Growth characteristics downstream of a shallow bump: Computation and experiment

Joslin, Ronald D.; Grosch, C. E.

doi:10.1063/1.868680

Cited by 60 publications

(40 citation statements)

References 7 publications

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“…10(b)). This behavior is similar to the observation in the flow over a shallow bump studied by Joslin and Grosch (Joslin & Grosch, 1995) and the steady heating case discussed earlier. The intensity of the excess region is at the same level as that in the steady heating (compare Fig.…”

Section: Perturbed Flow By Pulsed Bumpsupporting

confidence: 73%

“…They found that the disturbance was entirely confined to the boundary layer, and the spanwise profile of the disturbance field near the bump differed dramatically from that far downstream. Joslin and Grosch (Joslin & Grosch, 1995) performed a Direct Numerical Simulation (DNS) to duplicate the experimental results by Gaster et al (Gaster et al, 1994). Far downstream, the bump generated a pair of counter-rotating streamwise vortices just above the wall and on either side of the bump location, which significantly affected the near-wall flow structures.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, there has been considerable interest in the study of bump-based methods to modulate the stability of boundary layers (Breuer & Haritonidis, 1990;Breuer & Landahl, 1990;Fischer & Choudhari, 2004;Gaster et al, 1994;Joslin & Grosch, 1995;Rizzetta & Visbal, 2006;Tumin & Reshotko, 2005;White et al, 2005;Worner et al, 2003). These studies are mostly focused on the incompressible regime and have revealed several interesting aspects of bump modulated flows.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal Perturbations in Supersonic Transition

Yan¹

2012

Low Reynolds Number Aerodynamics and Transition

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Section: Perturbed Flow By Pulsed Bumpsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal Perturbations in Supersonic Transition

Yan¹

2012

Low Reynolds Number Aerodynamics and Transition

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“…They are all characterized by the formation of streamwise elongated velocity perturbations and differ in the relative position of the high and low speed streaks with respect to the roughness elements. For instance, in the experiments by Gaster et al (1994) and related simulations by Joslin & Grosch (1995); White (2002); Asai et al (2002) a region of defect velocity is formed straight behind the element. This is due to the presence of the wake, which persists downstream forming the low speed streak.…”

Section: Realizing Drag Reduction By Means Of a Passive Controlmentioning

confidence: 99%

Advanced Fluid Research On Drag reduction In Turbulence Experiments –AFRODITE–

Fransson

Fallenius

Shahinfar

et al. 2011

J. Phys.: Conf. Ser.

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Abstract. A hot topic in today's debate on global warming is drag reduction in aeronautics. The most beneficial concept for drag reduction is to maintain the major portion of the airfoil laminar. Estimations show that the potential drag reduction can be as much as 15%, which would give a significant reduction of NOx and CO emissions in the atmosphere considering that the number of aircraft take offs, only in the EU, is over 19 million per year. An important element for successful flow control, which can lead to a reduced aerodynamic drag, is enhanced physical understanding of the transition to turbulence process. AFRODITE in briefAFRODITE is a recently funded research programme by the European Reserach Council, and stands for Advanced Fluid Research On Drag reduction In Turbulence Experiments.In previous tuned wind tunnel measurements it has been shown that roughness elements can be used to sensibly delay transition to turbulence (cf. Fransson et al., 2006). The result is revolutionary, since the common belief has been that surface roughness causes earlier transition and in turn increases the drag, and is a proof of concept of the passive control method per se. The beauty with a passive control technique is that no external energy has to be added to the flow system in order to perform the control, instead one uses the existing energy in the flow.Within the research programme -AFRODITE-we will take this passive control method to the next level by making it twofold , more persistent and more robust. Transition prevention is the goal rather than transition delay and the method will be extended to simultaneously control separation, which is another unwanted flow phenomenon especially during airplane take offs. AFRODITE will be a catalyst for innovative research, which will lead to a cleaner sky. BackgroundToday, it is well known that the boundary layer can transition to turbulence via different routes depending on surrounding parameters, such as surface imperfections, free-stream turbulence (FST) and background acoustic noise (Kachanov, 1994). For a clean base flow, i.e. a flow with low background disturbance levels typically encountered in free flight, and a hydraulically smooth surface the classical transition scenario takes place with exponentially growing disturbance modes (Tollmien, 1929;Schlichting, 1933;Schubauer & Skramstad, 1947). The least stable mode, denoted Tollmien-Schlichting (TS) wave, starts to grow at some critical Reynolds number. Another modal scenario takes place on swept leading edges with favorable pressure gradient, where the primary exponential disturbance is denoted the cross-flow mode, which can both be stationary and/or traveling depending on the surrounding parameters (Saric et al., 2003). However, for an increasing level of FST disturbances will be induced from the boundary layer edge into the boundary layer, which give rise to streamwise oriented structures of low and high speed fluid (Kendall, 1985;Westin, 1997;Jacobs & Durbin, 2001;Matsubara & Alfredsson, 2001;Brandt & Henningson, 20...

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“…At the end of the interval, (x -Xrough) /H = 120, harmonics n = 1, 2, 3, and 5, as one can see from figure 2.17, are the dominating ones, whereas the experimental [WE97] and computational [FC04] data demonstrate that the harmonics are ordered as 3, 4, 1 and 2. Another example is associated with the numerical simulation of flow behind an array of roughness elements by Joslin and Grosch [JG95]. They solved nonlinear equations for perturbations, but the boundary conditions were linearized as in Eq.…”

mentioning

confidence: 99%

Theoretical and Computational Studies of Stability, Transition and Flow Control in High-Speed Flows

Tumin¹

2011

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Public Reporting burden for this collection of information is estimated to average I hour per response. including the time for reviewing instructions, searching existing data sources. gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services. Directorate for information Operations and Reports. 1215 AFOSR /t0P(f North Randolph Street AFRL-SR-AR-TR-08-0144Suite 325, Room 3112 Arlington, VA 2299 3-1768 I1. SUPPLEMENTARY NOTESThe views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy or decision, unless so designated by other documentation. Approved for public release; distribution unlimited. ABSTRACT (Maximum 200 words)A comprehensive study of stability and receptivity of hypersonic boundary layers has been carried out. The main results of the project: 1. Mathematical method of the multimode decomposition for three-dimensional perturbations in compressible boundary layers has been developed. The method provides analysis of experimental and computational results for modes of discrete and continuous spectra. 2. Theory of boundary-layer receptivity was developed for roughness-induced perturbations in incompressible and compressible boundary layers. 3. The transient growth phenomenon in compressible boundary layers over flat plate, sphere, and sharp cone has been studied. The work was accompanied by development of solvers for these geometries. IntroductionThe potential of sustained hypersonic flight to revolutionize military and commercial activity is well recognized, and is reflected in recent initiatives such as the National Aerospace Initiative. High-speed vehicles will substantially impact military strategy by providing new defensive options such as a rapid on-demand global strike capability with much shorter response times than currently possible. Furthermore, the development of new technologies based on air-breathing propulsion can be leveraged to considerably reduce the cost of accessto-space, the benefits of which are both military as well as commercial. However, daunting technical challenges remain in realizing such vehicles. The harsh environment imposed by the envelope of such future missions is manifested in the severe anticipated thermo-mechanical loads and various propulsion-related requirements. Although the diversity of the physical phenomena encountered is broad, several key limiting issues have been identified as primary challenges, including both local and global constraints such as, for example, cowl lip loading and airframe balance. A scrutiny of the problems identified reveals the pervasive importance of several basic fluid dynamic phenomena. One of these, and possibly the least understood, is that of high-speed transition.The impact of hypersonic boundary lay...

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Growth characteristics downstream of a shallow bump: Computation and experiment

Cited by 60 publications

References 7 publications

Thermal Perturbations in Supersonic Transition

Thermal Perturbations in Supersonic Transition

Advanced Fluid Research On Drag reduction In Turbulence Experiments –AFRODITE–

Theoretical and Computational Studies of Stability, Transition and Flow Control in High-Speed Flows

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