Receptivity Mechanisms For Görtler Vortex Modes

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NASA Contractor Report ICASE Report No. 90-31 ICASE

The above description of Görtler vortex growth in the linear and nonlinear regimes also applies to compressible flows if the Mach number is not too large, Hall and Malik (1989), Wadey (1990). in the hypersonic limit Hall and Fu (1989a,b) showed that the linear development of Görtler vortices becomes much simpler. In particular, for either a

AE 549 Linear Stability Theory and Laminar-Turbulent Transition

modes of the boundary-layer will be excited, which will result in the Tollmien-Schlichting waves. If initial amplitudes are large non-linear modes will be excited and premature transition will occur through the by-pass mechanisms. Mathematically, the receptivity problem is also different from the stability problem. 28

Intermittency and transition to chaos in the cubical lid

flow is unstable toward four different families of modes (Theofilis et al 2004). The first bifurcation for the square lid-driven cavity occurs at a critical Reynolds number Re S1 =780 for a spanwise wavenumber b 15.4. The associated branch is known as the S1 family of modes. It is a family of non-oscillating Taylor Görtler-like (TGL

reprinted from Journal of Algorithms & Computational Technology

mechanisms at work within the laminar-turbulent flow region. In the 1980s, experimental studies by Kobayashi et al. [10] and Kobayashi & Izumi [11] as well as by Kohama [4] and Mueller et al. [5] (for ogive-nose cones) observed the existence of spiral vortices, which are generated in the region of steep shear velocity gradients near the cone wall.

Excitation of 3D TS-waves in a swept-wing boundary layer by

Generation of unsteady CF-instability modes by vibrational and vibration-vortex localized receptivity mechanisms AIP Conference Proceedings 2027, 020010 (2018); 10.1063/1.5065088 New method of excitation of 3D instability modes in boundary layers and its application to experiments on control of unsteady Görtler vortices

reproduction in any medium, provided the original work is

J. Fluid Mech. (2017), vol. 817, pp. 138 170. c Cambridge University Press 2017 This is an Open Access article, distributed under the terms of the Creative Commons Attribution

J. Fluid Mech. (2015), 781, pp. doi:10.1017/jfm.2015.490

horseshoe vortex was found to be dominant over the sinuous mode. In the Ma D6 study by Li et al. (2010), however, the most dangerous mode was demonstrated to be the sinuous mode. Besides the secondary instability of Görtler vortices, the other routes towards transition, e.g. the Görtler Mack mode interactions, were also explored (Li et al

Receptivity coefficients of vortex-vibrational type at

(CF) instability modes by both vortex-roughness [8] and vortex-vibrational [9] localized receptivity mechanisms. The excitation of nonstationary Görtler instability modes due to scattering of freestream vortices on localized surface nonuniformities was investigated recently in experiments [10]. In the same period of time, several

On the receptivity problem for Görtler vortices: vortex

2. Formulation of the forced Gortler vortex problem 54 3. The small wavelength limit 57 4. Vortices of 0(1) wavelength 63 5. The most unstable Gortler vortex 72 6. The receptivity problem for the mostunstable Gortler vortex 80 7. Conclusions 83 References 84 The receptivity problem for Gortler vortices induced by wall roughness is

Surface roughness effects on hypersonic boundary layer transition

one or more mechanisms before causing breakdown and turbulence. These disturbances include freestream turbulence or acoustic noise, surface roughness, curvature discontinuities, surface vibration, etc. The transition roadmap Increasing Disturbance Amplitude External Disturbances Receptivity Transient Growth Primary Modes Secondary Mechanisms

PROPERTIES OF THE FLOWFIELD ON A

simulations of the transition mechanisms is a very complex and difficult problem. There are several known receptivity mechanisms, several different known forms of instability waves, many different parameters that affect the mean flow and therefore modify the stability properties, and many known nonlinear breakdown mechanisms.

The Role of Streamwise Vorticity in Flows Over Turbomachine

Furthermore the receptivity to external influences and by-pass mechanisms may intervene, resulting in an earlier and often relatively sudden transition. In the context of a separated flow this may result in the sudden collapse of a laminar separation bubble [5]. These mechanisms are strongly Reynolds number dependent so that

Vortex instabilities in three-dimensional boundary layers

a non-dimensional vortex wavenumber e-l % 1 linearized vortex modes within a two- dimensional basic flow are neutrally stable at a Gortler number G = go eP4 + , where go is a known O( 1) constant whose precise value is dependent upon the properties of the basic flow under consideration. For larger wavelengths the problem is fully non-

Mischenko final red 2 - CORE

2D freestream vortices on them. It is found that the two mechanisms lead to rather efficient excitation of CF-modes both at surface vibration frequency and at combination vortex-vibration frequencies. First estimations of the corresponding localized receptivity coefficients are obtained.