COANDA DRONE FLOW SIMULATION CFD

Hi everyone, my team and I are working on the design and production of a coanda-effect drone that will also be able to move. We're at the simulation stage, but we have several concerns:
1-We're trying to find the optimum shape that gives the most lift ie we're varying the radii of the fillet.
2- We want to have the total lift of the drone in simulation.

What we get:
1-negative lift, and we don't understand why
2-the current lines don't follow the exact curvature of the drone as required by the COANDA application

Please let me know if you can help me with this simulation so that we can achieve the desired objectives.
Perhaps a zoom exchange would be ideal.

1 Answer

An obvious but necessary question:
Did you apply surface roughness in the simulation?