A Post-processing Algorithm for Cfd Dispersion Error Annihilation
A class of transient computational uid dynamics (CFD) solutions is especially prone to dispersion error yielding moderate to high distortion. Speciically, the universally intrinsic zero phase velocity for \22x" waves induces an error cascading to smaller wave number modes that appear as mesh scale solution oscillations. Artiicial viscosity and/or ux correction operators can diiuse this error mode, but may produce unacceptable amounts of dissipation in multidi-mensional embodiments. In this paper, a discrete solution reconstruction (RCN) procedure is developed and validated for monotonicity enhancement of dispersed (poor quality) 1-D, 2-D and 3-D solutions produced by nite diierence and nite element CFD algorithms. Reconstructed results for the veriication 1-D wave propagation, the benchmark 2-D rotating cone and the validation 3-D room species mass fraction contamination document that RCN can yield an absolutely dispersion-free reconstruction of any algorithm solution.
CFD experiment characterization of airborne contaminant transport for two practical 3-D room air flow fields
Abstract With the increasing concern for, and focus on, indoor air quality, determination of the distribution of airborne contaminants within rooms becomes of great interest. Computational fluid dynamics (CFD) techniques offer a means for simulation of contaminant transport processes, with quantitative richness of detail rarely possible in laboratory testing. Results of such “CFD experiments” are documented herein for two practical, low turbulence-level, thermal room air flow fields. The supply flow is tagged with a distinguishable species, and the resulting time-dependent concentration evolution throughout the room is predicted. The simulated full-scale room air flow field Reynolds numbers are 15,000 and 30,000, the Archimedes number ranges from 0.83 to 4.3, and simulation turbulent Schmidt number ranges an order of magnitude.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.