Mistakes for the first case setup

Using simpleFoam, an image is obtained as shown in Fig. 1.

As you can see, the fingers are experiencing high pressure. At some regions at the back of my hand, you can see some blue areas. Those regions are suction zone. I also use streamtrace visualization technique for surrounding flow identification. As you can see, there is a trailing edge vortex forming at the far wake.

However, if we look at the drag history shown in Fig. 2. You will notice that the majority of the time, drag is in negative values, which does not make sense.