| Autor: |
Biswas, Neelakash, Sharma, Aviral, Saha, Sandeep, Das, Debopam |
| Rok vydání: |
2022 |
| Předmět: |
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| Druh dokumentu: |
Working Paper |
| Popis: |
We explore the laminar to turbulence transition of round jets at low Reynolds number (Re < 1000) using a novel experimental setup and linear stability theory (LST). The setup has a large domain and a low disturbance environment which increases the critical Re to approximately 500, permitting the appearance of a hitherto unknown puff-like instability (PFI). The instability is identified in the self-similar region of the jet through clean flow visualizations (FV) and further corroborated by particle image velocimetry (PIV) measurements. For 400< Re <700, the flow exhibits PFI embedded in a puff-train encapsulated by a laminar flow analogous to 'puffs' in pipe-flow transition; the latter being symbolic of the finite-amplitude disturbance transition scenario. The observation that PFI convects close to the average local velocity with an inflectional velocity profile further strengthens the analogy. LST predicts that PFI is effectively a superposition of the helical mode (HM) pair with azimuthal wavenumbers n=+-1. Hence, PFI can also appear in the infinitesimal-amplitude supercritical route to transition of linearly unstable flows. |
| Databáze: |
arXiv |
| Externí odkaz: |
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