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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, direct numerical simulation approach has only been applied for a limited class of simple low Reynolds number applications.
Presently, turbulence modelling 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 modelling 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 judgement to choose from a number of different alternatives sine the accuracy and effectiveness of each model varies depending on the application.
Course Process and Details
This course is completely code independent - No software is required.
Successful application of turbulence modelling requires engineering judgement depending on physics of the flow, accuracy, project requirements, turnaround time, and computational resources available.
This course offers the attendees the practical knowledge for using turbulence modelling for complex engineering applications.
Through a simple and moderately technical approach, this course describes why we need turbulence modelling and how these models represent turbulent flows. Various approaches and number of popular turbulence models will be discussed along with advantages and disadvantages of these models. Many of the governing and transport equations will be presented for illustration purposes and may not be dealt in depth in this course. Strong effort is made for the course to be software neutral. However, examples from some of the more well known and popular simulation cases and software will be used throughout the session.
Full notes are provided for the attendees.
Students will join the audio portion of the meetings by utilizing the VoIP (i.e. headset connected to the computer via headphone and microphone jacks) or by calling into a standard toll line. If you are interested in additional pricing to call-in using a toll-free line, please send an email to: e-learning @ nafems.org.
Who Should Attend?
This course will be valuable to all engineers aiming to use Computational Fluid Dynamics as a reliable predictive tool for complex flow problems. The target audience for this course is practising engineers who wish to learn more about how to choose and apply effective turbulence modelling in their CFD analysis. Ideally, the participant should have some knowledge of Computational Fluid Dynamics 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 modelling
- 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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