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Reynier P.,Ingenierie et Systmes Avances | Bugel M.,Ingenierie et Systmes Avances | Smith A.,Fluid Gravity Engineering Ltd
International Journal of Aerospace Engineering

In the frame of future sample return missions to Mars, asteroids, and comets, investigated by the European Space Agency, a review of the actual aerodynamics and aerothermodynamics capabilities in Europe for Mars entry of large vehicles and high-speed Earth reentry of sample return capsule has been undertaken. Additionally, capabilities in Canada and Australia for the assessment of dynamic stability, as well as major facilities for hypersonic flows available in ISC, have been included. This paper provides an overview of European current capabilities for aerothermodynamics and testing of thermal protection systems. This assessment has allowed the identification of the needs in new facilities or upgrade of existing ground tests for covering experimentally Mars entries and Earth high-speed reentries as far as aerodynamics, aerothermodynamics, and thermal protection system testing are concerned. © 2011 Mathilde Bugel et al. Source

Joiner N.,University of Saskatchewan | Joiner N.,Fluid Gravity Engineering Ltd | Dorland W.,University of Maryland University College
Physics of Plasmas

Advanced tokamak schemes which may offer significant improvement to plasma confinement on the usual large aspect ratio Dee-shaped flux surface configuration are of great interest to the fusion community. One possibility is to introduce square shaping to the flux surfaces. The gyrokinetic code GS2 [Kotschenreuther, Comput. Phys. Commun. 88, 128 (1996)] is used to study linear stability and the resulting nonlinear thermal transport of the ion temperature gradient driven (ITG) mode in tokamak equilibria with square shaping. The maximum linear growth rate of ITG modes is increased by negative squareness (diamond shaping) and reduced by positive values (square shaping). The dependence of thermal transport produced by saturated ITG instabilities on squareness is not as clear. The overall trend follows that of the linear instability, heat and particle fluxes increase with negative squareness and decrease with positive squareness. This is contradictory to recent experimental results [Holcomb, Phys. Plasmas 16, 056116 (2009)] which show a reduction in transport with negative squareness. This may be reconciled as a reduction in transport (consistent with the experiment) is observed at small negative values of the squareness parameter. © 2010 American Institute of Physics. Source

Joiner N.,University of Saskatchewan | Joiner N.,Fluid Gravity Engineering Ltd | Hirose A.,University of Saskatchewan | Dorland W.,University of Maryland University College
Physics of Plasmas

At low Β it is common to neglect parallel magnetic field perturbations on the basis that they are of order Β2. This is only true if effects of order Β are canceled by a term in the ∇B drift also of order Β [H. L. Berk and R. R. Dominguez, J. Plasma Phys. 18, 31 (1977)]. To our knowledge this has not been rigorously tested with modern gyrokinetic codes. In this work we use the gyrokinetic code GS2 [Kotschenreuther, Comput. Phys. Commun. 88, 128 (1995)] to investigate whether the compressional magnetic field perturbation B is required for accurate gyrokinetic simulations at low Β for microinstabilities commonly found in tokamaks. The kinetic ballooning mode (KBM) demonstrates the principle described by Berk and Dominguez strongly, as does the trapped electron mode, in a less dramatic way. The ion and electron temperature gradient (ETG) driven modes do not typically exhibit this behavior; the effects of B are found to depend on the pressure gradients. The terms which are seen to cancel at long wavelength in KBM calculations can be cumulative in the ion temperature gradient case and increase with e. The effect of B on the ETG instability is shown to depend on the normalized pressure gradient Β′ at constant Β. © 2010 American Institute of Physics. Source

Neeb D.,German Aerospace Center | Gulhan A.,German Aerospace Center | Merrifield J.A.,Fluid Gravity Engineering Ltd
AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Surface roughness, especially if enhanced due to ablative form change, increases skin friction drag and convective heat transfer over re-entry vehicles. Although the corresponding heat flux augmentation is usually lower compared to increased friction, careful consideration in the prediction of the resulting heat load levels is required. Within the European Mars mission ExoMars, the potential roughness impact on the thermal protection system of the descent module has been analyzed based on analytical predictions, numerical calculations and dedicated experimental campaigns. This paper describes the experimental efforts in the compressible flow regime to study the impact of roughness at representative conditions. The data is discussed based on comparisons with prediction methods and results of other investigators. Based on this data the numerical predictive capabilities within the ExoMars program is characterized and validated. Source

Frost D.L.,McGill University | Ruel J.-F.,McGill University | Zarei Z.,McGill University | Goroshin S.,McGill University | And 4 more authors.
Journal of Physics: Conference Series

A coherent jet of particles may be generated by accelerating a conical volume of particles by detonating a layer of explosive lining the outside of the cone. Experiments have been carried out to determine the dependence of the velocity history and coherency of the jet on the particle properties and the ratio of the masses of the particles and explosive. Steel particles form thin, coherent jets, whereas lighter glass particles lead to more diffuse jets. For steel particles, the cone angle had little effect on the coherency of the jet. The efficiency of the conversion of chemical to kinetic energy is explored by comparing the experimental jet velocity with the velocity predicted from a formulation of the Gurney method for a conical geometry. The effect of particle density and cone angle on the jet formation and development was also investigated using a multimaterial hydrocode. The simulations give insight into the extent of the deformation of the particle bed in the early stages of explosive particle dispersal. © Published under licence by IOP Publishing Ltd. Source

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