfield data. In particular, the interaction of the crossflow vortices and the surface-pressure distribution are discussed. It is shown that the crossflow vortices consist of helical vortex tubes as the dominant coherent structures, which are more distinct at large α. For α ≥ 15◦, four high-vorticity regions were observed. A pair of upper vortex tubes, originate on the windward side of the model, while a lower vortex tube is formed on the strong curvature region on the leeward side of the model. The vortex dynamics are further characterized through stretching and tilting terms via the vorticity-transport equation. Larger incidence angles α lead to a stronger alignment of the crossflow vortices with the mean flow direction, which is reflected in the tilting terms. A weak Re dependency of the loads and flow structures within the range 1.0 × 106 ≤ Re ≤ 1.5 × 106 is reported, while a significantly different result was captured for separation at Re = 0.5 × 106. An increase in separation size at Re = 0.5 × 106 at 20◦ results in an additional flow structure; a pair of secondary vortices is formed, leading to a change in the pressure distribution on the model surface when compared to higher Re.

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“…[2,5] for a detailed discussion). Gee et al [6] compared several implementations of the Baldwin-Lomax model for computing the flow about a 6:1 prolate spheroid at high angle of attack, and also proposed an extension similar to the Degani-Schiff corrections [2] for the Johnson-King model. Murman and Chaderjian [5] compared two implementations of the Degani-Schiff corrections to the Baldwin-Lomax model for computing the flow about a tangentogive cylinder at α = 20 • , and found that the original implementation is necessary in order to predict the correct primary crossflow separation from smooth bodies.…”

Section: Introductionmentioning

confidence: 99%

Vortex filtering for turbulence models applied to crossflow separation

Murman

2001

39th Aerospace Sciences Meeting and Exhibit

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The application of turbulence models to the flow about slender bodies at high angles of attack poses many difficulties. Regions of threedimensional crossflow separation and strong vortices outside the boundary layer usually force the modification of standard models which have been developed for attached boundary layers and wake flows. This work examines the performance of three turbulence models for predicting crossflow separation; the Baldwin-Lomax model with corrections due to Degani-Schiff, the Spalart-Allmaras model, and Menter's shear-stress transport (SST) model. These models are applied to the crossflow separation from a smooth tangentogive cylinder at 20 • angle of attack. The current work utilizes a scheme for generating gridindependent solutions for these types of flows. From this it's found that the production of turbulent eddy-viscosity in the leeward vortices must be reduced for the one-and two-equation models to provide accurate results. A vortex filter which is Galilean-invariant and computationally efficient is developed for this purpose. Computed results indicate that this filter can substantially improve the prediction of the surface pressure and crossflow separation locations for the one and two-equation turbulence models considered.

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Turbulence model effects on separated flow about a prolate spheroid

Cited by 36 publications

References 17 publications

Computational challenges in high angle of attack flow prediction

Computational challenges in high angle of attack flow prediction

Vortex-wake formation and evolution on a prolate spheroid at subcritical Reynolds numbers

Vortex filtering for turbulence models applied to crossflow separation

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