Theoretical study. Disks are one above the other. Turn at same rotationnal speed [itex]w[/itex]. Is it possible to choose good parameters for: - density - radius - rotationnal speed - position of d3/gas: d3 in disk1 at radius R1, d3 in disk2 at radius R2, gas in disk1 at radius R2, gas in disk2 at radius R1 - size of disk For have forces like I drawn on the system ? NB: disk must be big enouh for have gravity effect (1000 km for example). Center of rotation is supposed fixed.