Large eddy simulation of flow over a three-dimensional hill with different slope angles

Abstract

Slope variation will significantly affect the characteristics of the wind field around a hill. This paper conducts a large-eddy simulation (LES) on an ideal 3D hill to study the impact of slope on wind field properties. Eight slopes ranging from 10° to 45° at 5° intervals are considered, which covers most conventional hill slopes. The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation accuracy. The time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively analyzed. The accuracy of the present method is verified by comparison with experimental data. The slope can affect both the mean and fluctuating wind flow fields around the 3D hill, especially on the hilltop and the leeward side, where a critical slope of 25° can be observed. The fluctuating wind speeds at the tops of steep hills (with slope angles beyond 25°) decrease with increasing slope, while the opposite phenomenon occurs on gentle hills. With increasing slope, the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface, resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of turbulence. The vortex shedding trajectory in the wake region becomes wider and longer, suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.

Graphical abstract

Keywords

large eddy simulation / inflow turbulence / topographic wind field / critical slope / flow mechanism

Liang Li, received the B.S. degree in civil engineering from Henan University of Technology, Zhengzhou, China, in 2018, and the M.S. degree in structural engineering from Henan University of Technology, Zhengzhou, China, in 2021. He is currently working toward the Ph.D. degree in civil engineering with School of Henan University of Technology, Zhengzhou, China. His research interests include computational fluid dynamics, especially in large eddy simulation of wind flow field around hilly terrains. Email: [e-mail]

Deqian Zheng, received the B.S. degree in civil engineering and the M.S. degree in structural engineering from Zhengzhou University, Zhengzhou, China, in 2003 and 2006, respectively, and got the Ph.D. degree in wind engineering from Tongji University, Shanghai, China, in 2011. He is now working in the School of Civil Engineering as an Associate Professor of Henan University of Technology, and now he is Vice President. His research interests include computational fluid dynamics, especially in large eddy simulation of wind flow field around hilly terrains, wind environment, wind load and fluid structure interaction of building structures. Dr. Zheng was Part-time Researcher Fellow of Wind Engineering Research Center at Tamkang University in 2017-2020. He got three second prizes for scientific and technological achievements of Henan Provincial Department of Education. Email: [e-mail]

References

[1] Aboshosha H, Elshaer A, Bitsuamlak G T, El Damatty A (2015). Consistent inflow turbulence generator for les evaluation of wind-induced responses for tall buildings.J Wind Eng Ind Aerodyn, 142: 198–216

[2] CaoS, TongW, GeY, TamuraY (2012). Numerical study on turbulent boundary layers over two-dimensional hills-effects of surface roughness and slope. J Wind Eng Ind Aerodyn, (104–106): 342–349

[3] Castro H G, Paz R R (2013). A time and space correlated turbulence synthesis method for large eddy simulations.J Comput Phys, 235: 742–763

[4] de Mello P E B, Yanagihara J I. (2010). Numerical prediction of gas concentrations and fluctuations above a triangular hill within a turbulent boundary layer.J Wind Eng Ind Aerodyn, 98(2): 113–119

[5] Debray B G (1973). Atmospheric shear flows over ramps and escarpments.Industrial Aerodynamics Abstracts, 9: 1–4

[6] Fang P Z, Zheng D Q, Li L, Ma W Y, Tang S M (2019). Numerical and experimental study of the aerodynamic characteristics around two-dimensional terrain with different slope angles.Front Earth Sci, 13(4): 705–720

[7] Ferreira A D, Lopes A, Viegas D X, Sousa A (1995). Experimental and numerical simulation of flow around two-dimensional hills.J Wind Eng Ind Aerodyn, 54(94): 173–181

[8] Finnigan J J, Belcher S E (2004). Flow over a hill covered with a plant canopy.Q J R Meteorol Soc, 130(596): 1–29

[9] Flay R G J, King A B, Revell M, Carpenter P, Turner R, Cenek P, Safaei Pirooz A A (2019). Wind speed measurements and predictions over belmont hill, wellington, new zealand.J Wind Eng Ind Aerodyn, 195: 104018

[10] Garcia Sagrado A P, van Beeck J, RambaudP, Olivari D (2002). Numerical and experimental modelling of pollutant dispersion in a street canyon. J Wind Eng Ind Aerodyn, 90(4–5): 321–339

[11] GB 5009-2012 (2012). Load code for the design of building structures. Ministry of Construction, China (in Chinese)

[12] Germano M, Piomelli U, Moin P, Cabot W H (1991). A dynamic subgrid scale eddy viscosity model.Phys Fluids A Fluid Dyn, 3(7): 1760–1765

[13] GongW, Ibbetson A (1989). A wind tunnel study of turbulent flow over model hills. Boundary-Layer Meteorol, 49(1–2): 113–148

[14] He Y C, He J Y, Chen W C, Chan P W, Fu J Y, Li Q S (2020). Insights from Super Typhoon Mangkhut (1822) for wind engineering practices.J Wind Eng Ind Aerodyn, 203: 104238

[15] Hewer F E (1998). Non-linear numerical model predictions of flow over an isolated hill of moderate slope.Boundary-Layer Meteorol, 87(3): 381–408

[16] Hu P, Li Y, Han Y, Cai S C S, Xu X (2016). Numerical simulations of the mean wind speeds and turbulence intensities over simplified gorges using the sst k-ω turbulence model.Eng Appl Comput Fluid Mech, 10(1): 359–372

[17] Huang G Q, Jiang Y, Peng LL, Solari G, Liao H L, Li M S (2019). Characteristics of intense winds in mountain area based on field measurement: focusing on thunderstorm winds.J Wind Eng Ind Aerodyn, 190: 166–182

[18] Hunt J C R, Leibovich S, Richards K J (1988). Turbulent shear flows over low hills.Q J R Meteorol Soc, 114(484): 1435–1470

[19] Iizuka S, Kondo H (2004). Performance of various sub-grid scale models in large-eddy simulations of turbulent flow over complex terrain.Atmos Environ, 38(40): 7083–7091

[20] Ishihara T, Fujino Y, Hibi K (2001). A wind tunnel study of separated flow over a two-dimensional ridge and a circular hill.J Wind Eng Ind Aerodyn, 89: 573–576

[21] Ishihara T, Hibi K (2002). Numerical study of turbulent wake flow behind a three-dimensional steep hill.Wind Struct, 5: 317–328

[22] Ishihara T, Hibi K, Oikawa S (1999). Wind tunnel study of turbulent flow over a three-dimensional steep hill.J Wind Eng Ind Aerodyn, 83: 95–107

[23] Jackson P S, Hunt J (1975). Turbulent wind flow over a low hill.Q J R Meteorol Soc, 101(430): 929–955

[24] Kim H G, Lee C M, Lim H C, Kyong N H (1997). An experimental and numerical study on the flow over two-dimensional hills.J Wind Eng Ind Aerodyn, 66(1): 17–33

[25] Kim J J, Baik J J, Chun H Y (2001). Two-dimensional numerical modeling of flow and dispersion in the presence of hill and buildings.J Wind Eng Ind Aerodyn, 89(10): 947–966

[26] KondoK, Tsuchiya M, SanadaS (2002). Evaluation of effect of micro-topography on design wind velocity. J Wind Eng Ind Aerodyn, 90(12–15): 1707–1718

[27] Lilly D K (1992). A proposed modification of the Germano subgrid-scale closure method.Phys Fluids A Fluid Dyn, 4(3): 633–635

[28] Liu Z, Ishihara T, Tanaka T, He X (2016). LES study of turbulent flow fields over a smooth 3-d hill and a smooth 2-d ridge.J Wind Eng Ind Aerodyn, 153: 1–12

[29] Loureiro J B R, Alho A T P, Silva Freire A P (2008). The numerical computation of near-wall turbulent flow over a steep hill.J Wind Eng Ind Aerodyn, 96(5): 540–561

[30] Mathey F Cokljat D, Bertoglio J P, Sergent E (2006). Assessment of the vortex method for large eddy simulation inlet conditions.Prog Comput Fluid Dy, 6(1–3): 58–67

[31] Pearse J R, Lindley D, Stevenson D C (1981). Wind flow over ridges in simulated atmospheric boundary layers.Boundary-Layer Meteorol, 21(1): 77–92

[32] Smagorinsky J (1963). General circulation experiments with the primitive equations.Mon Weather Rev, 91: 99–164

[33] Sykes R I (1980). An asymptotic theory of incompressible turbulent boundary layer flow over a small hump.J Fluid Mech, 101(3): 647–670

[34] Takahashi T, Ohtsu T, Yassin M F, Kato S, Murakami S (2002). Turbulence characteristics of wind over a hill with a rough surface.J Wind Eng Ind Aerodyn, 90(12–15): 1697–1706

[35] TamuraT (2008). Towards practical use of LES in wind engineering. J Wind Eng Ind Aerodyn, 96(10–11): 1451–1471

[36] Tamura T, Okuno A, Sugio Y (2007). LES analysis of turbulent boundary layer over 3D steep hill covered with vegetation.J Wind Eng Ind Aerodyn, 95: 1463–1475

[37] Uchida T (2018). Large-eddy simulation and wind tunnel experiment of airflow over bolund hill.Open J Fluid Dyn, 8(1): 30–43

[38] WoodN (2000). Wind flow over complex terrain: a historical perspective and the prospect for large-eddy modelling. Boundary-Layer Meteorol, 96(1–2): 11–32

[39] Wood N, Mason P (1993). The pressure force induced by neutral, turbulent flow over hills.Q J R Meteorol Soc, 119(514): 1233–1267

[40] Wurtele M G, Sharman R D, Datta A (1996). Atmospheric Lee Waves.Annu Rev Fluid Mech, 28(1): 429–476

[41] XuD, TaylorP A (1992). A non-linear extension of the mixed spectral finite difference model for neutrally stratified turbulent flow over topography. Boundary-Layer Meteorol, 59(1–2): 177–186

[42] Yang Q S, Zhou T, Yan B W, Liu M, Van Phuc P, Shu Z R (2021). LES study of topographical effects of simplified 3D hills with different slopes on abl flows considering terrain exposure conditions.J Wind Eng Ind Aerodyn, 210: 104513

[43] Yang Q S, Zhou T, Yan B W, Van Phuc P, Hu W C (2020). LES study of turbulent flow fields over hilly terrains – comparisons of inflow turbulence generation methods and sgs models.J Wind Eng Ind Aerodyn, 204: 104230

[44] Yang Y, Gu M, Chen S Q, Jin X Y (2009). New inflow boundary conditions for modelling the neutral equilibrium atmospheric boundary layer in computational wind engineering.J Wind Eng Ind Aerodyn, 97(2): 88–95

[45] Yu Y, Yang Y, Xie Z (2018). A new inflow turbulence generator for large eddy simulation evaluation of wind effects on a standard high-rise building.Build Environ, 138: 300–313

[46] Zheng D Q, Zhang A S, Gu M (2012). Improvement of inflow boundary condition in large eddy simulation of flow around tall building.Eng Appl Comput Fluid Mech, 6(4): 633–647

Acknowledgments

This study was jointly supported by the National Key R & D Plan of China (No. 2018YFB1501104), the National Natural Science Foundation of China (Grant No. 52278511), the Natural Science Foundation of Hebei Province (No. E2021210053) and the Young Backbone Teacher Cultivation Program of Henan University of Technology.

RIGHTS & PERMISSIONS

2023 Higher Education Press