Several functional enhancements have been added to the Solver. These are a mix of physical models and performance improvements.
The Heat Exchanger material device is another new physical model that required Solver development. Because it is classified as a Material, it is described in the Materials What's New topic.
Surface Erosion
One of the leading causes of equipment failure in harsh flow environments is surface erosion due to high-velocity liquid flow impingement. Understanding where erosion may occur is essential for designing for greater durability and longer service life.
Contaminants such as sand, quartz, and fly ash cause material erosion as they recirculate and impinge against valves and other machinery. In the oil and gas industry, engineers evaluate this Ductile erosion based on the "mesh size" of the particle. The mesh size is the largest particle size that is likely to be found in a system. This phenomenon is also referred to as "washout."
Autodesk Simulation CFD uses Lagrangian particle tracking with the Edwards Model to compute erosion. A low particle concentration assumption (not a slurry erosion model) is employed, and results are presented as a scalar result quantity. This facilitates design comparison, and removes the guesswork from interpreting erosion predictions.
The erosion model uses angle of attack bounce data and the Brinell material hardness to compute the material volume removal rate. This approach qualitatively identifies areas subject to erosion. It illustrates the relationship between the flow and erosion trends, which can lead to erosion reduction through design improvements.
Scenario Status Icons
To better communicate the current state of the simulation, status icons are displayed with the Scenario branch of the Design Study bar. These icons correspond to different states of the simulation process:
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Queued |
The scenario is in the Queue. One or more scenarios are scheduled to run before this one. |
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Running |
The simulation is meshing or solving. |
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Completed |
The simulation is finished, but results have not been downloaded from the solver computer. |
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Failed |
The simulation did not run. This can be caused by several factors. |
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Canceled |
The simulation did not run due to user-requested termination. |
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Upload |
The simulation model is transferring to the solver computer. |
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Download |
The results from the completed simulation are returning from the solver computer. |
Notes:
- Simulations that have been run display a status icon (Completed, Failed, or Canceled) before they are activated and results are loaded into the Graphics window.
- Status icons are not shown for simulations that have not been started.
- No Status icon is displayed after results are downloaded into a completed simulation.
Performance Improvements
Faster computational performance, shorter simulation times, and improved process efficiency are three standing objectives in the evolution of CAE Solver technology. These were all realized in Autodesk Simulation CFD 2013 through the following enhancements:
Broader numerical parallelization coverage across physical models
Autodesk Simulation CFD is composed of hundreds of foundational algorithms that compute all aspects of the numerical model. These range from basic matrix operations to material models such as distributed resistances and internal fans. The scope of solver parallelization in Autodesk Simulation CFD 2013 has been expanded to encompass nearly all of these algorithms, thereby expanding High Performance Computing (HPC) coverage to nearly every physical model in the software. The result is improved performance for a wider range of CFD analysis types.
Reduced message passing
Operational efficiency was improved by reducing communication levels between the "master" and "slave" nodes. This empowers the "slaves" with greater autonomy, allowing each "slave" node to keep track of more information than in previous versions. The result is better computational performance with more uniform distribution of work across computing cores.
Radiation Model Performance Improvements
In previous versions, the maximum amount of memory (RAM) available to the view factor calculation was 2 GB. This limit prevented accurate calculation of reciprocity for very large models that contained thousands of surfaces.
The default amount of memory currently available for radiation view factor calculation is 4 GB.
To increase this amount, modify the value for the rad_matrix_size flag in the Flag Manager . The argument is the amount of RAM in megabytes. For example, to set the limit to be 10 GB of RAM, specify a value of 10000.
To improve the performance of the view factor calculation (as well as to reduce memory use), a face clustering scheme has been implemented. This scheme reduces the effective number of view factor faces by grouping element faces belonging to the same surface into larger polygons. The result is faster view factor forming, better reciprocity enforcement, and faster solution of the radiosity matrix at each iteration.
Radiation face clustering occurs automatically, but can be controlled by a flag, ClusterFaces, in the Flag Manager.
New Advection Scheme
A new advection scheme, "ADV 5," has been introduced into the Solver.
ADV 5 is a more stable variation of ADV 2, the Petrov-Galerkin advection scheme. It is suitable for all application types recommended with ADV 2, but typically produces more globally conservative results. ADV 5 has demonstrated improvements over ADV 2 in the following areas:
- Accuracy of recirculating and secondary flows
- Pressure drop prediction
- Natural convection stability
- Compressible flow accuracy and stability
- Rotating (turbomachinery) and Motion accuracy and stability
- Energy balance stability