Sökning: "absolute instability"

Visar resultat 1 - 5 av 18 avhandlingar innehållade orden absolute instability.

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

   Författare :Shintaro Imayama; Henrik Alfredsson; Rebecca Lingwood; Benoît Pier; KTH; []
   Nyckelord :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.;

   Sammanfattning : 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. LÄS MER

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

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

   Sammanfattning : 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. LÄS MER

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

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

   Sammanfattning : 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. LÄS MER

5. 4. The rotating-disk boundary-layer flow studied through numerical simulations

   Författare :Ellinor Appelquist; Philipp Schlatter; Henrik Alfredsson; Rebecca Lingwood; Benoît Pier; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; laminar-turbulent transition; convective instability; absolute instability; crossflow instability; direct numerical simulations; Fysik; Physics;

   Sammanfattning : This thesis deals with the instabilities of the incompressible boundary-layer flow thatis induced by a disk rotating in otherwise still fluid. The results presented include bothwork in the linear and nonlinear regime and are derived from direct numerical sim-ulations (DNS). LÄS MER

7. 5. Dynamic ultrasonography in neonatal hip instability and acetabular dysplasia

   Författare :Thröstur Finnbogason; Karolinska Institutet; Karolinska Institutet; []
   Nyckelord :;

   Sammanfattning : The clinical hip examination, although highly sensitive in expert hands in detecting neonatal hip instability, can lead to considerable overtreatment. Ultrasound is increasingly being used to complement the clinical examination in assessing neonatal hip instability and acetabular dysplasia, often leading to increased treatment rate. LÄS MER