Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.

Velocity field for Taylor–Couette flow with an axial flow

Abstract: The flow in the gap between an inner rotating cylinder concentric with an outer stationary cylinder with an imposed pressure-driven axial flow was studied experimentally using particle image velocimetry (PIV) in a meridional plane of the annulus. The radius ratio was η=0.83 and the aspect ratio was Γ=47. Velocity vector fields for nonwavy toroidal and helical vortices show the axial flow winding around vortices. When the axially averaged axial velocity profile is removed from the velocity field in a meridional plane, the velocity field looks much like it would with no imposed axial flow except that the vortices translate axially and the distortion of the azimuthal velocity contours in meridional plane related to the vortices is shifted axially by the axial flow. The velocity vector fields for wavy vortices also show axial flow winding around the vortices. Again, removing the axial velocity profile results in a flow that appears similar to that with no axial flow. The path of the vortices is generally axial, but the vortices periodically move retrograde to the imposed axial flow due to the waviness of the vortices. The axial velocity of helical vortices, both nonwavy and wavy, is twice the rotational frequency of the inner cylinder indicating a coupling between the axial translation of the vortices and the cylinder rotation. Little fluid transport between vortices occurs for nonwavy vortices, but there is substantial transport between vortices for wavy vortex flow, much like supercritical cylindrical Couette flow with no axial flow.

Darcian, Transitional, and Turbulent Flow through Porous Media

Abstract: The study of flow through media consisting of large-sized grains is important in a number of civil engineering applications. Employing the square root of permeability as the characteristic length in defining friction factor and Reynolds number, theoretical curves, relating friction factor and Reynolds number—similar to the Moody diagram used in pipe flow to estimate the friction factor—have been developed using the ratio of characteristic length \id and square root of permeability √\ik as the third parameter. The existing experimental data on flow through porous media have been sorted based on the \id/√\ik ratio and are used to verify the theory developed. The agreement is good. From the set of theoretical curves so obtained, the Reynolds number at which the friction factor–Reynolds number relationship deviates from Darcy’s law and the Reynolds number at which turbulent flow is fully established are identified. Empirical equations for these Reynolds numbers in terms of media parameters have been obtained. The factors affecting linear parameter \ia and nonlinear parameter \ib have been brought out. The empirical power law applicable for high Reynolds number flows is given a theoretical justification.

Scaling of the mean velocity profile for turbulent pipe flow

Abstract: An experimental investigation was conducted to determine the scaling of the mean velocity profile for a fully developed, smooth pipe flow. Measurements of the mean velocity profiles and static pressure gradients were performed at 26 different Reynolds numbers between $31\ifmmode\times\else\texttimes\fi{}{10}^{3}$ and $35\ifmmode\times\else\texttimes\fi{}{10}^{6}$. The profiles indicate two overlap regions: one which scales as a power law and one which scales as a log law, where the log law is only evident when the Reynolds number exceeds approximately $300\ifmmode\times\else\texttimes\fi{}{10}^{3}$. It is proposed that the velocity scales for the inner and outer regions are different, which is contrary to commonly accepted beliefs.

A Modified Low-Reynolds-Number Turbulence Model Applicable to Recirculating Flow in Pipe Expansion

Abstract: A modified low-Reynolds-number k-e turbulence model is developed in this work. The performance of the proposed model is assessed through testing with fully developed pipe flows and recirculating flow in pipe expansion. Attention is specifically focused on the flow region around the reattachment point. It is shown that the proposed model is capable of correctly predicting the near-wall limiting flow behavior while avoiding occurrence of the singular difficulty near the reattachment point as applying to the recirculating flow in sudden-expansion pipe.