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Transition to turbulent flow in finite length curved pipe using nek5000

Hashemi, Seyyed Amirreza
http://rave.ohiolink.edu/etdc/view?acc_num=akron1450458762

Abstract Details

2016, Master of Science, University of Akron, Mechanical Engineering.
Transition to turbulent flow in curved pipe has been well studied through experiments and numerical simulations. Numerical simulations often use helical pipe geometry with infinite length such that the inlet and outlet boundary conditions can be modeled as periodic which reduces computational time. In the present study, we examined a finite length curved pipe with a Poiseuille flow imposed at the inlet and a stress-free boundary condition at the outlet. Direct numerical simulation of the Navier-Stokes equations for rigid walls and a Newtonian fluid was performed using nek5000. Straight extensions were added to the inlet and the outlet such to diminish the impact of boundary conditions on the flow field in the region with curvature. The examined model has a pipe radius of curvature that is three times that of the pipe radius. The model has over 300 million nodes and required an order of magnitude greater computational time when compared to the infinite length curved pipe. Results show that the critical Reynolds number (initiation of instabilities) is greater compared to a straight pipe and occurs near Re=5000-5200. This Re is also larger than the critical Reynolds number typically reported for an infinite length curved pipe (Re= 4200-4300). As expected, flow patterns in the finite length curved pipe were shown to be evolving through the curvature as opposed to that of an infinite length curved pipe where it remains constant. In addition, the initial instabilities observed in the flow did not originate from a Dean flow instability, initiated through secondary flow, but rather were first observed near the outer wall.
Francis Loth, Dr. (Advisor)
Paul Fischer, Dr. (Advisor)
Sergio D. Felicelli, Dr. (Committee Member)
Fluid Dynamics
Transitional flow, Direct numerical simulation, Curved pipe, Secondary flow, Turbulent instabilities

Recommended Citations

Citations

  • Hashemi, S. A. (2016). Transition to turbulent flow in finite length curved pipe using nek5000 [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1450458762

    APA Style (7th edition)

  • Hashemi, Seyyed Amirreza. Transition to turbulent flow in finite length curved pipe using nek5000. 2016. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1450458762.

    MLA Style (8th edition)

  • Hashemi, Seyyed Amirreza. "Transition to turbulent flow in finite length curved pipe using nek5000." Master's thesis, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1450458762

    Chicago Manual of Style (17th edition)

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