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Bir Kara Aracının Aerodinamik Sürüklenmesi Üzerine Yan Cihazların ve Yan Rüzgâr Akışının Etkisinin İncelenmesi

Bu çalışmada, yakıt tüketimini doğrudan etkilediği için basitleştirilmiş bir kara aracının (Ahmed gövdesi) aerodinamik sürükleme katsayısını gözlemlemek için yan cihazların ve yan rüzgâr akışının etkisi araştırılmıştır. Literatür incelendiğinde eğik açı, hız ve geometrik modifikasyonların etkisini araştıran çalışmalar sunulmuştur. Ancak, kara araçları için farklı sapma açılarında hem yan cihaz etkisini hem de yan rüzgâr akışını öneren az sayıda çalışma bulunmaktadır. Bu nedenle, HAD (Hesaplamalı Akışkanlar Dinamiği) çözümü hem yan cihazlara sahip modelde hem de yan rüzgâr akış koşulunda gerçekleştirilmiştir. Yan rüzgâr akış durumu, sürükleme katsayısının nasıl etkilendiğini gözlemlemek için farklı sapma açılarında (β=5°, 10°, 20° ve 30°) analiz edilmiştir. Sürükleme kuvvetinin büyük bir kısmı akış ayrılması veya ters basınç gradyanından dolayı meydana geldiğinden, yan cihazlara sahip olan ve olmayan modeller için ve yan rüzgâr akış koşulları altında gövdenin arka bölgesindeki basınç konturları sunulmuştur. Yan rüzgâr akış koşulları altında, yan cihazların konumlandığı x-düzleminde akım çizgilerinin hızları sunulmuştur. Ek olarak, girdap büyüklüğü, farklı sapma açılarında yan cihazları olan ve olmayan her iki model için de verilmiştir. Çalışma sonuçlarında, akış ayrılması meydana geldiği ve basınç direncinin artmasına neden olduğu için yan cihazların aerodinamik performansı olumsuz etkilediği gözlemlenmiştir. Yan rüzgâr akış durumu nedeniyle modelin arka bölgesinde de basınç düşüşü gözlemlenmiştir. Bu, sürükleme kuvvetlerinin artmasına neden olmaktadır.

Anahtar Kelimeler:

Ahmed gövdesi, HAD, Akış ayrılması, Sapma açısı, Sürükleme katsayısı

Investigation of the Effect of Side Devices and Crosswind Flow on Aerodynamic Drag of a Ground Vehicle

In the present study, effect of side devices and crosswind flow are investigated to observe aerodynamic drag coefficient for a simplified ground vehicle (Ahmed body) since it directly effects fuel consumption. When the literature was examined, the studies that were investigated effect of slant angle, velocity and geometric modifications were presented. However, there are few studies that proposed both side device effect and crosswind flow for ground vehicles at different yaw angles. The CFD (Computational Fluid Dynamic) solution is performed both model with side devices and crosswind flow condition. The crosswind flow condition has been analyzed at different yaw angles (β=5°, 10°, 20°, and 30°) to observe how to affected drag coefficient. Pressure contours have been presented for model with and without side devices and under the crosswind flow conditions at rear region of body since the most of the drag force occurs flow separation or adverse pressure gradient. The streamlines velocities have been presented at x-plane which is positioned side devices location under the crosswind flow conditions. In addition, vorticity magnitude has been given for both models with and without side devices at different yaw angle. In the results of study are observed that side devices adversely effects aerodynamic performance since flow separation occurs on the side of body and it causes to increase pressure drag. The pressure drop is also observed at rear region of model due to crosswind flow condition. This causes the increase of drag forces.

Keywords:

Ahmed body, CFD, Flow separation, Yaw angle, Drag coefficient,

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