由於現在石油價格不斷地上漲與環保意識的興起，因此必須要逐漸減少能源的消耗。在交通運輸方面，負責運輸貨物的卡車消耗了交通運輸中相當比例的能源。但卡車因功能上的限制，造成一般的外型較不流線，使得卡車相較於一般客車有著更大的空氣阻力係數。本研究的方向是針對卡車的空氣阻力著手，藉由減少卡車的空氣阻力進而減少能源的消耗。關於卡車的空氣阻力，有很大一部分是由車尾低壓造成的。車尾低壓是由於在卡車後方的流場分離，此流場分離形成了較大的渦流與較低的壓力，因而產生較大的阻力。本研究的減阻方式是在車尾的兩側角落裝設二維噴嘴，藉由此方式來改善卡車後方的流場。
本研究是運用風洞實驗的方式，來量測一具 1/8 縮尺比例的重型卡車模型之空氣阻力。並藉由改變二維噴嘴的導流角度與噴嘴出入口面積比的方式來比較不同實驗參數時的空氣阻力，以此來探討導流角度與噴嘴出入口面積比對減阻效果的影響。經由一系列的實驗跟比較的結果發現，在低雷諾數的實驗條件下，當導流的角度大約在45度到60度之間會有較佳的減阻效果，且漸擴型噴嘴其減阻效果會優於漸縮型噴嘴。

In recent years, the oil price is getting higher and higher. People are looking for vehicles with better energy efficiency and lower fuel consumption. Among all types of vehicles, the aerodynamic drag of trucks is significantly higher than that of other passenger vehicles because of their shapes are limited by their functions. The purpose of this research is to study the reduction of truck’s fuel consumption by aerodynamic drag reduction. To achieve this, this research focuses on the improvement of the low pressure region at truck rear end by using 2-dimensional nozzles installed at the rear end corners. The presence of the nozzle flow is to change the vortex and flow separation at truck end, so that the aerodynamic drag is reduced. To verify the drag reduction efficiency of this device, the corner nozzles are installed on a 1/8 scale heavy truck model. Wind tunnel experiments were performed to measure the drags. Variables of flow turning angle and the area ratio of the nozzles were studied to identify the effectiveness of drag reduction. The results show that the highest drag reduction efficiency is achieved in divergent nozzle with turning angle between 45 to 60 degrees at low Reynolds numbers.

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