Pipe flow

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

Transition to turbulence in particulate pipe flow.

Abstract: We investigate experimentally the influence of suspended particles on the transition to turbulence. The particles are monodisperse and neutrally buoyant with the liquid. The role of the particles on the transition depends upon both the pipe to particle diameter ratios and the concentration. For large pipe-to-particle diameter ratios the transition is delayed while it is lowered for small ratios. A scaling is proposed to collapse the departure from the critical Reynolds number for pure fluid as a function of concentration into a single master curve.

On the instability of viscous flow in a rapidly rotating pipe

Abstract: The stability of almost fully developed viscous flow in a rotating pipe is considered. In cylindrical polar co-ordinates (r, o, z) this flow has the velocity components \[ \{W_0o(1),\quad\Omega r[1+o(\epsilon)],\quad W_0[1-r^2/r^2_0+o(1)]\},_{+}^{+} \] where e = Wo/2Ωr0 and is bounded externally by the rigid cylinder r = r0, which rotates about its axis with angular velocity Ω. In the limit of small e, the disturbance equations can be solved in terms of Bessel functions and it is shown that, in that limit, the flow is unstable for Reynolds numbers R = Wor0/v greater than Rc [asymp ] 82[sdot ]9. The unstable disturbances take the form of growing spiral waves, which are stationary relative to the rotating cylinder and the critical disturbance at R = Rc has azimuthal wave-number 1 and axial wavelength 2πr0/e. Furthermore, it is shown that the most rapidly growing disturbance for R > Rc has an azimuthal wave-number which increases with R. Some of the problems involved in testing the results by experiment are discussed and a possible application to the theory of vortex breakdown is mentioned. In an appendix this instability is shown to be an example of inertial instability.

A comparison between snapshot POD analysis of PIV velocity and vorticity data

Abstract: Proper orthogonal decomposition (POD) was performed on both the fluctuating velocity and vorticity fields of a backward-facing step (BFS) flow at Reynolds numbers of 580 and 4,660 The data was obtained from particle image velocimetry (PIV) measurements The vorticity decomposition captured the fluctuating enstrophy more efficiently than the equivalent velocity field decomposition for a given number of modes Coherent structures in the flow are also more easily identifiable using vorticity-based POD A common structure of the low-order vorticity POD modes suggests that a large-scale similarity, independent of the Reynolds number, may be present for the BFS flow The POD modes obtained from a vorticity-based decomposition would help in determining a basis for constructing simplified vortex skeletons and low-order flow descriptions based on the vorticity of turbulent flows