Cognitive approach to the solution of hypersonic flow problems
Mathematics. Physics. Mechanics
Moscow Institute of Physics and Technology, 9, Institutskiy per., Dolgoprudny, Moscow region, 141701, Russia
To create a useful engineering program for determination of main aerodynamic characteristics of complex-shaped bodies in rarified atmosphere. The program should provide for sufficiently short calculation time to be applied at early stages of high-speed vehicle design. To determine the main aerodynamic characteristics of reentry vehicles in rarified atmosphere on all segments of their trajectories – from orbital flight to landing on Earth.
Cognitive approach in computer science is a combination of methods; algorithms and software used for modeling the cognitive abilities of the human brain to solve specific application problems. Numerical methods are considerably complex, which makes it difficult to apply them at the preliminary design stage when a lot of options are considered. Therefore, models, which are based on cognitive approach, become useful. They are built on the basis of scientific and intuitive analysis of data obtained by means of theoretical, experimental and numerical studies. Even specialized computer systems such as Knowledge Based Engineering are created to reduce project time and the number of expensive full-scale tests. Two engineering methods of calculation of aerodynamic characteristics of actual hypersonic vehicles are described in this paper. Cognitive approach was used for selecting the method for solution of the posed problem. Thus engineering research method was used to determine the aerodynamic characteristics of the hypersonic vehicles with the additional application of semi-empirical theories. The hypothesis that the momentum flux on a surface element is determined by its local pitch angle relative to the approach flow was used as well.
A detailed description is given for the process of calculation of aerodynamic characteristics of hypersonic vehicles according to the selected engineering method. In particular, the results are presented for the investigation of the layout aerodynamic characteristics of actual hypersonic vehicles: “Clipper” Russian project and “Falcon HTV-2” USA project.
The method does not take into account the interaction of the boundary layer with the non viscous flow. Thus during calculations for low angles of attack it is necessary to use more detailed models, which take into account the boundary layer presence. This method works well for nearly spherical and other blunt bodies and cannot be used for very thin bodies.
The program and its results can be used for the development of advanced hypersonic vehicles and estimation of their characteristics at early design stages. The method gives good results for the drag coefficient of simple body shape; the trend for the lift coefficient is also correct. The proposed method is also suitable for taking into account the influence of Reynolds number in various design modifications and provides for research of various body shapes as well as taking into account the boundary conditions at a molecular level.
Keywords:engineering methods in aerodynamics, characteristics of aerodynamics hypersonic cruise vehicle, Reynolds number , transient aerodynamics
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