Effects of Low Reynolds Number on Decay Exponent in Grid Turbulence

This present work is to investigate on the decay exponent (n) of decay power law is the total turbulent kinetic energy, t is the decay time, t0 is the virtual origin) at low Reynolds numbers based on Taylor microscale . 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 14.15 mm and solidity 43%) and woven mesh grid (mesh size 5 mm and solidity 36%). The decay exponent (n) is determined using three different methods: (i) decay of , (ii) transport equation for ɛ, the mean dissipation of the turbulent kinetic energy and (iii) λ method (Taylor microscale , angular bracket denotes the ensemble). Preliminary results indicate that the magnitude n increases while decreases, in accordance with the turbulence theory.