**Note:**We recommend going through the tutorial in Get started before running this case.

The following is an unsteady aerodynamic shape optimization case for a cylinder

Case: Unsteady flow over a cylinder Geometry: Cylinder Objective function: CD Design variables: 16 FFD points moving in the x direction Constraints: Cylinder volume does not decrease; FFD symmetry wrt z=0 and y=0 Inlet velocity: 10 m/s Mesh cells: 2450 Solver: DAPimpleFoam

Fig. 1. Mesh and FFD points for the Cylinder case

To run this case, first download tutorials and untar it. Then go to tutorials-main/Cylinder_Unsteady and run the “preProcessing.sh” script to generate the mesh:

./preProcessing.sh

We recommend running this case with 4 CPU cores:

mpirun -np 4 python runScript_v2.py 2>&1 | tee logOpt.txt

We ran this case using the SNOPT optimizer. The case ran for 14 major iterations and took about 10 hours. According to “opt_snopt_summary.txt”, the initial CD is 6.5587285E-01 and the optimized CD is 5.3605074E-01 with a percentage decrease of **18%**.
Comparison of the unsteady velocity animation and CD time series between the baseline and optimized designs are shown as follows.

Fig. 2. Time-series of CD for the baseline and optimized design

Fig. 3. Animation of velocity contours for the baseline (left) and optimized (right) designs.