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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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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Going Hybrid

Nothing is as beneficiary for the flight industry as the ability to cut substantially on fuel budget. From a CFD perspective, such a goal could potentially be achieved by high fidelity simulation for a detailed design full airborne vehicle . A naive approach for the highest physical fidelity could be a Direct Numerical Simulation (DNS) of Navier-Stokes equations. …

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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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Know Thy Solver- PART I: Introduction to NSE Algorithms

A successful CFD analysis workflow consists of the following key elements (sometimes by repeating cycles, and sometimes with additional elements as-per-cause): Definition CFD modeling goals according to the model problem at hand: Physics gives us a description of reality or in other words, a model, by such CFD modeling goals should conform to the level …

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Modeling Transition…

Turbulence prediction has an enormous impact airliners fuel budget, weather information, automotive industry, turbomachinery, biomedical industry and could be easily linked to many other aspects of our daily lives. A lot of focus has been given to the prediction of turbulence through numerical modeling to level of physical fidelity depending on the goal of the …

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