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

Year 2018, , 785 - 795, 01.12.2018

Cihan Bayındırlı , Mehmet Çelik Mehmet Demiralp

https://doi.org/10.2339/politeknik.403993

Cited By: 5

Abstract

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.   

Keywords

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

Abstract

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 (C_D) 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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