濱水草類受水流倒伏之阻力與升力分析

The Drag and Lift Forces for Riparian Grasses That are Deflected by Channel Flow

10.29417/JCSWC.201706_48(2).0003

李津甫(Jin-Fu Li)；彭奎元(Kuei-Yuan Peng)；陳樹群(Su-Chin Chen)

濱水植物 ； 阻力係數 ； 升力係數 ； Riparian vegetation ； drag coefficient ； lift coefficient

中華水土保持學報

48卷2期（2017 / 06 / 01）

86 - 91

繁體中文

本研究以水槽試驗探討濱水草類在不同流況下對拖曳力及抬升力的影響，其中量測濱水草類在水流中抬升力的裝置為本研究首創。研究結果發現，柔性草類受水流衝擊而倒伏所造成的正投影面積變化，會使拖曳力及抬升力與流速的一次方呈線性相關與剛性物體極為不同。然而，隨著水流雷諾數的增加，濱水草類的正投影面積、阻力係數及升力係數皆會逐漸降低且最終趨於定值。濱水草類穩定後的阻力係數為0.6 (Re =40,000)，而升力係數則為1.15 (Re = 24,000)。此時，濱水草類會具有剛性物體的特性，其中升力係數會較阻力係數更快的達到穩定。

This study determines the effect of drag and lift forces for riparian grasses under different flow conditions using a series of flume experiments. A novel installation is used to measure the lift force in the channel flow. Flow changes the front projection area for the riparian grasses, so the drag and lift forces are linearly correlated with velocity. This correlation differs from that for a rigid object. However, as the Reynolds number increases, the front projection area, the drag coefficient and the lift coefficient gradually decrease and approach a constant value. The constant drag coefficient is found to be 0.6 (Re = 40,000) and the constant lift coefficient is 1.15 (Re = 24,000). At this stage, the characteristics of riparian grasses are similar to those for rigid objects, for which the lift coefficient reaches a constant value earlier than the drag coefficient.

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