# Bulk carrier hullΒΆ

**NOTE**: Before running this case, please read the instructions in NACA0012 airfoil incompressible to get an overall idea of the DAFoam optimization setup.

This is a hydrodynamic optimization case for a bulk carrier hull (JBC). The summary of the case is as follows:

Case: Ship hydrodynamic optimization with self-propulsionGeometry: Japan Bulk Carrier (JBC) hullObjective function: Weighted drag and wake distortionDesign variables: 32 FFD points moving in the y directionConstraints: Volume, thickness, symmetry, and curvature constraints (total number: 83)Mach number: <0.01Reynolds number: 7.5 millionMesh cells: 40KAdjoint solver: simpleDAFoam

The configuration files are available at Github. To run this case, first source the DAFoam environment (see Tutorials). Then you can go into the **run** folder and run:

```
./Allrun.sh 4
```

The optimization progress will then be written in the **log.opt** file.

For this case, the optimization converges in 20 steps, see the following figure. The baseline design has C_D=001773 and the optimized design has C_D=0.001692.

We use simpleDAFoam and ignore the free surface. We generate the unstructure mesh using `snappyHexMesh`

. The mesh and FFD setup is as follows.

The runScript.py is written for multi objectives configurations where we can combine drag and wake distortion. In this case, the weight for wake distortion is set to be 0. We need to use more refined mesh to obtain an accurate wake distortion value. We also have a curvature constraint for this case.