Special Sessions within Technical Session Track/Topics

Track/topic:     2. CWE model development, validation, and applications linked to future computing software and hardware

Special Session: Verification, validation and certification in CWE – where are we and where do we want to go?
Chairpersons:  Dr. J. Franke (University of Siegen, Germany) and Dr. N.P. Waterson (Imperial College London, UK)

The quality assurance of Computational Fluid Dynamics (CFD) codes and simulations is nowadays accepted as being most important to further increase the confidence in this approach. The general methodology for quality assurance is based on verification of the computer models, verification of the calculations/solutions (increasingly known as numerical error estimation) and validation of the simulation results. This methodology is increasingly used in many disciplines of CFD applications and should therefore also play an important role in CWE. This session therefore aims at the discussion of the following topics:

• Code verification with the method of manufactured solutions (MMS)
• Solution verification/numerical error estimation for RANS and URANS
• Solution verification/numerical error estimation for LES and DES
• Validation metrics
• Certification/Accreditation of codes and simulation results
• Treatment of uncertainties in validation and certification
• Editorial policies of journals

While the acronym CWE is in general only used for the application of CFD to wind engineering problems, verification, validation and certification are clearly also required for any other numerical simulation in the field of wind engineering. Therefore contributions from other areas like computational structure mechanics, probabilistic wind field generation, etc., are also welcome.

Track/topic:  3.  Development, validation, and application of atmospheric boundary layer models and turbulence models for CWE

Special Session: Model evaluation for flow and dispersion processes in urban environments.
Chairperson:  Professor M.  Schatzmann (Meteorological Institute, University of Hamburg, Germany)

The emergence of increasingly powerful computers enabled the development of tools that have the potential to predict flow and transport processes within the urban canopy layer. These tools are micro-scale meteorological models based on the Reynolds-averaged Navier-Stokes (RANS) equations. It is to be expected, however, that these models will sooner or later be replaced by the even more complex Large Eddy Simulation (LES) models. Typically these models contain a substantial amount of empirical knowledge, not only in the turbulent closure schemes but also in the use of wall functions and in other parameterisation schemes.

Models have begun to play an important and often dominant role in environmental assessment and urban climate studies that are undertaken to investigate and to quantify the effects of human activity on air quality and the local climate. Their increasing use, however, is paralleled by a growing awareness that the majority of these models have never been the subject of rigorous evaluation. Consequently, to a certain degree, there is a lack of confidence in the modelled results. The main objective of the session is to discuss strategies on how the quality of these models can be assured in a structured way.

Track/topic:  6. Benchmark studies

Special Session: Aerodynamics of rectangular cylinders: the BARC benchmark
Chairpersons: Professor F. Ricciardelli (University of Reggio Calabria, Italy), Professor L. Bruno (Politecnico di Torino, Italy)

The BARC benchmark study addresses the high Reynolds number, external, unsteady flow around and past a stationary, sharp-edged 5:1 rectangular cylinder, and the associated aerodynamic actions.
The BARC Special Session is devoted to the presentation of computational results and of comparisons between computational and experimental results on the aerodynamics of rectangular cylinders, in particular those with an aspect ratio of 5 to 1. The session is meant as a BARC mid-term meeting which will allows the participants to exchange ideas, to compare in-progress studies and to discuss not conclusive results.

Track/topic:  9. Transport, dispersion and deposition of pollutants

Special Session 1: Application of CFD to practical environmental assessment in the atmosphere.
Chairpersons: Dr. H. Kondo (National Institute of Advanced Industrial Science and Technology, Japan)

Due to recent development of general purpose CFD models and computer technologies, CFD software has been more often used in the world for practical environmental assessment in the atmosphere. However, it is probable that those users of CFD are not always specialists of CFD, of fluid dynamics, or of meteorology. The accuracy and applicability of sub models in the commercial and free CFD software to practical assessment are not always clear. This session aims to discuss the following issues:

• Application and problems of CFD to practical environmental assessment in the atmosphere
• Guideline to use CFD for the practical assessment
• How to validate the CFD results with errors
• Databases obtained from field or laboratory experiments for the evaluation of CFD results in the application to practical assessment.

Special Session 2: State of the art in computational evaluation of dispersion of building exhaust and potential re-ingestion.
Chairpersons:  Professor T. Stathopoulos (Concordia University, Montreal, Canada), Dr. B. Blocken (Eindhoven University of Technology, The Netherlands)

Air pollution can have a wide range of negative consequences for human health and
productivity. Emissions from single-standing stacks, rooftop vents and stacks can affect
indoor air quality if the plume impinges on air intakes of the emitting building or the
surrounding buildings. Pollutants can be transferred from the outdoor to the indoor environment by mechanical or natural ventilation (induced by wind and/or buoyancy). Alternatively, natural ventilation can also remove pollutants from the indoor environment. The precise prediction of pollutant concentration distributions on or near buildings is very important for building engineers to design proper exhaust stacks and set proper ventilation air intakes. The same holds for the prediction of concentration distributions inside buildings in natural ventilation design. Predicting these concentration distributions however is a difficult task, especially in the urban environment, since it requires the knowledge of air pollution meteorology and dispersion, as well as building aerodynamics. 

This session focuses on the computational evaluation of dispersion of building exhaust and potential re-ingestion and on natural ventilation focused on pollutant transfer between the outdoor and indoor environment. More specifically, papers are invited on:

• Modeling of pollutant concentration distributions around buildings and on building surfaces
• Modeling of pollutant transfer between the outdoor and indoor environment of buildings (both pollutant intake from the outdoor environment and pollutant removal from the indoor environment)
• Wind-induced ventilation and indoor air quality
• Reviews of pollutant dispersion studies
  

Special Session 3:  Rapid CFD and CFD-like Transport and Dispersion Models
Chairpersons: Dr M. Brown (Los Alamos National Laboratory, USA), Dr. I Senocak (Boise State University, USA)

A new generation of 3D Transport and Dispersion models are being developed for computing contaminant transport and dispersion around buildings and in cities.  Papers on CFD models that have been developed to significantly speed up run-time and models that are approximated but give "CFD-like" solutions are invited for this session.

Track/topic:    14. Aerodynamics of wind turbines, vehicles and buildings

Special Session:  Modeling wakes behind bluff bodies
Chairpersons: Professor S. Parameswaran (CFD Lab, Texas Tech University, USA), Dr. R. Sun (Chrysler, USA), and Dr. S. Xue (Vestas Technology, USA)

Wakes play an important role in designing parachutes, arranging wind turbines in wind farms and vehicles. In general, wakes behind vehicles and wind turbines are unsteady and three-dimensional. This session is dedicated to the current status of  wake modeling in the CWE community. Papers that address following topics or related ones will be included in this session:

• Application of turbulence models ranging from two-equation models to Large eddy Simulation to wakes .
• Computational and experimental studies of near- and  far-wakes behind wind turbines.
• Novel computational procedures interfacing a three-dimensional near-wake model with a far-wake boundary layer model.
• Computational studies describing the development of far-wakes with and without swirl.
• Turbulence models for wakes with significant swirl and their validation.
• Influence of rear end geometries such as boat tailing, fastback and notchback on vehicle drag coefficients.
• Influence of wakes behind airport terminal buildings on landing aircrafts.
  
  

Track/topic:  17. Wind loads on buildings

Special Session: Computational evaluation of external and internal wind pressure for buildings.
Chairpersons:  Professor G. Bitsuamlak (Florida International University) and Professor P. Karava (Purdue University)
 
Aerodynamic flows around buildings are complex three-dimensional flows due to the immersion of the buildings in turbulent atmospheric boundary layers and to the presence of flow separation and reattachment phenomena due to the building’s own geometry, which play significant roles in determining wind loads and whose simulation is particularly challenging.  In addition, effects of immediate, irregular surroundings encountered in engineering practice add to the modeling challenges.   

This session focuses on the computational evaluation of wind induced external and internal pressure for buildings and related papers are invited on:

• Turbulence model evaluation for wind pressure predictions
• Modeling of external and internal pressures for buildings with or without neighbouring buildings
• Modeling of external and/or internal wind flow for buildings with dominant openings
• Computational assessment of aerodynamic (geometrical) modifications
• Review of computational evaluation of wind pressures
• Validation/bench mark experimental (full-scale or boundary layer wind tunnel) wind pressure data
  
  

Track/topic:  19. Wind-structure interaction: including bridges/cables and tall structures

Special Session 1: Numerical evaluation of interaction among wind and/or rain and bridge/cable
Chairpersons: Professor Y. Ge (Tongji University, China), Professor H. Li (Haerbin Institute of Technology, China)

With the ever-growing of span length, bridge structures or stay cables are becoming lighter, more flexible, and, in particular, more sensitive to wind and/or rain action. Besides wind and/or rain loading on bridges or cables, one of the most important phenomena is aero-elastic interaction among wind and/or rain and long-span bridges or long stay cables. Computational methods have begun to play an important and often dominant role in evaluation of aero-elastic interaction since there are some difficulties in experimental simulation of wind and/or rain environment and bridge or cable models. The main objective of the session is to discuss the effectiveness of these computational models and procedures in numerical evaluation of aero-elastic interaction, including:

1. Theoretical models of wind and/or rain induced loads
2. Torsional divergence of bridge structure
3. Buffeting vibration of bridge deck
4. Flutter instability of bridge structure
5. Wind and/or rain induced vibration of stay cables

Special Session 2: Aerodynamic loading and aero-elastic interaction of flexible structures
Chairperson: Professor Z. Li (Chongqing University, China)

More and more tall buildings and large-span structures have been built in recent years all over the world, in particular in China. With the increase of height and span, wind loading is becoming much more important than ever before for these flexible structures, especially for super-tall or very large-span structures. There are basically two main challenges for numerical investigation of wind-induced action on these structures, aerodynamic loading on structures and aero-elastic interaction between wind and structure. Since wind loading and its induced response of these structures at special locations in hilly terrain is significantly different from that in flat terrain, the influence of hilly terrain may result in another challenge, namely wind environmental effects on structures. Based on these three challenges in computational methods, the main objective of the session is to discuss aerodynamic loading on these structures and aero-elastic interaction between wind and structures, including:

1. Numerical simulation of wind environment around structures
2. Wind-induced effects on tall buildings
3. Wind loading on membrane structures
4. Wind environmental effects in hilly terrain