cropped-OpenWam001.pngOpenWAM is a free open source tool for gas dynamics modelling, mainly developed for Internal Combustion Engines. This code was initially developep in CMT-Motores Térmicos in 1984  sing the Method of Characteristics . The model was initially based on the Benson’s work .

Later, in 1986 Payri, Corberán and Boada improved the algorithm to generate and remove the characteristic lines, mainly for the cases where the flow undergoes changes in the flow sense at the end of the pipes.

In 1991 Payri, Benajes and Chust improved the resolution of the boundary conditions at the pipe’s ends. Nowadays this proposal is still used to solve the boundaries. In the next step, the Method of Characteristics was substituted by a more modern finite difference scheme, faster and less diffusive. Desantes, Chust and Llorens carried out a comparative study in 1993, where different schemes were tested. The conclusion was that the most suitable schemes to solve the compressible flow throug the engine pipes were two step Lax&Wendroff and the predictor-corrector MacCormak. Both schemes were second order acurate. Few years ago, another comparative study was carried out by Payri, Galindo, Serrano and Arnau where modern high resolution schemes like TVD schemes or FCT techniques were tested to be used in the code for solving the flow through the pipes. Nowadays, an OpenWAM user can choose between different schemes in order to obtain fast or acurate results.

Parallel to the improvement in the resolution of conservation equations system in the ducts, OpenWAM has undergone continuous development of submodels for calculating the fluid dynamic behavior of each of the different elements that form the engine. Zero-dimensional filling and emptying submoder for the calculation of cylinders and plenums were included in the first version of the code . In 1996, a submodel for the resolution of the turbine boundary condition  which was later adapted to variable geometry turbine .


  1. Introduction
  2. General features
    1. Calculation methodology
    2. Chemical species transport model
  3. Engine block
    1. 4-stroke cylinders
      1. Combustion model
        1. Four Wiebes simulation
        2. ACT model
      2. Heat transfer in cylinders
    2. 2-stroke cylinders
  4. Pipes
    1. Numerical methods
    2. Heat transfer
    3. Friction
  5. Plenums and 0-dimensional models
    1. Constant volume 0-dimensional element
    2. Venturi
    3. Directional junction
    4. Turbine
  6. Boundary conditions
    1. Open end boundary
    2. Closed end boundary
    3. Anechoic end
    4. Incident pressure
    5. Static pressure
    6. Pipe to volume connection
    7. Pipe to cilinder connection
    8. Roots compressor
    9. Two pipes connection
      1. Sudden enlargement
      2. Sudden contraction
    10. Two pipes connection with pressure loss
    11. Multi-pipe connections
    12. Two volumes connection
    13. Compressor connection
      1. Plenum to pipe compressor connection
      2. Pipe to pipe compressor connection
      3. Plenum to plenum compressor connection
  7. Valves
    1. Constant discharge coefficient
    2. Cam controlled valve
    3. Cylinder controlled port
    4. Rotating disk
    5. Reed valve
    6. Stator of the turbine
    7. Rotor of the turbine
  8. Turbocharger
    1. Axis
    2. Turbine
    3. Compressor
      1. Plenum to pipe compressor model
      2. Pipe to pipe compressor model
      3. Plenum to plenum compressor model
  9. Control unit
    1. Sensors
    2. Controllers
  10. Other complex models
    1. Intercooler
  11. Input data
    1. Wamer interface
  12. Output data

F. Payri, J. Benajes, and M. D. Chust, “Programme pour étude assistée par ordinateur de systémes d’admision et d’echappement de moteurs,” Entropie, vol. 162, pp. 17–23, 1991.
J. R. Serrano, F. J. Arnau, P. Piqueras, and O. García-Afonso, “Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths,” International Journal of Computer Mathematics, pp. 1–14, Apr. 2013.
F. Payri, J. Galindo, and J. R. Serrano, “Variable geometry turbine modelling and control for turbocharged diesel engine transient operation,” in Conference Proceedings of THIESEL2000 Thermofluidynamic Processes in Diesel Engine., 2000, pp. 173–189.
F. Payri, J. Benajes, and M. Reyes, “Modelling of supercharger turbines in internal combustion engines,” International Journal of Mechanical Science, vol. 38, no. 8–9, pp. 835–869, 1996.
F. Payri, J. M. Corberán, and F. Boada, “Modifications to the method of characteristics for the analysis of the gas exchange process in internal combustion engines,” in Proceedings of the Institution of Mechanical Engineers, 1986, vol. 200, pp. 259–266.
J. M. Desantes, M. D. Chust, and J. Llorens, “Análisis comparativo de métodos numéricos para la resolución del flujo no estacionario en colectores de motores de combustión interna alternativos,” in II Congreso de Métodos Numéricos en Ingeniería, 1993.
J. M. Corberán, “Contribución al modelado del proceso de renovación de la carga en motores de combustión interna alternativos,” Universidad Politécnica de Valencia, 1984.
R. S. Benson, The thermodynamics and gas dynamics of internal-combustion engines, vol. 1. Clarendon Press Oxford, 1982.

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