Yan rüzgar koşullarında ön kısmı düz plakalı bir otobüs modeli üzerindeki aerodinamik direncin düşürülmesi

Akaryakıt fiyatları ve insanların çevrenin mevcut durumu üzerinde meydana getirdiği değişimler ticari taşıtların yakıt ekonomisinin iyileştirilmesine olan ilgiyi arttırmıştır. Büyük olasılıkla, bir taşıtın yakıt ekonomisini iyileştirmenin en ekonomik yolu taşıtı aerodinamik açıdan daha verimli yapmaktır. Bu çalışmada, sıfır ve sıfırdan farklı sapma açılarında (β≤9°), 1:25 ölçekli otobüs modelinin ön alt yüzeyine paralel ve modele göre daha önde olacak şekilde yerleştirilen düz plakaların aerodinamik performansı deneysel olarak incelenmiştir. Kıyaslama çalışmaları, düz plakasız otobüs modelini de hesaba katarak, genişliğe-dayalı Reynolds sayısının Rew=104000±3000 değerinde gerçekleştirilmiştir. Kuvvet ölçümleri, zaman ortalamalı sürükleme katsayısında, , dik bir artışın gözlemlendiği kritik bir plaka genişliğinin varlığını ortaya koymaktadır. Sıfır sapma açısında, otobüs genişliğinin (w) onda yedisi kadar genişlikli bir plakanın otobüs modelinin 0,16w daha önüne yerleştirildiği bir geometrik kurulum, plakasız otobüs modeline etkiyeninkinin %92,9’u kadarlık bir zaman-ortalamalı direnç oluşturmaktadır. Bu kurulumun, yan akış şartları altında da düşürmede etkin olduğu görülmüştür.

Anahtar Kelimeler:

Direnç düşürme, Düz plaka, Otobüs, Rüzgar tüneli, Aerodinamik

Aerodynamic drag reduction on a bus model with upstream flat plate under crosswind conditions

Fuel costs and environmental pressures increase interest in improving fuel economy in the commercial vehicles. Presumably, the most economical way to improve a vehicle’s fuel economy is to make it more aerodynamically efficient. In this work, the aerodynamic performance of flat plates placed upstream of and parallel to the front lower surface of a 1:25 coach model at zero and non-zero yaw angles (β≤9°) has been experimentally investigated. Comparative studies have been performed at a width-based Reynolds number Rew=104000±3000, considering the coach model without flat plate. The force measurements suggest the existence of a critical plate width at which a steep increase in time-averaged drag coefficient, , was observed. At zero yaw, a geometrical configuration consisting of a plate width seven tenth of the coach’s width (w) placed 0.16w upstream of the coach model produces a time-averaged drag that is 92.9% that of the coach model without plate. It is seen that this configuration is also effective in reducing under crosswind conditions.

Keywords:

Drag reduction, Flat plate, Coach, Wind tunnel, Aerodynamics,

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