Ricerc@Sapienza

We use DNS to analyze the cooling of a heated curved surface due to a cold subsonic impinging jet. The configuration resembles several industrial applications such as impingement cooling in gas turbine blade. The ratio between the distance from the nozzle (H) and the jet diameter (D) is equal to 5. The results in terms of velocity, turbulence and heat transfer are compared with a reference simulation with where a subsonic jet impingesing on a flat surface. The results allowed to assess the influence of the curvature on the velocity and Nusselt number distribution is assessed.

This paper reports on a two-phase flow Direct Numerical Simulation (DNS) aimed at analyzing the resuspension of solid particles from a surface hit by a transonic jet inside a low pressure container. Conditions similar to those occurring in a fusion reactor vacuum vessel during a Loss of Vacuum Accident (LOVA) have been considered. Indeed, a deep understanding of the resuspension phenomenon is essential to make those reactors safe and suitable for a large-scale sustainable energy production. The jet Reynolds and Mach numbers are respectively set to 3300 and 1.

A DNS study of the interaction between an oblique laminar jet and a particle-laden crossflow is presented. The delivery tube is included in the simulation and jet in crossflow blowing ratio is set equal to 0.5, typical for gas turbine film cooling applications. The solid phase is polydisperse and it is simulated by adopting a Lagrangian two-way coupling point-particle approach. Wall-particle interaction is also taken into account.

The effects of swirled inflows on the evaporation of dilute acetone droplets dispersed in turbulent jets are investigated by means of direct numerical simulation. The numerical framework is based on a hybrid Eulerian–Lagrangian approach and the point-droplet approximation. Phenomenological and statistical analyses of both phases are presented. An enhancement of the droplet vaporization rate with increasing swirl velocities is observed and discussed.

Direct numerical simulations are employed to investigate the flow properties of a shock wave interacting with a turbulent boundary layer at free-stream Mach number M∞ = 2.28 with distinct wall thermal conditions. Adiabatic, heating and cooling wall conditions are considered for a wide range of deflection angles. While heating contributes to increase the extent of the interaction zone, wall cooling turns out to be a good candidate for flow control.

Direct numerical simulations are employed to investigate a shock wave impinging on a turbulent boundary layer at free-stream Mach number M=2.28 with different wall thermal conditions, including adiabatic, cooled, and heated, for a wide range of deflection angles. It is found that the thermal boundary condition at the wall has a large effect on the size of the interaction region and on the level of pressure fluctuations.

We perform direct numerical simulations of shock-wave/boundary-layer interactions at Mach number M = 1.7 to investigate the influence of the state of the incoming boundary layer. The flow configuration includes a spatially evolving laminar boundary layer that is tripped by an array of distributed roughness elements and impinged further downstream by an oblique shock wave. Four SBLI cases are considered, based on two different shock impingement locations, corresponding to transitional and turbulent interactions, and two different shock strengths (3,6 deg).

Direct Numerical Simulations of a turbulent channel flow have been performed. The lower wall of the channel is made of staggered cubes with a second fluid locked in the cavities. Two viscosity ratios have been considered, m=μ1/μ2=0.02 and 0.4 (the subscript 1 indicates the fluid in the cavities and 2 the overlying fluid) mimicking the viscosity ratio in super–hydrophobic surfaces (SHS) and liquid infused surfaces (LIS) respectively.