TY - JOUR
T1 - Laminarization through annular gap injection in turbulent pipe flows
T2 - A large eddy simulation study
AU - Nozarian, Sina
AU - Hansen, Christoffer
AU - Forooghi, Pourya
AU - Abkar, Mahdi
PY - 2025/5/1
Y1 - 2025/5/1
N2 - This study employs wall-resolving large eddy simulations (LES) to investigate whether and how laminarization occurs in turbulent pipe flows through annular gap fluid injection. The investigations focus on the effects of injection velocity ratio ( U ratio ) and inflow bulk Reynolds number (ReB) on the flow dynamics, examining key characteristics such as mean velocity profiles, Reynolds stresses, turbulent production, and friction factors. Sustained laminar flow was observed at Re B = 3700 for U ratio values between 1.8 and 2.6 over a pipe length of 100D, achieving a significant 45% reduction in the friction factor for U ratio = 2.6 . This laminarization is attributed to the suppression of the turbulence regeneration cycle, as evidenced by a pronounced downstream reduction in peak streamwise velocity fluctuations, Reynolds shear stress, and turbulence production. Conversely, at Re B = 5500 , sustained laminarization was unattainable for any tested U ratio , as turbulence persisted due to suboptimal injection conditions or adverse Reynolds number effects. Nonetheless, these cases with non-laminarizing conditions still exhibited reductions in the friction coefficient—up to 30%, as observed for Re B = 5500 and U ratio = 1.6 —over a certain pipe length before ultimately reverting to a fully turbulent state further downstream. Our LES results demonstrate good qualitative agreement with the experimental findings of Kühnen et al. (Flow Turbul. Combustion, 100(4), 2018, pp. 919-943), effectively capturing the dynamics of flow laminarization and turbulence regeneration.
AB - This study employs wall-resolving large eddy simulations (LES) to investigate whether and how laminarization occurs in turbulent pipe flows through annular gap fluid injection. The investigations focus on the effects of injection velocity ratio ( U ratio ) and inflow bulk Reynolds number (ReB) on the flow dynamics, examining key characteristics such as mean velocity profiles, Reynolds stresses, turbulent production, and friction factors. Sustained laminar flow was observed at Re B = 3700 for U ratio values between 1.8 and 2.6 over a pipe length of 100D, achieving a significant 45% reduction in the friction factor for U ratio = 2.6 . This laminarization is attributed to the suppression of the turbulence regeneration cycle, as evidenced by a pronounced downstream reduction in peak streamwise velocity fluctuations, Reynolds shear stress, and turbulence production. Conversely, at Re B = 5500 , sustained laminarization was unattainable for any tested U ratio , as turbulence persisted due to suboptimal injection conditions or adverse Reynolds number effects. Nonetheless, these cases with non-laminarizing conditions still exhibited reductions in the friction coefficient—up to 30%, as observed for Re B = 5500 and U ratio = 1.6 —over a certain pipe length before ultimately reverting to a fully turbulent state further downstream. Our LES results demonstrate good qualitative agreement with the experimental findings of Kühnen et al. (Flow Turbul. Combustion, 100(4), 2018, pp. 919-943), effectively capturing the dynamics of flow laminarization and turbulence regeneration.
UR - http://www.scopus.com/inward/record.url?scp=105005603654&partnerID=8YFLogxK
U2 - 10.1063/5.0264788
DO - 10.1063/5.0264788
M3 - Journal article
SN - 1070-6631
VL - 37
JO - Physics of Fluids
JF - Physics of Fluids
IS - 5
M1 - 055128
ER -