Sökning: "shear waves"

Visar resultat 21 - 25 av 45 avhandlingar innehållade orden shear waves.

1. 21. A Linearized Navier-Stokes Equations Methodology for Aeroacoustic and Thermoacoustic Simulations

   Författare :Wei Na; Susann Boij; Gunilla Efraimsson; Niklas Andersson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Linearized Navier-Stokes Equations LNSE ; frequency domain; tube row heat exchanger; hybrid liner; thermoacoustic instabilities; entropy waves; Rijke-tube; nozzle; Engineering Mechanics; Teknisk mekanik;

   Sammanfattning : Aeroengine noise is one of the dominating noise sources in today’s aircraft. Reduction of the aeroengine noise is related to multiphysics phenomena, and that is subject to different mechanisms, e.g., the coupling between turbulence, flame and sound waves. LÄS MER

3. 22. Numerical Investigation of Rotating and Stratified Turbulence

   Författare :Enrico Deusebio; Erik Lindborg; Johan Nilsson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Geostrophic turbulence; stable stratification; rotation; wall-bounded turbulence; gravity waves; atmospherical dynamics; direct numertical simulations; SRA - E-Science SeRC ; SRA - E-vetenskap SeRC ;

   Sammanfattning : Atmospheric and oceanic flows are strongly affected by rotation and stratification. Rotation is exerted through Coriolis forces which mainly act in horizontal planes whereas stratification largely affects the motion along the vertical direction through buoyancy forces, the latters related to the vertical variation of the fluid density. LÄS MER

4. 23. Spiritum sidus : The star of our life – On internal tides in the ocean

   Författare :Gaspard Geoffroy; Jonas Nycander; Christian Stranne; Aurélien Ponte; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Internal waves; Tides; Argo floats; Time series analysis; Flow-topography interaction; Atmospheric Sciences and Oceanography; atmosfärvetenskap och oceanografi;

   Sammanfattning : Tidal currents flowing over rough bathymetry generate internal tides. These internal waves with tidal frequency can be decomposed into vertical modes. Low modes generally travel thousands of kilometers, until they break due to shear flow instabilities, while high modes are believed to break close to the generation site. LÄS MER

5. 24. Drift and Mirror Modes in Magnetized Plasmas

   Författare :Ingmar Sandberg; Padma Shukla; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; tokamak plasma; drift waves; space plasma; mirror instability.; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Space and Plasma Physics; rymd- och plasmafysik;

   Sammanfattning : Low frequency plasma instabilities driven by plasma inhomogeneity and velocity anisotropies are major candidates for the explanation of various phenomena observed in fusion and space plasmas. For low-β fusion plasma, the influence of plasma rotation and finite ion temperature on the structure and the type of toroidal drift eigenmodes in tokamaks is investigated rigorously, including the effects induced by the toroidal geometry such as the coupling mode, the radial variation of plasma rotation velocity and the magnetic shear. LÄS MER

7. 25. Flow control and reduced-order modelling of transition in shear flows

   Författare :Reza Dadfar; Dan Henningson; Vasssilis Theofilis; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Flow control; plasma actuator; wing; leading edge; flat plate; wind turbine; optimal controller; model reduction; proper orthogonal decomposition; dynamic mode decomposition.;

   Sammanfattning : In this thesis direct numerical simulation is used to investigate the possibility to delay the transition from a laminar to a turbulent flow in boundary layer flows. Furthermore, modal analysis techniques are used to identify the coherent structures in wind turbine wake. LÄS MER