Sökning: "Arne V. Johansson"

Visar resultat 1 - 5 av 10 avhandlingar innehållade orden Arne V. Johansson.

1. 1. A study of turbulence and scalar mixing in a wall-jet using direct numerical simulation

   Författare :Daniel Ahlman; Arne V. Johansson; Lars-Erik Eriksson; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningmekanik; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : Direct numerical simulation is used to study the dynamics and mixing in a turbulent plane wall-jet. The investigation is undertaken in order to extend the knowledge base of the influence of the wall on turbulent dynamics and mixing. The mixing statistics produced can also be used to evaluate and develop models for mixing and combustion. LÄS MER

3. 2. Turbulence and scalar flux modelling applied to separated flows

   Författare :Johan Gullman-Strand; Arne V. Johansson; Suad Jakirlic; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Space and plasma physics; fluid physics; plasma physics; applied mechanics; aerospace; Rymd- och plasmafysik; Space physics; Rymdfysik;

   Sammanfattning : The turbulen flow in an asymmetric diffuser has been en studied by the means of Reynold average Navier-Stokes equations with both differential and explict algebraic expressions to model the Reynolds stress tensor. Modifications to the differential stress model have been derived, using the inverse turbulence timescale to obtain the dissipation of turbuence kinetic energy. LÄS MER

4. 3. Modelling of subgrid-scale stress and passive scalar flux in large eddy simulations of wall bounded turbulent flows

   Författare :Linus Marstorp; Arne V. Johansson; Pierre Comte; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulence; large-eddy simulation; subgrid-scale model; Fluid mechanics; Strömningsmekanik;

   Sammanfattning : The aim of the thesis is to develop and validate subgrid-scale models that are relevant for large eddy simulations of complex flows including scalar mixing. A stochastic Smagorinsky model with adjustable variance and time scale is developed by adding a stochastic component to the Smagorinsky constant. LÄS MER

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

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

   Sammanfattning : 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. LÄS MER

7. 5. Fundamental studies of non-premixed combustion in turbulent wall jets using direct numerical simulation

   Författare :Zeinab Pouransari; V. Arne Johansson; Christer Fureby; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Turbulence; non-premixed combustion; global reaction; direct numerical simulation; wall-jet; heat release; mixing scales; heat transfer; Other engineering mechanics; Övrig teknisk mekanik;

   Sammanfattning : The present thesis deals with the fundamental aspects of turbulent mixingand non-premixed combustion in wall-jet flows. Direct numerical simulations(DNS) of compressible turbulent flows are performed in a wall-jet configura-tion, which has a close resemblance to many industrial combustion applica-tions. LÄS MER