Modeling drag reduction in turbulent flows by Brownian fiber additives
Başlık çevirisi mevcut değil.
- Tez No: 401871
- Danışmanlar: DR. AMIN MOOSAIE
- Tez Türü: Yüksek Lisans
- Konular: Fizik ve Fizik Mühendisliği, Makine Mühendisliği, Physics and Physics Engineering, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2011
- Dil: İngilizce
- Üniversite: Technische Universität München
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 64
Özet
Özet yok.
Özet (Çeviri)
A new algebraic closure model for the non-Newtonian Navier-Stokes equations has been proposed in order to get more realistic turbulent statistics for dilute Brownian fiber suspensions in wall-bounded turbulent flows. Our new model is an improvement on existing VAF model which is capable of showing the basic features of drag reducing behavior of the non-Brownian fibers. Our new model (VAFB) also considers the Brownian motion of the fiber additives. Two-way coupled simulations of fully-developed turbulent channel flows have been conducted with a nominal shear Reynolds number of Re = 180 with different rotary Brownian diffusivities in order to show the effects of the Brownian motion in turbulent flows. A validation has been done by comparing the results with those of VAF model with the same flow configuration. After simulating different test cases with different Péclet numbers, we have presented the mean streamwise velocity, the turbulence intensity, the Reynolds shear stress and the mean non-Newtonian stress profiles. Results have shown that when the intensity of the Brownian motion increases, the flow tends to the Newtonian state. Therefore, we get the maximum drag reduction in case of high Péclet numbers. We also observed that when the Péclet number is 100, the results of that specific flow case are very similar to those of the Newtonian flow, and by further increase in Brownian diffusivity produces not a drag reduction but a frictional drag increase in the flow. These findings are in accordance with the previous findings in literature. Therefore, VAFB model is able to represent the main characteristics of wallbounded turbulent flows of dilute Brownian fiber suspensions with a significant decrease in computational costs when compared to that of direct solution of Fokker-Planck equation.
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