Alexandre Martin

Bio: Alexandre Martin is an academic researcher from University of Kentucky. The author has contributed to research in topics: Solver & Charring. The author has an hindex of 23, co-authored 138 publications receiving 1659 citations. Previous affiliations of Alexandre Martin include University of Michigan & Ames Research Center.

Multidimensional Modeling of Pyrolysis Gas Transport Inside Charring Ablative Materials

Abstract: The behavior of pyrolysis gas transport in arcjet test samples is numerically studied. The simulation of the pyrolysis gas flow inside a porous material is presented, using two different geometries...

High performance modeling of atmospheric re-entry vehicles

Abstract: Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain better predictions, an appropriate gas flow chemistry model needs to be included in the CFD calculations. Using a recently developed chemistry model for ablating carbon-phenolic-in-air species, a CFD calculation of the Stardust re-entry at 71 km is presented. The code used for that purpose has been designed to take advantage of the nature of the problem and therefore remains very efficient when a high number of chemical species are involved. The CFD result demonstrates the need for such chemistry model when modeling the flow field around an ablative material. Modeling of the nonequilibrium radiation spectra is also presented, and compared to the experimental data obtained during Stardust re-entry by the Echelle instrument. The predicted emission from the CN lines compares quite well with the experimental results, demonstrating the validity of the current approach.

Strongly Coupled Computation of Material Response and Nonequilibrium Flow for Hypersonic Ablation

Abstract: The steps necessary to achieve the strong coupling between a flowfield solver and a material response solver are presented. This type of coupling is required to accurately capture the complex aerothermodynamic physics occurring during hypersonic atmospheric entries. A blowing boundary condition for the flowfield solver is proposed. This allows the ablating gas calculated by the material response solver to be correctly injected in the boundary layer. A moving mesh algorithm for the flowfield solver that implicitly enforces the geometric conservation law is presented. Using that capability, a mesh movement procedure for surface recession and for accurate shock capturing is proposed. The entire technique is tested using a material response solver with surface ablation and pyrolysis coupled to a hypersonic solver for weakly ionized flows in thermochemical nonequilibrium. Results using the reentry trajectory of the IRV-2 test vehicle are presented, showing that the surface heat fluxes remain accurate as the ve...

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

The Structure of Turbulent Shear Flow

Abstract: The Structure of Turbulent Shear Flow By Dr. A. A. Townsend. Pp. xii + 315. 8¾ in. × 5½ in. (Cambridge: At the University Press.) 40s.

Journal of Fluid Mechanics创刊50周年

Abstract: 流体力学杂志“Journal of Fluid Mechanics”由剑桥大学教授George Batchelor在1956年5月创办，在国际流体力学界享有很高的学术声望，被公认为是流体力学最著名的学术刊物之一，2005年的影响因子为2．061，雄居同类期刊之首．在它创刊50周年之际，2006年5月JFM出版了第554卷的纪念特刊，其中刊登了现任主编（美国西北大学S．H．Davis教授和英国剑桥大学T．J．Pedley教授）合写的述评：“Editorial：JFM at50”，以JFM为背景，从独特的视角对近50年来流体力学的发展进行了简明的回顾和展望，并归纳了一系列非常有启发性的有趣统计数字．2006年7月21日在剑桥大学应用数学和理论物理研究所（DAMTP）举行了创刊50周年的庆祝会．下午2点，JFM的新老编辑和来宾会聚一堂，Pedley教授致开幕词，其后是5个精彩的报告：The mysterious rattleback and its fluid counterpart（Keith Moffatt），Developments in shear instabilities（Patrick Huerre），Falling clouds（Elisabeth Guazzelli），Ecotectural fluid mechanics（Paul Linden），The success of JFM（Herbert Huppert），最后由Davis教授致闭幕词．