A Novel Intermittency Distribution Based Transition Model For Low-Re Number Airfoils

Bas, Onur; Cakmakcioglu, Samet C.; Kaẏnak, Ünver

doi:10.2514/6.2013-2531

Cited by 14 publications

(9 citation statements)

References 10 publications

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“…13,14 Menter et al model 8 was further developed and extended into the realm of more physics such as the cross-flow instability effects by Grabe and Krumbein, 15 the so-called secondary effects such as roughness by Dassler et al 16 and compressibility by Kaynak. 17 A very pragmatic approach was taken by Bas et al 18 with the introduction of an algebraic, or a zero-equation model that successfully mimics the results of the two-and three-equation models. Meanwhile, Menter et al 19 proposed a oneequation model that is a simplified version of the earlier À Re model which possesses similar quality of results as in the original model with one less equation.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, the algebraic transition model, which was first proposed by the authors, 18 herein called as the Bas-Cakmakcioglu (B-C) model, is further developed and a variety of flat plate cases, a low Re airfoil case, a turbine cascade case and a three-dimensional transonic wing and a low-speed wind turbine cases are successfully compared with relevant data. In the original Menter et al À Re model, 8 instead of the momentum thickness Reynolds number (Re , an integral parameter), the vorticity Reynolds number (Re v , a locally calculated term) is used in order to trigger the onset of transition.…”

Section: Introductionmentioning

confidence: 99%

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A correlation-based algebraic transition model

Cakmakcioglu

Bas

Kaẏnak

2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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A correlation-based algebraic transition model that relies on local flow information is proposed. The model is qualified as an algebraic model, or a zero-equation model since it includes an intermittency function in place of an intermittency equation that is found in one- or two-equation models. The basic idea behind the model is that, instead of deriving new equations for intermittency transport, existing transport terms of the Spalart–Allmaras (S-A) turbulence model can be used. To this end, the production term of the S-A model is multiplied with the proposed intermittency function γBC; thereby the turbulence production is damped until it satisfies some turbulence onset requirements. The proposed formulation also depends on local information that uses empirical correlations to detect the transition onset using less equations and less calibration constants than other higher order models. The model is first validated against some widely-used zero and variable pressure gradient flat plate test cases with quite successful results. Second, the model is employed for some low Reynolds number airfoil cases with very promising results. Third, the model is applied for a turbine cascade case with success. Finally, two different three-dimensional wing flow cases were calculated under transonic and low subsonic flow conditions. To this end, the DLR-F5 wing subject to a transonic Mach number of 0.82 and the low-speed NREL wind turbine flow case are simulated and good agreement with experiments are observed. The results indicate that the proposed model may become an alternative for other models as it uses less computational resources with equivalent or higher accuracy characteristics that is quite advantageous for the computational fluid dynamics design in industry.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A correlation-based algebraic transition model

Cakmakcioglu

Bas

Kaẏnak

2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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“…In the same line of thought, Nagapetyan-Agarwal constructed the so-called two-equation transition model of WA-γ [24] by incorporating the Wray-Agarwal (WA) wall-distance-free one-equation turbulence model [23] based on the k-ω closure with the one-equation intermittency transport γ-equation of Menter et al [22]. These two models paved the way for developing yet another leaner transition model by Bas et al [19] with the introduction of the algebraic Bas-Cakmakcioglu (B-C) model by incorporating an algebraic γ-function with the one-equation S-A turbulence model [28].…”

Section: Discussionmentioning

confidence: 99%

“…The Bas-Cakmakcioglu (B-C) [19] model qualifies as a zero-equation model that solves for an intermittency function rather than an intermittency transport (differential) equation. The main approach behind the B-C model follows again the pragmatic idea of further reducing the total number of equations.…”

Section: Discussionmentioning

confidence: 99%

“…To this end, cross-flow instability effects by Seyfert and Krumbein [16], surface roughness effects by Dassler et al [17], and compressibility effects by Kaynak [18] were included. Meanwhile, Bas et al [19] proposed a very pragmatic approach by introducing an algebraic or a zero-equation model called later as the Bas-Cakmakcioglu (B-C) model [20]. Herein, it was shown that an equivalent level of prediction compared with the two-and three-equation models could be achieved with less equations provided that physics was correctly modeled.…”

Section: Introductionmentioning

confidence: 99%

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Transition Modeling for Low to High Speed Boundary Layer Flows with CFD Applications

Kaẏnak¹,

Bas²,

Cakmakcioglu³

et al. 2020

Boundary Layer Flows - Theory, Applications and Numerical Methods

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Transition modeling as applied to CFD methods has followed certain line of evolution starting from simple linear stability methods to almost or fully predictive methods such as LES and DNS. One pragmatic approach among these methods, such as the local correlation-based transition modeling approach, is gaining more popularity due to its straightforward incorporation into RANS solvers. Such models are based on blending the laminar and turbulent regions of the flow field by introducing intermittency equations into the turbulence equations. Menter et al. pioneered this approach by their two-equation γ-Reθ intermittency equation model that was incorporated into the k-ω SST turbulence model that results in a total of four equations. Later, a range of various three-equation models was developed for super-/hypersonic flow applications. However, striking the idea that the Reθ-equation was rather redundant, Menter produced a novel one-equation intermittency transport γ-equation model. In this report, yet another recently introduced transition model called as the Bas-Cakmakcioglu (B-C) algebraic model is elaborated. In this model, an algebraic γ-function, rather than the intermittency transport γ-equation, is incorporated into the one-equation Spalart-Allmaras turbulence model. Using the present B-C model, a number of two-dimensional test cases and three-dimensional test cases were simulated with quite successful results.

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Conservative preconditioning techniques for efficient compressible and incompressible flow simulations on unstructured meshes

Khorasani,

Mohammadi,

Djavareshkian

2024

Z Angew Math Mech

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Three preconditioning methods suggested by Eriksson, Choi, Merkel, and Turkel have been utilized within a 2D upwind Euler flow solver designed for unstructured grids. These strategies efficiently address the complexities of steady inviscid flows at low Mach numbers. The conservative formulations of the preconditioning matrices are rigorously derived. This implementation enables a more accurate evaluation of high‐gradient flows. Extensive simulations are conducted on various flow scenarios, including flows over the NACA0012 airfoil, a multi‐element three‐element airfoil, and a smooth bump with varying Mach numbers, to validate the effectiveness of the aforementioned preconditioning strategies. Compared to the non‐preconditioned approach, the results demonstrate significant accuracy and convergence speed improvements for all three preconditioning methods. These strategies exhibit remarkable efficiency for low Mach and incompressible flows. Among the three approaches, the Turkel preconditioner stands out with its optimal condition number, leading to superior performance. For low Mach numbers, convergence is accelerated by up to 88%, while at transonic speeds, it still achieves a notable 38% increase in convergence speed. Additionally, the preconditioning techniques preserve solution accuracy near challenging stagnation points. This study establishes a unified conservative framework for assessing preconditioning approaches and highlights their ability to resolve the complex fluid physics of low Mach number flows on unstructured grids. The findings underscore the significance of employing such strategies to enhance accuracy and computational efficiency in evaluating high‐gradient flows.

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A Novel Intermittency Distribution Based Transition Model For Low-Re Number Airfoils

Cited by 14 publications

References 10 publications

A correlation-based algebraic transition model

A correlation-based algebraic transition model

Transition Modeling for Low to High Speed Boundary Layer Flows with CFD Applications

Conservative preconditioning techniques for efficient compressible and incompressible flow simulations on unstructured meshes

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