Reacting Flow: Explosion

What You'll Build

This lesson walks you through a CFD simulation of a TNT explosion — a problem central to engineering safety, military applications, structural protection, and blast planning. An explosion is a very fast exothermic reaction that suddenly produces large volumes of hot gaseous products, spiking pressure and temperature and launching compression waves that travel outward through the surrounding air.

In this project, you'll model the rapid decomposition of TNT — where 2 moles of TNT generate 22 moles of gaseous products — and watch the resulting spherical pressure wave propagate and dissipate across the domain.

What You'll Learn

• The physics of an explosion: fast exothermic reaction, sudden pressure rise, and the sequence of compression and expansion waves

• How to set up a half-sphere domain (5 m radius) with a central TNT charge (5 cm radius half-sphere) in SpaceClaim, using symmetry to reduce cost

• How to generate a large structured mesh (~2.67 million elements) capable of resolving a traveling wave

• Why this problem requires a transient solver to capture moving pressure waves

• How to set up the Species Transport model with a defined species mixture and volume reaction

• How to configure finite-rate turbulence–chemistry interaction and the direct source chemistry solver

• How to apply the k-ε Realizable turbulence model with the energy equation activated

• A critical modeling choice: defining the mixture density as an ideal gas so the simulation can capture wave travel

• How to post-process temperature and pressure contours over time, plus an animation of the propagating compression wave, and quantify the wave speed (~420 m/s)

Why It Matters

Blast modeling protects buildings, vehicles, and people. The reacting-flow + ideal-gas + transient workflow you build here transfers directly to detonations, deflagrations, gas explosions, and pressure-vessel safety analysis across defense, oil and gas, and process industries.