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Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles./
Author:	Zhang, Yuxin.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
Description:	132 p.
Notes:	Source: Dissertation Abstracts International, Volume: 79-12(E), Section: B.
Contained By:	Dissertation Abstracts International79-12B(E).
Subject:	Aerospace engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10748715
ISBN:	9780438206304

Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles.
Zhang, Yuxin.

Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 132 p.

Source: Dissertation Abstracts International, Volume: 79-12(E), Section: B.

Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 2018.

The dynamics of inviscid-limit, incompressible and axisymmetric swirling flows in finite-length, long circular pipes with varying geometries is studied through global analysis techniques and numerical simulations. The inlet flow is described by fixed-in-time profiles of the circumferential and axial velocity together with a fixed azimuthal vorticity, while the outlet flow is characterized by a state with zero radial velocity. A numerical algorithm based on the upwind finite-difference method for the evolution of the circulation and azimuthal vorticity together with a Poisson solver for the solution of the streamfunction in terms of the azimuthal vorticity is developed. The convergence of computed results with mesh refinement is demonstrated. Moreover, a mathematical analysis that is based on the Squire-Long equation (SLE) is formulated to identify steady-state solutions of the problem with special conditions to describe states with separation zones. These solutions include the base columnar flow state, a decelerated flow along the centerline, an accelerated flow along the centerline, a vortex-breakdown state and a wall-separation state. The problem is then reduced to the columnar (axially independent) SLE, with centerline and wall conditions for the solution of the outlet flow streamfunction. The numerical simulations realize the various flow states and show correlation between time-asymptotic states and steady states predicted according to the SLE and the columnar SLE problems. The simulations also shed light on the stability of the various steady states. The computed results provide the bifurcation diagrams of steady states in terms of the incoming swirl ratio and size of pipe divergence or contraction. Critical swirls for first appearance of the various types of states are identified. Results show that pipe divergence promotes the appearance of breakdown states at lower inlet swirl levels while pipe contraction delays the appearance of vortex breakdown to higher swirl levels and promotes formation of wall-separation states. The influence of various in- let swirling flow profiles on the manifold of steady states in a straight, finite-length pipe and on flow dynamics is also investigated. Depending on the inlet profiles, flows may first exhibit vortex breakdown while others wall-separation states.

ISBN: 9780438206304Subjects--Topical Terms:

686400
Aerospace engineering.

Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles.
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245 1 0 $a Swirling Flow States in Finite-length Pipes with Various Geometries and Inlet Flow Profiles.
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300 $a 132 p.
500 $a Source: Dissertation Abstracts International, Volume: 79-12(E), Section: B.
500 $a Adviser: Zvi Rusak.
502 $a Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 2018.
520 $a The dynamics of inviscid-limit, incompressible and axisymmetric swirling flows in finite-length, long circular pipes with varying geometries is studied through global analysis techniques and numerical simulations. The inlet flow is described by fixed-in-time profiles of the circumferential and axial velocity together with a fixed azimuthal vorticity, while the outlet flow is characterized by a state with zero radial velocity. A numerical algorithm based on the upwind finite-difference method for the evolution of the circulation and azimuthal vorticity together with a Poisson solver for the solution of the streamfunction in terms of the azimuthal vorticity is developed. The convergence of computed results with mesh refinement is demonstrated. Moreover, a mathematical analysis that is based on the Squire-Long equation (SLE) is formulated to identify steady-state solutions of the problem with special conditions to describe states with separation zones. These solutions include the base columnar flow state, a decelerated flow along the centerline, an accelerated flow along the centerline, a vortex-breakdown state and a wall-separation state. The problem is then reduced to the columnar (axially independent) SLE, with centerline and wall conditions for the solution of the outlet flow streamfunction. The numerical simulations realize the various flow states and show correlation between time-asymptotic states and steady states predicted according to the SLE and the columnar SLE problems. The simulations also shed light on the stability of the various steady states. The computed results provide the bifurcation diagrams of steady states in terms of the incoming swirl ratio and size of pipe divergence or contraction. Critical swirls for first appearance of the various types of states are identified. Results show that pipe divergence promotes the appearance of breakdown states at lower inlet swirl levels while pipe contraction delays the appearance of vortex breakdown to higher swirl levels and promotes formation of wall-separation states. The influence of various in- let swirling flow profiles on the manifold of steady states in a straight, finite-length pipe and on flow dynamics is also investigated. Depending on the inlet profiles, flows may first exhibit vortex breakdown while others wall-separation states.
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