Fix Large MELD Loads At A Few Nodes On TE Spar In UCRM

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Introduction

In the context of computational fluid dynamics (CFD) and structural analysis, the MELD (Mesh-based Elastic Load Distribution) method is a crucial tool for simulating the behavior of complex systems. However, when dealing with large MELD loads at a few nodes on the TE (trailing edge) spar in uCRM (Unified Computational Research Model), several issues can arise. In this article, we will delve into the causes and potential solutions for these problems.

Improved MELD Kernel Parallelization on GPU

One of the recent improvements made to the MELD kernel parallelization on GPU is the ability to run a higher number of nearest neighbors. This enhancement has significantly improved the performance of the MELD method, allowing for more accurate and efficient simulations. However, this improvement also highlights the importance of addressing the persisting numerical issues with the SVD (Singular Value Decomposition) iterative Jacobian.

Numerical Issues with SVD Iterative Jacobian

The SVD iterative Jacobian has been implemented to improve the accuracy of the MELD method. However, this implementation has introduced some small anomalies in the transferred loads (not displacements) of the MELD GPU. These anomalies are not significant enough to affect the overall displacement field, but they do warrant further investigation.

Investigating Problematic Nodes

The uCRM test case has revealed a few nodes with high forces on the TE spar. Most nodes are fine, but one node in particular has a load that is three orders of magnitude higher than the others. This node may be influencing the work or force conservation, which is a concern. To address this issue, the following tasks need to be completed:

  • Investigate the problematic nodes for H and R Jacobians.
  • Recreate the SVD Jacobian as a test case in tests/svd_3x3.
  • Double-check the work and force conservation to see if these few nodes influence the result.
  • Try a higher number of nearest neighbor nodes.
  • Try using an actual aero surf mesh, especially on the TE spar, where the nodes are not as close and the point cloud of nearest neighbors may not be dense enough for a good conditioned covariance matrix at some points.

Force Field Visualization

The force field is shown below at a scale factor of 10. As can be seen, the force profile is not uniform, with some nodes experiencing much higher loads than others.

Force Field at Scale Factor 10

At a scale factor of 1.0, the general force profile is more apparent, with greater load magnitude per node outboard due to the higher mesh density in that region.

Force Field at Scale Factor 1.0

Conclusion

In conclusion, the large MELD loads at a few nodes on the TE spar in uCRM are a complex issue that requires a multi-faceted approach. By investigating the problematic nodes, recreating the SVD Jacobian, and trying different configurations, we can improve the accuracy and efficiency of the MELD method. Additionally, using an actual aero surf mesh and increasing the number of nearest neighbor nodes can help to address the issues with the force field. By addressing these issues, we can ensure that the MELD method provides accurate and reliable results for complex systems.

Recommendations

Based on the analysis and investigation, the following recommendations are made:

  • Investigate the problematic nodes for H and R Jacobians.
  • Recreate the SVD Jacobian as a test case in tests/svd_3x3.
  • Double-check the work and force conservation to see if these few nodes influence the result.
  • Try a higher number of nearest neighbor nodes.
  • Try using an actual aero surf mesh, especially on the TE spar.
  • Visualize the force field at different scale factors to better understand the load distribution.

Introduction

In our previous article, we discussed the issue of large MELD loads at a few nodes on the TE spar in uCRM and potential solutions to address this problem. In this article, we will provide a Q&A section to further clarify the causes and solutions to this issue.

Q: What is the MELD method and why is it used in uCRM?

A: The MELD (Mesh-based Elastic Load Distribution) method is a computational fluid dynamics (CFD) technique used to simulate the behavior of complex systems. It is used in uCRM to distribute loads on a mesh and calculate the resulting forces and displacements.

Q: What are the causes of large MELD loads at a few nodes on the TE spar?

A: The causes of large MELD loads at a few nodes on the TE spar are complex and multifaceted. Some possible causes include:

  • Numerical issues with the SVD (Singular Value Decomposition) iterative Jacobian.
  • Inadequate mesh density on the TE spar.
  • High forces on a few nodes due to the geometry of the system.

Q: How can I investigate the problematic nodes for H and R Jacobians?

A: To investigate the problematic nodes for H and R Jacobians, you can follow these steps:

  1. Identify the nodes with high forces on the TE spar.
  2. Check the H and R Jacobians for these nodes to see if they are contributing to the high forces.
  3. Recreate the SVD Jacobian as a test case in tests/svd_3x3 to see if it is causing the numerical issues.
  4. Double-check the work and force conservation to see if these few nodes influence the result.

Q: How can I try a higher number of nearest neighbor nodes?

A: To try a higher number of nearest neighbor nodes, you can follow these steps:

  1. Increase the number of nearest neighbor nodes in the MELD kernel parallelization on GPU.
  2. Check the force field at different scale factors to see if the high forces on a few nodes are reduced.
  3. Recalculate the work and force conservation to see if the result is improved.

Q: How can I try using an actual aero surf mesh on the TE spar?

A: To try using an actual aero surf mesh on the TE spar, you can follow these steps:

  1. Generate an actual aero surf mesh on the TE spar.
  2. Check the mesh density on the TE spar to ensure it is adequate.
  3. Recalculate the MELD loads on the TE spar using the new mesh.
  4. Check the force field at different scale factors to see if the high forces on a few nodes are reduced.

Q: What are the benefits of using an actual aero surf mesh on the TE spar?

A: The benefits of using an actual aero surf mesh on the TE spar include:

  • Improved accuracy of the MELD method.
  • Reduced numerical issues with the SVD iterative Jacobian.
  • Improved force conservation and work calculation.

Q: What are the next steps to address the issue of large MD loads at a few nodes on the TE spar?

A: The next steps to address the issue of large MELD loads at a few nodes on the TE spar include:

  • Investigating the problematic nodes for H and R Jacobians.
  • Recreating the SVD Jacobian as a test case in tests/svd_3x3.
  • Trying a higher number of nearest neighbor nodes.
  • Trying using an actual aero surf mesh on the TE spar.
  • Visualizing the force field at different scale factors to better understand the load distribution.

By following these steps and recommendations, we can improve the accuracy and efficiency of the MELD method and ensure that it provides reliable results for complex systems.