Elements of Turbulence Modeling

Two-session eLearning course

This course has been expanded from the original one session to two sessions, in order to cover even more content and allow more time for questions and tutor interaction

Course Overview

The 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, 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

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 utilising 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?

• Valuable to all engineers aiming to use Computational Fluid Dynamics as a reliable predictive tool for complex flow problems.
• 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.
• eLearning classes are ideal for companies with a group of engineers requiring training. eLearning classes can be provided to suit your needs and timescale. Contact us to discuss your requirements.

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 Validations

Special Note(s):

Telephony surcharges may apply for attendees who are located outside of North America, South America and Europe. These surcharges are related to individuals who join the audio portion of the web-meeting by calling in to the provided toll/toll-free teleconferencing lines. We have made a VoIP option available so anyone attending the class can join using a headset (headphones w/ microphone) connected to the computer. There is no associated surcharge to utilize the VoIP option, and is actually encouraged to ensure NAFEMS is able to keep the eLearning course fees as low as possible. Please send an email to the eLearning coordinator (e-learning @ nafems.org ) to determine if these surcharges may apply to your specific case.

Just as with a live face-to-face training course, each registration only covers one person. If you plan to register a large group (10+), please send an email to e-learning @ nafems.org in advance for group discounts.

PSE Competencies addressed by this training course

 ID Competence Statement CFDkn2 State the Reynolds Averaged Navier Stokes equations. CFDkn6 List in order of complexity the range of turbulence models for RANS modelling approaches. CFDco4 Explain why turbulence models are required and classify the range of models currently available. CFDco5b Review the available turbulence models for RANS approaches and discuss their strengths, weaknesses and their applicability to a range of different flow conditions. CFDco8 Explain the difference between RANS and LES turbulence modelling approaches.

Upcoming Session:

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View the NAFEMS Professional Simulation Engineer competence statements addressed by this training course.

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