MODELLING AND SIMULATION OF A SUBSTRATE THERMOMECHANICAL BEHAVIOR DURING THE PLASMA SPRAYING

In our study, a 3D thermal plasma jet was simulated using the ANSYS-CFX code with two turbulence models and for different cases of effective powers. The analysis of the turbulent flow during the thermal jet using the RNG k-ε and SST k-ω models was also presented. The velocity and temperature profiles at the nozzle outlet were deduced from the literature and used as inlet boundary conditions. The results obtained from the two turbulence models show that the RNG k-ε model with different effective powers (790 W; 1050 W; 1350 W and 1780 W) is in good agreement with the experimental results. The RNG k-ε model gave results closer to the experiment than the results obtained from the SST k-ω model. It can also be concluded that when increasing the power supplied to the gas used, the temperature increases and it is maximum in the central axis. In the second step, the flow analyzed by the RNG k-ε model generated the initial conditions for the unsteady flow. Transient simulations for the 2D plasma jet are performed to obtain the velocity and temperature fields and also to obtain the temperature distribution in the substrate for the different time values. The transient simulations in the substrate for the different time values have also been studied. The results showed that the variation of the temperature of the plasma jet is always insignificant near the substrate for any value of time (flat curves) this says that the maximum of the temperatures obtained at the level of the substrate in the axial direction (Z axis) are maximum at the interface between the flow and the substrate (i.e. the contact surface at the centerline), and the maximum of the temperatures obtained at the substrate in the radial direction (y-axis) are maximum at the center of the substrate (i.e. x=0 and y= 0)

Hysteresis and Bistability Bifurcation Induced by Combined Fluid Shear Thickening and Double-Diffusive Convection in Shallow Porous Enclosures Filled with Non-Newtonian Power-Law Fluids

This paper presents a numerical study of the linear and non-linear stability of thermosolutal convection within a porous medium saturated by a non-Newtonian binary fluid. The power-law model is utilized for modeling the behavior of the working medium. The given statement implies that the horizontal boundaries experience thermal and solutal flow rates, whereas the vertical walls are impermeable and thermally isolated. The relevant factors that govern the problem being investigated are the Rayleigh number, , the power-law index, , the cavity aspect ratio, , the Lewis number, , and the buoyancy ratio, . An analytical solution is obtained for shallow enclosures ( ) using the parallel flow approximation and a modified form of the Darcy equation. By solving the entire set of governing equations, a numerical investigation of the same phenomenon was conducted. One of the most intriguing discoveries from this research is that it identifies a bi-stability phenomenon, this particular phenomenon signifies the existence of two stable solutions. The results obtained from both methods demonstrate a good level of agreement across a diverse range of these governing parameters