Fanlı karayolu tünellerinde kavis yarıçapının karbonmonoksit dağılımları üzerindeki etkisinin sayısal incelenmesi

Abstract

Bu çalışmada, karayolları tünellerinde biriken karbonmonoksitin fan etkisiyle dağılımları sayısal olarak incelenmiştir. Tünel içerisinde taşıtların olmadığı ve tünel girişinden 100 m ileride tünel tavanına yakın bir konuma yerleştirilmiş tek fan durumu için, 500 m uzunluğundaki iki şeritli düz bir tünel ve R=950 m ve R=1900 m yarıçap değerlerine sahip iki çemberin 500 m uzunluğundaki yay parçalarıyla oluşan iki farklı kavise sahip iki şeritli iki tünel içerisindeki üç boyutlu akış alanları zaman bağımlı olarak Standart k-ε türbülans modeli ile çözülmüştür. Tünel içerisindeki karbonmonoksit düzeylerinin çalışan fan etkisiyle zamana göre değişimlerinin incelendiği çalışmada, başlangıçtaki karbonmonoksit seviyesi 100 ppm olarak dikkate alınmıştır. Zaman adımı 1 dakika seçilerek 60 dakikalık çözümler gerçekleştirilmiştir. Ağdan bağımsız çözümler, düz tünelde 8,5 milyon ve kavisli tünellerde 16 milyon ağ yoğunluğu değerlerinde sağlanmıştır. Fan itme kuvvetinin 950 N olduğu çalışmada, fan çalışma süresinin sonunda tünel içerisindeki hız ve karbonmonoksit değerleri grafiklere yansıtılmıştır. Kavis etkisi nedeniyle, karbonmonoksit değerleri tünel kesitinin dış bükey tarafındaki sol bölgesinde düşük, iç bükey tarafındaki sağ bölgesinde büyük olmaktadır. Tünel hacmi içerisinde karbonmonoksit seviyelerindeki azalmada kavis yarıçapındaki değişim etkili olmamaktadır. Sayısal çalışmada kullanılan Standart k-ε modeli ile elde edilen sonuçlar deneysel verilerle iyi bir uyum göstermektedir.

Keywords

• Kavisli tünel
• Fan itme kuvveti
• Karbonmonoksit dağılımı
• Standart k-ε türbülans modeli

Numerical investigation of the effect of curve radius on carbon monoxide distributions in ventilated road tunnels

Abstract

In this study, the distribution of carbon monoxide accumulating in road tunnels due to the fan effect was investigated numerically. For the case of a single fan positioned near the tunnel ceiling 100 m ahead of the tunnel entrance, with no vehicles present in the tunnel, the three-dimensional flow fields within two-lane tunnels, one consisting of a 500 m long straight tunnel and two different curves formed by 500 m long arc segments of two circles with radii R=950 m and R=1900 m, were solved time-dependently using the Standard k -ε turbulence model. In the study, which examined the time-dependent changes in carbon monoxide levels inside the tunnel under the effect of the operating fan, the initial carbon monoxide level was considered to be 100 ppm. Solutions were performed for 60 minutes with a time step of 1 minute. Grid independence was achieved at mesh densities of 8,5 million for the straight tunnel and 16 million for the curved tunnels. In the study, where the fan thrust force was 950 N, the velocity and carbon monoxide values inside the tunnel at the end of the fan operating time were reflected in the graphs. Due to the curvature effect, carbon monoxide values are low in the left region on the convex side of the tunnel cross-section and high in the right region on the concave side. Changes in the curvature radius did not affect the decrease in carbon monoxide levels within the tunnel volume. The results obtained using the Standard k-ε model in the numerical study showed good agreement with the experimental data.

Keywords

• Curved tunnel
• Fan Thrust Force
• Carbon monoxide distribution
• Standard k-ε turbulence model

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