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An Improved Process for Mapping Aeroelastic Loads Across Structural Meshes

An Improved Process for Mapping Aeroelastic Loads Across Structural Meshes. Douglas J. Neill, Jack F. Castro, Patricia E. Jones MSC.Software Corporation. Agenda. Typical loads processes and issues Proposed process The ADB/AEDB collections Methodology Results Summary. CFD or WT.

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An Improved Process for Mapping Aeroelastic Loads Across Structural Meshes

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  1. An Improved Process for Mapping Aeroelastic Loads Across Structural Meshes Douglas J. Neill, Jack F. Castro, Patricia E. Jones MSC.Software Corporation

  2. Agenda • Typical loads processes and issues • Proposed process • The ADB/AEDB collections • Methodology • Results • Summary

  3. CFD or WT “Panel Code” An Aeroelastic Loads Process Critical Loads Survey Stress Group Other tools Rigid Aero Loads AIC Corrected Loads On Internal Loads FE “Flexibility” FE Aeroelastic Solver Loads Transfer Tools Corrected Loads On Coarse FE

  4. Issues with Typical Process • 2 common approaches to transfer coarse loads to the internal loads model • Smearing component integrated loads • Heuristic • Prone to error • Slow, engineer-in-the-loop • Loss of balance during smear • Re-balancing is itself heuristic and slow • “Common Loads Points” • Difficult to coordinate • Tends to degrade FE model quality • Degrades computational performance

  5. Issues with Typical Process • The outlined approach works, but it’s a problem in many organizations • Too slow • Cannot keep up with critical loads survey needs • Too easy to make mistakes • Cannot be repeated reliably • Too many engineer-in-the-loop heuristics • Too easy to lose the association of loading event (on coarse FE) to critical load (on internal loads FE).

  6. The Proposed Process • “Remember” the elastically corrected loads on the aerodynamic mesh • As MSC.FlightLoads does now on the ADB and AEDB • Re-evaluate the mapping of these load increments onto the new structural FE • Re-use standard coupling methods • Gather the loads onto an updated AEDB for use downstream • Downstream tools don’t realize a two-step process was applied upstream

  7. CFD or WT “Panel Code” The Proposed Process Critical Loads Survey Stress Group Other tools MSC.FlightLoads “ADB” MSC.FlightLoads “AEDB” (Internal Loads FE) Aeroelastic Solver Can be applied recursively New Mapping Tool “Flexibility” FE Spline To New FE MSC.FlightLoads “AEDB” (Coarse FE) “Internal Loads” FE

  8. The ADB/AEDB Collections • The ADB contains the aerodynamic model • Mesh topology • Rigid aerodynamic loads • The AEDB contains the ADB and “flexible increments” (FI) • FI include forces and displacements • Forces arise from rigid and from the displacements passing thru the AIC • All forces (except rigid inertial) are on both the aero and structural meshes • These are “unbalanced”, but all balanced states are a linear combination

  9. Mapping Methodology • From equations of motion for static aeroelasticity 1. rigid load + AIC  deformation 2. AIC * deformation  elastic increment force 3. rigid load + elastic force  corrected load • From 2 on the aero mesh, we map to the new structural FE via DMAP alter (for now) • From these loads, a statics solution on new FE yields deformations on new FE • Restore inertial loads (rigid) from new FE • Proceed with normal AEDB creation to complete the AEDB collection

  10. Advantages • No heuristic methods • Two mappings of the same kind • Repeatable • Recursively applicable • Full vehicle balanced loads are immediately available • Trim on the new structure • Using mass of the new structure • BUT using inertial aeroelastic correction of the original FE • FASTER for superior FIDELITY

  11. An Example The built-up structure The common aero mesh The beam-stick structure

  12. Cases • All analyses represent a 1g Level Flight Trim at M=0.4, Sea Level • 3 variants were run • Aero + Beam FE • Aero + Built-up FE • Starting with Aero + Beam, Map to Built-up FE and then trim • Model Sizes • Aero: 554 Boxes • Beam FE: 141 nodes • Built-up FE 3171 nodes • All runs were made on NEC laptop, Pentium II

  13. Beam FE Solution Built-up FE Solution Beam Solution Mapped to Built-up ANGLEA 1.740 degrees 1.702 degrees 1.740 degrees SIDES 0.300 degrees 0.338 degrees 0.211 degrees RUDDER -0.552 degrees -0.623 degrees -0.603 degrees ELEV 8.311 degrees 8.159 degrees 8.310 degrees AILERON(s) 0.450 degrees 0.292 degrees 0.463 degrees CPU (ADB/Mach) 13.1 13.1 0 (taken from ADB) CPU (Structural) 22.2 32.3 29.1 CPU (AEDB/Mach&Q) 13.4 128.8 16.7 CPU (Total) 49.0 174.4 46.5 Results and Timing Summary

  14. 1/1 2/2 2/6 5/30 Number of Mach/M-Q Pairs Results and Timing Summary

  15. Qualitative Results Trimmed Forces On Aero Mesh Trimmed Forces On Beam Mesh

  16. Qualitative Results (cont.) Trimmed Forces On Aero Mesh Trimmed Forces On Built-up Mesh

  17. Zoom into Tip Area Quantitative Results

  18. Quantitative Results

  19. Summary of New Approach • Costs • It approximates the inertial aeroelastic effect • It requires two spline models • Benefits • It is computational (not heuristic) • It preserves full-vehicle balance • It is faster (process) and uses less CPU, too • CPU savings accumulate as more Mach/Q pairs are used • It creates fully reusable databases • easy to generate new trim states • able to recursively map the “mapped” solution to other models

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