Numerical rebuilding of a free-flying ring interfering with a two-dimensional shock wave
Creators: name:  L. CUTRONE 
name:   A. SCHETTINO 
name:   A. FRENCH 
Publisher: name: Proceedings of the Aerospace Europe Conference - EUCASS - CEAS - 2023
Year: 2023
Subjects: CFD
AEROTHERMODYNAMICS
DESIGN FOR DEMISE

description: In the frame of the ATD3 working group, coordinated by ESA and CNES, a test case was proposed, representative of the interaction between two fragments generated by the break-up of a space vehicle during re-entry. A ring is initially suspended over a cylinder, and when the flow enters the test chamber the wires are cut and the ring follows a trajectory over the cylinder, interacting with the shock wave generated by the cylinder itself. In this study, a numerical rebuilding of that test case is presented by using the NExT code, developed at CIRA. A particular effort has been made in generating a structured multi-block topology that allows the deformation of the grid without changing the cell number and distribution for each block. Two strategies have been followed, one using the grid generator ZENG RID, available at CIRA, the other using the commercial grid generator ICEMCFD. In both cases the grid generation was automated in order to dynamically adapt the mesh to the ring position. 1. Background and motivation The presence of a large amount of space debris in orbit around the earth, resulting from the destruction of satellites or other objects in orbit, poses a major safety problem. In fact, this debris, even if often very small, due to their very high kinetic energy can cause serious damage to other satellites or spacecraft orbiting the earth. For this reason, the scientific community has been committed for many years to reducing the presence of space debris; on the one hand there is an attempt to design the satellites so that they are completely destroyed when they re-enter the atmosphere ( design for demise); on the other hand, ways are being sought to eliminate the debris already present in the Earth\'s orbit. In order to predict the re-entry trajectory of a satellite, its break-up and the subsequent trajectory of the fragments deriving from the destruction, numerous object-oriented codes have been developed (eg. SESAM, DEBRISK, SCARAB, PAlv.lPERO) which, based on simplified approaches, seek to model the relevant phenomena and estimate the characteristics of the fragments generated and the area in which they will fall. These codes include, among other things, a simplified modelling of the aerodynamics of the individual fragments. To verify the uncertainty resulting from these simplified methods it is necessary to carry out, in a limited number of representative cases, a comparison with results obtainable by means of accurate CFD calculations. For example, in [I] an extensive database of numerical data obtained by means of numerical Direct Simulation Monte Carlo DSMC simulations on various representative reference geometries is calculated; the numerical results are then compared with those obtained from approximation models typically implemented in object-oriented codes. This evaluation, already complex in itself due to the great variety of possible shapes, does not consider another important aspect which is represented by the interaction between the individual fragments, which can lead to significant differences with respect to the aerodynamics of a single isolated fragment. To study the effect of this interaction, and to provide useful data for the validation of both CFD and simplified codes, some dedicated experiments were carried out at the Von Karman Institute in Brussels. One of these experiments was then used, within the ATD3 Working Group, coordinated by ESA and CNES, with the aim of validating the numerical tools of the various participants in the Working Group. The test case performed at the VKI is described in the next paragraph, while a more detailed description can be found in [2]. Copyright 2023 by First Author. Posted online by the EUCASS association with permission.