Sökning: "koherenta strukturer"

Visar resultat 1 - 5 av 7 avhandlingar innehållade orden koherenta strukturer.

1. 1. Coherent structures and control in wall-bounded turbulent flows

   Författare :Marco Atzori; Philipp Schlatter; Ricardo Vinuesa; Oscar Flores; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulent boundary layers; numerical simulations; coherent structures; predetermined flow control.; Turbulenta gränsskikt; numeriska simuleringar; koherenta strukturer; förutbestämd flödeskontroll; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : This thesis is concerned with two distinct topics related to the study of wall-bounded turbulence: the connection between instantaneous three-dimensional coherent structures and mean-flow properties, and the development and analysis of pre-determined control techniques for adverse-pressure-gradient boundary layers.We examined regions with intense velocity fluctuations in various flowcases. LÄS MER

3. 2. Space-adaptive simulation of transition and turbulence in shear flows

   Författare :Daniele Massaro; Philipp Schlatter; Saleh Rezaeiravesh; Alfredo Pinelli; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulence; global stability; coherent structures; adaptive mesh refinement; Turbulens; global stabilitet; koherenta strukturer; adaptiv nätförfining; Teknisk mekanik; Engineering Mechanics;

   Sammanfattning : Transitional and turbulent shear flows are ubiquitous, from the boundary layer developing on an aeroplane wing to the flow within the aortic arch. In this thesis, we study wall-bounded and free shear flows through direct numerical simulations. LÄS MER

4. 3. Picosecond X-ray Diffraction Studies of Bulk and Nanostructure Materials

   Författare :Andrius Jurgilaitis; Atomfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; solid-liquid transitions; X-ray diffraction and scattering; nanowires; laser beam impact phenomena; phonons in crystal lattices; Fysicumarkivet A:2012:Jurgilaitis;

   Sammanfattning : Fast phenomena occurring after laser excitation were studied using time-resolved X-ray diffraction (TXRD). In most experiments, a femtosecond laser pulse was used to excite the sample, and X-rays were used as a probe. LÄS MER

5. 4. Effect of drag reducing plasma actuators using LES

   Författare :Romain Futrzynski; Gunilla Efraimsson; P. Henrik Alfredsson; Emma Alenius; Johan Revstedt; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flow control; drag reduction; plasma actuator; DMD; LES; optimization; pulsating flow; strömningskontroll; motståndsminskning; plasmaaktuator; DMD; LES; optimering; pulserande strömning; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : The work performed in this thesis explores new ways of reducing the drag of ground vehicles. Specifically, the effect of plasma actuators are investigated numerically with the intention to delay separation around a half-cylinder, a geometry chosen to represent a simplified A-pillar of a truck. LÄS MER

7. 5. Detailed Numerical Simulations of Turbulent Premixed Flames at Moderate and High Karlovitz Numbers

   Författare :Henning Carlsson; Strömningsteknik; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Direct numerical simulation; Large eddy simulation; Turbulent premixed combustion; Flow-flame interaction; High Karlovitz number;

   Sammanfattning : In generally accepted and applied flamelet combustion models, a turbulent flame is mainly assumed distorted by the large-scale turbulence eddies, whereas small-scale turbulence effects on the local flamelet structures are neglected. However, in a lot of industrial applications rather high turbulent intensities are often imposed, which induce turbulence scales at ranges smaller than the flame thickness. LÄS MER