RESUMEN
A technique to create a localized pressure perturbation by laser heating the absorbing gas inside the flow field is described. The effect of the laser-induced pressure pulse is to trigger the development of turbulent structures, which then evolve in time. With such external perturbation, the nozzle gas concentration is measured simultaneouslyat 10(4) points within a plane intersecting the flow by using two-dimensional imaging of the Lorenz-Miescatteredlight from aerosols seeded in the flow. The instantaneous and time-averaged spatial distributions of the perturbed flow field are presented as is the rms fluctuation of the concentration.
RESUMEN
A new technique has been developed that permits simultaneous two-dimensional mapping of two scalar components (e.g., species and temperature) in a turbulent reacting flow. The technique uses two optical multichannel analyzers, each of which detects light scattered by a different mechanism (e.g., Rayleigh and Raman) and thus provides different information. The technique has been applied to both premixed and nonpremixed flames, and results are reported for each. The simultaneous information obtained in these experiments should provide new data on the interaction of turbulence and combustion in these chemically reacting flows.
RESUMEN
The 3-D measurement of the gas concentration in a photoacoustically forced gas jet is described. A pulsed laser focused onto a laminar gas flow was used to trigger a localized disturbance which evolved with time. After a fixed time delay, the gas concentration in a 2-D cross section of the jet was measured by recording Rayleigh scattering from a second laser used to illuminate a thin sheet intersecting the flow. A series of these 2-D measurements made at the same time delay resulted in a full 3-D mapping of structures within the flow. Computer graphics enabled the subsequent reconstruction and visualization of the 3-D surfaces of constant concentration as well as the magnitude of the concentration gradient on such surfaces.
RESUMEN
The first reported instantaneous two-dimensional map of the fuel-gas concentration in a turbulent diffusion flame using quantitative Ramanography is described. Details of the experimental configuration are presented, along with data obtained in both cold flows and turbulent reacting flows.