Computational Mechanics Research and Support for Aerodynamics ...

the controllable EMSA. Simulations will be performed to compare the performance of the EMSA
suspension system with the passive suspension system.
3.2.2.4. References
1) Gupta, A.; Jendrzejczyk, J. A.; Mulcahy, T. M.; Hull, J. R.; “Design of Electromagnetic Shock
Absorbers”, International Journal of Mechanics and Materials in Design, Vol. 3, No. 3, 2007, pp.
285-291.
2) Gao, H.; Lam, J.; Wang, C.; “Multi-objective Control of Vehicle Active Suspension Systems Via
Load-dependent Controllers,” Journal of Sound and Vibration, Vol. 290, 2006, pp. 654-675.
3) Du, H.; Sze, K.Y.; Lam, J.; “Semi-active H[infinity] control of vehicle suspension with magnetorheological
dampers”, Journal of Sound and Vibration, Vol. 283, No. 3-5, 2005, pp. 981-996.
3.3. A Coupling of CFD and CSM Codes for Scour Shape Prediction
3.3.1. Introduction
As detailed in Section 4 of the TRACC Y5Q3 Progress Report, TRACC CFD researchers have been
investigating approaches to simulate the formation of scour holes and have been enhancing the
simulation models. A current area being addressed is the unreasonably steep slopes of the scour walls
that are produced by the STAR-CCM+ CFD program when a sand slide model is not included.
A very simple sand slide model that does not include soil mechanics models is descriped in the TRACC
Y5Q3 report. A second approach to accounting for the effects of sand slides during scour hole formation
in non-cohesive sediments is to model the soil mechanics using the structural mechanics software LS-
DYNA to compute sand slides. In this approach the CFD simulation calculates soil erosion around the pier
while the CSM simulation calculates the slope stability and final slope shape after the material
undergoes a sand slide.
3.3.2. Scour Slope Stability Based on Soil Mechanics
In the CFD simulations based on the described approach most of the soil material is eroded in the close
proximity to the pier. The deformations tend to be localized and lead to a very steep slope in the scour
hole. Comparison to the limited experimental results indicates that this is not the case. Depending on
the size of the particles in the river bed, the entrained sand would either be transported away from the
scour hole or would be deposited at the bottom of it. Additionally localized erosion of the bed material
would cause slope instability and the material would slide creating slopes with the base angle close to
the angle of repose for the sand.
In the approach presented here the second phenomenon (sand slide) is addressed through the coupling
of the STAR-CCM+ computational fluid dynamics solver with the LS-DYNA multiphysics solver. The soil is
treated as a deformable body subject to gravitational forces in the Multi-Material Arbitrary Lagrangian
Eulerian (MM-ALE) approach.
TRACC/TFHRC Y1Q3 Page 71