- 期刊
小型競賽車風阻之實驗與數值探討及設計改進
Experimental and Numerical Investigation on Drag: Design Improvement for Go-Karts
摘要
本研究以風洞實驗與計算流體力學數值模擬之方法，探討小型競賽車輛外流場之空氣動力特性。藉由流場與壓力分布，了解主要造成風阻之因素，並藉以改善原型車減低風阻之設計。將實際含人偶的小型競賽車以1:8的比例做成縮小模型置於風洞中測試，同時利用計算流體力學軟體對模型在風洞測試中相同的情形做數值模擬，藉由風洞量測的風阻數據來選擇適切的數值計算紊流模型。並由數值模擬在高於風洞可量測雷諾數之實用範圍的延伸，比較市售小型競賽車與本研究新設計原型車之空氣動力特性。 實驗與數值模擬結果顯示，數值計算採用k-ω紊流模型所得結果與風洞實驗數據最相吻合，而k-ε模型也有合理的吻合度。利用k-ω紊流模型做高雷諾數之延伸，由數值計算結果提出風阻係數曲線。模擬結果顯示前擋板與前整流罩的外型對風阻的影響最大，對整車外型作減低風阻之設計後，本研究新設計原型車之風阻比市售小型競賽車有明顯的降低。
並列摘要
This study investigated the aerodynamic characteristics of external flow field of go-karts by experimental testing in a wind tunnel with numerical modeling using a computational fluid dynamics (CFD) software package. From the distributions of flow and pressure fields, the major factors affecting drag were identified and the shape design of go-karts was improved. In our experiments, one-to-eight scaled models including the driver and the go-karts were tested in a wind tunnel. The same tested conditions were numerically modeled with a CFD package. Using a comparison of the experimental and numerical results, the most appropriate turbulence model was selected. Using the selected numerical model, aerodynamic characteristics of a commercially available go-kart, and our newly designed go-kart were compared for an extended Reynolds number (Re) range, which was realistic but beyond the measuring capability of the wind tunnel we used. Our results show that the computation with the k-ω turbulence model gave the best agreement between numerical and experimental results, while the k-ε model also had reasonable agreement. The drag coefficient curves were obtained with the k-ω turbulence model for the extended Re range. The computational results indicated that the front fairing and the front panel were the most influential to the drag. With improved shape design, the new go-kart showed a remarkable reduction in the drag compared with the commercial go-kart.