Showing papers by "Kozo Fujii published in 2001"
TL;DR: In this paper, an unsteady flowfield around the capsule under the forced pitching oscillation in the transonic flow of M = 1.3 is numerically simulated based on the three-dimensional thin-layer Navier-Stokes equations.
Abstract: Dynamic stability of a reentry capsule in transonic speeds is discussed. An unsteady flowfield around the capsule under the forced pitching oscillation in the transonic flow of M = 1.3 is numerically simulated based on the three-dimensional thin-layer Navier-Stokes equations. The numerical result reveals that the dynamic instability is caused by the phase delay of the base pressure. It is also found that the base pressure, the recompression shock wave, and the wake behind the recompression shock wave all oscillate with the same delay time. The flow mechanism is proposed based on the idea that the phase delay of the base pressure is caused by a feedback loop of the flowfield behind the capsule. This flow mechanism reasonably explains the features observed in the present numerical simulation, as well as the experimental fact that the dynamic instability occurs at very low reduced frequencies.
47 citations
08 Jan 2001
18 citations
01 Jan 2001
TL;DR: It has been pointed out that the pre-processing stage of such large-scale simulations occupies large part of the total analysis time, and the time required for the post-processing increases as the simulation becomes sophisticated.
Abstract: Advances in computing technology have enabled us to carry out large-scale simulations, and unsteady simulations for complicated flowfields are carried out using tens of millions grid points within reasonable time. It has been pointed out that the pre-processing stage of such large-scale simulations occupies large part of the total analysis time. At the same time, the time required for the post-processing increases as the simulation becomes sophisticated.
01 Dec 2001
TL;DR: In this paper, an axi-symmetric nozzle configuration using compressible Navier-Stokes equations is used to simulate flow fields over annular plug nozzles and the boat-tail drag characteristics are clarified and discussed.
Abstract: Flow fields over annular plug nozzles are computationally simulated and the boat-tail drag characteristics are clarified and discussed based on the simulation results. The plug nozzle configuration is taken from the ATREX (Air Turbo Ramjet) engine under development at the ISAS. The simulations are carried out for the axi-symmetric nozzle configuration using compressible Navier-Stokes equations. The computed result shows that there exists a low pressure region downstream of the Prandtl-Meyer expansion on the boat-tail region and the separation shock wave appears due to the interaction of the main flow and the nozzle plume downstream. The result also shows that the primary cause of the boat-tail drag turns out to be the low pressure region downstream of the Prandtl-Meyer expansion. The flow field with the secondary flow injection is then simulated and the computed result shows that the pressure in the region in front of the separation shock wave increases and the secondary flow injection successfully reduces the boat-tail drag. The effect of the turbulence model used in the computation is discussed to ensure the reliability of the solutions.