Sökning: "Arne Johansson"

Visar resultat 21 - 25 av 37 avhandlingar innehållade orden Arne Johansson.

  1. 21. A new high-order method for direct numerical simulations of turbulent wall-bounded flows

    Författare :Peter Lenaers; Arne Johansson; Hans Kuerten; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Incompressible wall-bounded flows; direct numerical simulations; high-order; compact finite differences; collocated grid; influence matrix method;

    Sammanfattning : A new method to perform direct numerical simulations of wall-bounded flows has been developed and implemented. The method uses high-order compact finite differences in wall-normal (for channel flow) or radial direction (for pipe flow) on a collocated grid, which gives high-accuracy results without the effectfof filtering caused by frequent interpolation as required on a staggered grid. LÄS MER

  3. 22. 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

  4. 23. Subgrid-scale modelling for large-eddy simulation including scalar mixing in rotating turbulent shear flows

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

    Sammanfattning : The aim of the present study is to develop subgrid-scale models that are relevant for complex flows and combustion. A stochastic model based on a stochastic Smagorinsky constant with adjustable variance and time scale is proposed. LÄS MER

  5. 24. 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. 25. Analysis of laminar and turbulent flows with turbomachinery, biotechnology and biomechanical applications

    Författare :Gustaf Mårtensson; Arne Johansson; Gertjan van Heijst; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Fluid mechanics; Strömningsmekanik;

    Sammanfattning : The goal of this study was initially to gain a better understanding of the effects of rotation on turbulent flow in ducts. Knowledge concerning the influence of rotation on the structures of turbulence is of fundamental importance in many applications, e.g. LÄS MER