Sökning: "waves and vortices"

Visar resultat 1 - 5 av 23 avhandlingar innehållade orden waves and vortices.

  1. 1. Space Plasma Dynamics : Instabilities, Coherent Vortices and Covariant Parametrization

    Författare :David Sundkvist; Jan-Erik Wahlund; Andris Vaivads; Stuart Bale; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; space physics; plasma; instabilities; turbulence; coherent structures; vortex; self-organization; magnetosphere; waves; electromagnetism; covariant; space instrumentation; Rymd- och plasmafysik; Space physics; Rymdfysik;

    Sammanfattning : The magnetospheric cusps are two funnel-like regions of Earth's magnetosphere where solar wind plasma can have direct access to the ionosphere. The cusps are very dynamic regions where wave-particle interactions continuously take place and redistribute energy among different particle populations. LÄS MER

  3. 2. Attenuation of boundary layer disturbances by means of streamwise vortices

    Författare :Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Valery Chernoray; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer stability; Tollmien-Schlichting waves; oblique waves; transition to turbulence; streamwise vortices; miniature vortex generators; instability control; drag reduction;

    Sammanfattning : The stability of the boundary layer developed on a flat plate is studied in the presence of streamwise streaks where disturbances of different types are introduced in the wall-bounded shear layer. The experimental investigations are aimed at flow control by means of passively damping the energy growth of the disturbances in the streaky boundary layer and furthermore delay the onset of the transition in the streamwise direction. LÄS MER

  4. 3. Advancements in stratified flows through simulation, experiment and open research software development

    Författare :Ashwin Vishnu Mohanan; Erik Lindborg; Pierre Augier; James J. Riley; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; geophysical flows; shallow water wave turbulence; energy cascade; stratified turbulence; waves and vortices; open source software; geofysikaliska strömningar; vågturbulens i grunt vatten; energi- kaskad; stratifierad turbulens; vågor och virvlar; öppen mjukvara; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : Two studies of two-dimensional models of flows influenced by stratification and stratification/rotation are carried out in order to investigate whether a two-dimensional model can reproduce a downscale energy cascade with an associated k − 5/3 wavenumber spectrum. Firstly, a series of highly resolved numerical simulations of the classical shallow water model is carried out. LÄS MER

  5. 4. On stability and receptivity of boundary-layer flows

    Författare :Nima Shahriari; Ardeshir Hanifi; Dan S. Henningson; Peter J. Schmid; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer receptivity; acoustic receptivity; swept-wing flow; crossflow vortices; roughness element; global stability analysis; direct numerical simulation; plasma actuator; Engineering Mechanics; Teknisk mekanik;

    Sammanfattning : This work is concerned with stability and receptivity analysis as well as studies on control of the laminar-turbulent transition in boundary-layer flows through direct numerical simulations. Various flow configurations are considered to address flow around straight and swept wings. LÄS MER

  7. 5. Numerical studies of transtion in wall-bounded flows

    Författare :Ori Levin; Dan Henningson; Nikolaus Adams; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer; suction; wall jet; streaks; waves; periodic disturbance; localized disturbance; turbulent spot; algebraic growth; exponential growth; stability; transition thresholds; transition prediction; PSE; DNS; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : Disturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. LÄS MER