Applied Numerical Mathematics 47 (2003) 515–530 www.elsevier.com/locate/apnum Numerical simulation of time-dependent reacting flows in pulse facilities José P. Tamagno a , Sergio A. Elaskar a,∗ , Gustavo A. Ríos b a Departamento de Aeronáutica, Universidad Nacional de Córdoba, Av.Velez Sarfield 1601, Córdoba 5000, Argentina b Instituto Universitario Aeronáutico Ruta 20, km 5.5, Córdoba 5022, Argentina Abstract A numerical methodology for simulating time-dependent reacting flows inside several types of pulse facilities is outlined in this paper. The numerical approach uses a finite-volume Harten–Yee TVD scheme for the quasi- one-dimensional Euler equations coupled with finite rate chemistry. To track gas interfaces a Riemann solver is included and to reduce the number of nodes without smearing the interfaces, a moving mesh is used. The source terms representing the finite-rate chemical kinetics and vibrational relaxation are often large and make the algorithm too stiff to be advanced explicitly. To avoid this stiffness an implicit treatment of these source terms is implemented. The numerical program can work with 13 chemical reacting species and 33 different reactions of a hydrogen–oxygen–nitrogen combustion mechanism, each of which may proceed forward or backward. Since helium is often used in pulse facilities it is also included, although it is considered as an inert species. Numerical simulations showing the potential of the computer code for the prediction of fluid mechanic properties and the chemical composition of the flow inside pulse facilities, are presented.  2003 IMACS. Published by Elsevier B.V. All rights reserved. Keywords: Compressible flow; Time-dependent; Chemical reactions; Finite rate; Implicit upwind TVD 1. Introduction The expansion and shock tubes are facilities capable of accelerating the flow to velocities several times greater than the speed of sound and can be used to carry out experimental studies with supersonic and hypersonic flows. However, such high-speed flows can be obtained only for short periods of time (of the order of 0.5 to 10 milliseconds). Because of this combination of high-speed test flow with short testing times, they are known as high enthalpy pulse facilities. This work presents a numerical study * Corresponding author. E-mail address: selaskar@gtwing.efn.uncor.edu (S.A. Elaskar). 0168-9274/$30.00  2003 IMACS. Published by Elsevier B.V. All rights reserved. doi:10.1016/S0168-9274(03)00090-4