This present work is to investigate on the decay exponent (n) of decay power law (q'2∼(t - To)n , q'2is the total turbulent kinetic energy, t is the decay time, t0 is the virtual origin) at low Reynolds numbers based on Taylor microscale Rλ(= u 'λ/ v) ≤ 64 . Hot wire measurements are carried out in a grid turbulence subjected to a 1.36:1 contraction. The grid consists in large square holes (mesh size 43.75 mm and solidity 43%); small square holes (mesh size 14.15mm and solidity 43%) and woven mesh grid (mesh size 5mm and solidity 36%). The decay exponent (n) is determined using three different methods: (i) decay of q'2, (ii) transport equation for s , the mean dissipation of the turbulent kinetic energy and (iii) λ method (Taylor microscale λ = √5( q2)/ (εd)} , angular bracket denotes the ensemble). Preliminary results indicate that the magnitude n increases while Rλ (= u'λ/v)decreases, in accordance with the turbulence theory.
Kamruzzaman, M., Djenidi, L., & Antonia, R. A. (2014). Effects of low Reynolds number on decay exponent in grid turbulence. In Procedia Engineering (Vol. 90, pp. 327–332). Elsevier Ltd. https://doi.org/10.1016/j.proeng.2014.11.857