Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session M39: Pipe Flow |
Hide Abstracts |
Chair: Xiaohua Wu, Royal Military College of Canada Room: Georgia World Congress Center Ballroom 3/4 |
Tuesday, November 20, 2018 8:00AM - 8:13AM |
M39.00001: Scalar flashes as memory carrier and turbulent spots composed of reverse and forward hairpins in pipe flow Xiaohua Wu, Parviz Moin, Ronald J Adrian Feasibility and accuracy of direct simulation of spatially-developing pipe transition from weakly perturbed laminar inflow was demonstrated in Wu et al (PNAS, 112, 7920-7924, 2015). Here, we study scalar flash, turbulent spot and transition statistics in a 500 radii-long pipe configuration at Reynolds number 6500. During the late stage of transition, second-order statistics such as the rate of dissipation of turbulent kinetic energy exhibit substantial overshoot, which is accounted for by the observed stronger mid-to-high frequency content in the spectra of the rate of dissipation. Transitional turbulent spots are found to have a dual-type structural composition. The near-wall region consists of primarily reverse hairpin vortices with their head element directing towards the upstream direction and towards the wall. The core region of the spots on the other hand is populated by normal hairpin vortices. Passive scalar injected at the center of the inlet plane develops during transition into what we call the Type-1 and Type-2 flashes. At several hundred radii downstream of transition where the flow is fully-developed and turbulent, the Type-2 scalar flashes serve as carriers of persistent memory of the far upstream transition. |
Tuesday, November 20, 2018 8:13AM - 8:26AM |
M39.00002: New friction factor and mean velocity profile for turbulent pipe flow at extreme Reynolds number Fabio Ramos, Daniel Cruz, Hamidreza Anbarlooei We report on a novel power-law formula for evaluating the friction factor of turbulent incompressible Newtonian fluid flows, f ∼ 1/Re2/13. The formula is based on a new phenomenology for coherent structures dominating the momentum exchange in mesoregions that are set by the geometric mean of the viscous and outer length scales that have recently been shown to provide the missing link between the flow's viscous and inertial regions. |
Tuesday, November 20, 2018 8:26AM - 8:39AM |
M39.00003: Direct numerical simulation of pulsatile rough-wall turbulent pipe flow Thomas Jelly, Rey Chin, Simon Illingworth, Jason Monty, Ivan Marusic, Andrew Ooi Direct numerical simulations (DNS) of pulsatile rough-wall turbulent pipe flow have been performed at a friction Reynolds number of 540. The rough walls have a three-dimensional sinusoidal height distribution and were resolved explicitly using a body-fitted grid. Three geometrically-scaled surfaces with a common amplitude-to-wavelength ratio have been considered. An unsteady axial pressure gradient was imposed to simulate a current-dominated pulsatile flow in the very-high-frequency regime. The resulting flow field exhibits axial-azimuthal periodicity, as well as phase dependence in time, and permits instantaneous quantities to be decomposed into four separate parts: (i) a global-averaged component; (ii) a roughness-induced component; (iii) a pulsation-induced component and (iv) the remaining turbulent fluctuation. We compare statistics of (i)-(iv) against their non-pulsatile counterparts using past results related to the current work (Chan et al., J. Fluid Mech., 771:743-777, 2015). Whilst the pulsatile and non-pulsatile data collapse well in the outer region, clear differences are evident in the near-roughness region and the region below the roughness crests. These differences will be examined in the context of phase-averaged statistics (in both space and time). |
Tuesday, November 20, 2018 8:39AM - 8:52AM |
M39.00004: Large-scale motions in turbulent minimal pipe flows at Reτ ≈ 930, 2000 and 3000 Juhyung Han, Jinyul Hwang, Min Yoon, Hyung Jin Sung Direct numerical simulations of turbulent minimal pipe flow at Reτ ≈ 930, 2000 and 3000 are performed to elucidate spanwise behavior of large scales. The streamwise domain is set to Lx+ ≈ 1000, which corresponds to the characteristic streamwise length of near-wall streaks. The large scales of streamwise velocity fluctuations (u) are enhanced due to the periodic boundary condition with short streamwise length. In the premultiplied spanwise energy spectra of u, two outer peaks appear at λz/R = 0.6 and 1.3 with the increase in their magnitudes compared to those observed in a long streamwise domain (Lx = 30R). The conditional two-point correlations of the large scales (λz < 0.8R) in the outer region show that the large scales penetrate close to the wall with increasing Reτ. At Reτ ≈ 3000, the conditional correlations of the very large scales (λz > 0.8R) coincide with each other regardless of the reference wall-normal location, indicating the spatial confinement of very large scales. This behavior enhances the energy at the large scales, which ultimately leads to the presence of the two outer peaks in the spanwise energy spectra. |
Tuesday, November 20, 2018 8:52AM - 9:05AM |
M39.00005: Turbulent coherent structures in an obstructed pipe flow with favorable pressure gradient Theresa A Saxton-Fox, Liuyang Ding, Alexander John Smits, Marcus Hultmark A fully-developed turbulent pipe flow at Reτ = 3400 was perturbed by an axisymmetric obstruction in the center of the pipe, causing favorable pressure gradients and streamline curvature in the flow. The pipe flow was studied with and without the obstruction using particle image velocimetry (PIV). Changes in flow statistics and in the shapes and inclination angles of turbulent coherent structures were observed from the addition of the obstruction. Conditional averaging and proper orthogonal decomposition were used to examine the turbulent structures. This talk will discuss the changes observed in the structures and connect these observations to the existing literature on turbulent coherent structures in favorable pressure gradients. The implications of the results for future reduced-order modeling efforts will be discussed. |
Tuesday, November 20, 2018 9:05AM - 9:18AM |
M39.00006: Statistics of a fully developed turbulent pipe flow perturbed by a streamlined axisymmetric body Liuyang Ding, Theresa Saxton-Fox, Alexander Smits, Marcus Hultmark |
Tuesday, November 20, 2018 9:18AM - 9:31AM |
M39.00007: Abstract Withdrawn Measurements were conducted in the transitional range of Reynolds numbers (Re) for a plane channel flow using Particle Image Velocimetry (PIV). Fluctuating spanwise vorticity contour animations were used to understand the evolution of near-wall structures in the transitional regime. In the lower-Re range of the regime, hairpin-like structures are formed intermittently. They are fairly wall-bound with the head of the hairpin also attached to the wall in most cases. They are confined to within 10% of the channel half-height with rest of the channel being mostly quiet. With increase in Re, lift-up of the head of the hairpin can be observed though the tail is mostly attached. Rarely does the structure detach completely and break-up into the rest of the flow. Vortical activity is observed within 25% of the channel half-height in this case. At higher transitional Re but lesser than the marginal Re for sustained turbulence, vortical activity becomes very dynamic. Continuous formation, lift-up, detachment and breakup of hairpin vortices is observed and the vortical blobs could be convected to as high as the channel half-height. |
Tuesday, November 20, 2018 9:31AM - 9:44AM |
M39.00008: Power law scaling of the friction factor in pipe flow Jose Lopez, Davide Scarselli, Balachandra Suri, Bjoern Hof We present a study of the friction factor scaling for pipe and duct flows at moderate Reynolds numbers (5000<Re<150 000) in experiments and highly resolved direct numerical simulations. |
Tuesday, November 20, 2018 9:44AM - 9:57AM |
M39.00009: On the Development of an Apparatus to Examine Rotating Pipe Flow at High Rotation Numbers Colby Borchetta, Christoph Brehm, Sean Bailey Previous experiments and simulations have demonstrated that rotation can potentially stabilize, and possibly even relaminarize, turbulent flows. However, the mechanism behind this suppression is not well understood. Prior research studies for different classes of flow indicate that hydrodynamic stability theory can utilized to extract important information about the relaminarization process. Rotating pipe flow is a canonical example of this problem, however the stabilization process is particularly sensitive to the rotation rates and Reynolds number. Experimental studies covering this range are rare and do not cover the higher rotation rates where relaminarization may manifest. Here we present progress on the development of a turbulent pipe flow apparatus designed to study a large envelope of Reynolds numbers and rotation rates and provide data facilitating and verifying detailed stability analysis of the problem. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2023 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700