森林上方粗糙次層之風洞實驗

Wind Tunnel Experiment of Roughness Sublayer above the Plant Canopy

陳政諭(Cheng-yu Chen)

指導教授 ： 朱佳仁

國立中央大學/工學院/土木工程學系/碩士(2015年)

摘要

大氣與森林之間的動量、熱量和質量（水汽、二氧化碳、氧氣、種子、花粉等）的傳輸不僅會影響到植物的呼吸與光合作用，亦對森林區的蒸發散和地表附近的微氣候有重大的影響，為全球環境的變遷中重要的一環。本研究以一系列的風洞實驗來探討森林樹冠層附近的紊流風場，實驗中放置模型樹於風洞中的紊流邊界層之中，並改變樹木的排數，在不同的下風距離量測平均風速和紊流參數，以瞭解紊流流場的相關性，以釐清單排與雙排樹的尾流與多排樹木的森林的粗糙次層之間的影響。本研究也探討了樹木孔隙率與阻力係數之間的關係，並量測不同孔隙率障礙物之下風處建築物表面的壓力係數，探討樹木所產生的遮蔽效應。

關鍵字

風洞實驗 ； 樹冠層 ； 森林流場 ； 粗糙次層

並列摘要

The turbulence transport of momentum, heat and mass (water vapor, CO2, O2, seed and pollen) between the plant canopies and atmosphere not only affect the photosynthesis, evaporation and transpiration of plants, but also influence the micro-meteorology of forest area. This study used wind tunnel experiments to investigate the turbulent flow above the plant canopy and the wake flow of the canopy. Mean velocity profiles and turbulence parameters are measured at several down-wind distances. The friction velocity u** calculated from the logarithmic profile and the friction velocity u*c computed from the Reynolds stress are in good agreement. This study also investigates the influence of porosity on the drag coefficient and the friction factor of the canopy. The experimental results indicate that the drag coefficient is much larger than the friction factor.

並列關鍵字

Wind tunnel experiment ； Mixing layer flow ； Plant canopy ； Roughness Sublayer

參考文獻

[1] Amiro, B.D. 1990, Drag coefficients and turbulence spectra within three boreal forest canopies, Boundary-Layer Meteorol. 52, 3, 227-246.

[2] Banarjee, T., Katul, G.G. Fontan, S. Poggi, D. and M. Kumar. 2013, Mean flow near edges and within cavities situated inside dense canopies, Boundary-Layer Meteorol. 49, 14-41.

[3] Belcher S.E., Jerram N., and Hunt J.C.R. 2003, Adjustment of a turbulent boundary layer to a canopy of roughness elements, J. Fluid Mech. 488, 369-398.

[4] Lalic, B., Mihailovic, D.T. Rajkovic, B., Arsenic, I.D. and Radlovic, D. 2003, Wind profile within the forest canopy and in the transition layer above it. Environmental Modeling & Software, 18, 943-950.

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