Feflo-Urban Cfd Model Evaluation Of The Must Experiment.

Abstract

The focus of the current paper is the Mock Urban Setting Test (MUST) carried out at
Dugway Proving Ground. The MUST experiment was designed to represent an urban complex
of about 120 buildings with symmetric characteristics. Throughout the 19 day MUST experiment,
63 puff and continuous releases were carried out using propylene as a tracer gas. In
order to understand the importance of capturing these spatial variations and unsteadiness, the
multipurpose finite element code FEFLO-URBAN was used to perform a Very Large Eddy Simulation
(VLES) of MUST. One of the continuous release trials (2682353) was selected for a
detailed study. The terrain surface was modeled with geometric roughness in order to circumvent
the problem of lack of turbulence production in the vertical direction. The FEFLO-URBAN
simulations of the concentrations of the passive tracer were compared with the experimental
measurements, resulting in agreement within an order of magnitude about 76% of the time. A
study of sensitivity of the model results to resolution was made with four different mesh resolutions
(500K, 4M, 8.1M and 32M elements). In addition, a sensitivity study concerning the wind
direction inflow boundary condition is presented.