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Showing 1 to 14 of 14 for “"Tollmien-Schlichting"”.
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The Tollmien-Schlichting instability of laminar viscous flows
In this work, an analysis of the Tollmien-Schlichting instability of laminar viscous flows is presented. For two-dimensional incompressible flow past a flat plate with porous suction strips, we use linear triple-deck, closed-form solutions for the mean flow to do a linear, parallel, spatial …
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Untersuchungen zum laminar-turbulenten Transitionsprozess bei Anregung und Dämpfung schräglaufender Tollmien-Schlichting-Wellen
… Entwicklung der Instabilitäten, der sogenannten Tollmien-Schlichting Wellen, von deren Schräglaufwinkel zur Plattenvorderkante. Weiterhin wird der Einfluss zahlreicher Parameter wie z.B. des Schalldruckpegels und der Anregungsfrequenz diskutiert. Die Anregung der Tollmien-Schlichting Wellen …
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Characterization and mitigation of blade waviness effects on fan performance
… via geometric resonance between the Tollmien-Schlichting wavelength and the surface wavelength. An effective numerical framework, referred to as the extended eN method, is established to assess the occurrence of the start of transition by tracing the energy transfer from freestream …
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Development and application of transition detection using infrared thermography for characterization of fan blade waviness effects
… transition location based on the growth of Tollmien-Schlichting waves in the boundary layer. Infrared thermography is used to determine the effects of surface waviness on natural transition in the regime of operation of civil aero engine fan blades. Surface waviness on fan blades arises from …
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Effect of roughness element on the stability of boundary layers
… results for flat plates. The method accounts for Tollmien-Schlichting waves, the shear layer instability, and their interaction. Separation is found to increase significantly the amplification factor.
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Receptivity to free stream acoustic disturbances due to a roughness element on a flat plate
… a forcing at a wave number equal to that of the Tollmien-Schlichting (TS) eigenmode and a frequency equal to that of the free-stream acoustic disturbance. The basic (mean) flow is calculated using an interacting boundary layer (IBL) scheme that accounts for viscous/inviscid interactions. Then, …
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On subharmonic instability in boundary layers
… mode originates from the three-dimensional Tollmien-Schlichting modes. For a weak interaction results from the resonant triad model and the parametric instability model get close to each other.
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High-order implicit large-eddy simulation for transitional aerodynamics flows
… Two-dimensional unstable modes in the form of Tollmien-Schlichting and Kevin-Helmholtz instabilities are found to be responsible for natural transition to turbulence through a laminar separation bubble. In short, this thesis aims to demonstrate the potential of high-order ILES for simulating …
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Investigation of transition to turbulence at low Reynolds numbers using Implicit Large Eddy Simulations with a Discontinuous Galerkin method
… surface over which ow transitions to turbulence. Tollmien-Schlichting waves are observed in the boundary layer upstream of separation, and their streamwise amplification factor shows they are responsible for transition. The major effects of cross-flow on low Reynolds number transition are studied …
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Instability and Transition to Turbulence in Complex Viscoelastic Flows Overlying Porous Surfaces
… analysis reveals a transition from viscoelastic Tollmien--Schlichting (TS)-type modes at low WWWW to a distinct elastic wall mode (EWM) localized near the fluid-porous interfaces at low RRRR. This EWM instability is observed for the first time in this configuration and represents a new mode of …
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Flow Between a Cylinder and a Rotating Coaxial Cylinder, Axisymmetric Shaft With Axially-Periodic Radius Variation, or Screw
… instability of circular Couette flow to Tollmien-Schlichting (TS) instability of nonrotating annular Poiseuille flow is elucidated. This transition is quite abrupt, with SPF being unstable at all Taylor numbers (Ta) beyond the Re at which annular Poiseuille flow becomes unstable. For the …
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Evolution of an Acoustic Disturbance to Transition in the Boundary Layer on an Airfoil
… mean flow conditions, forcing two-dimensional Tollmien-Schlichting (T-S) waves in the boundary layer using modulated acoustic bursts in the free-stream, and acquiring the mean boundary-layer data and fluctuating disturbance data using hot-wire probes. The acoustic receptivity due to surface …
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Secondary instabilities of boundary layers
… is taken in the form of a two-dimensional (2-0) Tollmien-Schlichting (T-S) wave. The subharmonic wave is taken in the form of a three-dimensional (3-D) wave. Results from both models are presented and compared with the experimental data and numerical simulation. It is found that the results of …
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Hydrodynamic stability of liquid films adjacent to incompressible gas streams including effects of interface mass transfer
… numbers and it is therefore associated with the Tollmien-Schlichting type of stability. Several other eigenvalues are obtained numerically using a Newton-Raphson technique. One of these modes has nearly the same speed of propagation as a Kelvin-Helmholtz wave for small wave numbers and hence it …