AUTHORS: Neihad Hussen Al-Khalidy
Download as PDF
ABSTRACT: Wind shear and turbulence caused by buildings in the vicinity of airports have been recognised as a cause of aircraft instability during landing or take-off for some time. The study of the pre and post-development winds has been undertaken using a quantitative Computational Fluid Dynamics (CFD) analysis. Turbulent (gust) wind flow in an urban environment is better modelled with wind tunnel when compared with CFD models employing low end turbulence models (e.g. the standard k-epsilon model). On the other hand small building features are better modelled in CFD versus wind tunnel testing, where model buildings are typically built to a scale of around 1:400 or 1:300. This is important when modelling small structures in the vicinity of airports or assessing the benefit of rounding the corners, adding small canopies, trees, porous screens and blades provided to mitigate adverse wind conditions. Wind tunnel measurements are also performed at a few selected points within the tested model while CFD can provide comprehensive output of the entire flow field. With advances in computational method Scale Resolving Simulation (SRS) models are used for high Reynolds number flows with strong separation. SRS models such as Large Eddy Simulation (LES) or hybrid LES/Reynolds Averaged Navier Stokes (RANS) approaches are used to overcome the limitation of statistical RANS models and resolve significant parts of the turbulence spectrum in CFD simulations. LES is still prohibitively computationally expensive when used for solving external high Re numbers flows in complex built environment even with today’s computational power. In this study hybrid Detached Eddy Simulation (DES) is used to assess the risks of buildings near the threshold of runways and predict wind shear and turbulence for critical flight paths. DES is proposed due to ability to combine the benefits of RANS and LES while minimising their disadvantages. The RANS (Realizable k-epsilon in this study) can achieve good prediction for attached boundary layers while LES can capture unsteady motions of large eddies in separated regions. The paper provides a procedure to reliably assess the risk of building generated wind shear and discusses some of the parameters that may have influence on the results accuracy.
KEYWORDS: - CFD, Airport Wind Shear, Turbulence, Detached Eddy Simulation, Built Environment.
REFERENCES:
[1] H. Krüs, J. Haanstrab, R. van der Hama and B Wichers, Numerical Simulations of Wind Measurements at Amsterdam Airport Schiphol, Journal of Wind Engineering and Industrial Aerodynamics, No.91, 2003, pp.1215-1223.
[2] P. Chan, W. Lo and D. Leung, Low Level Wind Effects of the Hangars at the Hong Kong International Airport. The 5th International Symposium on Computational Wind Engineering, 23 - 27 May 2010, Chapel Hill, NC, USA.
[3] G., Nieupoort, de Pins, Wind criteria due to obstacles at and around airports, Report NLRCR-2006-261, National Aerospace Laboratory of The Netherlands, May 2008.
[4] Managing the Risk of Building Generated Wind shear and Turbulence at Airports, Guideline B, National Airports Safeguarding Frame work, Department of Infrastructure and Regional Development, Australia, 2018.
[5] J. Fröhlich and D. von Terzi, Hybrid LES/RANS methods for simulation of turbulent flows, Progress in Aerospace Sciences, Vol. 44, Issue 5, 2008, pp. 349-377.
[6] N. Al-Khalidy, The Role of Computational Fluid Dynamics in Solving Wind Engineering Problems, 3rd International Conference on Mathematics and Computers in Sciences and in Industry, Crete, Greece, 2016.
[7] M. Glanville and N. Al-Khalidy, Comparison of CFD Prediction with Wind Tunnel and FullScale Measurements for Bounded and Unbounded Wind Flow Scenarios, 5th International Colloquium on Bluff Body Aerodynamics and Applications, Ottawa, Canada, 2004.
[8] W. Janssen, B. Blocken and T. van Hoof, Computational Evaluation of Pedestrian Wind Comfort and Wind Safety around a High-rise Building in an Urban Area, 7th Int. Congress on Environmental Modelling and Software, San Diego CA, USA, 2014.
[9] B. Blocken; T. Stathopoulos, F. ASCE and J. Carmeliet, Wind Environmental Conditions in Passages between Two Long Narrow Perpendicular Buildings, Journal of Aerospace Engineering, Issue 4, Vol. 21, 2008.
[10] R. Dadioti and S. Rees, Validation of a Detached Eddy Simulation Model in Complex Urban Environment, Athens, Journal of Sciences, June 2016.
[11] P. Spalart, W. Jou, M. Strelets and S. Allmaras: Comments on the Feasibility of LES for wings, and on a hybrid RANS/LES approach, 1st AFOSR Int. Conf. on DNS/LES, Ruston, LA, 1997.
[12] P. Spalart, Young person’s guide to DetachedEddy Simulation grids, NASA CR-2001– 211032, 2001.
[13] K. Squires, Detached Eddy Simulation: Current Status and Perspectives, Part of the ErRCO Direct and Large Eddy Simulation, Vo. 9, 2004, pp. 465-480.
[14] F. Menter and Y. Egorov, Scale Adaptive Simulation Method for Unsteady Flow Predictions, Part 1: Theory and Model Description, J. Flow Turbulence and Combustion, No. 1, Vol 85, 2010, pp.113-138.
[15] F., Menter, Best Practice: L Scale –Resolving Simulation in ANSYS CFD, Version 2, 2015, ANSYS USA.
[16] Ansys Fluent Theory Manual, Ansys Inc., 2017.
[17] J. Frank, A. Hellsten, H. Schlunzen and B. Carissimo, Best Practice Guideline for the CFD Simulation of Flows in the Urban Environment, Cost Action 732, 2007
[18] Best Practices for Large Eddy Simulations (LES), Ansys Fluent, KR527, 2010.
