Stochastic modeling and simulation of turbulent flows with chemical reactions

Stochastic methods and Monte Carlo numerical techniques are used to estimate the evolution of velocities, temperatures and mean concentrations in flow with and without chemical reactions, and of dispersion parameters (variance and higher order moments). Predictions are compared with experimental data and with results obtained using direct numerical simulation. New techniques have been developed and implemented to solve this type of flows.

Currently, these methods are combined with Large Eddy Simulation (LES) to obtain a more accurate description of the flow evolution.


Direct numerical simulation of mixing / reaction in turbulent flows

Pseudo-spectral methods are used to numerically solve the velocity field and inert or reactive scalars in homogeneous, isotropic turbulence. The obtained results are used as experimental data to model and calculate turbulent reacting flows. Results are also used to study the velocity and scalar topological behavior.


Flow computation with finite element methods

Development of stabilized finite element methods to calculate incompressible and compressible flows, both laminar and turbulent. The methods are also extended to free surface flows.


Application of artificial neural networks in chemical kinetics

Artificial neural networks are applied to the analysis, reduction and representation of complex thermo-chemical systems.


Hydrodynamic cavitation to induce chemical reactions

Experiments are combined with numerical simulations of the bubble dynamics, temperature fields and chemical species concentrations when subjected to the very high temperatures and pressures typical in the bubble collapse process. The final objective is to be able to apply hydrodynamic cavitation to treat sewage and other wastewaters.


Experimental studies in particle/droplet laden natural and forced jets

Experiments are performed in axisymmetric jets with particles/droplets dragged by air to characterize and control the different phenomena responsible for dispersion and mixing of the particles in the flow. Research includes measurement of mean values, variance and correlations of the velocity components for both phases, simultaneous determination of velocity and particle size, and computation of local mass flow rates. Measurements are obtained with a phase-Doppler anemometer (PDA), particle image velocimetry (PIV), and flow visualization. Free, forced and swirling jets have been analyzed.


Development of optical diagnostic techniques for turbulent multiphase flows

Improvement and adaptation of velocimetry and dynamic granulometry techniques to be used in multiphase flows. Some of these developments include:

  1. Tomographic determination of droplet/particle size distribution applying laser diffractometry.
  2. Numerical analysis of the detected signal in laser-Doppler LDV or PDA systems. Development of calibration and correction relations.
  3. Simplified scalar model for optimized configurations in PDA systems.
  4. Determination of mass flow rates with Phase Doppler anemometry.
  5. Development and application of techniques to measure the three velocity components in a complete flow section or volume. Stereo- and tomo- PIV.


Liquid atomization and droplet formation

Experiments are performed to study basic atomization phenomena, including pressure, gas-assisted, or other alternative methods (for example ultrasonic atomization). Both planar liquid sheets and axisymmetric configurations have been considered. Influence of different parameters (pressure, flow rate, viscosity, surface tension) has been analyzed. Linear instability analysis considering liquid and gas viscosities have been completed.


Nozzle design and characterization

Characterization of atomizing nozzles, either commercial or designed in LITEC, analyzing parameters such as pressure and flow rate, droplet mean diameter and droplet size distribution, spray angle, droplet velocity and spray structure. Nozzle design for specific purposes, for example for high viscosity liquids, or for microscopic droplet generation.