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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The Prince of RANS: k-ω SST Turbulence Model

"Every mathematician believes that he is ahead of the others. The reason none state this belief in public is because they are intelligent people" - Andrey Kolmogorov Most of nowadays CFD simulations are conducted with the Reynolds Averaging approach. Reynolds-Averaged Navier-Stokes (RANS) simulation is based on the Reynolds decomposition according to which a flow variable …

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Know Thy Solver- PART II: Projection Methods

Hopefully upon finishing reading Know Thy Solver- PART I, we have consolidated the logic and motivation behind NSE solver segregated algorithms. Our task now is to present an important cornerstone which serves as a building block for ANSYS Fluent pressure-based algorithms as in most other commercial CFD codes - Projection Methods. It is important to note …

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