Passive scalar transport in polymer drag‐reduced turbulent channel flow

Turbulent Heat Transfer in Drag-Reducing Channel Flow of Viscoelastic Fluid

“…The profiles of R vθ and R uv for each case exhibit similar shapes throughout the channel, which also implies similarity between the variations of −v ′ θ ′ and −u ′ v ′ affected by DR. These features at Pr = 1.0 can be seen also at the other Prandtl numbers (figure not shown) and also agree well with those of experimental results and DNS for water (Gupta et al, 2005;Li et al, 2004a). This less correlation between θ ′ and v ′ is responsible for the decrease of the wall-normal turbulent heat flux and the increase of HTR%, in the same way that the decrease of the Reynolds shear stress due to the lower correlation between u ′ and v ′ should be responsible for DR%.…”

“…Similarly, Kim et al (2008) reported that the autogeneration of new hairpin vortices typical of wall turbulence, which are closely related to the buffer layer, can be suppressed by the polymer stresses, thereby resulting in DR. Although research on drag-reducing flow with heat transfer is important for various kinds of heat-transport systems and interesting from a scientific perspective, there have been very few studies on this issue (Aguilar et al, 1999;Dimant & Poreh, 1976;Gasljevic et al, 2007;Li et al, 2004a;, particularly in terms of numerical simulations (Gupta et al, 2005;Kagawa, 2008;Yu & Kawaguchi, 2005). Early experiments presented some empirical models for heat transfer in drag-reducing flows (Dimant & Poreh, 1976) and showed that the heat-transfer coefficient was reduced at a rate faster than the accompanying DR (Cho & Hartnett, 1982), and that an analogous reduction of HTR was observed in the case of drag-reducing surfactant solution (Qi et al, 2001).…”

Turbulent channel flow of dilute polymeric solutions: Drag reduction scaling and an eddy viscosity model

“…Consequently, RANS modeling has enjoyed considerable success in this regime [20]. However, as DR is increased, the streamwise vortices are stabilized significantly and the flow structure is qualitatively modified leading to the establishment of a buffer region that remains quiescent for a fairly long period of time punctuated only by occasional (intermittent) turbulence producing events [24,25]. Under such circumstances, the use of modified Newtonian RANS models may not be appropriate.…”

“…In the absence of detailed information on the spectral characteristics of drag-reduced flows (except for the recent work on isotropic turbulence by Vaithianathan and Collins [26]), single-point turbulence closures are used. In addition to the prediction of the friction factor, estimation of heat/mass transfer coefficients in polymer drag reduced turbulent flows [25], is also of technological relevance. Although there have been research efforts in this direction [27][28][29][30] in the 1970s, DNS studies of scalar transport have been only recently performed [25].…”

A Short Review on Drag-Reduced Turbulent Flow of Inhomogeneous Polymer Solutions

“…With the increasing DRs, they also decrease and the peaks in the wall-normal profiles move away from the wall. However, as the polymers begin to mix quickly and lose effectiveness at farther downstream positions in the slot-injection case, the magnitudes of the wall-normal turbulent mass fluxes increase which indicates an increase in the wall-normal mixing in the boundary layer [48,87,90].…”