Dissimilarity between turbulent heat and momentum transfer induced by a streamwise travelling wave of wall blowing and suction

Heat transfer enhancement and torque reduction by traveling wave-like blowing and suction in turbulent Taylor-Couette flow

“…In Case 3, the analogy factor is positive due to the reduction of the skin-friction (or torque) and the increase of the heat transfer. The analogy factor shows a similar trend in terms of wavenumber to that in a plane channel flow (Kaithakkal et al, 2020). However, a large peak is observed at large and positive c and it seems to be effect of the current curved flow.…”

“…Three-component decomposition is introduced to understand the contribution from the traveling wave to the TC flow. In previous studies, decomposition is used to distinguish contributions from the direct effect and indirect effect from the traveling wave Kaithakkal et al, 2020). Ogino et al(2019) employed the three-component decomposition to distinguish them in the TC flow and concluded that the contribution from the coherent component on the torque was small.…”

“…Uchino et al(2017) discussed a DNS to investigate the dissimilar effect by the traveling wave-like wall-deformation instead of blowing and suction. Recently, Kaithakkal et al(2020) performed a parametric study by DNS to study optimal control parameter sets of the traveling wave-like blowing and suction for the dissimilar control effect in a fully developed turbulent channel flow. The mechanism is discussed based on the unsteady Reynolds averaged Navier-Stokes approach.…”

Much faster heat/mass than momentum transport in rotating Couette flows

“…The ratio HTE = Nu h /Nu m , shown in figure 3, is a measure of heat transfer efficiency since Nu m is proportional to the power input (van Gils et al 2011). An equivalent measure is considered in heat transfer optimization studies by Yamamoto et al (2013), Motoki et al (2018) and Kaithakkal et al (2020). A high similarity between momentum and heat transport can be expected at R = 0 in PCF because Pr = 1, and momentum and heat transport are similarly forced.…”

“…Efficient advective transport contributes to energy savings in buildings (Lake, Rezaie & Beyerlein 2017), process industry (Keil 2018) and data centres (Alben 2017), and can be obtained by, e.g., applying wall roughness (Zhu et al. 2019) and flow control (Yamamoto, Hasegawa & Kasagi 2013; Kaithakkal, Kametani & Hasegawa 2020). In particular, optimal transport given minimal power input generates energy savings in applications (Alben 2017; Motoki, Kawahara & Shimizu 2018), but optimization is challenging since flow vortices and eddies generally transport momentum and heat/mass at similar rates.…”