Simulation of Fire Dynamics in a Midscale Test Tunnel
We took advantage of CONVERGE’s Adaptive Mesh Refinement (AMR) and accurate combustion and radiation models to simulate an experimental tunnel fire setup. Fires pose a significant safety threat to tunnel users, and proper ventilation strategies are key to mitigating harm to individuals and damage to the tunnel infrastructure. The experiment was carried out in a ⅓-scale tunnel with a ventilation device mounted downstream of the fire. A pool of heptane was ignited in a test gallery, and temperature, velocity, and heat flux measurements were taken at multiple locations within the tunnel. Numerical simulations of tunnel fires are a valuable complement or alternative to experimental tests, providing greater insight into the fire behavior at a lower cost. We used CONVERGE’s eddy dissipation model to simulate the turbulent combustion, and we captured the effect of thermal radiation with the Discrete Ordinates finite volume method. AMR dynamically adjusted the mesh throughout the simulation to efficiently capture the complex physics of the tunnel fire. The numerical results agreed well with the experimental measurements, demonstrating that CONVERGE is a powerful tool for studying tunnel fire incidents.
The first view in the video (0:07) shows an isometric view of the fire in the test tunnel. The flame is represented by an iso-volume of temperature, with contours indicating temperature (red denotes lower temperatures and light yellow denotes higher temperatures). The smoke is represented using an iso-volume of smoke density. The next view (0:21) shows a zoomed-in isometric view of the fire, highlighting the combustion of the heptane. You can see the formation and fluctuations of the flame and smoke, and how AMR is employed to capture the fire dynamics. The third view (0:30) shows a vertical slice with contours illustrating variations in smoke density. The colors range from gray, indicating low smoke density, to black, indicating high smoke density. The contours transition (0:34) to illustrate visibility levels inside the tunnel due to the smoke, with red representing low visibility and blue representing high visibility. The final view (0:39) shows the interaction of the flow field and the flame. The colored mesh lines represent velocity, with light blue indicating high velocity and dark blue indicating low velocity.
Convergent Science's CONVERGE is an innovative computational fluid dynamics (CFD) software package that eliminates the grid generation bottleneck from the simulation process through autonomous meshing.