A flux splitting scheme is proposed for the general nonequilibrium flow equations with an aim at removing numerical dissipation of Van-Leer-type flux-vector splittings on a contact discontinuity. The scheme obtained is also recognized as an improved Advection Upwind Splitting Method (AUSM) where a slight numerical overshoot immediately behind the shock is eliminated. The proposed scheme has favorable properties: high-resolution for contact discontinuities; conservation of enthalpy for steady flows; numerical efficiency; applicability to chemically reacting flows. In fact, for a single contact discontinuity, even if it is moving, this scheme gives the numerical flux of the exact solution of the Riemann problem. Various numerical experiments including that of a thermo-chemical nonequilibrium flow were performed, which indicate no oscillation and robustness of the scheme for shock/expansion waves. A cure for carbuncle phenomenon is discussed as well.

A Flux Splitting Scheme with High-Resolution and Robustness for Discontinuities(Proceedings of the 12th NAL Symposium on Aircraft Computational Aerodynamics)

Progress in shock wave/boundary layer interactions

The challenges in understanding hypersonic flight are discussed and critical hypersonic aerothermodynamics issues are reviewed. The ability of current analytical methods, numerical methods, ground testing capabilities, and flight testing approaches to predict hypersonic flow are evaluated. The areas where aerothermodynamic shortcomings restrict our ability to design and analyze hypersonic vehicles are discussed, and prospects for future capabilities are reviewed. Considerable work still needs to be done before our understanding of hypersonic flow will allow for the accurate prediction of vehicle flight characteristics throughout the flight envelope from launch to orbital insertion.

/pdf/critical-hypersonic-aerothermodynamic-phenomena-ahf6pytiml.pdf

Critical Hypersonic Aerothermodynamic Phenomena

Physico–chemical modelling in hypersonic flow simulation

Machine learning (ML) techniques applied to chemical reactions have a long history. The present contribution discusses applications ranging from small molecule reaction dynamics to computational platforms for reaction planning. ML-based techniques can be particularly relevant for problems involving both computation and experiments. For one, Bayesian inference is a powerful approach to develop models consistent with knowledge from experiments. Second, ML-based methods can also be used to handle problems that are formally intractable using conventional approaches, such as exhaustive characterization of state-to-state information in reactive collisions. Finally, the explicit simulation of reactive networks as they occur in combustion has become possible using machine-learned neural network potentials. This review provides an overview of the questions that can and have been addressed using machine learning techniques, and an outlook discusses challenges in this diverse and stimulating field. It is concluded that ML applied to chemistry problems as practiced and conceived today has the potential to transform the way with which the field approaches problems involving chemical reactions, in both research and academic teaching.

Machine Learning for Chemical Reactions.

Assessment of CFD capability for prediction of hypersonic shock interactions

After the successful flight of SHEFEX I the next mission is under development. Within this
paper the basic goals and architecture of the SHEFEX II mission will be presented. Also
launched by a two staged sounding rocket system SHEFEX II will be a consequent next step
in technology test and demonstration. Considering all experience and collected flight data
obtained during the SHEFEX I Mission, the test vehicle will be re-designed and extended by
an active control system, which allows active aerodynamic control during the re-entry phase.
Thus, ceramic based aerodynamic control elements like rudders or flaps, mechanical
actuators and an automatic electronic control unit will be implemented. Special focus will be
taken on improved GNC Elements. In addition, some other experiments including an actively
cooled thermal protection element, advanced sensor equipment, high temperature antenna
inserts etc. are part of the SHEFEX II experimental payload.

/pdf/the-sharp-edge-flight-experiment-shefex-ii-a-mission-2o6s173gph.pdf

The Sharp Edge Flight Experiment SHEFEX II, a Mission Overview and Status

On Thursday, October 27th, 2005 the SHarp Edge Flight EXperiment SHEFEX has been successfully launched at the Andoya Rocket Range in northern
Norway. The project, being performed under responsibility of the German Aerospace Center (DLR) flew on top of a two-stage solid propellant sounding rocket. One purpose of the experiment is the investigation of possible new shapes for future launcher or re-entry vehicles applying a shape with facetted surfaces and sharp edges and to enable the time accurate investi-gation of the flow effects and their structural answer during the hypersonic flight from 90 km down to an altitude of 20 km. Additionally, the SHEFEX project is a starting point for a series of experiments which enable the acquisition of important knowledge in hypersonic free flight experimentation and which are an excellent test bed for new technological concepts. The present paper gives an overview about the philosophy and the layout of ex-
periment and introduces preliminary outcomes of the post-flight analysis.

/pdf/the-shefex-flight-experiment-pathfinder-experiment-for-a-sky-x8umd4iwd9.pdf

The Shefex Flight Experiment - Pathfinder Experiment for a Sky Based Test Facility

Aerothermodynamics - A critical review at DLR

*† ‡ The paper deals with the comparison of computations made at DLR and ISL on the interaction between a lateral jet issuing from a generic missile body and the oncoming supersonic cross-flow. Steady-state numerical simulations are carried out by 3D, viscous, turbulent, Reynolds-Averaged Navier-Stokes codes; at DLR, a hybrid mesh is used for the TAU calculation, whereas at ISL a hexahedral mesh is used for the CFX computation. Experimental data acquired in the DLR wind tunnel TMK in Cologne act as references for the computations. Calculations are made for a cross-flow Mach number of 2.8, for angles of attack of -5, 0 and 10 degrees and for a jet ejection pressure ratio of 100. The test model is a cone-cylinder-flare body with a side-jet nozzle located in the cylindrical part, representing a simple generic high-speed missile configuration. Surface pressure measurements were carried out in order to validate the corresponding computations. The agreement between the computations and the experiments in terms of pressure distribution is obtained with a high degree of accuracy by the codes, in spite of some small discrepancies.

/pdf/computational-comparisons-of-the-interaction-of-a-lateral-18esch9qkc.pdf

Jose M. A. Longo

Papers

Assessment of CFD capability for prediction of hypersonic shock interactions

The Sharp Edge Flight Experiment SHEFEX II, a Mission Overview and Status

The Shefex Flight Experiment - Pathfinder Experiment for a Sky Based Test Facility

Aerothermodynamics - A critical review at DLR

Computational Comparisons of the Interaction of a Lateral Jet on a Supersonic Generic Missile