Impact of atmospheric variations on sonic boom loudness over 10 years of simulated flights.

Relative humidity, temperature, and wind along flight paths from a 10-year simulation are used to investigate the effects of the atmospheric conditions on sonic boom loudness generated by the pseudo-Concorde and a low-boom supersonic aircraft using an acoustic wave propagation tool. Global meteorological conditions are simulated using the chemistry-climate model EMAC with ECMWF reanalysis data. The results show that atmospheric conditions lead to a seasonal variation of the perceived level for a N-wave over 10 years of flights, whereas it is difficult to identify the seasonal variation for the low-boom aircraft because the distribution of perceived levels is widely spread. The dominant effect from atmospheric conditions during acoustic propagation is found for the low-boom aircraft cruising at an altitude of 14.478 km. The molecular relaxation effect is dominant for an overpressure reduction at 10 km but does not impact the pressure waveform below 8 km. At altitudes below 8 km, the thermoviscous absorption exclusively influences the variations in pressure rise time. Moreover, acoustic wave propagation through the turbulent field was simulated at a single location. Even though the acoustic wave passed through the same turbulent field in the summer and winter cases, the loudness on the ground differs between them.

Fluid-particle-structure interaction in single shot peening.

Shot peening is a widely used cold-working process. Physical phenomena of shot peening are analyzed using the developed fluid-particle-structure coupled solver. The influences of the flow field and shot peening parameters such as the shot impact velocity and shot size are investigated in the case of the falling, impacting, and rebounding single particle. The weakly coupled solver applies the immersed boundary method which enables direct evaluation of the interactions between the unsteady flow field and moving/deforming objects. The elastoplastic object of AISI4340 during the collision of rigid steel shot is analyzed dynamically using the finite element method. Consequently, it is clarified that the flow field of the post-collision between the shot and structure can be characterized by the relative Reynolds number, which is based on the shot diameter and relative velocity between the uniform flow and rebounding shot velocities. As the relative Reynolds number increases, the complex flow field and vortex structures are generated at the collision location. These fluid structures affect the collision phenomena resulting in the random behavior of the shot and the asymmetric indentation in the structure.

Streamline pair selection for comparative flow field visualization.

Fluid dynamics simulation is often repeated under varying conditions. This leads to a generation of large amounts of results, which are difficult to compare. To compare results under different conditions, it is effective to overlap the streamlines generated from each condition in a single three-dimensional space. Streamline is a curved line, which represents a wind flow. This paper presents a technique to automatically select and visualize important streamlines that are suitable for the comparison of the simulation results. Additionally, we present an implementation to observe the flow fields in virtual reality spaces.