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Simulation of Drag Reduction via Microgrooves Using Lattice Boltzmann Method

Asadzadeh, Homayoun | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49577 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Moosavi, Ali; Arghavani, Jamal
  7. Abstract:
  8. Nowadays, the lattice Boltzmann method has been widely used by scientists and engineers as an alternative to conventional numerical solvers for the Naiver-Stokes equations. The drag force decrease on the surfaces in industrial applications special in transport industries has always been of special importance. In the current research, the effects of the drag decrease has been investigated by making some rectangular grooves on the millimeter and micrometer scale on a flat surface that has been under external laminar flow of a single-phase fluid with the uniform type. Making grooves on the surfaces usually lead to change the contact area from the solid-fluid to fluid-fluid in the grooves area. Hence, it leads to that the fluid tangents to the inner surfaces of groove. Instead of that, it passes through the upper surface of grooves and some vortices will be formed in the grooves. The formation of these vortices leads to decrease in the velocity gradient and so the friction drag force decreases. On the other hand, because of the flow separation phenomena, it leads to the pressure drag force increase. In some special cases and with the appropriate selection of the groove in the laminar flows, it is possible to decrease the surface total drag coefficient in a same way. Since these groove are formed in the mesoscopic scale, the Lattice Boltzmann method has been used for the simulation, since it is a new developed method with the low computational cost and also the high generalizability. It should be noted that the numerical simulation of this phenomena has not been performed by the Lattice Boltzmann method for the external flow on the rectangular surface. The same research activities in the similar aspects have been performed for the flows in the canal and most of them were in the form of the experimental tests or calculation were performed in the macroscopic scale. In the current study, after investigation of the independence from network, the dimension changes effect and also the grooves geometry effect on the drag reduction have been investigated and finally it has been concluded that it is possible to the total drag coefficient of groove up to 7 percent in comparison to the same flat surface by selecting the appropriate width and depth
  9. Keywords:
  10. Lattice Boltzmann Method ; Reynolds Number ; Drag Reduction ; Total Coefficient Average ; vortex Formation ; Optimizing Groove Geometry

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