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Showing result 1 - 5 of 45 swedish dissertations matching the above criteria.

2. 1. Effects of free-stream turbulence and three-dimensional roughness on boundary layer transition

   Author : Santhosh Babu Mamidala; Jens H. M. Fransson; Bengt E. G. Fallenius; Jonathan Morrison; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary-layer transition; intermittency; free-stream turbulence; electret microphones; isolated roughness; sinuous instability; varicose instability; Engineering Mechanics; Teknisk mekanik;

   Abstract : External disturbances such as free-stream turbulence (FST), and isolated three-dimensional roughness are strong disturbance sources to the laminar boundary layers (BLs), which can lead to a rapid transition to turbulence. The transition process eventuates to increase in skin-friction coefficient and heat transfer rate and hence, both of the aforementioned disturbance sources have practical importance. READ MORE

4. 2. Edge states and transition to turbulence in boundary layers

   Author : Taras Khapko; Dan Henningson; Philipp Schlatter; Yohann Duguet; Rich Kerswell; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; transition to turbulence; direct numerical simulation; edge state; free-stream turbulence; bypass transition; probabilistic cellular automaton; turbulence at the onset; laminar–turbulent coexistence; laminarisation; Engineering Mechanics; Teknisk mekanik;

   Abstract : The focus of this thesis is the numerical study of subcritical transition to turbulence in boundary-layer flows. For the most part, boundary layers with uniform suction are considered. Constant homogeneous suction counteracts the spatial growth of the boundary layer, rendering the flow parallel. READ MORE

5. 3. Transitional boundary layers caused by free-stream turbulence

   Author : Shahab Shahinfar; Jens Fransson; Johan Westin; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering mechanics; Teknisk mekanik;

   Abstract : The present measurement campaign on the free-stream turbulence (FST) induced boundary layer transition scenario has provided a unique set of experimental data, with potential to enhance the understanding of the eect of the free-stream turbulence characteristic length scales on the transition location and not only the turbulence intensity, which has been the focus in most previous studies. Recent investigations where the turbulence intensity has been kept essentially constant, while the integral length scale has been changed, show that the transition location is advanced for increasing length scale. READ MORE

6. 4. Laninar-turbulent boundary layer transition influenced by free stream turbulence

   Author : Jonas Westin; KTH; []
   Keywords : ;

   Abstract : Laminar-turbulent transition in a flat plate boundary layerhas been considered, with a special emphasis on the influencefrom free stream turbulence (FST)First, experiments on linear stability ofTollmien-Schlichting (TS) waves in a Blasius boundary layer wasstudied. This is a well-known example from hydrodynamicstability theory, which has hitherto suffered from unresolveddiscrepancies between experiments and linear theory. READ MORE

7. 5. Direct Numerical Simulation of Boundary-layer Transition with Free-stream Turbulence

   Author : Kristina Durovic; Dan Henningson; Ardeshir Hanifi; Philipp Schlatter; Tamer Zaki; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Engineering Mechanics; Teknisk mekanik;

   Abstract : This thesis considers the generation and influence of free-stream turbulence toboundary layer transition on both flat and curved bodies in the flow. Variousflow configurations such as flow around the flat plate with a sharp leading edgeand low-pressure turbine blades are considered. READ MORE