ARBITRARY LAGRANGIAN EULERIAN SIMULATION OF FREE PISTON COMPRESSION TUBE

One of the approach obtaining high-enthalpy flow environments is the pulse facility driven by free piston, including free piston shock tunnel and free piston expansion tube.When using a free piston compression tube as the driver part of an expansion tube or a shock tunnel, the performance of such a facility will be determined to a great extent by its driving ability.Numerical simulation of the piston motion and flow properties in the free piston compression tube has been performed by means of an arbitrary Lagrangian Eulerian approach(ALE).Moving mesh strategy was used for the piston boundary adaptation.The motion of mesh and fluid was solved by coupling method.A dual time-step approach developed in computational fluid dynamics was introduced in the construction of ALE time-integrator.The normal vector and surface area of the mesh element for dynamic mesh were verified to satisfy the geometric conservation law(GCL). Both the comparison of piston positions with those of Eulerian method and the comparison of piston base pressures, piston velocities and piston positions with those of theoretical model based on simple wave assumption are very well.This work established the base on which numerical simulation of the flow at different parts for free piston shock tunnel and for free piston expansion tube will be carried out at the next step such as compressor, shock tube and nozzle, etc.