Uniform-momentum zones in a turbulent pipe flow

Internal shear layers and edges of uniform momentum zones in a turbulent pipe flow

“…In their study, a larger range of Reynolds number, , was investigated. As a final note in this section, the number distribution of the UMZs found in this study is very similar to the one reported very recently by Chen et al (2020) in a turbulent pipe flow at , where the UMZs were determined using 3-D volumetric data.…”

“…This is again consistent with the observations in the above mentioned TBL study. Stronger jumps near the wall for Re τ = 340 can be explained by the low Reynolds number effect, as also observed in a very recent DNS study (Re τ = 500) of Chen et al (2020) in a turbulent pipe flow. Based on the conditional streamwise velocity profiles (figure 10a), the thickness of the layers is also determined (figure 11).…”

“…Later, several researchers treated the continuous edges of these large-scale motions as shear layers (e.g. Kwon et al 2014; de Silva, Hutchins & Marusic 2016; Laskari et al 2018; Chen, Yongmann & Wan 2020). In wall turbulence, these energetically significant coherent motions have been known to carry a substantial portion of the turbulent kinetic energy and Reynolds stress (Liu, Adrianand & Hanratty 2001; Ganapathisubramani, Longmire & Marusic 2003; Guala, Hommema & Adrian 2006; Wu, Baltzer & Adrian 2012; Ahn et al 2015).…”

Uniform-momentum zones in a turbulent boundary layer subjected to freestream turbulence

“…We know that a canonical TBL has UMZs, and that their number is Re τ dependent (de Silva et al 2016). UMZs also exist in internal flows, which feature a quiescent, but turbulent, core that is separate from the flow structure immediately adjacent to the walls (Kwon et al 2014;Yang et al 2016;Jie et al 2019;Chen et al 2020;Gul et al 2020). Moreover, the TBL experiments of Laskari et al (2018) detected UMZs beneath a freestream of approximately 3 % turbulence.…”

“…The general flow structure of UMZs located immediately above a wall with a bulk of fluid moving above them is not limited to zero-pressure-gradient TBLs. UMZs have been reported above the walls for turbulent channel (Kwon et al 2014;Anderson & Salesky 2021) and pipe flows (Chen, Chung & Wan 2020;Gul, Elsinga & Westerweel 2020), both of which have a 'core' region that is also turbulent. However, the existence of UMZs has not been rigorously assessed for a TBL subjected to freestream turbulence (FST).…”