S<scp>TABILITY AND</scp> T<scp>RANSITION OF</scp> T<scp>HREE</scp>-D<scp>IMENSIONAL</scp> B<scp>OUNDARY</scp> L<scp>AYERS</scp>

Saric, William S.; Reed, Helen L.; White, Edward B.

doi:10.1146/annurev.fluid.35.101101.161045

Cited by 573 publications

(236 citation statements)

References 91 publications

(181 reference statements)

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“…Experimental investigations on three-dimensional boundary layers were mainly carried in Germany (Deutsches Zentrum für Luft-und Raumfahrt (DLR) Göttingen) by Bippes and coworkers (Bippes 1999;Deyhle & Bippes 1996) and in United States by William Saric and his group (Arizona State University (ASU) first and Texas A&M University (TAMU) up to date) (Saric et al 2003;White & Saric 2005). These campaigns made use of very quiet wind tunnels, exhibiting a free stream turbulence level typically lower than 0.1% of the free stream velocity.…”

Section: Background and Present Workmentioning

confidence: 99%

“…This inviscid instability mechanism can be traced back to the flow topology of the boundary layer developing over the wing (e.g. Mack (1984); Saric et al (2003)). This flow, as well as the one around axisymmetric bodies at incidence or spinning about the symmetry axis, arranges follows three-dimensional trajectories.…”

Section: Introductionmentioning

confidence: 99%

“…In practice the boundary layer velocity profile along the direction orthogonal to the inviscid streamlines will have null values at the wall and at the outer edge but a finite local maximum at a given wallnormal position. This will create boundary layer velocity profiles that feature a point of inflection, giving rise to inviscid instability modes (Saric et al 2003). These can be of a travelling or stationary nature depending on the boundary layer receptivity to free stream turbulence and surface roughness (Bippes 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Dagenhart et al (1989); Bippes (1999); Saric et al (2003Saric et al ( , 2011) have shown a distinctive transition scenario for this type of boundary layers, characterised by sequences of streaks aligned with, within a few degrees, the flow direction. These streaks are the footprint of stationary boundary layer vortices causing a velocity modulation along the wing span and therefore of the wall skin friction and of the convective heat flux (quantities usually visualised in these experiments).…”

Section: Introductionmentioning

confidence: 99%

“…For more complete reviews the reader is instead referred to Bippes (1999); Arnal & Casalis (2000); Saric et al (2003) and to some more recent studies such as Wassermann & Kloker (2002; White & Saric (2005); Bonfigli & Kloker (2007); Downs & White (2013) and Hosseini et al (2013).…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional organisation of primary and secondary crossflow instability

2016

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An experimental investigation of primary and secondary crossflow instability developing in the boundary layer of a 45 • swept wing, at a chord Reynolds number of 2.17·10 6 is presented. Linear stability theory is applied for preliminary estimation of the flow stability while surface flow visualisation using fluorescent oil is employed to inspect the topological features of the transition region. Hot-wire anemometry is extensively used for the investigation of the developing boundary layer and identification of the statistical and spectral characteristics of the instability modes. Primary stationary as well as unsteady type-I (z-mode), type-II (y-mode) and type-III modes are detected and quantified. Finally, three-component, three-dimensional measurements of the transitional boundary layer are performed using tomographic particle image velocimetry. This research presents the first application of an optical experimental technique for this type of flow. Among the optical techniques tomographic velocimetry represents, to date, the most advanced approach allowing the investigation of spatially correlated flow structures in threedimensional fields. Proper orthogonal decomposition (POD) analysis of the captured flow fields is applied to this goal. The first POD mode features a newly reported structure related to low-frequency oscillatory motion of the stationary vortices along the spanwise direction. The cause of this phenomenon is only conjectured. Its effect on transition is considered negligible but, given the related high energy level, it needs to be accounted for in experimental investigations. Secondary instability mechanisms are captured as well. The type-III mode corresponds to low frequency primary travelling crossflow waves interacting with the stationary ones. It appears in the inner upwelling region of the stationary crossflow vortices and is characterised by elongated structures approximately aligned with the axis of the stationary waves. The type-I secondary instability consists instead of significantly inclined structures located at the outer upwelling region of the stationary vortices. The much narrower wavelength and higher advection velocity of these structures correlate with the higher-frequency content of this mode. The results of the investigation of both primary and secondary instability from the exploited techniques agree with and complement each other and are in line with existing literature. Finally, they present the first experimental observation of the secondary instability structures under natural flow conditions.

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Section: Background and Present Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three-dimensional organisation of primary and secondary crossflow instability

2016

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Flow Instabilities and Transition

Tumin

2010

Encyclopedia of Aerospace Engineering

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This paper introduces the flow instability concept and the problem of transition prediction. The discussion is aimed at the Tollmien–Schlichting type of instability in low‐speed two‐dimensional boundary layers. The discussion includes an outline of the linear stability theory, paths to turbulence in wall layers, and the e N method for transition prediction.

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Hypersonic Transition and Turbulence

Schneider¹,

Bowersox

2010

Encyclopedia of Aerospace Engineering

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Laminar‐turbulent transition and the subsequent development of the turbulent boundary layer at hypersonic speeds affect heat‐transfer, skin friction, and boundary‐layer separation. Particularly at high‐speeds, much remains unknown about the main mechanisms and the area remains one of active current research. The goal of this chapter is to provide the reader with an introduction to the current state of understanding, so it can serve as a starting point for further reading. Transition is the result of a complex, difficult to predict laminar‐instability process that can be very sensitive to apparently small factors. The transition process is summarized, with emphasis on those events that are specific to high speeds, along with the instability process and some parametric effects. In the second part of the chapter, the main properties of high speed turbulence are described to provide an understanding of qualitative and quantitative trends in surface loads at large Mach numbers where high‐temperature effects become active.

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STABILITY AND TRANSITION OF THREE-DIMENSIONAL BOUNDARY LAYERS

Cited by 573 publications

References 91 publications

Three-dimensional organisation of primary and secondary crossflow instability

Three-dimensional organisation of primary and secondary crossflow instability

Flow Instabilities and Transition

Hypersonic Transition and Turbulence

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