Topic
Pipe flow
About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.
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TL;DR: This study couples Particle Image Velocimetry (PIV) and multipoint wall pressure measurements using POD and LSE to estimate the full velocity field from the wall pressure alone and yields a sufficiently accurate estimate of the velocity field that the incipient condition can be detected.
Abstract: Low-dimensional methods including the Proper Orthogonal Decomposition (POD) and Linear Stochastic Estimation (LSE) have been applied to the flow between a backward facing ramp and an adjustable flap. A range of flap angles provide a flow which is incipiently separated and can be used to flesh out ideas for active feedback separation control strategies. The current study couples Particle Image Velocimetry (PIV) and multipoint wall pressure measurements using POD and LSE to estimate the full velocity field from the wall pressure alone. This technique yields a sufficiently accurate estimate of the velocity field that the incipient condition can be detected. The ability to estimate the state of the flow without inserting probes into the flow is important for the development of practical active feedback flow control strategies
180 citations
TL;DR: In this article, analytical expressions for the velocity vector, the stress components and the viscosity function in fully developed channel and pipe flow of Phan-Thien-Tanner (PTT) fluids were derived for both linearized and exponential forms of the PTT equation.
Abstract: Analytical expressions are derived for the velocity vector, the stress components and the viscosity function in fully developed channel and pipe flow of Phan-Thien–Tanner (PTT) fluids; both the linearized and the exponential forms of the PTT equation are considered. The solution shows that the wall shear stress of a PTT fluid is substantially smaller than the corresponding value for a Newtonian or upper-convected Maxwell fluid, with implications for comparing predicted and measured values in a non-dimensional form.
179 citations
TL;DR: The laminar-turbulent boundary Sigma is the set separating initial conditions which relaminarize uneventfully from those which become turbulent as discussed by the authors, and is defined as the boundary that separates initial conditions from those that become turbulent.
Abstract: The laminar-turbulent boundary Sigma is the set separating initial conditions which relaminarize uneventfully from those which become turbulent. Phase space trajectories on this hypersurface in cyl ...
179 citations
TL;DR: The steady-state and time-dependent flow transitions observed in a well-characterized viscoelastic fluid flowing through an abrupt axisymmetric contraction are characterized in terms of the Deborah number and contraction ratio by laser-Doppler velocimetry and flow visualization measurements.
Abstract: The steady-state and time-dependent flow transitions observed in a well-characterized viscoelastic fluid flowing through an abrupt axisymmetric contraction are characterized in terms of the Deborah number and contraction ratio by laser-Doppler velocimetry and flow visualization measurements. A sequence of flow transitions are identified that lead to time-periodic, quasi-periodic and aperiodic dynamics near the lip of the contraction and to the formation of an elastic vortex at the lip entrance. This lip vortex increases in intensity and expands outwards into the upstream tube as the Deborah number is increased, until a further flow instability leads to unsteady oscillations of the large elastic vortex. The values of the critical Deborah number for the onset of each of these transitions depends on the contraction ratio β, defined as the ratio of the radii of the large and small tubes. Time-dependent, three-dimensional flow near the contraction lip is observed only for contraction ratios 2 [les ] β [les ] 5, and the flow remains steady for higher contraction ratios. Rounding the corner of the 4:1 abrupt contraction leads to increased values of Deborah number for the onset of these flow transitions, but does not change the general structure of the transitions.
179 citations
TL;DR: In this article, the dual continuous flow pattern (both phases retain their continuity at the top and bottom of the pipe while there is interdispersion), which occurs during the pipe flow of two immiscible liquid phases, was studied in detail, and pressure gradient, in situ volume fraction and phase distribution data were obtained.
179 citations