3 edition of The Görtler vortex instability mechanism in three-dimensional boundary layers found in the catalog.
The Görtler vortex instability mechanism in three-dimensional boundary layers
by National Aeronautics and Space Administration, Langley Research Center in Hampton, Va
Written in English
|Series||ICASE report -- no. 84-17., NASA contractor report -- 172370., NASA contractor report -- NASA CR-172370.|
|Contributions||Langley Research Center., Institute for Computer Applications in Science and Engineering.|
|The Physical Object|
However, this critical amplitude decreases sharply for thinner, more unstable layers. In three-dimensional simulations of unstable layers, turbulence mixes the dust and gas, creating thicker, more stable layers. I find that layers with minimum Richardson numbers in the approximate range are stable in simulations with horizontal shear. Investigation of the global instability of the rotating-disk boundary equations for a disk of inﬁnite radius.1 The boundary layer consists of a three-dimensional axisymmetric ﬂow, in a global frame or the precise transition mechanism eventually leading to turbulent ﬂow.
The three-dimensional structure of an electromagnetically The three-dimensional structure of an electromagnetically generated dipolar vortex in a shallow ﬂuid layer R. A. D. Akkermans, A. R. Cieslik, L. P. J. Kamp, R. R. Trieling,Cited by: We also find that the strong polar vortex depends crucially on the magnetic field in the core. The simulation results are compared with the polar core flow reconstructed from secular variation observations. Citation: Sreenivasan, B., and C. A. Jones (), Structure and dynamics of the polar vortex in the Earth’s core, Geophys. Res.
dimensional. The lowest three-dimensional modes of a vortex-state magnetic disk have the in-plane magnetization distribution similar to the mode) 4, and are characterized by flexure oscillations of the vortex core line along the thickness of the disk (Fig.1). The mode number 0 R1 indicates the number of nodes. These instability-driven features may be tuned and guided in their assembly by altering the 2D materials' flexural rigidity (thickness/number of layers), substrate modulus, chemical functionalization, intrinsic defects, surface/interfacial energy (metallic, oxides, viscoelastic layers, etc), and by controlling the mechanical deformation regimes Cited by:
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Abstract. It is well known that the flow within a boundary layer over a curved plate is susceptible to longitudinal vortices. It has also been shown that if the underlying basic flow is three-dimensional, these modes will eventually be extinguished (perhaps in favour of crossflow vortices).Author: S.
Otto. In swept-wing flows the Görtler mechanism is probably not present for typical angles of sweep of about 20°. Some discussion of the receptivity problem for vortex instabilities in weakly three-dimensional boundary layers is given; it is shown that inviscid modes have a coupling coefficient marginally smaller than those of the fastest growing.
On the instability of a three-dimensional attachment-line boundary layer: weakly nonlinear theory and a numerical approach. Fluid Mech., Vol. () Cited by: effectsassociatedwith any vortex sheddingfrom the irregularity is alsosupported by the experimentalobservationsof Kachanovand Tararykin ().
2 Analysis Consider a three-dimensional incompressible boundary layer that encounters a three-dimensional surface hump (or indentation) on an otherwise smooth underlying surface. The edge velocity. Stability and three-dimensional evolution of a transitional dynamic stall vortex.
Abel-John Buchner G. Three-dimensional vortex dynamics in oscillatory flow separation. On the three-dimensional instability of laminar boundary layers on concave walls. In NACA Technical Memorandum Cited by: 6.
Abstract The recent progress in three-dimensional boundary-layer stability and transition is reviewed. The material focuses on the crossﬂow instability that leads to transition on swept wings and rotating disks.
Following a brief overview of instability mechanisms and the crossﬂow problem, a summary of the important ﬁndings of the s Cited by: systems lead to the instability of the flow in the form of counter- rotating, vortex-like disturbances.
Earlier transition measurements in the incompressible boundary layer next to a concave surface, indicate a steady three-dimensional vortex-like disturbance with a. Vortex organization in the outer region of the turbulent boundary layer - Volume - R. ADRIAN, C. MEINHART, C. TOMKINSCited by: Wall shear stress in Görtler vortex boundary layer flow.
The centrifugal instability mechanism in boundary layers over concave surfaces is responsible for the development of counter- rotating. This instability mechanism may lead laminar 87 boundary layer to transit to turbulence . The phenomena of such cen- 88 trifugal instability, known as Görtler instability, is relatively well.
Transition and Stability of High-Speed Boundary Layers Alexander Fedorov Annual Review of Fluid Mechanics Linear Stability Theory Applied to Boundary Layers H L Reed, W S Saric, and, and D Arnal Annual Review of Fluid Mechanics B OUNDARY-L AYER R ECEPTIVITY TO F REESTREAM D ISTURBANCES William S.
Saric, Helen L. Reed, and Edward J. KerschenCited by: in three-dimensional boundary layers. Both the lift-up and the Orr mechanism are identiﬁed as the physical mechanisms behind non-modal growth.
Furthermore, the modiﬁed PSE are used to determine the response of three-dimensional boundary layers to. Abstract The °ow over a rotating cone in still °uid is susceptible to cross°ow and centrifugal instability modes of spiral nature, depending on the cone half-angle.
For paramet. inflection point in the three-dimensional boundary layer profile. “On the Görtler vortex instability of boundary layers,” Prog. of the secondary instability in Görtler vortices using. The development of wall shear stress in concave surface boundary layer flows in the presence of Görtler vortices was experimentally studied by means of hot-wire measurements.
The wavelengths of the vortices were preset by thin vertical perturbation wires so to produce the most amplified wavelengths. Three different vortex wavelengths of 12, 15, and 20 mm were Cited by: Core dynamics of a strained vortex both having the same axial wavenumber ˇ-periodic strain couples mwith m 2 waves (S.
Le Dizespersonal communication). For m= 1, Tsai & Widnall found that for certain discrete values of kat which the oscillation frequency of both modes is zero, there is resonant ampli cation (i.e. instability). Vortex sheet approximation of boundary layers.
vortex method for the analysis of three dimensional turbulent boundary layers will be described elsewhere . PRINCIPLE OF THE METHOD The boundary layer equations can be written in the form (see e.g.
Schlichting ) (U ' V) 6 = va"e, (la) u, (l b) a~u + a"v = 0, (1C) where u = (u, v) is the Cited by: The existing articles, which reported vortex breakdown, were either based on 2-D visualization or using low pressure center as the vortex tube ; (6) the small vortices can be found on the bottom of the boundary layer near the wall surface (bottom of the boundary layer).
It is justified that the small vortices, and thus turbulence, are all Cited by: caused by Kelvin-Helmholtz instability. This instability leads to a rolling up and to a separation from the surface of the cylinder that result in the formation of the vortex street , -.
This breaking mechanism is the basic physics concept of vortex formation and the near wake; that can be an origin of technique for triggering vortex. vortex interaction is not singular, problem (ii) disappears, and the method can be used near boundaries in hybrid methods. A more general (but much more complicated) vortex method for the analysis of three dimensional turbulent boundary layers will be described elsewhere .
PRINCIPLE OF THE METHOD. The stability to three-dimensional disturbances of three classical steady vortex configurations in an incompressible inviscid fluid is studied in the limit of small vortex cross-sectional area and long axial disturbance wavelength.
The configurations examined are the single infinite vortex row, the Karman vortex street of staggered vortices and the symmetric vortex street.global response. The onset of global instability (and thus vortex shedding) is linked to both the sectional growth rates (characterized by the maximum-diameter location) and the spanwise extent of the zone of instability.
Unsteady numerical simulations are used to guide the global-stability analysis and to assess the ﬁdelity of the predictions.three-dimensional velocity gradient data to study the statisti-cal and instantaneous geometric structure of vortex cores in a zero pressure gradient turbulent boundary layer.
II. EXPERIMENTAL FACILITY AND METHODS Experiments were performed in a suction-type boundary layer wind tunnel. Measurement planes were located m.