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Force (N) Force (N) 350000 300000 250000 200000 150000 100000 50000 0 0 5 10 15 20 25 30 35 Displacement (mm) Figure 3.26: Plot of reaction force vs. the prescribed motion 100000 80000 y = 6657.3x - 4687.7 R² = 0.9951 60000 40000 20000 0 0 2 4 6 8 10 12 14 Displacement (mm) Figure 3.27: Plot of force vs. displacement, for displacements less than 15 mm The stiffness and damping values for the suspension of the F800 truck have yet to be obtained. Once these are obtained, the gains for the controller can be found. Once the gains are found, the controller can be evaluated in Matlab-Simulink, and further modification may be made in order to find the most suitable values for the gains. A sub-routine in LS-DYNA will then be created to mimic the operation of TRACC/TFHRC Y1Q3 Page 70
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
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ANL/ESD/11-39 Computational Mechani
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ANL/ESD/11-39 Computational Mechani
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Computational Mechanics Research an
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3.3.4. Simplifying Assumptions ....
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Figure 2.22: Velocity distribution
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List of Tables Table 2.1: Boundary
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experiments at TFHRC continued. A m
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2. Computational Fluid Dynamics for
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( ) ( ) (2.8) where A 0, A 1, and n
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efine the rate function to improve
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The objective of this work is to de
Page 23 and 24: 2.3.2. Mesh Refinement Study As det
Page 25 and 26: Table 2.2: Details of the various m
Page 27 and 28: indicating the surface averaged vel
Page 29 and 30: Figure 2.13: Line probes created at
Page 31 and 32: In Figure 2.15 the velocity and the
Page 33 and 34: Mesh 1 Mesh 2 Mesh 3 Mesh 4 Mesh 5
Page 35 and 36: Figure 2.20: Dimensional details of
Page 37 and 38: Figure 2.22: Velocity distribution
Page 39 and 40: Figure 2.25: CFD velocity contour p
Page 41 and 42: Figure 2.27: CFD velocity contour p
Page 43 and 44: Conclusions for Comparison with Exp
Page 45 and 46: 3.1.1.1. Approach To date, an initi
Page 47 and 48: Figure 3.4: Sampling domain [3] A c
Page 49 and 50: present. In addition during the sum
Page 51 and 52: For each level, the figures below s
Page 53 and 54: 0.0 sec 0.5 sec 1.0 sec 1.5 sec 2.0
Page 59 and 60: 3.2.1. Vehicle Stability under High
Page 61 and 62: ̇ = steer angle These equations co
Page 63 and 64: ̈ With the success to the above an
Page 65 and 66: command. This requires the creation
Page 67 and 68: Figure 3.17: FEM Model of a Ford F-
Page 69 and 70: 3) Chen, F. and Chen, S., “Assess
Page 71 and 72: 75 50 25 Force (N) 0 -25 -50 -75 -1
Page 73: while the passive system has fixed
Page 77 and 78: 4. Build a shell container with the
Page 79 and 80: Figure 3.32 Comparison of the initi
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