Research ArticleENGINEERING

The structure of the blue whirl revealed

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Science Advances  12 Aug 2020:
Vol. 6, no. 33, eaba0827
DOI: 10.1126/sciadv.aba0827

Figures

  • Fig. 1 The blue whirl observed in experiment, taken from (1).

    (A) Stable blue whirl. (B) Slightly unstable blue whirl with soot in the middle, suggesting a bubble mode of vortex breakdown. Photo credit: H. Xiao, University of Science and Technology of China.

  • Fig. 2 The flame structure of the blue whirl.

    (A) Volume rendering of the heat release rate from the numerical simulation described in the text. (B) Schematic diagram that summarizes a final result of the blue whirl simulation. (C) Observed blue whirl. Photo credit: H. Xiao, University of Science and Technology of China.

  • Fig. 3 Comparison of the experiment and the simulation.

    (A) Experimental OH* concentration measurement [taken from figure 8A in (12)]. (B) 3D volume rendering of heat release rate in the simulation. The volume rendering is taken from the side view.

  • Fig. 4 Slices through the center of the computational domain and parameters selected for combustion diagnostics.

    (A) Flame index. (B) Equivalence ratio. (C) Temperature. Contours of heat release rate are superimposed on top to indicate reaction regions. Slices are shown for a zoomed-in region that is 8 cm wide.

  • Fig. 5 Slices through the center of the computational domain and values selected for flow diagnostics.

    (A) Streamlines. (B) Tangential velocity. (C) Axial velocity. Contours of heat release rate are superimposed on top to indicate reaction regions. Slices are shown for a zoomed-in region that is 6 cm wide. (D) Line plot of tangential velocity taken below the blue whirl from the white dashed line in (B), shown for the entire width of the computational domain.

  • Fig. 6 Streamlines superimposed on a 3D heat release rate isocontour of 3 MW/m3.

    (A) Streamlines that originate at 0.5 mm from the lower boundary. (B) Streamlines that originate at 2.0 mm from the lower boundary. The streamlines are colored by the local temperature of the flow. A 2D map of fuel mass fraction along the bottom boundary is shown, indicating the region of fuel inflow. The box indicates the region of mesh refinement.

  • Fig. 7 Computational setup.

    (A) Schematic of the computational domain and the boundary conditions. (B) A center slice of the 3D computational mesh. The mesh is composed of cubical control volumes. The width of the control volume in each level of refinement is half the width of the coarser level. The mesh is refined around the blue whirl, which is shown as a volume rendering of the heat release rate. The size of the largest and smallest cells (ΔxMax and ΔxMin, respectively) and the number of cells in the coarsest and finest mesh are indicated in (B).

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