Aeronautic systems
http://hdl.handle.net/10204/907
2018-02-24T15:52:05ZQuasi-Newton methods for the acceleration of multi-physics codes
http://hdl.handle.net/10204/10049
Quasi-Newton methods for the acceleration of multi-physics codes
Haelterman, R; Bogaers, Alfred EJ; Degroote, J; Boutet, N
Often in nature different physical systems interact which translates to coupled mathematical models. Even if powerful solvers often already exist for problems in a single physical domain (e.g. structural or fluid problems), the development of similar tools for multi-physics problems is still ongoing. When the interaction (or coupling) between the two systems is strong, many methods still fail or are computationally very expensive. Approaches for solving these multi-physics problems can be broadly put in two categories: monolithic or partitioned. While we are not claiming that the partitioned approach is panacea for all coupled problems, here we will only focus our attention on studying methods to solve (strongly) coupled problems with a partitioned approach in which each of the physical problems is solved with a specialized code that we consider to be a black box solver and of which the Jacobian is unknown. We also assume that calling these black boxes is the most expensive part of any algorithm, so that performance is judged by the number of times these are called. Running these black boxes one after another, until convergence is reached, is a standard solution technique and can be considered as a non-linear Gauss-Seidel iteration. It is easy to implement but comes at the cost of slow or even conditional convergence. A recent interpretation of this approach as a rootfinding problem has opened the door to acceleration techniques based on quasi-Newton methods. These quasi-Newton methods can easily be "strapped onto" the original iteration loop without the need to modify the underlying code and with little extra computational cost. In this paper, we analyze the performance of ten acceleration techniques that can be applied to accelerate the convergence of a non-linear Gauss-Seidel iteration, on different multi-physics problems.
Article published in IAENG International Journal of Applied Mathematics, vol. 47(3): 352-360
2017-08-01T00:00:00ZA comparison of ANSYS Fluent and STAR-CCM+ simulations for a tangent ogive slender body with a structured mesh at incompressible flow conditions
http://hdl.handle.net/10204/10010
A comparison of ANSYS Fluent and STAR-CCM+ simulations for a tangent ogive slender body with a structured mesh at incompressible flow conditions
Schoombie, Janine
This presentation contains a comparison of ANSYS Fluent and STAR-CCM+ simulations for a tangent ogive slender body with a structured mesh at incompressible flow conditions.
2017-10-01T00:00:00ZQuantitative grading of store separation trajectories
http://hdl.handle.net/10204/9818
Quantitative grading of store separation trajectories
Jamison, Kevin A; Rossouw, Pieter S; Miles, Elizna
When a new store is integrated with an aircraft, it is necessary to verify that it separates safely for all possible release and emergency jettison scenarios. A large number of store separation analyses are required to comply with this requirement. This paper describes the development of an automated analysis process and software that can run a multitude of separation scenarios. A key enabler for this software is the development of a quantitative grading algorithm that scores the outcome of each release against clearly defined criteria. The separation grading algorithm eliminates the need for the analyst to assess each separate store separation scenario manually and subjectively by assigning scores based on a number of specific and measurable criteria. The scores obtained over a range of separation scenarios form a robust and quantitative basis for defining safe release envelopes for an aircraft/store combination and for motivating applicable pilot limitations. The application of this approach to the release/jettison dynamics of a typical aircraft/store configuration is described.
Paper presented at the 9th Ankara International Aerospace Conference, 20-22 September 2-17, METU, Ankara, Turkey
2017-09-01T00:00:00ZA comparative study on laser processing of commercially available titanium aluminide (TI-48AL-2CR-2NB) and in-situ alloying of titanium aluminide
http://hdl.handle.net/10204/9805
A comparative study on laser processing of commercially available titanium aluminide (TI-48AL-2CR-2NB) and in-situ alloying of titanium aluminide
Hoosain, Shaik E; Pityana, Sisa L; Tlotleng, Monnamme; Legopeng, T
Titanium aluminides (TiAl) are acknowledged as promising high temperature structural materials due to their high melting point, high strength to density, high elastic modulus and high creep strength. Due to their low ductility, it is difficult to machine post manufacturing with conventional manufacturing techniques. TiAl components have been successfully produced using the cast methods, but prove to be very expensive and time consuming. In situ alloying, using laser processing, is a potential method of manufacture of these alloys; as elemental powders can be fed separately from different powder feeders and the feed rate can be controlled, independently, to control the composition and resulting microstructure.
Paper presented at the 18th Annual International Rapid Product Development Association of South Africa (RAPDASA), 7-10 November 2017, Durban ICC, South Africa
2017-11-01T00:00:00Z