Complete Determination of the Velocity Gradient Tensor Upstream of the Flame Front with High-speed Tomo-PIV/Dual-plane-PIV/OH-PLIF Measurements

摘要

Accurate prediction of the flame stretch necessitates knowledge of the nine-component velocity-gradient tensor upstream of the flame front. However, stereo-PlV/PLlF, which has been commonly used in turbulent combustion research, only resolves the six in-plane velocity gradients. As a first step toward volumetrically- and temporally-resolved, i.e. 4D, characterization of turbulent combustion, we propose to completely determine the nine-component velocity-gradient tensor with simultaneous, high-speed, tomographic-PIV/OH-PLIF measurements and simultaneous, high-speed, dual-plane stereo-PIV/OH-PLIF measurements. The high-speed Tomo-PIV/OH-PLIF technique is demonstrated on a turbulent, transverse, non-premixed reacting jet, and the high-speed dual-plane stereo-PIV7OH-PLIF technique is demonstrated on a turbulent, swirling, reacting jet. Depending on the orientation of vortices, the magnitude of the leading eigenvalue (‖A‖2) for the 3x3 velocity-gradient matrix can be substantially larger than that for the 2x3 velocity-gradient matrix based on stereo-PIV measurements, strongly suggesting the importance of fully resolving the nine-component velocity-gradient tensor upstream of the flame front.