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Majority of flows in nature and in engineering applications are turbulent. Turbulent flow fields are three dimensional, chaotic, diffusive, dissipative, and random. These flows are characterized by velocity fluctuations in all directions with infinite number of scales. Exact analytical solution of Navier-Stokes equations for turbulent flows is not currently possible since these equations are elliptic, non‐linear, and coupled. Furthermore, direct numerical simulation (DNS) of turbulent flows is not currently practical due to significant computational resources required. So far, DNS approach has only been applied for a limited class of simple low Reynolds number applications.
Presently, turbulence modeling based on Reynolds-Averaged Navier Stokes (RANS) equations is the most common and practical approach for turbulence simulation. RANS are time-averaged modification of Navier-Stokes equations and turbulence models are semi-empirical mathematical relations that are used to predict the general effect of turbulence. The objective of turbulence modeling is to develop equations that will predict the time-averaged velocity, pressure, and temperature fields without calculating the complete turbulent flow pattern as a function of time. Unfortunately, there is no single universally accepted turbulence model that works for all flows and all regimes. Therefore, users have to use engineering judgment to choose from a number of different alternatives sine the accuracy and effectiveness of each model varies depending on the application.
This course is completely code independent. No software is required.
The target audience for this course is practicing engineers who wish to learn more about how to choose and apply effective turbulence modeling in their CFD analysis. Ideally, the participant should have some knowledge of CFD analysis, but this is not essential. The material that is presented is independent of any particular software package, making it ideally suited to current and potential users of all commercial and non-commercial CFD software systems.
Course Content
- Understanding turbulence
- Turbulence energy cascade & vortex stretching
- Turbulence scales
- Turbulence generation and destruction
- Discussion on DNS & LES
- Turbulent stresses
- RANS simulation
- Turbulence modeling
- First order models: One-equation & Two-equations models
- Wall integration & wall function
- Detached eddy simulation
- URANS
- Model comparison: advantages and disadvantages
- Model Validations
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