**V.A. Shargatov, Cand. Sci. (Phys.-Math.), Associate Professor
S.I. Sumskoi, Cand. Sci. (Eng.), Senior Lector
NIYAU MEPhI, Moscow, Russia
A.S. Sofyin, Cand. Sci. (Eng.), Department Head, toxi@safety.ru
STC «Industrial Safety» CJSC, Moscow, Russia**

The article describes the topicality, formulation of the problem, the structure, the basic equations and the solution method, as well as the specifics of using TOXI+CFD software package that implements the numerical solution of the hydrodynamic equations (the so-called CFD methods — Computational Fluid Dynamics). The simulation is based on an approach based on standard partial differential equations of the laws of conservation of mass, momentum and energy. The use of CFD methods will allow more accurate modeling of cloud formation and explosions of fuel-air mixtures in three-dimensional space. The software for calculating the propagation of waves of overpressure in the 3D cluttered environment developed and tested in this work. The verification of the TOXI+CFD calculation results obtained by comparison with the analytical solution of the Sod’s problem, as well as experimental studies of shock waves in a shock sphere. The results of measurements obtained in experiments, as well as using TOXI+CFD demonstrate the limiting deviations of the results for the grid of 3,4 million cells — no more than 9 %, and for the grid of 8 million cells — no more than 7 %, which is an indicator of the satisfactory quality of the model. It also follows from the results that as the number of cells increases, the calculated pressure becomes closer to the experimental values by 1–2 %, which indicates the convergence of the solution. The features of the software package are presented, such as the presence of a graphical user interface, the ability to work under Windows and Linux operating systems, support for cluster computing, as well as the main stages of its use. At the next stage of works on TOXI+CFD improvement it is planned to add turbulence and gravity model to the software package, and subsequently the atmosphere model taking into account stratification and combustion model.

1. On industrial safety of hazardous production facilities: Federal Law of July 21, 1997 № 116-FZ (as amended of 07.03.2017). Moscow: ZAO NTTs PB, 2017. 52 p. (In Russ.).

2. General Rules of Explosion Safety for Fire and Explosion Hazardous Chemical, Petrochemical and Oil Processing Plants: Federal Norms and Regulations in the Field of Industrial Safety. 3-e izd., ispr. i dop. Ser. 09. Iss. 37. Moscow: ZAO NTTs PB, 2018. 132 p. (In Russ.).

3. Efremov K.V., Lisanov M.V., Sofin A.S., Samuseva E.A., Sumskoj S.I., Kirienko A.P. Calculation of zones of destruction of buildings and constructions at explosions of fuel and air mixes on dangerous production objects. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2011. № 9. pp. 70–77. (In Russ.).

4. Degtyarev D.V., Lisanov M.V., Sumskoy S.I., Shvyryaev A.A. Quantitative risk analysis at the substantiation of buildings and structures blast resistance. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2013. № 6. pp. 82–89. (In Russ.).

5. Sverchkov A.M., Sumskoy S.I. Verification of TOXI+Gidroudar software for modeling unsteady processes in pipelines. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2017. № 10. pp. 5–10. (In Russ.).

6. Gelfand B.E., Gubin S.A., Mikhalkin V.N., Shargatov V.A. Calculation of shock wave parameters during detonation of combustible gaseous mixtures of variable composition. Fizika goreniya i vzryva = Physics of Burning and Explosion. 1985. Vol. 21. № 3. pp. 92–97. (In Russ.).

7. Gubin S.A., Shargatov V.A. Parameters of air shock waves in the transition of combustion into detonation. Fizika goreniya i vzryva = Physics of Burning and Explosion. 1989. Vol. 25. № 5. pp. 111–115. (In Russ.).

8. Borisov A.A., Gelfand B.E., Gubin S.A., Odincov V.V., Shargatov V.A. Parameters of air shock waves at different modes of explosive transformation of combustible gas mixtures. Khimicheskaya fizika = Chemical Physics. 1986. Vol. 3. № 5. p. 435. (In Russ.).

9. Gostintsev Y.A., Gubin S.A., Sumskoi S.I., Shargatov V.A. Numerical modeling of the detonation of a submerged hydrogen-air jet. Combustion, Explosion, and Shock Waves. 1990. Vol. 26. № 4. p. 473.

10. Borisov A.A., Gelfand B.E., Gubin S.A., Sumskoj S.I., Shargatov V.A. Detonation of fuel-air mixtures above the ground. Fizika goreniya i vzryva = Physics of Burning and Explosion. 1988. Vol. 24. № 2. pp. 124–126. (In Russ.).

11. Methods of assessment of consequences of accidents at explosion and fire hazardous chemical plants: Safety Guide. Ser. 09. Iss. 43. Moscow: ZAO NTTs PB, 2015. 32 p. (In Russ.).

12. Agapova E.A., Degtjarjov D.V., Lisanov M.V., Krjukov A.S., Kulberg S.B., Sumskoj S.I. Comparative analysis of Russian and foreign methods and software for emergency emission modeling and risk assessment. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2015. № 9. pp. 71–78. (In Russ.).

13. Ankit Dasgotra, G.V.V. Varun Teja, Ankit Sharma, Kirti Bhushan Mishra. CFD modeling of large-scale flammable cloud dispersion using FLACS. Journal of Loss Prevention in the Process Industries. 2018. DOI: 10.1016/j.jlp.2018.01.001

14. Hansen O.R., Mathieu R., Davis S.G. Validation of FLACS for Vapor Dispersion from LNG Spills: Model Evaluation Protocol. 12th Annual International Symposium of the Mary Kay O’Connor Process Safety Center. Texas, 2009.

15. Rian K.E., Evanger T., Vembe B.E., Lilleheie N.I., Laksa B., Hjertager B.H., Magnussen B.F. Coherent Computational Analysis of Large-Scale Explosions and Fires in Complex Geometries — From Combustion Science to a Safer Oil and Gas Industry. Chemical engineering transactions. 2016. Vol. 48. pp. 175–180. DOI 10.3303/CET1648030

16. Chang Bong Jang, Seungho Jung. Numerical computation of a large-scale jet fire of high-pressure hydrogen in process plant. Energy Science and Engineering. 2016. Vol. 4. Iss. 6. DOI 10.1002/ese3.143

17. Riddle A., Carruthers D., Sharpe A., McHugh C., Stocker J. Comparisons between FLUENT and ADMS for atmospheric dispersion modeling. Atmospheric Environment. 2004. Vol. 38. Iss. 7. pp. 1029–1038. DOI 10.1016/j.atmosenv.2003.10.052

18. Solodovnikov A.V., Akhmatvalieva E.R. Improving the safety of the pumping station on the basis of modeling the formation and dispersion of fire-explosive mixtures. Neftegazovoe delo = Oil and Gas Business. 2013. № 2. pp. 395–406. (In Russ.).

19. Kuptsov A.I., Akberov R.R., Islamkhuzin D.Ya., Gimranov F.M. Numerical simulation of the atmospheric boundary layer taking into account its stratification. Fundamentalnye issledovaniya = Fundamental Researches. 2014. № 9–7. pp. 1452–1460. (In Russ.).

20. Antonov A.S. Parallel programming using MPI technology: Textbook. Moscow: Izd-vo MGU, 2004. 71 p. (In Russ.).

21. SALOME. The Open Source Integration Platform for Numerical Simulation. Available at: http://salome-platform.org/ (accessed: May 12, 2017).

22. Kolgan V.P. Application of the principle of minimal values of derivatives to the construction of finite difference schemes for the calculation of discontinuous solutions of gas dynamics. Uchenye zapiski TsAGI = Uchenie Zapiski TsAGI. 1972. Vol. 3. № 6. pp. 68–77. (In Russ.).

23. Sod G.A. A survey of several finite difference methods for systems of nonlinear hyperbolic conservation laws. Journal of Computational Physics. 1978. Vol. 27. № 1. pp. 1–31. DOI: 10.1016/0021-9991(78)90023-2

24. Boyer D.W. An experimental study of the explosion generated by a pressurized sphere. Journal of Fluid Mechanics. 1960. Vol. 9. Iss. 3. pp. 401–429.

25. Sumskoj S.I., Pchelnikov A.V., Lisanov M.V., Pecherkin A.S., Shargatov V.A. Verification of methodologies for assessing the consequences of accidental releases of gas from sources over long term. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2005. № 8. pp. 28–35. (In Russ.).

26. Gubin S.A., Lykov S.M., Maklashova I.V., Pecherkin A.S., Sidorov V.I., Sumskoj S.I. Verification of procedures for the consequences of chemical accidents. Khimicheskaya promyshlennost = Chemical Industry. 1999. № 10. pp. 58. (In Russ.).