Numerical Investigation of the Effect of Surface Geometry on Bullet Aerodynamic Behaviours

Öz

Developing gun systems require the study on and development of the bullets that are consumable supplies. With the improvement works in the field of materials and geometry, the production of bullets whose destroying forces, ranges, stabilization of movement and access to the target has been improved is being studied. In this study, the effect of riblet or dimple formed body surface of a 9mm parabellum type light core bullet on the aerodynamic flow behaviour around the bullet is discussed. Air flow around the bullet core has been investigated by the computational fluid dynamic base software Fluent. The compressible air flow has been analysed with the Spalart Allmaras turbulence flow model, considering the viscous effects due to Sutherland’s law. In this study, it was concluded that the riblet and dimpled surface formed bullet geometry can lead to the increase of bullet velocity and decrease in shear stress and drag force. It has been evaluated that the dimple and riblet formed bullet surface provides positive contributions to its range as well as stabilization in bullet movement.

Anahtar Kelimeler

• riblet and dimpled surface,Bullet,turbulent flow,drag force

Yüzey Geometrisinin Mermi Aerodinamik Davranışları Üzerine Etkisinin Nümerik İncelenmesi

Öz

Gelişen silah sistemleri, sistemlerde kullanılan sarf malzeme niteliğindeki mermilerin üzerinde de çalışılması ve geliştirilmesi ihtiyacını gerektirmektedir. Malzeme ve geometri alanında gerçekleştirilen iyileştirme çalışmaları ile tahrip güçleri, menzilleri, hareket ve hedefe ulaşım stabilizasyonları iyileştirilmiş mermilerin üretimi çalışılmaktadır. Bu çalışmada, 9 mm parabellum tip hafif mermi çekirdeği yüzeyine oluşturulan kanal yapı ve çukur yapının mermi etrafında oluşan aerodinamik akış davranışı üzerine etkisinin incelenmesi konu edinilmiştir. Mermi çekirdeği etrafında oluşan hava akışı hesaplamalı akışkanlar dinamiği tabanlı Fluent yazılımı ile incelenmiştir. Sıkıştırılabilir hava akışı, Sutherland’s kanununa bağlı viskoz etkiler dikkate alınarak Spalart Allmaras türbülans akış modeli ile analiz edilmiştir. Çalışmada mermi geometrisi üzerine oluşturulan kanal veya çukur yüzey formunun mermi hızında artışa, kayma gerilimi ve sürükleme kuvvetinde ise azalışa sebep olabildiği sonucuna ulaşılmıştır. Mermi yüzey formunda meydana getirilecek çukur veya kanal yapının mermi hareketinde stabilizasyon yanında menziline de olumlu katkılar sağlayacağı değerlendirilmiştir.

Anahtar Kelimeler

• kanal ve çukur yüzey,Mermi,türbülans akış,sürükleme kuvveti

Kaynakça

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