Experimental Study of Oscillating Freestream Effect on the Spatiotemporal Distributions of Leading-Edge Film Cooling

An experimental study was conducted to investigate the influence of mainstream oscillations on spatio-temporal variation of leading-edge film cooling effectiveness. The investigation utilized fast-response pressure-sensitive paint (Fast-PSP) technique at high frame rate. During the experiment, coolant (i.e., CO2, DR = 1.53) was discharged into three rows of cylindrical holes. Various blowing ratios (i.e., M = 0.50, 0.75, 1.00, and 1.50) were tested under the steady (i.e., f = 0 Hz) and oscillating (i.e., f = 7 Hz and 25 Hz) conditions. The measured instantaneous effectiveness was analyzed in terms of time-averaged and phase-averaged results. The results revealed that the mainstream oscillation, consisting of simultaneous pressure and velocity oscillation, significantly influences the behavior of the film cooling effectiveness. The time-averaged effectiveness significantly decreased at high oscillating frequency (i.e., 13.0–19.8% reduction at M = 0.50, f = 25 Hz compared with f = 0 Hz), especially at low blowing ratios (i.e., M = 0.50 and 0.75). The phase-averaged results captured significant decay in the film distributions associated with backflow caused by negative pressure gradients in coolant holes at certain phases. However, the mainstream oscillation effect was relatively insignificant at high blowing ratios (i.e., M = 1.00 and 1.50), which revealed the robustness of coolant coverage at low coolant Strouhal number (i.e., high blowing ratio) under the same oscillating frequency. Furthermore, the unsteady coolant intermittency showed highly unstable film coverage at high coolant Strouhal number. The coolant decay associated with backflow at high coolant Strouhal number should be considered by the gas-turbine designers in order to improve the lifecycle of turbine blades.

Theoretical study of the forced oscillation effect on subsoil tillage

The work presents a tillage machine with vibrational electronic elements mounted on the working bodies, which allow reciprocal oscillating movements of the chisel bit and duckfoot shovels. Theoretical studies of the dependence of traction resistance reduction of a tillage machine on the influence of oscillations of the working bodies on the soil and on the unit’s speed. The oscillating movements of the working bodies will improve the quality of the main processing of heavy soils in gardens, reduce the energy intensity of a given process and increase productivity by increasing the unit’s speed.

An oscillation effect on MHD radiative Casson fluid flows in an asymmetric channel through group theoretical analysis

The flow has been made by considering oscillation and radiation effects for the magnetohydrodynamic (MHD) Casson fluid model within an asymmetric wavy channel. Oscillation occurs during the flow by taking into account the pressure gradient across the ends of the channel. The governed mathematical statement is handled analytically by choosing the group theoretical method. The partial differential equations (PDEs) of the governed system are transformed into ordinary differential equations (ODEs) by calculating the symmetries. Further, the mathematical problem is concluded and the graphical results are shown for the following emerging parameters: Casson fluid parameter β, wavelength λ, oscillation parameter ω, Reynolds number Re, Hartmann number M, radiation parameter R, heat source–sink parameter Q, and Peclet number Pe. The magnitude of velocity profile f(η) increased with an increase in β, λ, Re, and K. With variations of H and ω, f(η) decreased. The temperature profile θ(η) increased when the values of Pe, Q, and R increased.