Yüzey Geometrisinin Mermi Aerodinamik Davranışları Üzerine Etkisinin Nümerik İncelenmesi

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

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

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.

Keywords:

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

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[1] Thakur V., Yadav T., Rajiv B., "Drag Optimization of Bluff Bodies using CFD for Aerodynamic Applications", Int J Comput Eng Res,7(4):25–32, (2017).
[2] Sahoo S., Laha M.K., "Coefficient of drag and trajectory simulation of 130 mm supersonic artillery shell with recovery plug or fuze", Def Sci J., 64(6):502–508, (2014).
[3] Litz B., "Aerodynamic Drag Modeling for Ballistics Part 1 Aerodynamic Drag 101", Applied Ballistics,1:1–13, (2016).
[4] Gemba K., "Shape Effects on Drag",90840:2–5, (2007).
[5] Lorite-Díez M, Jiménez-González JI, Gutiérrez-Montes C, Martínez-Bazán C., "Drag reduction of slender blunt-based bodies using optimized rear cavities", J Fluids Struct,74:158–77, (2017).
[6] Khan TH, Saha S., "Numerical Simulation and aerodynamic characteristic analysis of a Paraboloid-tip Bullet", 4th Global Engineering, Science and Technology Conference, Bangladesh, pp.1–8, (2013).
[7] Bixler GD, Bhushan B., "Fluid drag reduction with shark-skin riblet inspired microstructured surfaces", Adv Funct Mater, 23(36), 4507–4528, (2013).
[8] Choi J, Jeon W-P, Choi H., "Mechanism of drag reduction by dimples on a sphere", Phys Fluids, 18(4):041702, (2006).
[9] Lim HC, Lee SJ., "PIV measurements of near wake behind a U-grooved cylinder", J Fluids Struct,18(1):119–130, (2003).
[10] Taheri A., "On the Hydrodynamic Effects of Humpback Whale’s Ventral Pleats", 8(2):47–62, (2018).
[11] Bogdanović-Jovanović JB, Stamenković ŽM, Kocić MM., "Experimental and numerical investigation of flow around a sphere with dimples for various flow regimes", Therm Sci, 16(4):1013–1026, (2012).
[12] Stanly R, Sagaram BS, Suneesh SS, Kumar SSV, "Effect of Passive Flow Controlling Dimples on Drag Reduction and Improved Fuel Efficiency", 20th Australasian Fluid Mechanics Conference, Australia, pp. 2-4, (2016).
[13] Chowdhury H, Loganathan B, Wang Y, Mustary I, Alam F, "A Study of Dimple Characteristics on Golf Ball Drag", Procedia Eng, 147: 87–91, (2016).
[14] Thakur V, Yadav T, Rajiv B., "Drag Optimization of Bluff Bodies using CFD for Aerodynamic Applications", Int J Comput Eng Res, 7(4):25-32, (2017).
[15] Muruganantham VR, Babin T, "Numerical Investigation of Hybrid Blend Design Target Bullets", Matec Web of Conferences, 172:4–7, (2018).
[16] El Maani R, Elouardi S, Radi B, El Hami A, "Study of the turbulence models over an aircraft wing", Incert Fiabilité Des Systèmes Multiphysiques, 2(2):1–11, (2018).
[17] Rakowitz M, "Grid Refinement Study with a UHCA Wing-Body Configuration Using Richardson Extrapolation and Grid Convergence Index GCI", New Results in Numerical and Experimental Fluid Mechanics III, 77, Springer, pp. 97-303, Berlin, (2002).
[18] Sukri Mat Ali M, Doolan CJ, Wheatley V, "An assessment method for Grid Convergence of two-dimensional Direct Numerical Simulation of flow around a square cylinder at a low Reynolds number", Proc Seventh Int Conf CFD Miner Process Ind, Australia, pp. 1-6, (2009).
[19] Yamagata T, Hayase T, "Grid Convergence Property of Three-Dimensional Measurement-Integrated Simulation for Unsteady Flow behind a Square Cylinder with Karman Vortex Street", J Flow Control Meas Vis, 4:125–142, (2016).
[20] Sundaram S, Viswanath PR, Rudrakumar S., "Viscous drag reduction using riblets on NACA 0012 airfoil to moderate incidence", AIAA J, 34(4):676–682, (1996).
[21] Choi J, Jeon WP, Choi H., "Mechanism of drag reduction by dimples on a sphere", Phys Fluids,18(4):16–19, (2006).
[22] Lee SJ, Choi YS., "Decrement of spanwise vortices by a drag-reducing riblet surface", J Turbul, 9:1–15, (2008).
[23] Viswanath PR., "Aircraft viscous drag reduction using riblets", Prog Aerosp Sci, 38(6-7):571–600, (2002).
[24] Lienhart H, Breuer M, Köksoy C., "Drag reduction by dimples? - A complementary experimental/numerical investigation", Int J Heat Fluid Flow, 29(3):783–791, (2008).
[25] Duan L, Choudhari MM., "Effects of Riblets on Skin Friction and Heat Transfer in High-Speed Turbulent Boundary Layers", 50th AIAA Aerosp. Sci. Meet. Incl. New Horizons Forum Aerosp. Expo., Nashville, pp.1-17, (2012).
[26] Sun ZS, Ren YX, Larricq C., "Drag reduction of compressible wall turbulence with active dimples", Sci China Physics, Mech Astron, 54(2):329-337, (2011).