Sökning: "transient instability"

Visar resultat 1 - 5 av 41 avhandlingar innehållade orden transient instability.

1. 1. Protection Strategies to Mitigate Major Power Systems Breakdowns

   Författare :Mattias Jonsson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; system protection schemes; transient instability; distance protection; power swing detectors; voltage instability; generator coherency; wide area protection; out-of-step protection;

   Sammanfattning : This thesis deals with new methods to improve the performance of power system protection in the case of voltage- and transient instability. These methods are designed primarily to mitigate power system breakdown. Relay algorithms are proposed where conventional distance protection is combined with additional relay criteria. LÄS MER

3. 2. Study of generation, growth and breakdown of streamwise streaks in a Blasius boundary layer

   Författare :Luca Brandt; KTH; []
   Nyckelord :Fluid mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; lift-up effect; receptivity; free-stream turbulence; streak instability; secondary instability; Direct Numerical Simulation.;

   Sammanfattning : Transition from laminar to turbulent flow has beentraditionally studied in terms of exponentially growingeigensolutions to the linearized disturbance equations.However, experimental findings show that transition may occuralso for parameters combinations such that these eigensolutionsare damped. LÄS MER

4. 3. The role of Landau-Darrieus instability in flame dynamics and deflagration-to-detonation transition

   Författare :Damir Valiev; Börje Johansson; Vladimir Karlin; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; flame; premixed; instability; front; Landau; Darrieus; fractal; freely; deflagration; detonation; transition; DDT; modeling; simulation; Other materials science; Övrig teknisk materialvetenskap;

   Sammanfattning : The role of intrinsic hydrodynamic instability of the premixed flame (known as Landau-Darrieus instability) in various flame phenomena is studied by means of direct numerical simulations of the complete system of hydrodynamic equations. Rigorous study of flame dynamics and effect of Landau-Darrieus instability is essential for all premixed combustion problems where multidimensional effects cannot be disregarded. LÄS MER

5. 4. Effective Spatial Mapping for Coupled Code Analysis of Thermal–Hydraulics/Neutron–Kinetics of Boiling Water Reactors

   Författare :Joanna Peltonen; Weimin Ma; Maria Avramova; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Boiling Water Reactor; RELAP5; TRACE; PARCS; Coupled TH NK analysis; Spatial Mapping; Turbine Trip; Feedwater Transient; Control Rod Drop; Reactor Stability; Hierarchical Clustering; kokvattenreaktor; reaktoranalys; RELAP5; TRACE; PARCS; TH NK analys; turbin tripp; matarvatten transient; fallande styrstav; reaktor stabilitet; hierarkisk klustringsmetodik; SRA - Energy; SRA - Energi;

   Sammanfattning : Analyses of nuclear reactor safety have increasingly required coupling of full three dimensional neutron kinetics (NK) core models with system transient thermal–hydraulics (TH) codes.  In order to produce results within a reasonable computing time, the coupled codes use two different spatial description of the reactor core. LÄS MER

7. 5. Numerical studies of bypass transition in the Blasius boundary layer

   Författare :Luca Brandt; KTH; []
   Nyckelord :Fluid Mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; secondary instability;

   Sammanfattning : Experimental findings show that transition from laminar toturbulent ow may occur also if the exponentially growingperturbations, eigensolutions to the linearised disturbanceequations, are damped. An alternative non-modal growthmechanism has been recently identi fied, also based on thelinear approximation. LÄS MER