Search for dissertations about: "skin-friction reduction"

Found 5 swedish dissertations containing the words skin-friction reduction.

2. 1. 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

4. 2. Attenuation of boundary layer disturbances by means of streamwise vortices

   Author : Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Valery Chernoray; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

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

   Author : Sohrab Sattarzadeh Shirvan; Jens H. M. Fransson; Edward B. White; KTH; []
   Keywords : 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;

   Abstract : 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. READ MORE

6. 4. Numerical and modelling aspects of large-eddy and hybrid simulations of turbulent flows

   Author : Matteo Montecchia; Arne V. Johansson; Gert Brethouwer; Stefan Wallin; Dominic Von Terzi; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; turbulence; wall-bounded flows; large-eddy simulation; SGS modelling; OpenFOAM; hybrid RANS-LES; Engineering Mechanics; Teknisk mekanik;

   Abstract : In this study, the explicit algebraic sub-grid scale (SGS) model (EAM) has been extensively validated in wall-resolved large-eddy simulations (LES) of wall-bounded turbulent flows at different Reynolds numbers and a wide range of resolutions. Compared to eddy-viscosity based models, the formulation of the EAM is more consistent with the physics and allows to accurately capture SGS anisotropy,which is relevant especially close to walls. READ MORE

7. 5. Experimental studies in jet flows and zero pressure-gradient turbulent boundary layers

   Author : Ramis Örlü; P. Henrik Alfredsson; Tim B. Nickels; KTH; []
   Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Axisymmetric jet; swirling jet; coaxial jet; heated jet; zero pressuregradient turbulent boundary layer; wall-bounded turbulent flows; overlap region; passive scalar mixing; hot-wire anemometry; spatial resolution.; Fluid mechanics; Strömningsmekanik;

   Abstract : This thesis deals with the description and development of two classical turbulent shear flows, namely free jet and flat plate turbulent boundary layer flows. In both cases new experimental data has been obtained and in the latter case comparisons are also made with data obtained from data bases, both of experimental and numerical origin. READ MORE