Basic experiments on transition in three-dimensional boundary layers dominated by crossflow instability

Bippes, H.

doi:10.1016/s0376-0421(99)00002-0

Cited by 288 publications

(223 citation 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%

“…In his review article, Bippes (1999) reported several experiments, conducted over a period of years at DLR (e.g. Deyhle & Bippes (1996)), making use of different models placed in several facilities in order to see the effect of model geometry and tunnel free stream turbulence on the instability development.…”

Section: Primary Instabilitymentioning

confidence: 99%

“…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: Primary Instabilitymentioning

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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On the instability of Ekman boundary‐layer flow over a rough disk with a wavy surface profile

Alveroğlu

2020

Numerical Methods Partial

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We apply the method of lines and the backward difference method to solve highly nonlinear governing mean flow equations of the Ekman boundary‐layer flow over a rough disk with a wavy surface profile. These equations are derived using the YHP roughness model that imposes a wavy surface profile in terms of the radial position r, assuming rotational symmetry. Our main interest is to determine the effect of roughness on the local linear convective instability of the Ekman flow, and we solve the local linear stability equations of the disturbances stationary relative to the disk using the Chebyshev polynomials. The crossflow and viscous types of instability modes, the Type I and Type II modes respectively, are analyzed. Our theoretical findings prompts that an adequately designed rough disk can be a useful tool for a passive flow‐control method for the Ekman flow. The underlying physical mechanisms are investigated applying a fundamental energy analysis.

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Observations of Crossflow Transition on a Swept Wing With Gaw-2 Airfoil Section

Krishnan

Mukund²,

Viswanath³

Fluid Mechanics and Its Applications

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Basic experiments on transition in three-dimensional boundary layers dominated by crossflow instability

Cited by 288 publications

References 0 publications

Three-dimensional organisation of primary and secondary crossflow instability

Three-dimensional organisation of primary and secondary crossflow instability

On the instability of Ekman boundary‐layer flow over a rough disk with a wavy surface profile

Observations of Crossflow Transition on a Swept Wing With Gaw-2 Airfoil Section

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