Asymmetry propagation in a pipe flow downstream of a 90° sharp elbow bend

Mikuž, Blaž (avtor), Cerkovnik, Klemen (avtor), Tiselj, Iztok (avtor)

Pipe bends disrupt the flow, resulting in an asymmetric velocity field across the pipe diameter (D). We examined the recovery length required for the flow to return to a symmetric velocity profile downstream of a sharp elbow. The wall-resolved Large Eddy Simulation (LES) approach was applied to reproduce turbulent fluid flow at Reynolds numbers (Re) of 5600 and 10,000. An additional case in the transitional laminar-turbulent-laminar regime was analyzed at Re = 1400. This analysis explored the behavior of the Dean vortices downstream of the elbow and revealed that, in turbulent cases, these vortices reverse their vorticity direction in the region between 8 D and 10 D. However, they eventually decay in structure as far as 25 D from the elbow. Flow asymmetry was analyzed in a 100 D long pipe section downstream of the elbow using four different criteria: wall shear stress (WSS), streamwise velocity, its fluctuations, and vorticity fields. This study found that in turbulent flows, the distance required for flow recovery is a few tens of D and decreases with increasing Re. However, in the transitional case, the flow separation within the elbow induces instabilities that gradually diminish downstream, and flow asymmetry persists even longer than the 100 D length of our outlet pipe section. WSS proved sensitive for detecting asymmetry near walls, whereas flow profiles better revealed bulk asymmetry. It was also shown that asymmetry indicators derived from velocity fluctuations and vorticity were less sensitive than those obtained from streamwise velocity.

• Jezik: Angleški jezik
• Ključne besede: flow asymmetry, pipe elbows, secondary flow, flow separation, turbulent flow, recovery length, Large Eddy Simulation, LES
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FMF - Fakulteta za matematiko in fiziko
• Status publikacije: Objavljeno
• Različica publikacije: Objavljena publikacija
• Leto izida: 2024
• Št. strani: 15 str.
• Številčenje: Vol. 14, iss. 17, art. 7895
• PID: 20.500.12556/RUL-169394
• UDK: 53
• ISSN pri članku: 2076-3417
• DOI: 10.3390/app14177895
• COBISS.SI-ID: 206573315
• Datum objave v RUL: 27.05.2025

Gradivo je del revije

• Naslov: Applied sciences
• Skrajšan naslov: Appl. sci.
• Založnik: MDPI
• ISSN: 2076-3417
• COBISS.SI-ID: 522979353

Licence

• Licenca: CC BY 4.0, Creative Commons Priznanje avtorstva 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by/4.0/deed.sl
• Opis: To je standardna licenca Creative Commons, ki daje uporabnikom največ možnosti za nadaljnjo uporabo dela, pri čemer morajo navesti avtorja.

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: cevno koleno, dinamika tekočin, cevi

Projekti

• Financer: ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
• Številka projekta: P2-0026
• Naslov: Reaktorska tehnika

• Financer: ARRS - Agencija za raziskovalno dejavnost Republike Slovenije
• Številka projekta: NC-0026
• Naslov: Eksperimentalne in numerične raziskave vertikalnih čepastih tokov