防風網密度對防風功效之數值模擬

Numerical Simulation on the Effect of Wind Reduction by the Windbreak Net with Different Densities

黃隆明(Long-Ming Huang) ； 林信佑(Hsing-Yu Lin)

《農林學報》 54卷4期 (2005/12) Pp. 309-323

https://doi.org/10.30089/JAF.200512.0004

摘要

本研究目的以數值模擬防風網之鄰近流場，探討防風網密度對防風功效之影響。經由5組不同密度防風網之數值計算結果，不但證實防風網之遮蔽功效與其配置及密度有關，而且獲致防風網密度之設計準則，可提供工程規劃之重要參考依據；此外，經由3組不同密度防風網之現地與風洞實驗，監測獲得非恆定流之模式與特性，據此對數值方罄應用加以修正進而確認結果。風場計算係採用微可壓縮配合大渦模擬及有限體積法，以模擬防風網之鄰近紊流流場。經由數值分析結果得知，防風網密度以70%之防風效果最佳，保護距離達14.7H，而密度50%和90%最差，保護距離僅11H和12H；經由迴歸分析獲得密度（X）與保護具離（Y）之關係式為：Ŷ=-21.691+1.041X-0.0071X^2 (r=0.9488*)式中為估算之保護距離（H），X為防風網密度（%），r為相關係數，“*”表達5%顯著水準。（註：H為防風網高）

關鍵字

防風網密度 ； 風洞 ； 數值模擬

並列摘要

This study simulate flow phenomena around windbreak net, probed into the influence on wind reduction by the windbreak net with different densities. To gain additional insight into the density designs of windbreak net, a series of computations with five different densities was carries out to find out the shelter effect of the windbreak nets in relation to the density as will as its arrangements. Furthermore, the unsteady flow pattern and its characteristics have to be monitored and measured through field and tunnel experiments with three different densities, in order to guide the application of the numerical method and to confirm its results.The computational code used is based on a weakly-compressible-flow method, together with a large-eddy-simulation and finite volume method technique is applied to account for the turbulence effect in the flow. The results from the numerical analysis, suggest that we could know that the windbreak net with 70% density is the best and the protective distance is about 14.7H. The windbreak net with 50% and 90% density are the worst and the protective distance is only about 11H and 12H respectively. The relationship of windbreak net's density and protective distances is:Ŷ=-21.691+1.041X-0.0071X^2 (r=0.9488*) Ŷ is the estimated protective distance (H). X is the density of windbreak net(%). r is the correlative coefficient. ”*” is the mark of 5% significant level. (H: the height of windbreak net)

並列關鍵字

the density of windbreak net ； wind tunnel ； numerical simulation