Effects of Compressibility and Turbulence Level on Bypass Transition

Schook, R.; Lange, H. C. de; Steenhoven, A.A. van

doi:10.1115/98-gt-286

Cited by 4 publications

(2 citation statements)

References 6 publications

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“…However, the turbulence level giving a certain distribution is lower in our case (our 1.25% distribution is comparable to Blair's 2% distribution). This also was observed in earlier experiments [17]. It was found that increasing the Mach number results in a decrease of the turbulence level, while no in¯uence on the transition was recognised (when the turbulence grid is unchanged).…”

Section: Transition Experimentssupporting

confidence: 68%

Heat transfer measurements in transitional boundary layers

Schook¹,

Lange²,

Steenhoven³

2001

International Journal of Heat and Mass Transfer

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High velocity boundary layer transition experiments are performed in a Ludwieg tube set-up. At a Mach number of 0.36, the transition is studied by using several turbulence generating grids. These grids cause turbulence levels varying from 0.25% to 3.5%. It is found that, depending on the turbulence level, dierent intermittency distributions should be used to describe the transition zone well. For low turbulence levels, the Narasimha and the Johnson models, which are based on turbulent spots, show good agreement with the measurements. For intermediate levels, the front part of the transition zone follows a distribution which is described by turbulent spots which decrease in size. In these cases, the latter part of transition also shows agreement with the Narasimha and Johnson models. A major dierence with thè classical' intermittency distributions is obtained for high turbulence levels. Assuming that for these levels non-growing turbulent spots are initiated in the whole transition zone, an exponential intermittency is derived. In the measurements these distributions indeed are found. Ó

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Section: Transition Experimentssupporting

confidence: 68%

Heat transfer measurements in transitional boundary layers

Schook¹,

Lange²,

Steenhoven³

2001

International Journal of Heat and Mass Transfer

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“…Thus, Narasimha [14] found the effect of Mach number was a delayed transition onset. In contrast, Schook et al [15] found the transition onset Re θ to be consistently lower than that correlated by Mayle [6] for the incompressible range. However, Walsh [13] found reasonably good agreement with the incompressible correlations of Mayle [6] for Mach numbers of the order of 1.…”

Section: Effect Of Mach Numbermentioning

confidence: 69%

On The Use of Entropy to Predict Boundary Layer Stability

Walsh

Davies

McEligot

2004

Entropy

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Boundary layer transition is a critical parameter in the design of fluid flow systems. This situation is due to the dramatic change in both entropy production and heat transfer that accompanies it. It is well recognized that many parameters affect the location of transition onset, however, no models exist which unify all these parameters. This paper presents a new hypothesis that the driving force of boundary layer transition onset is the entropy generation rate alone, with all other parameters being functions of this higher order quantity. At present this hypothesis is speculative, but encouraging since good compatibility is found with more established transition models.

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High Frequency Surface Heat Flux Imaging of Bypass Transition

Anthony

Jones

LaGraff

2004

Journal of Turbomachinery

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A high-frequency surface heat flux imaging technique was used to investigate bypass transition induced by freestream turbulence. Fundamental experiments were carried out at the University of Oxford using high-density thin film arrays on a flat plate wind tunnel model. Bypass transition was induced by grid-generated turbulence with varying intensities of 2.3%, 4.2%, and 17% with a fixed integral length scale of approximately 12mm. Unique high resolution temporal heat flux images are shown which detail significant differences between unsteady surface heat flux events induced by freestream turbulence and the classical Emmons-type spots which many turbomachinery transition models are based on. The temporal imaging technique presented allows study of unsteady surface heat transfer in detail, and helps elucidate the complex nature of transition in the high-disturbance environment of turbomachinery.

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Effects of Compressibility and Turbulence Level on Bypass Transition

Cited by 4 publications

References 6 publications

Heat transfer measurements in transitional boundary layers

Heat transfer measurements in transitional boundary layers

On The Use of Entropy to Predict Boundary Layer Stability

High Frequency Surface Heat Flux Imaging of Bypass Transition

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