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Combustion simulation at Thiot Ingénierie

In a number of Thiot Ingénierie’s fast dynamics applications and equipment, already complex gas dynamics get yet further complexified by combustion physics. Thiot Ingénierie’s capability to simulate such largely chaotic flows proves essential both for the thorough understanding of violent phenomena that constitute our core expertise and for the related risk engineering.

The attached animation demonstrates the extent to which flame dynamics can be hard to predict and control, even when confined to the combustion chamber of a gun. Here, the ignition of the flammable gas mixture quickly leads to a wrinkled flame front that moves faster through the boundary layer at the chamber walls, then leading to very inhomogeneous combustion of the mixture with large pockets of unburnt gas funneled into the launch tube.

Gas dynamics in a gun or launcher is as beautiful as it is infernal in its complexity and transience. It furthermore spans vastly different temporal and spatial scales, from the largest eddies to the finest shockwave interactions. Such dynamics gather nearly every possible source of complication: those highly compressible, intensely turbulent and violently reactive flows feature all existing types of waves or fronts, alongside their numerous interaction patterns, all this in a volume that depends on the pressure history of the very flow that it confines.

This strongly intricate set of parameters put equipment dealing with combustion or explosion risks in the scope of chaos theory, making them arduous to predict without accurate and robust simulation tools: minute variability in the initial conditions may lead to vast phenomenological differences, the predictability horizon of which is counted in milliseconds.

For the numerical resolution of these CPU-intensive flow problems, Thiot Ingénierie uses a broad range of numerical methods among the most flexible and robust, avoiding the need for a supercomputer, and enabling us to solve such flows within an affordable time frame.

Among the numerical approaches and methods that we use, Automatic Mesh Refinement (AMR), Large Eddy Simulation (LES) and fully coupled detailed chemistry, enable us to tackle every kind of gas dynamics problems, from hypervelocity launchers to industrial accidents (dispersion, explosions and fires).