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Turbulence: New knowledge, characterisation and modelling techniques
Vestas Technology Centre,  Hedeager 42, 8200 Århus N (see map and see entrance )
Wednesday, October 7, 2009 at 9.00 - 16.30

Turbulence is one of the largest challenges in mechanical engineering and energy technology. This seminar will focus on our current state of knowledge on the physics and the models for turbulence.

  9.00 Registration and tour in the Vestas VR environment
Welcome coffee and opportunity for a tour in Vestas VR environment (read more or see video)
10.00 Welcome
Finn Strøm Madsen - President, Vestas Technology R&D
10:15 Introduction to turbulence - update on our current knowledge

Professor of Turbulence Emeritus William K. George, Division of Fluid Dynamics, Chalmers, Sweden

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This introductory lecture will try to explain why the turbulence problem has been so difficult to solve over the past 100 years or so, and why there probably is little hope for a general turbulence model. Read full abstract

11.00 Coffee break
11.15 Critical review of turbulence modeling

Professor Thomas B. Gatski, Ph.D., Directeur de Rechearche, Laboratoire d'Etudes Aérodynamiques (LEA), Université de Poitiers, ENSMA

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What constitutes turbulence modeling has evolved over the last few decades as different types of solution methodologies have emerged. The focus will be on differential formulations where early modeling or closure efforts were based on the Reynolds-averaged Navier-Stokes (RANS) equations. These formulations required closure of unknown correlations appearing in the Reynolds stress transport equations (RSTE). Such efforts continue today with varying degrees of effort and somewhat dependent on whether the flows of interest are incompressible or compressible. A synopsis of these various approaches will be presented. In addition, some of the approaches used to adapt these RANS type closures to hybrid methods and large eddy simulation (LES) sub-filter scale closures will also be presented. 

12.00 Lunch and further opportunity for a tour in the Vestas VR environment 
13.00 Advances in turbulence modeling of unsteady flows

Dr. Florian Menter, ANSYS Germany Gmbh 

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The presentation will cover Scale-Resolving Simulation (SRS) strategies for the prediction of turbulent flows in industry. An overview over currently available approaches will be given, ranging from URANS to LES. The pros and cons of each approach will be discussed from an application oriented perspective. The SRS strategies at ANSYS will be presented. They comprise:

·         Advanced URANS and Scale-Adaptive Simulation (SAS)

·         DES in different forms

·         Exchange of modeled to resolved turbulence energy using forcing

·         Embedded LES

Generic and application specific examples will be given for all methods.

13.45 Characterization of atmospheric turbulence over forest edges

Professor Jacob Mann, Wind energy Division, Risø National laboratory, Denmark

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It is estimated that 20-30% of the total European wind energy growth takes place in areas where the wind flow is affected by forests. The description of the wind conditions near and above forests poses a challenge, because the canopy is porous. Turbines are designed for maximal turbulence intensity and wind profile gradient. In forested areas, these limits are often violated possibly leading to reduced turbine life-time. We investigate the mean wind profile and turbulence statistics above an 85 years old dense beech forest by use of a laser Doppler anemometer and compare the profiles with a CFD model specifically made for the modelling of flow over vegetation canopies.

14.15 Coffee break
14.45 Global Flow Solutions

Dr. Line Gulstad, Manager, Global Flow Solutions, Wind and site competence centre, Vestas technology R&D

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In the continuously growing wind energy market an increased pressure is put on the wind and site community to reduce the cost of energy and minimize the risk of failing turbines. A good understanding of the atmospheric boundary layer is crucial in this aspect. Turbulence is one of the dynamic key features in the atmospheric boundary layer and hence of major interest in the wind turbine siting work.
The increase in computer power over the last few years has given the opportunity to move from the traditionally linear approach to more sophisticated applications and methods. To be competitive in responding to market demands there is a need for an atmospheric model portfolio that spans all relevant spatial and temporal scales.
The atmospheric modeling capabilities at Vestas Wind & Site Competence Centre (WSCC) will be presented. Advantages and disadvantages connected to the current CFD and meso-scale modeling tools at WSCC will be discussed and the importance of merging scales will be highlighted.
Transient vs. stationary approaches will be discussed and evaluated from a wind turbine siting point of view.
Case studies will be presented and future plans briefly discussed.

15.15 Influence of turbulence modeling on fluid structure interaction phenomena

Dr. Johan Gullman-Strand, Lloyd's Register ODS 

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The possibility to couple the flow field of a fluid in or around a structure with the deformation of the structure has been possible on an industrial level for some years. The level of maturity of the interaction technology has increased but at the same time so has the possibility to capture more of the small scale fluctuations of the flow field itself. The turbulence community has seen the development of Hybrid LES-RANS methods. The presentation will show examples from the industrial application of gas turbine exhaust ducts and the effects of the level of turbulence modelling available in commercial softwares.

15.45 Panel discussion

Discussions on aspects of turbulence and turbulence modelling with the presenters of the day 

16.30 Conclusion
The meeting is now fully booked. You can still register for the meeting, but you will be put on a waiting list - click here for Registration.
DANSIS - The Danish Society for Industrial Fluid Dynamics     Email: dansis@dansis.dk