It has been estimated that about 50 tonnes of small meteoroids enter the Earth’s atmosphere every day. In their rush to the ground, these bodies, from 1 m size to micron-size grains, intersect the atmosphere with velocities up to 72 km/s. As the meteoroid interacts with the atmosphere, its surface temperature can reach several thousands of Kelvin causing the ablation, i.e. melting and evaporation, of the material. Due to their small size and the exceptional high speeds, meteors already burn up at very high altitudes where the atmosphere is extremely rarefied, the gas cannot be treated as a continuum and the classical equations employed in Gas Dynamics fail. Moreover, due to the high energies involved, coupled physico-chemical phenomena, i.e., strong departure from thermo-chemical equilibrium, radiative heating, ionization, plasma effects and complex gas-surface interactions, occur, making the prediction of these flows an extremely challenging task. We propose to focus on developing comprehensive models for the description of the meteor phenomenon in rarefied regime. The current state-of-the-art modelling of meteor ablation is drastically simplified, totally disregarding the phenomena taking place in the gas phase and the rarefied gas effects. The proposed research has the ambition of being a breakthrough in the field by applying and developing predictive techniques, which have their origins in the aerospace world. For the scientists, the aerothermodynamic modelling of meteors is vital for the interpretation of many sets of data coming from observations and for answering questions that are still open in planetary and atmospheric sciences. This goal will be reached through a multidisciplinary approach which will take advantage of the experience in complementary fields of 3 different centres: the von Karman Institute for Fluid Dynamics (VKI), the Vrije Universiteit Brussels (VUB) and the Belgian Institute for Space Aeronomy (BISA). VKI will provide the know-how in the numerical and experimental characterization of re-entry plasma flows. The Plasmatron facility, which is the most powerful inductively coupled plasma wind tunnel in the world, will be used for the experimental activities. The Electrochemical and Surface Engineering team at VUB masters innovative techniques for the multiscale analysis of materials. In addition, the group guided by prof. Claeys at VUB will be able to supply the necessary knowledge in meteorite science. The results of this research will be extremely useful for the interpretation of the degradation processes which can be observed on the micrometeorites collected during the Antarctic SAMBA expedition. Finally, recent efforts have been made by BISA to predict velocity, trajectory and composition of the meteors. By means of an innovative technique, the Belgian RAdio Meteor Stations (BRAMS) experiment consists in a series of receivers spread all over Belgium to collect and standardize the meteor observations. BRAMS measurements will give access to an incredible number of natural flight experiments which will help to validate the developed ablation models. The project will consist of 4 main segments. 1. Development of the physico-chemical models for the description of the ablation process in meteors in rarefied regime. This will consist of an accurate description of both the gas-surface and the gas phase chemical interactions. An innovative treatment for the ablative surface will be developed. Transport and chemical kinetic properties of ablated vapours will be considered by constructing a database of cross-sections. Moreover, both ionization (plasma effects) and radiation cooling play a major role due to the extremely high energies of the impact. They will be considered by implementing already existing models with a progressive approach. 2. Implementation of cutting-edge schemes in the framework of an open source Direct Simulation Monte Carlo (DSMC) software. We will benefit of the already well established capabilities of the OpenFOAM solver, while others will be added: starting from the developed cross-section database, chemistry of ablated products will be implemented into the DSMC method; an Immersed Boundary will be adopted to obtain an exhaustive description of complex geometries; Adaptive Mesh Refinement will be provided to automatize post-processing procedures. 3. Experimental characterization of the material response in the VKI plasma wind tunnel. Experiments will be preceded and followed by a thorough multiscale analysis of the surface which will allow to gain a better understanding of the thermo-chemical mechanisms occurring. Meteor samples will be employed to study their material response in a wide range of conditions. The experimental activity will allow a validation of the ablation model by means of an iterative process which will lead to the refinement of the model itself. 4. Application to BRAMS and SAMBA projects. In the last part, the developed tool will be used for the study of data from the BRAMS radar network and from the SAMBA meteoroid archive. These applications will permit further validation of models and, at the same time, they will help BRAMS and SAMBA teams in the interpretation of their data.
|Effective start/end date||1/01/16 → 31/12/19|
- Rarefield flows
Flemish discipline codes
- Environmental chemistry