Computational Mechanics Research and Support for Aerodynamics ...

experiments at TFHRC continued. A methodology to use transient CFD scour analysis itself to iteratively
refine entrainment function parameters to match experimental results is proposed. Using the CFD
software to tune empirical functions for the scour physics models is expected to produce more robust
models for CFD analysis than those that are determined outside of the CFD framework. Work reported
under the USDOT Y5Q3 report has been nearly completed on scour model enhancements needed to
displace the bed in a direction normal to the bed instead of simply vertically, to account for the effect of
bed slope on the scour rate, and to include a simple sand slide model to keep the bed slope less than or
equal to the angle of repose of the sediment. These scour model enhancements will be incorporated
into future scour modeling work.
Culvert analysis focused on determination of detailed velocity distributions to improve design
procedures for culverts that need to allow for fish passage continued. A mesh refinement study for
22.86 cm (9 inch) flow depth cases was completed, and a 5 mm base mesh size with a 67% refinement in
the corrugated region is recommended for CFD analysis of these cases in the TFHRC culvert test matrix.
In another study, culvert modeling results were compared to experimental data obtained in two ways
using Particle Image Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV). Differences between
modeling results were within the range obtained with the two experimental methods and the results
appear to be good enough to use for engineering analysis of culvert flow to improve the design
procedures that allow for fish passage under low flow conditions.
1.2. Computational Multiphyics Mechanics Summary
Computational Multiphysics Mechanics Research for Turner-Fairbank Highway Research Center
continued in the following four areas: (1) multiphysics simulation of salt spray transport; (2) simulation
of a semi-trailer truck passing through a bridge underpass; (3) vehicle stability under high wind loadings;
and (4) electromagnetic shock absorber for vehicle stability under high wind conditions. In Area 1, a
literature search identified previous research performed at Lawrence Livermore National Laboratory
from which estimates of the spatial distribution of the salt spray created by truck tires and the resulting
density of the airborne salt water cloud behind the truck were extracted.
In Area 2, simulations were performed to study the motion of air as a semi-trailer truck approaches and
passes through a bridge underpass and, in particular, to evaluate the transport of tire-generated salt
spray onto the underside of bridges made from weathering steel. Marker particles at several levels
above the roadbed were identified in the model and their motion as the truck approached and passed
through the underpass was studied. In the direction of vehicle travel, only the particles near the top of
the truck were found to reach the lower portions of the bridge support beams. This implies that should
salt-laden air be at this level – which is implied from the Livermore research – then the salt spray could
reach at least the flange level of the support beams. In the direction perpendicular to travel, it was
found that as the truck approaches, the air from the roadway is pushed into the space between the
beams, and as the truck exits, the air reverses direction and tends to move into the space vacated by the
truck. TRACC staff and NIU staff (professor/student) continued working on two Wind Engineering
projects.
TRACC/TFHRC Y1Q3 Page 9