Proposed modelling approach for the preliminary design stage in bridge engineering
| No. | Step | Description |
|---|---|---|
| 1. | Defining the geometry | The geometry is simplified by removing small-scale features such as curbs and steps Barriers should be included with the actual porosity level; however, the number of holes in the barrier may be varied with negligible effect on the results |
| 2. | Building the computational grid and model | The computational domain is divided in such a way that cell size can be conveniently controlled in the areas important for the aerodynamic profile of the deck. If the end goal is producing the FSI results, care should be given to the regions that will undergo re-meshing. Re-meshing should be done away from the regions with small cell sizes RANS-based simulation should be employed with the SST turbulence model. Mesh dependency study and the verification of the y+ value should be done. It is noted that these should be undertaken for the highest Reynolds number that will be simulated |
| 3. | Performing simulations on the static model | Static force coefficients The results may be compared to those estimated by the design codes to verify for any inconsistencies. Possible issues with the divergent response of the cross-section should be investigated by applying the Den Hartog criterion. Should these be identified, the deck shape should be modified, for example by incorporating different leading-edge geometry. The process should be repeated until no issues with the divergent response are identified Strouhal number estimate Transient analysis can provide estimates of the Strouhal number, which in turn provides the critical wind velocity for vortex shedding. It should be noted that this value may be different to the one obtained for the vibrating system |
| 4. | Performing simulations on the dynamic model | Prescribed motion model This analysis will yield useful results should a damping sensitivity analysis be of interest. A range of flow velocities and displacement amplitudes should be defined over which the analysis is to be run. Care should be given to the time needed for the generation of a single data point and an estimate of the total wall clock time needed should be made Free-to-oscillate model If the damping value is set with little possibility for variation, a free-to-oscillate model should be developed and simulations on it performed for a range of flow velocities. The starting wind velocity should be the critical wind velocity identified from the static model. Should the deck experience low VIV, a model with an initial displacement kick should be tested to verify the possible manifestation of the motion-induced vortices |
| No. | Step | Description |
|---|---|---|
| 1. | Defining the geometry | The geometry is simplified by removing small-scale features such as curbs and steps |
| 2. | Building the computational grid and model | The computational domain is divided in such a way that cell size can be conveniently controlled in the areas important for the aerodynamic profile of the deck. If the end goal is producing the FSI results, care should be given to the regions that will undergo re-meshing. Re-meshing should be done away from the regions with small cell sizes |
| 3. | Performing simulations on the static model | |
| 4. | Performing simulations on the dynamic model |
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