The course syllabus is not adopted.
Overview
- Swedish nameTurbulensmodellering
- CodeMTF271
- Credits7.5 Credits
- OwnerMPAME
- Education cycleSecond-cycle
- Main field of studyMechanical Engineering
- DepartmentMECHANICS AND MARITIME SCIENCES
- GradingTH - Pass with distinction (5), Pass with credit (4), Pass (3), Fail
Course round 1
- Teaching language English
- Application code 03117
- Open for exchange studentsYes
Credit distribution
Module | Sp1 | Sp2 | Sp3 | Sp4 | Summer | Not Sp | Examination dates |
---|---|---|---|---|---|---|---|
0120 Written and oral assignments, part A 1.5 c Grading: UG | 1.5 c | ||||||
0220 Written and oral assignments, part B 1.5 c Grading: UG | 1.5 c | ||||||
0320 Examination 4.5 c Grading: TH | 4.5 c |
In programmes
- MPAME - Applied Mechanics, Year 1 (compulsory elective)
- MPCAS - Complex Adaptive Systems, Year 1 (compulsory elective)
- MPENM - Engineering Mathematics and Computational Science, Year 1 (compulsory elective)
Examiner
- Lars Davidson
- Full Professor, Fluid Dynamics, Mechanics and Maritime Sciences
Eligibility
General entry requirements for Master's level (second cycle)Applicants enrolled in a programme at Chalmers where the course is included in the study programme are exempted from fulfilling the requirements above.
Specific entry requirements
English 6 (or by other approved means with the equivalent proficiency level)Applicants enrolled in a programme at Chalmers where the course is included in the study programme are exempted from fulfilling the requirements above.
Course specific prerequisites
MTF073 - Computational fluid dynamics: The finite volume method (CFD) eller TME226Mechanics of fluid sor any corresponding courseAim
The object of the course is to give the students a thorough knowledge and understanding of modern,
advanced turbulence models for unsteady fluid flow simulations.
Learning outcomes (after completion of the course the student should be able to)
- describe different RANS turbulence models such as Reyonlds stess models, algebraic Reynolds stress models, k-eps, k-omega, V2F, k-omega SST.
- understand and outline the difference between LES, RANS, URANS, DES and hybrid LES-RANS.
- derive the exact transport turbulence equations using tensor notation.
- describe the modeling assumptions, using tensor notation, in turbulence models.
- identify and interpret the different terms in the turbulence models presented in the course.
- understand the basics in machine learning.
- describe the difference between resolved and modeled Reynolds stresses.
- describe different approaches to handle the near-wall problem in LES.
- describe the advantages of second-moment closures compared to eddy-viscosity models.
- derive the V2F model.
- reproduce the different spatial filtering approaches in LES.
- derive the SGS models using tensor notation.
- understand and describe the concept of modeled (for example SGS) dissipation between resolved and modeled scales.
- describe the method for how to prescribe unsteady, fluctuating inlet boundary conditions.
- be able to carry out an simulation with a commercial CFD code.
Content
In LES, DES, URANS and Hybrid LES-RANS the large-scale part of the turbulence is solved for by the discretized equations whereas the small-scale turbulence is modeled. The definition of ''large-scale'' varies in the different methods. Furthermore, the limit between ''large-scale'' and ''small-scale' is often not well defined. Since turbulence is three-dimensional and unsteady, it means that in all the methods the simulations must always be carried out as three-dimensional, unsteady simulations.
- How should I make my mesh?
- Why should I in LES use a non-dissipative discretization scheme?
- Is it necessary to use central differencing in DES and URANS?
- What is the different between LES and unsteady RANS?
- What turbulence models can I use in DES and unsteady RANS?
- To enhance numerical stability, can a turbulence model with high dissipation be used?
- How do I prescribe inlet boundary conditions?
- Inlet boundary conditions: can I use steady inlet boundary conditions? Which is best, synthesized turbulence or a pre-cursor DNS?
- When is the flow fully developed so that I can start time-averaging?
- For how long time do I need to time-average?
- Is it enough if I get accurate mean flow or do I also need accurate resolved turbulent stresses?
- How do I estimate the quality of my LES or hybrid LES-RANS? Spectra? 2-point correlations? SGS dissipation?
Organisation
11 prerecorded lectures are uploaded to Canvas.
There will be five discussion seminars during lectures on Campus.
- The students will register in groups (8-10 in each).
- Each discussion seminar will last 45 minutes.
- Python (recommended), (recommended),
- Matlab or
For Assignment 2b, only Python scripts are available.
1. In the first part of Assignment 1, the students will be given data from a numerical simulation (LES or DNS). The data will be two-dimensional, time-averaged velocity (recirculating flow) and pressure fields, the Reynolds stresses and the (SGS) dissipation. The data will be analyzed.
We will start analyzing the transport equations of the turbulent Reynolds stresses, u_iu_j. We identify regions of large production terms, which should correspond to regions of large Reynolds stresses. Reynolds stresses will be computed using the
eddy-viscosity assumption, and these will be compared to their exact counter-parts.
In the second part of Assignment 1, the students will use Machine Learning and try to improve turbulence models. The first attempt could be to improve the standard k-eps model my optimizing the C_mu coefficient. Influence parameters may be velocity gradients (coordinate-invariant) and/or the turbulent time-scale, k/ε, both functions of x and y. The output parameter will be C_mu = C_mu (x,y). For more details, see Course Plan
2. In Assignment 2, the students will be given flow fields of channel flow at high Reynolds number and the flow
over a hump. Both flows have been obtained using PANS/DES/IDDES.These flows will be analyzed using different modeling assumptions such as DES, DDES, PANS and SAS. For more detail, see Assignment 2a and 2b in the eBook Course home page
Literature
The eBook can be downloaded from the course home pageExamination including compulsory elements
Grades. failed, passed; grade 4; grade 5- Part 1: Two assignments including written presentations. This part is mandatory.
- Part 2: Discussion seminars. This part is not mandatory.
- Part 3: Oral exam is mandatory.
- Oral exam based on the questions in the Discussion seminars and the Assignments.The teachers will also ask follow-up questions.There we try to test if the student has understood the topic or if he/she has memorized it. A good understanding gives grade 4 or 5. Two students at the time. .
- To get grade 'passed', you must have passed the Oral exam and get passed on the two assignment reports.
The course examiner may assess individual students in other ways than what is stated above if there are special reasons for doing so, for example if a student has a decision from Chalmers about disability study support.