F-18C JDAM Weapon Separation

The F-18 JDAM weapon separation problem originated in 1998 as a technical challenge to the CFD community. Our original work on this and the problem definition is documented in AIAA 1999-0122 A Solution on the F-18C for Store Separation Simulation using Cobalt60. In 2007, the first version of the Cobalt Overset module was used to simulate the flow. The same job inputs were used for the V6 and V7 solutions discussed below.

In the F-18 JDAM weapons separation problem run on 1080 processors, the time to set-up the flow (1,000 iterations) was reduced by 80%.

Flow Set-Up F-18 JDAM Cobalt v6 Cobalt v7
Iterations 1000 1000
Grid Assembly 5.871 3.842
Flow Solution Rate 3.56749 0.62568
Post-Processing 11.11 5.833
Total 3663.04 705.5

Overall solution time for the 200 iterations to compute the motion of the weapons drop using 6DoF was reduced by 33% on 1080 processors.

F-18 JDAM Motion 6DoF Cobalt V6 Cobalt V7
Iterations 200 200
Grid Assembly 5.5-6.0 2.81
Flow Solution Rate 14.587 4.3068
Post-Processing 207.28 128.56
Total 3025.3 1989.41
Posted in Overset, Solutions.


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