Distribution of local velocities in a circular pipe with accelerating fluid flow
DOI:
https://doi.org/10.15587/1729-4061.2019.162330Keywords:
cylindrical pipe, fluid flow, flow structure, turbulence generation, hot-wire equipment.Abstract
The results of experimental studies of accelerating fluid flow in a cylindrical pipe from rest are presented. With accelerated fluid flow, a delay of laminar-turbulent transition with instantaneous Re numbers, which are several orders of magnitude higher than critical Re in stationary conditions is observed. To determine the local characteristics of the unsteady flow, hot-wire equipment was used. For measuring the local velocity in the pipe, a hot-wire cone sensor was used, and for measuring shear stresses – a sensor mounted flush with the inner pipe wall. To process the experimental data, in addition to ensemble averaging, smoothing by time averaging over five adjacent points was also carried out. It turned out that in order to obtain smoother functions for the desired characteristic, it is necessary to have much more experiments the ensemble, especially in the wall area. It is found that with accelerated fluid flow from rest to the onset of turbulence, a uniform velocity distribution remains in the pipe section and velocity gradients are observed only in a thin surface layer. A sharp transition in the shear stress characteristic on the pipe wall τ0 with the laminar-turbulent transition is also observed in the characteristics of local velocities. At the moment of transition to the turbulent regime, a turning point appears on the average velocity graph, and velocity distribution and turbulence intensity undergo significant changes compared with steady turbulent flows. Turbulence is generated in the wall area and distributed to the pipeline section center at an almost constant velocity. The front of laminar-turbulent transition with unsteady fluid flow in the pipe is distributed towards the section center at an almost constant velocityReferences
- Mochalin, E. V. (2002). Variacionnaya formulirovka zadachi o prostranstvennom dvizhenii neszhimaemoy zhidkosti. Sb. nauchn. Trudov DGMI, 15, 269–280.
- Bondarenko, N. I., Terent'ev, Yu. I. (2009). O neustanovivshemsya dvizhenii szhimaemoy zhidkosti v napornom truboprovode. Mosk. gos. tekhn. un-t. Moscow, 54. Dep. v VINITI RAN 15.10.2009, No. 620-V2009.
- Kozlov, L. F., Babenko, V. V. (1985). Razvitie teorii pogranichnogo sloya. Vestnik AN USSR, 3, 91–92.
- Chung, D., Pullin, D. I. (2009). Large-eddy simulation and wall modelling of turbulent channel flow. Journal of Fluid Mechanics, 631, 281. doi: https://doi.org/10.1017/s0022112009006867
- Hnativ, R. M. (2012). Eksperymentalne vyznachennia pulsatsiyi dotychnykh napruzhen na stintsi truboprovodu pry perekhidnomu rezhymi rukhu ridyny. Promyslova hidravlika i pnevmatyka, 3 (37), 52–54.
- Hnativ, R. M. (2013). Doslidzhennia rozpodilu shvydkostei pry neustaleniy techiyi ridyny v truboprovodi. Promyslova hidravlika i pnevmatyka, 2 (40), 57–59.
- Adamkowski, A., Lewandowski, M. (2006). Experimental Examination of Unsteady Friction Models for Transient Pipe Flow Simulation. Journal of Fluids Engineering, 128 (6), 1351. doi: https://doi.org/10.1115/1.2354521
- Rahmatullin, Sh. I., Kim, D. P. (2006). Vliyanie stepeni turbulentnosti i chastoty turbulentnyh pul'saciy na gidravlicheskoe soprotivlenie krugloy truby. Neftyanoe hozyaystvo, 11, 110–111.
- Maruyama, T., Kuribayashi, T., Mizushina, T. (1976). The structure of the turbulence in transient pipe flows. Journal of Chemical Engineering of Japan, 9 (6), 431–439. doi: https://doi.org/10.1252/jcej.9.431
- Maruyama, T., Kato, Y., Mizushina, T. (1978). Transition to turbulence in starting pipe flows. Journal of Chemical Engineering of Japan, 11 (5), 346–353. doi: https://doi.org/10.1252/jcej.11.346
- Yahno, A., Hnativ, R. (2013). Dependence of the average flow rate from rising pressure in unsteady fluid movement in pipeline. Visnyk Natsionalnoho tekhnichnoho universytetu Ukrainy "Kyivskyi politekhnichnyi instytut". Ser.: Mashynobuduvannia, 3, 198–202.
- Yakhno, O. M., Hnativ, R. M., Shcherbata, N. V., Hnativ, I. R. (2018). Doslidzhennia rozpodilu lokalnykh shvydkostei za rozghinnoho rukhu realnoi ridyny zi stanu spokoiu. Materialy XXIII mizhnarodnoi naukovo-tekhnichnoi konferentsiyi “Hidroaeromekhanika v inzhenerniy praktytsi”, 56–58.
- Tuzi, R., Blondeaux, P. (2008). Intermittent turbulence in a pulsating pipe flow. Journal of Fluid Mechanics, 599. doi: https://doi.org/10.1017/s0022112007009354
- Manuylovich, S. V. (2005). Issledovanie mekhanizmov vozbuzhdeniya i rosta neustoychivyh vozmushcheniy v pul'siruyushchih techeniyah. Izvestiya Rossiyskoy akademii nauk. Mekhanika zhidkosti i gaza, 4, 15–28.
- Magrakvelidze, T. (2005). K voprosu raspredeleniya skorostey pri turbulentnom techenii zhidkosti v krugloy trube. Sb. trudov In-t sistem upr. AN Gruzii, 9, 96–101.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2019 Roman Hnativ, Orest Verbovskiy
This work is licensed under a Creative Commons Attribution 4.0 International License.
The consolidation and conditions for the transfer of copyright (identification of authorship) is carried out in the License Agreement. In particular, the authors reserve the right to the authorship of their manuscript and transfer the first publication of this work to the journal under the terms of the Creative Commons CC BY license. At the same time, they have the right to conclude on their own additional agreements concerning the non-exclusive distribution of the work in the form in which it was published by this journal, but provided that the link to the first publication of the article in this journal is preserved.
A license agreement is a document in which the author warrants that he/she owns all copyright for the work (manuscript, article, etc.).
The authors, signing the License Agreement with TECHNOLOGY CENTER PC, have all rights to the further use of their work, provided that they link to our edition in which the work was published.
According to the terms of the License Agreement, the Publisher TECHNOLOGY CENTER PC does not take away your copyrights and receives permission from the authors to use and dissemination of the publication through the world's scientific resources (own electronic resources, scientometric databases, repositories, libraries, etc.).
In the absence of a signed License Agreement or in the absence of this agreement of identifiers allowing to identify the identity of the author, the editors have no right to work with the manuscript.
It is important to remember that there is another type of agreement between authors and publishers – when copyright is transferred from the authors to the publisher. In this case, the authors lose ownership of their work and may not use it in any way.
