Search for dissertations about: "secondary instability"

Showing result 1 - 5 of 41 swedish dissertations containing the words secondary instability.

2. 1. Experimental study of the rotating-disk boundary-layer flow

   Author : Shintaro Imayama; Henrik Alfredsson; Rebecca Lingwood; Benoît Pier; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Fluid mechanics; boundary layer; rotating disk; laminar-turbulent transition; convective instability; absolute instability; secondary instability; crossflow instability; hot-wire anemometry.;

   Abstract : Rotating-disk flow has been investigated not only as a simple model of cross flow instability to compare with swept-wing flow but also for industrial flow applications with rotating configurations. However the exact nature of laminar-turbulent transi- tion on the rotating-disk flow is still major problem and further research is required for it to be fully understood, in particular, the laminar-turbulent transition process with absolute instability. READ MORE

4. 2. Direct numerical simulations of the rotating-disk boundary-layer flow

   Author : Ellinor Appelquist; Philipp Schlatter; Henrik Alfredsson; Rebecca Lingwood; Christopher Davies; KTH; []
   Keywords : Fluid mechanics; boundary layer; rotating disk; laminar-turbulent transition; convective instability; absolute instability; secondary instability; crossflow instability; direct numerical simulations; Teknisk mekanik; Engineering Mechanics;

   Abstract : This thesis deals with the instabilities of the incompressible boundary-layer flow that is induced by a disk rotating in otherwise still fluid. The results presented are mostly limited to linear instabilities derived from direct numerical simulations (DNS) but with the objective that further work will focus on the nonlinear regime, providing greater insights into the transition route to turbulence. READ MORE

5. 3. Studies of the rotating-disk boundary-layer flow

   Author : Shintaro Imayama; Henrik Alfredsson; Rebecca Lingwood; Peter Thomas; KTH; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Fluid mechanics; laminar-turbulent transition; convective instability; absolute instability; secondary instability; hot-wire anemometry; Teknisk mekanik; Engineering Mechanics;

   Abstract : The rotating-disk boundary layer is not only a simpler model for the study of cross-flow instability than swept-wing boundary layers but also a useful simplification of many industrial-flow applications where rotating configurations are present. For the rotating disk, it has been suggested that a local absolute instability, leading to a global instability, is responsible for the small variation in the observed laminar-turbulent transition Reynolds number however the exact nature of the transition is still not fully understood. READ MORE

6. 4. Numerical studies on flows with secondary motion

   Author : Jacopo Canton; Philipp Schlatter; David Moxey; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; nonlinear dynamical systems; instability; bifurcation; flow control; skin-friction reduction; Engineering Mechanics; Teknisk mekanik;

   Abstract : This work is concerned with the study of flow stability and turbulence control - two old but still open problems of fluid mechanics. The topics are distinct and are (currently) approached from different directions and with different strategies. READ MORE

7. 5. Study of generation, growth and breakdown of streamwise streaks in a Blasius boundary layer

   Author : Luca Brandt; KTH; []
   Keywords : 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.;

   Abstract : 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. READ MORE