burning velocity, νb

of a flame front, in flame emission and absorption spectrometry
https://doi.org/10.1351/goldbook.B00762
The mean velocity of the flame front (in mm s1) towards the unburnt gas mixture (usually vertically downwards). The quantity applies to gas mixtures and not to injection burners, and depends on the flame temperature and the solvent nebulized.
Source:
PAC, 1986, 58, 1737. (Quantities and units in clinical chemistry: Nebulizer and flame properties in flame emission and absorption spectrometry (Recommendations 1986)) on page 1742 [Terms] [Paper]