Turbomachinery Load-Mapping Verification Example
Illustrative example verifying a CFD-to-FEA pressure load transfer by comparing total force and moment before and after mapping.
Problem
A CFD analysis of a turbine blade reports a total tangential force of 850 N and a total axial force of 320 N on the blade surface. After mapping the CFD pressure onto the FEA mesh, the FEA applied loads are checked. The FEA reports a tangential force of 842 N and an axial force of 314 N. Verify the load mapping.
Given
- CFD tangential force = 850 N
- CFD axial force = 320 N
- FEA tangential force = 842 N
- FEA axial force = 314 N
Step 1 — Tangential force error
Error_t = (FEA - CFD) / CFD = (842 - 850) / 850 = -8/850 = -0.94%
Step 2 — Axial force error
Error_a = (FEA - CFD) / CFD = (314 - 320) / 320 = -6/320 = -1.88%
Step 3 — Assessment
The tangential force error is 0.94% and the axial force error is 1.88%. Both are within a typical acceptance tolerance of 2%. The mapping is acceptable. The small under-prediction (negative error) is likely from interpolation loss at the leading and trailing edges where the pressure gradient is high and the FEA mesh is coarser than the CFD mesh.
Result
The load mapping is verified — the force errors are within 2%. The FEA model correctly represents the CFD aerodynamic loads. If the errors exceeded 2-5%, the mapping method or mesh density should be reviewed.
Assumptions and limitations
- The verification checks total force only — local pressure distribution errors are not detected
- The moment should also be checked — a force match with a moment mismatch indicates a distribution error
- The tolerance (2%) is typical — the actual tolerance should be specified in the analysis plan
- The CFD force itself should be verified against test data or an independent CFD run