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.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.