The computational results indicate that the mean velocity was observed to increase dramatically around the crest of the upwind slope of the hill.

The computational results agreed well with the results obtained from the wind tunnel experiments. The mean velocity and turbulent structures such as turbulence intensity and turbulent kinetic energy were investigated in the upwind and downwind regions over the hill, and the numerical models were validated against the wind-tunnel results to optimize the turbulence model. Rough surface conditions were modeled using a number of windbreak fences regularly spaced on the hill. The flow was assumed to be 2D and modeled using computational fluid dynamics (CFD) models, which were numerically solved using Reynolds-averaged Navier-Stokes equations. In this study, a computational model on atmospheric turbulence flow over a terrain hill shaped with rough surface was investigated under neutral atmospheric conditions. The behavioral distribution of the atmospheric turbulence flow over the terrain with changes in a rough surface has become one of the most important topics of air pollution research, among such other topics as transportation and dispersion pollutants.

These researches can be divided into the following: wind tunnel experiments (Gong and Ibbetson, 1989 Ferreira et al., 1995 Kim et al., 1997 Neff and Meroney, 1998 Ishihara et al., 1999 Carpenter and Locke, 1999 Takahashi et al., 2002Takahashi et al.,, 2005Tamura, 2006, 2007 Lubitz and White, 2007, etc.), water tunnel experiments (Hunt and Snyder, 1980 Loureiro et al., 2007aLoureiro et al.,, 2007b2008), numerical simulations (Kobayashi et al., 1994, Ferreira et al., 1995, Apsley and Castro, 1997, Kim et al., 1997, Uchida and Ohya, 1997, Ishihara and Hibi, 2000, Kim et al., 2001, Iizuka and Kondo, 2004Loureiro et al., 2008 Paiva et al., 2009 Mello and Yanagihara, 2010 Griffiths and Middleton, 2010 Balogh et al., 2012 Cao et al., 2012 Pieterse and Harms, 2013 Balogh and Parente, 2015 Liu et al., 2016aLiu et al.,, 2016bMa and Liu, 2017 Chang et al., 2018, etc.), and field measurements Mickle et al., 1988 Coppin et al., 1994).

As a starting point to predicting flow fields over real complex terrains, many researches have been conducted to study flows over isolated hills.

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