syoukera
commented
3 years ago - the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field.（火炎は，燃焼場からの電流の急上昇を伴い，潤安定な平面に近い形状からノズルに定在した円錐状の形へと急激に遷移する）
- the flow velocity at the upstream of the flame front decreases to zero（火炎上流の流速はゼロに減少する）
- transient balance between the fluid inertia and the electric body force around the instability threshold（流体の慣性と静電気力のバランスが不安定性の閾値を決定する）
@article{PhysRevE.97.013103, title = {Electrohydrodynamic instability of premixed flames under manipulations of dc electric fields}, author = {Ren, Yihua and Cui, Wei and Li, Shuiqing}, journal = {Phys. Rev. E}, volume = {97}, issue = {1}, pages = {013103}, numpages = {8}, year = {2018}, month = {Jan}, publisher = {American Physical Society}, doi = {https://doi.org/10.1103/PhysRevE.97.013103}, url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.97.013103} abstruct={We report an electrohydrodynamic instability in a premixed stagnation flame under manipulations of a dc electric field. This instability occurs when the electric field strength is at a certain value below the breakdown threshold, which is 0.75 kV/cm in the experimental setup. Above this value the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field. At the transition moment, the flame spontaneously propagates upstream to the nozzle while the flow velocity at the upstream of the flame front decreases to zero, as revealed by high-speed photographs and PIV measurements. These phenomena indicate a transient balance between the fluid inertia and the electric body force around the instability threshold. A quantitative model suggests that the flame instability can be explained by a positive feedback loop, where the electric field applies a nonuniform electric body force, pulling the flame front upstream, and the pulled flame front in turn enhances the local electric body force. The electrohydrodynamic instability occurs when the electric pulling is strong enough and both the growth rates and the magnitudes of the electric body force on flame exceed those of the fluid dynamic pressure.} }