Abstract: Systems and methods for activating a down hole tool in a wellbore. A piston is moveable from a first position to a second position for activating the down hole tool. The piston includes a first side exposed to a first chamber, and a second side exposed to a second chamber. A rupture member has a first side exposed to the first chamber and a second side exposed to a third chamber. The rupture member is configured to rupture when a pressure differential between the first chamber and the third chamber reaches a predetermined threshold value, at which point the rupture member allows fluid communication between the first chamber and the third chamber. When the rupture member is intact, the piston is in the first position, and when the rupture member ruptures, the piston moves to the second position and activates the down hole tool.

Abstract: A fluid flow control device disposable in a bore can include channels that can direct fluid flow based on one or more properties of the fluid more robustly. The channels may include a side channel between two other channels. The side channel can allow fluid flow to affect fluid flowing in one of the channels. Devices according to some aspects can differentiate between fluids having close, but different, properties and direct the fluid accordingly. Examples of fluid properties based on which the device can direct fluid include fluid density, fluid velocity, fluid viscosity, and Reynolds number of the fluid flow.