A Linearized \(k-\epsilon \) Model of Forest Canopies and Clearings
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- 作者：Antonio Segalini ; Tetsuya Nakamura ; Koji Fukagata
- 关键词：Canopy flows ; Forest clearings ; Linearized Reynolds ; averaged Navier–Stokes equations
- 刊名：Boundary-Layer Meteorology
- 出版年：2016
- 出版时间：December 2016
- 年：2016
- 卷：161
- 期：3
- 页码：439-460
- 全文大小：1,827 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Meteorology and Climatology
Atmospheric Protection, Air Quality Control and Air Pollution - 出版者：Springer Netherlands
- ISSN：1573-1472
- 卷排序：161
文摘
A linearized analysis of the Reynolds-averaged Navier–Stokes (RANS) equations is proposed where the \(k-\epsilon \) turbulence model is used. The flow near the forest is obtained as the superposition of the undisturbed incoming boundary layer plus a velocity perturbation due to the forest presence, similar to the approach proposed by Belcher et al. (J Fluid Mech 488:369–398, 2003). The linearized model has been compared against several non-linear RANS simulations with many leaf-area index values and large-eddy simulations using two different values of leaf-area index. All the simulations have been performed for a homogeneous forest and for four different clearing configurations. Despite the model approximations, the mean velocity and the Reynolds stress \(\overline{u'w'}\) have been reasonably reproduced by the first-order model, providing insight about how the clearing perturbs the boundary layer over forested areas. However, significant departures from the linear predictions are observed in the turbulent kinetic energy and velocity variances. A second-order correction, which partly accounts for some non-linearities, is therefore proposed to improve the estimate of the turbulent kinetic energy and velocity variances. The results suggest that only a region close to the canopy top is significantly affected by the forest drag and dominated by the non-linearities, while above three canopy heights from the ground only small effects are visible and both the linearized model and the simulations have the same trends there.