CİHAN BAYINDIRLI, MEHMET ÇELİK, MEHMET DEMİRALP

Bir Otobüs Modeli Etrafındaki Akış Yapısının CFD Yöntemi İle İncelenmesi ve Sürükleme Kuvvetinin Pasif Akış Kontrol Yöntemi İle İyileştirilmesi

Bu çalışmada, 1/64 ölçekli bir otobüs modelinin aerodinamik direnç katsayısı hesaplamalı akışkanlar dinamiği (CFD) yöntemi ile tespit edilmiştir. Akış analizleri x yönünde 15 m/s, 20 m/s, 25 m/s ve 30 m/s serbest akış hızlarında 173000-346000 Reynolds sayısı aralığında gerçekleştirilmiştir. Akış analizleri Fluent® programında yapılmıştır. Otobüs modelinin aerodinamik direnç katsayısı ortalama 0.657 olarak tespit edilmiş, toplam direncin basınç ve sürtünme kaynaklı dağılımı belirlenmiştir. Model otobüs üzerinde basınç kaynaklı direnç oluşturan bölgeler akış görüntülemeleri ile tespit edilmiştir. Akış yapısını iyileştirilmek ve basınç kaynaklı direnci azaltmak için üçgen kesitli akış kontrol elemanı geliştirilmiştir. Akış kontrol elemanı 15 mm çapında eşkenar üçgen şeklinde olup model otobüsün ön tampon üzerine konumlandırılmıştır. Model 1 otobüsün aerodinamik direnç katsayısı 0.623 olarak tespit edilmiştir. Bu pasif akış kontrol yöntemi ile aerodinamik direnç katsayısında ortalama % 5.27 iyileşme sağlanmıştır. Elde edilen bu iyileşmenin yüksek taşıt hızlarında yakıt tüketimine etkisi yaklaşık %3’tür. Bu orandaki bir aerodinamik iyileşmenin bir otobüste yıllık yakıt tüketimine etkisi değerlendirilmiştir.

Anahtar Kelimeler:

Sürükleme kuvvet katsayısı, pasif akış kontrolü, akış kontrol elemanı, hesaplamalı akışkanlar dinamiği (HAD)

The Investigation Of Flow Characteristic Around A Bus Model By CFD Method And Improvement Of Drag Force By Passive Flow Control Method

In this study, aerodynamic drag coefficient of 1/64 scaled bus model was determined by the Computational Fluid Dynamics (CFD) method. Flow analyzes were performed at 15 m/s, 20 m/s, 25 m/s ve 30 m/s in x direction, between the range of 173000-346000 Reynolds numbers. Flow analysis was made in Fluent® program. The aerodynamic drag coefficient (CD) of the bus model was determined as 0.657 on average, the distribution of total drag was determined as pressure-friction based. After the flow visualization, the areas are detected where forms aerodynamic drag on the model bus. A triangular section flow control element has been developed to improve the flow structure and decrease the pressure based drag. The flow control element is an equilateral triangle with a diameter of 15 mm and positioned on the front bumper of the model bus. The aerodynamic drag coefficient of model 1 bus was determined as 0.623. With this passive flow control method, the aerodynamic drag coefficient improved by %5.27. The effect of this improvement on fuel consumption is about 3 % at the high vehicle speed. The effect of this aerodynamic improvement on the annual fuel consumption of a bus has been evaluated.

Keywords:

The drag force coefficient, passive flow control, flow control part, Computational Fluid Dynamics (CFD),

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