One-Point Closures Applied to Transition

Savill, A. M.

doi:10.1007/978-94-015-8666-5_6

Cited by 58 publications

(28 citation statements)

References 20 publications

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“…In other words, Length is an empirical correlation which controls the length of the transition region. New correlations for Length are obtained through combination of ERCOFTAC's results [1,2] and experimental results of the present authors already performed on a flat plate. In addition, current authors' experimental results obtained for their model (a linear cascade of axial compressor blades of NGTEC4 type) were used for tuning this new correlation.…”

Section: New Correlations Formentioning

confidence: 83%

“…The well-known transitional test cases of ERCOFTAC [1,2] T3 series, which are usually used as the benchmark for transitional flow studies, are used to examine and validate the new model. Zierke blade (PSU), corresponding to Deutsch Compressor Cascade [8], is also tested to approve the capability of the new correlation in modeling the transitional flows.…”

Section: Validation Of the New Empirical Correlationsmentioning

confidence: 99%

“…It should be noted that although this formulation seems to be rather efficient, experimental results have shown that other factors like freestream turbulence intensity, streamwise pressure gradient and wall roughness may affect the transition [1][2][3]. As a result, damping functions could not reliably predict such a different and complex physical process alone.…”

Section: Introductionmentioning

confidence: 97%

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Newly Developed Empirical Correlations for Simulation of Transitional Flows

Zenouz

Etemadi

2013

Advances in Mechanical Engineering

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An effective new formulation is developed for simulation of transitional flows. This formulation is based on modifications made to the latest numerical model utilizing vorticity and momentum thickness Reynolds numbers concepts. In this respect, rigorous experiments were conducted in a wind tunnel to modify the existing formulation to a more reliable form suitable for modeling of transitional flows. Test model was a linear cascade of axial compressor blades. Wind tunnel tests consisted of measurements of surface pressure distributions and velocity profiles utilizing hot film anemometry. Different freestream turbulence intensities, flow incidences, and Reynolds numbers were examined. New correlations were imposed to a commercial numerical flow solver; applying them to some standard objects produced more reliable results than those obtained from other formulations, presented so far. This attribution is more emphasized especially while dealing with modeling laminar separation bubbles, where transition occurs within the free shear layer.

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Section: New Correlations Formentioning

confidence: 83%

Section: Validation Of the New Empirical Correlationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Newly Developed Empirical Correlations for Simulation of Transitional Flows

Zenouz

Etemadi

2013

Advances in Mechanical Engineering

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“…An overview of the early developments on simulation of bypass transition with low-Reynolds-number turbulence models was given by Savill [96,97]. Models, like the Launder-Sharma model, in which the near-wall behaviour is described by the turbulence Reynolds number, Re T , perform the best.…”

Section: Low-reynolds-number Turbulence Modelsmentioning

confidence: 99%

Transition Models for Turbomachinery Boundary Layer Flows: A Review

Dick

Kubacki

2017

IJTPP

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Current models for transition in turbomachinery boundary layer flows are reviewed. The basic physical mechanisms of transition processes and the way these processes are expressed by model ingredients are discussed. The fundamentals of models are described as far as possible, with a common structure of the equations and with emphasis on the similarities between the models. Tests of models reported in the literature are summarized and our own test is added. A conclusion on the performance of models is formulated.Keywords: turbomachinery flows; transition models; boundary layers; bypass transition; separationinduced transition; wake-induced transition; Reynolds-averaged Navier-Stokes; intermittency; laminar kinetic energy Transition MechanismsWith the objective of modelling with Reynolds-averaged Navier-Stokes (RANS) or URANS (unsteady or time-accurate RANS) description of a flow, generally, four types of transition from laminar state to turbulent state in turbomachinery boundary layer flows are distinguished [1,2]. These are: natural transition in attached boundary layer state, bypass transition in attached boundary layer state under a statistically steady mean flow, separation-induced transition in the free shear layer formed by separation of a boundary layer under a statistically steady mean flow, and wake-induced transition due to periodically unsteady impact of wakes on boundary layers in attached or separated state. Despite the vast amount of studies on these transition types during the last 4 or 5 decades, understanding of the mechanisms is still not complete, although large progress has been made in the last decade thanks to direct numerical simulation (DNS) and large-eddy simulation (LES). Hereafter, we summarise the mean mechanisms, taking into account the inherent limitations of modelling with Reynolds-averaged Navier-Stokes description of a flow. This means that secondary effects, which mostly are the least understood and sometimes still are a matter of controversy, are not discussed, because, anyhow these features cannot be represented by RANS or URANS. Natural TransitionUnder a statistically steady mean flow of low turbulence level, transition in an attached boundary layer is initiated by 2D viscosity-dependent Tollmien-Schlichting instability waves, followed by a 3D instability, leading to formation of spanwise periodic hairpin vortices, which, farther downstream, cause breakdown of the laminar layer with generation of turbulent spots. These spots finally merge resulting in the formation of a turbulent boundary layer [1,2]. This type of transition is called natural transition. It is a rather slow process and, under a very low mean-flow turbulence level, as in external Int.

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“…This approach was later extended to secondmoment turbulence closures by Kim and Chung [27]. An alternative Reynolds stress transport-intermittency modelling approach was also successfully developed and applied to the prediction of by-pass transitional flows by Savill [28], with a similar scheme applied by Alvani and Fairweather [29] to improve predictions of scalar mixing.…”

Section: Introductionmentioning

confidence: 99%

External Intermittency Simulation in Turbulent Round Jets

Gilliland

Ranga-Dinesh

Fairweather

et al. 2012

Flow Turbulence Combust

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Direct numerical and large eddy simulation (DNS and LES) are applied to study passive scalar mixing and intermittency in turbulent round jets. Both simulation techniques are applied to the case of a low Reynolds number jet with Re=2,400, whilst LES is also used to predict a high Re=68,000 flow. Comparison between time-averaged results for the scalar field of the low Re case demonstrate reasonable agreement between the DNS and LES, and with experimental data and the predictions of other authors. Scalar probability density functions (pdfs) for this jet derived from the simulations are also in reasonable accord,although the DNS results demonstrate the more rapid influence of scalar intermittency with radial distance in the jet. This is reflected in derived intermittency profiles, with LES generally giving profiles that are too broad compared to equivalent DNS results, with too low a rate of decay with radial distance. In contrast, good agreement is in general found between LES predictions and experimental data for the mixing field, scalar pdfs and external intermittency in the high Reynolds number jet. Overall, the work described indicates that improved sub-grid scale modelling for use with LES may be beneficial in improving the accuracy of external intermittency predictions by this technique over the wide range of Reynolds numbers of practical interest.

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One-Point Closures Applied to Transition

Cited by 58 publications

References 20 publications

Newly Developed Empirical Correlations for Simulation of Transitional Flows

Newly Developed Empirical Correlations for Simulation of Transitional Flows

Transition Models for Turbomachinery Boundary Layer Flows: A Review

External Intermittency Simulation in Turbulent Round Jets

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