Numerical investigation of the effect of pulsation on various types of impinging jet

In this thesis, the effects of single and multi-impact pulsatile nanofluid jets on heat transfer and flow characteristics were investigated. The study aimed to determine optimum values using different variables. The variable parameters under investigation in the study were the different volumetric concentrations of water and water-based Al2O3 nanofluid (1%, 2%, 4% and 5%), Reynolds numbers (Re = 1000, 5000, 7500, 10000 and 15000), dimensionless jet-to-plate distances (H/D = 2, 4, 5, 6), pulsation wave types (sinusoidal, square and triangular), frequency values (10, 20 and 30 Hz), and amplitude values (0.3, 0.4 and 0.5 m/s).In the experimental study carried out for verification purposes, the air jet was impinged on heated surfaces with and without vibration at H/D = 4, Re = 5000 conditions. In the numerical study, when comparing sinusoidal, triangular, and square waves with a 5% volumetric concentration of nanoparticles to the non-nanoparticle case at H/D = 4, Re = 7500, f = 20 Hz, and A = 0.5 m/s, the triangular and sinusoidal waves each showed a 53% increase, while the square wave showed a 40% increase. Comparing different frequencies for Re = 5000 and A = 0.3 m/s, there was a 13% increase between f = 10 Hz and f = 30 Hz. Under the same conditions, using dual jets as opposed to single jets resulted in an 18% increase for a 5% volumetric concentration. For volumetric concentrations of 4% and 2%, there was a 16% increase, and finally, for a 1% volumetric concentration, there was a 13% increase. For triple jets, compared to the non-nanoparticle case, there was a 22% increase in heat transfer for a 5% volumetric concentration. Also, there was a 19% increase for 4% and 2% volumetric concentrations, and a 14% increase for a 1% volumetric concentration. As a result, it was found that nanoparticle-added jets increased heat transfer and more heat transfer was achieved with increasing volumetric concentration ratio. Moreover, different wave types, frequencies, and amplitudes had varying effects on the jet performance. Importantly, we determined that multi-jets yielded more heat transfer than single jets. The use of nanofluids and multi-jets enhanced heat transfer, and pulsations improved the Nusselt number.