AbstractBionic non-smooth surfaces

Abstract
Bionic non-smooth surfaces (BNSS) can reduce drag. Much attention has been paid to the mechanism of shear stress
reduction by riblets. The mechanism of pressure force reduction by bionic non-smooth surfaces on bodies of revolution
has not been well investigated. In this work CFD simulation has revealed the mechanism of drag reduction by BNSS,
which may work in three ways. First, BNSS on bodies of revolution may lower the surface velocity of the medium, which
prevents the sudden speed up of air on the cross section. So the bottom pressure of the model would not be disturbed
sharply, resulting in less energy loss and drag reduction. Second, the magnitude of vorticity induced by the bionic model
becomes smaller because, due to the sculpturing, the growth of tiny air bubbles is avoided. Thus the large moment of
inertia induced by large air bubble is reduced. The reduction of the vorticity could reduce the dissipation of the eddy. So
the pressure force could also be reduced. Third, the thickness of the momentum layer on the model becomes less which,
according to the relationship between the drag coefficient and the momentum thickness, reduces drag.
Keywords: bionic non-smooth surface, drag reduction mechanisms, boundary layer, pressure force
Copyright 0 2007, Jilin University. Published by Science Press and Elsevier Limited. All rights reserved.

Hasil (Bahasa Indonesia) 1:

AbstrakBionic bebas-halus permukaan (BNSS) dapat mengurangi drag. Banyak perhatian telah dibayarkan kepada mekanisme sesarpengurangan oleh riblets. Mekanisme tekanan memaksa pengurangan oleh bionik permukaan bebas-halus pada tubuh revolusitelah tidak baik diteliti. Dalam karya ini simulasi CFD telah mengungkapkan mekanisme pengurangan drag oleh BNSS,yang dapat bekerja dalam tiga cara. Pertama, BNSS pada tubuh revolusi dapat menurunkan kecepatan permukaan jangka menengah, yangmencegah kecepatan tiba-tiba ke udara di bagian salib. Jadi tekanan bawah model akan tidak akan terganggutajam, mengakibatkan kurang energi kerugian dan tarik pengurangan. Kedua, besarnya vorticity disebabkan oleh model bionikmenjadi lebih kecil karena, karena memahat, pertumbuhan gelembung udara kecil dihindari. Dengan demikian besar saatinersia disebabkan oleh gelembung udara besar berkurang. Pengurangan vorticity dapat mengurangi disipasi eddy. Jadikekuatan tekanan juga dapat dikurangi. Ketiga, ketebalan lapisan momentum pada model menjadi kurang yang,menurut hubungan antara koefisien drag dan ketebalan momentum, mengurangi drag.Kata kunci: bionik permukaan bebas-halus, mekanisme pengurangan drag, lapisan batas, kekuatan tekananCopyright 2007 0, Jilin Universitas. Diterbitkan oleh Sains Tekan dan Elsevier Limited. Semua Hak, milik.