Engineering Turbulence – Part II: Lifting The Wright Way!

"It's easy to explain how a rocket works, but explaining how a wing works takes a rocket scientist..." - Philippe Spalart (senior technical fellow - the Boeing company) The intention of this set of posts is to embark on a journey of connecting the dots between CFD and turbulence modeling with the phenomenological and practical …

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Engineering Turbulence – Part I: Phenomenology

" If you want to be a Millionaire, start with a billion dollars and launch a new airline ..." - Richard Branson The intention of this set of posts is to embark on a journey of connecting the dots between CFD and turbulence modeling with the phenomenological and practical concepts of engineering aerodynamics. Even though …

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GEKO – And Then There Were Six… – PART I

"with four parameters I can fit an elephant, with five I can make him wiggle his trunk..." - John von Neumann Most of nowadays CFD simulations of engineering applications are conducted via the Reynolds Averaging approach. Reynolds-Averaged Navier-Stokes (RANS) simulation is based on the Reynolds decomposition according to which a flow variable is decomposed into …

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Know Thy Mesh – Mesh Quality – Part I

Many would argue that your CFD solution is as good as the mesh behind it. Many aspects of the mesh have a vital contribution to simulation accuracy, and include among others the type of physics models simulated, the details of the solution to the particular simulation, chosen discretization scheme and geometric mesh properties having to …

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Know Thy Solver – Part III: Pressure Equation Methodologies for Incompressible Flow

In compressible flows the continuity equation can be used to determinethe density and the pressure can be calculated from an equation of state. This approach is not appropriate for incompressible or low Mach number flows. When considering the incompressibility assumption as valid, Navier-Stokes equations supplemented by continuity take the following recognizable form (body forces neglected): …

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Law of the Wall

We begin our discussion by noting that there are three quite general and distinct types of turbulent flows: namely, Homogeneous and/or isotropic turbulence, free shear flows and wall-bounded shear flows. Homogeneous and/or Isotropic Turbulence Homogeneous turbulence is such that statistics are invariant under spatial translations, while isotropic turbulence is invariant under rotations and reflections. As rotations and reflections can …

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Numerical Schemes in ANSYS Fluent: Upwinding and The Cell-Reynolds Problem

There are three broad methods employed for discretizing the governing partial differential equations of a fluid flow: Finite Difference Methods (FDM) Finite Element Methods (FEM) Finite Volume Methods (FVM) Finite element and finite volume methods (FEM and FVM) are both based on dividing the flow domain into small cells, or volumes. These may possibly take any shape …

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