Search for dissertations about: "flow instability"

Showing result 1 - 5 of 142 swedish dissertations containing the words flow 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. Instability in Settling Fibres : A Numerical Study

   Author : Feng Zhang; Anders A. Dahlkild; Fredrik Lundell; Mark Martinez; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; bre suspensions; sedimentation; instability; mixture model; point-particle mode;

   Abstract : Sedimenting suspensions exist in a varity of natural phenomena and industrial applications. It is already observed in experiments that the dilute fibre suspensions experience a concentration instability under gravity at low Reynolds numbers. Initially well-mixed suspensions become inhomogeneous and anisotropic due to this instability. READ MORE

6. 4. Effects of free-stream turbulence and three-dimensional roughness on boundary layer transition

   Author : Santhosh Babu Mamidala; Jens H. M. Fransson; Bengt E. G. Fallenius; Jonathan Morrison; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary-layer transition; intermittency; free-stream turbulence; electret microphones; isolated roughness; sinuous instability; varicose instability; Engineering Mechanics; Teknisk mekanik;

   Abstract : External disturbances such as free-stream turbulence (FST), and isolated three-dimensional roughness are strong disturbance sources to the laminar boundary layers (BLs), which can lead to a rapid transition to turbulence. The transition process eventuates to increase in skin-friction coefficient and heat transfer rate and hence, both of the aforementioned disturbance sources have practical importance. READ MORE

7. 5. 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