| 1. |
- Gong, C., et al.
(författare)
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The acquisition and measurement of surface waves of high-speed liquid jets
- 2015
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Ingår i: Journal of Visualization. - : Springer Science and Business Media LLC. - 1343-8875 .- 1875-8975.
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: The instability analysis of the liquid jet issuing into ambient air was conducted with an emphasis placed upon the evolution of surface waves of the jet. An experiment was designed to visualize the microscopic morphology on the surface of a liquid jet. A spectral method was proposed to measure wavelength from the obtained jet images. We also discuss key setup parameters that significantly affect the resolution of desired jet features and the accuracy of the spectral measurement. The results show that the liquid jet near the nozzle exit can be divided into a laminar section, a transition section, an instability section, and a turbulence section. Surface wave scales range from 0.06 to 0.11 times of the nozzle diameter with the atomization breakup regime. For the atomization breakup regime, the growth ratio of the surface waves of the instability section is 0.06 which is 1.5 times the value of the second wind-introduced breakup regime and 3 times the value of the first wind-introduced breakup regime. Graphical abstract: [Figure not available: see fulltext.]
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| 2. |
- Kalpakli Vester, Athanasia, et al.
(författare)
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Combined hot-wire and PIV measurements of a swirling turbulent flow at the exit of a 90° pipe bend
- 2015
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Ingår i: Journal of Visualization. - : Springer. - 1343-8875 .- 1875-8975.
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of turbulent swirling flow by means of hot-wire anemometry and stereoscopic particle image velocimetry were performed, 0.67 pipe diameters downstream a 90° pipe bend. The flow for a wide range of swirl numbers up to (Formula presented.), based on the angular velocity of the pipe wall and bulk velocity, was investigated and compared to the non-swirling case. The limitations and advantages of using a single hot-wire probe in a highly complex flow field are investigated and discussed. The present paper makes available a unique database for a kind of flow that has been neglected in literature and which is believed to be useful for validation purposes for the computational fluid dynamics community.
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| 3. |
- Vester, Athanasia Kalpakli, et al.
(författare)
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Unravelling tumble and swirl in a unique water-analogue engine model
- 2018
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Ingår i: Journal of Visualization. - : Springer. - 1343-8875 .- 1875-8975. ; 21:4, s. 557-568
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Tidskriftsartikel (refereegranskat)abstract
- The in-cylinder flow prior to combustion is considered to be one of the most important aspects controlling the combustion process in an engine. More specifically, the large-scale structures present in the cylinder, so-called tumble and swirl, before compression are believed to play a major role into the mixing and combustion processes. Their development during the intake stroke and their final strength depend mainly (but not only) on the inlet port design. In the present study, the turbulent large-scale structures during the intake stroke are investigated in a unique water-analogue engine where inlet ports and valve timings can easily be configured and tested. The flow field in the cylinder volume is reconstructed through multi-planar stereoscopic particle image velocimetry measurements which reveal a wealth of vortical structures during the stroke's various phases. The aim of the present paper is to present and show results from a unique setup which can serve as a test bench for optimisation of inlet port designs to obtain a desired vortical pattern in the cylinder after the intake stroke is finished. This setup can simulate the intake stroke in a much more realistic way as compared to a through-flow setup with a fixed valve lift.
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| 4. |
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