Sökning: "vortex generators"

Visar resultat 6 - 10 av 14 avhandlingar innehållade orden vortex generators.

1. 6. Flow Control and Shape Optimization of Intermediate Turbine Ducts for Turbofan Engines

   Författare :Fredrik Wallin; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; CFD; response surface methodology; intermediate turbine duct; vortex generators; turbine intermediate case; endwall contouring; turbine center frame; body-force model; shape optimization; mid-turbine frame; flow control;

   Sammanfattning : Demands on improved efficiency, reduced emissions and lowered noise levels cause a strive towards high by-pass ratios of commercial turbofan engines. This results in an increased radial offset between the high- and low-pressure turbines. Thus the design of the intermediate turbine duct connecting the two turbines becomes more challenging. LÄS MER

3. 7. Aerodynamic Design and Optimization of Intermediate Ducts for High By-pass Ratio Jet Engines

   Författare :Fredrik Wallin; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Intermediate transition ducts; vortex generators; S-shaped ducts; response surface methodology; source term model; optimization;

   Sammanfattning : Demands on improved efficiency and reduced noise levels cause a strive toward high by-pass ratio commercial aero engines. This results in multi-spool aero engines with small high-pressure ratio cores and large fans. The low-pressure system has a lower rotational speed and a larger radius than the high-pressure core system. LÄS MER

4. 8. 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

5. 9. Boundary layer streaks as a novel laminar flow control method

   Författare :Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Edward B. White; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; boundary layer stability; laminar to turbulent transition; laminar flow control; drag reduction; Tollmien-Schlichting waves; oblique waves; streaky boundary layers; miniature vortex generators; discrete suction;

   Sammanfattning : A novel laminar flow control based on generation of spanwise mean velocity gradients (SVG) in a flat plate boundary layer is investigated where disturbances of different types are introduced in the wall-bounded shear layer. The experimental investigations are aimed at; (i) generating stable and steady streamwise streaks in the boundary layer which set up spanwise gradients in the mean flow, and (ii) attenuating disturbance energy growth in the streaky boundary layers and hence delaying the onset of turbulence transition. LÄS MER

7. 10. Experimental study of the turbulent flow in a plane asymmetric diffuser

   Författare :Olle Törnblom; KTH; []
   Nyckelord :fluid mechanics; wind-tunnel. Burbulence; turbulence modelling; earsm; asymmetric diffuser; boundary layer;

   Sammanfattning : The separating turbulent flow in a plane asymmetric diffuseris investigated experimentally. The considered flow case issuitable for fundamental studies of separation, separationcontrol and turbulence modelling. The flow case has beenstudied in a specially designed wind-tunnel under wellcontrolled conditions. LÄS MER