Hello everyone! I am running a 3D simulation of UAV(Unmanned Aerial Vehicle) at Mach ~0.04. However when i plot the cd vs alpha(-15 to 15) im getting unrealistic values. Could anyone look into it? Would be a great help! For example im getting low Cd at high alpha. Attached below are the results. Runs and their corresponding angle of attack are as: Boundary conditions are velocity inlet, pressure outlet, wall at the uav surface free stream on the 4 remaining enclosure faces
I checked your project, and I found that the runs look stable. The result also seems to correspond really well with the boundary conditions that you set.
The problem is that you are not plotting “cd vs alpha (-15 to 15)”, since the x-axis is not the alpha it self, rather the Run number. In your parametric Boundary Condition for Velocity inlet you defined an alternating positive-negative value for the y-velocity (see image), which then if you plot with x-axis as the Run number this would be cd vs alpha (0, 1, -1, 2, -2, 3, -3…), and in that case the plot seems to be physically make-sense.
Additionally, you use a moving wall as your side walls, however you specify a constant velocity of 13.89 m/s in x-direction (see image), this creates a non physical region around the edge connecting the side-walls and the inlet, making the solution less accurate. I would advise you to use slip-wall instead.
