Numerical investigation of pulsating flows in abrupt expansion pipes

Numerical investigations aimed at understanding the flow and heat transfer characteristics for the pulsating turbulent flow in abrupt-expansion pipes were carried out. The computations employed control volume method to solve the Navier-Stokes equations and energy equation. Turbulence was simulated via standard k-;The presented results consist of computed streamline distributions, mean time-averaged Nusselt number, time-averaged maximum Nusselt number and location of maximum Nusselt number at different Reynolds number and diameter ratios under the influence of pulsation. The results show the increase in the mean time-averaged Nusselt number with the frequency of pulsation. The effect of pulsation on the mean time-averaged Nusselt number is insignificant for fluids having Prandtl number less than unity (around 10% increase in the value of mean time-averaged Nusselt number for Prandtl number of 0.7 at frequency of 35 Hz, Reynolds number of 30000 and diameter ratio of 0.5). Whereas, this effect is appreciable for the fluids having Prandtl number greater than unity (around 30% increase in the value of mean time-averaged Nusselt number for Prandtl number of 7.0 at Reynolds number of 20000, frequency of 40 Hz and diameter ratio of 0.5). At all pulsation frequencies variation in mean time-average Nusselt number, maximum Nusselt number and its location with Reynolds number and diameter ratio exhibit similar characteristics as steady flows.