Many fuel tanks incorporate valves to prevent fuel from flowing away from the boost pump or tank outlet when the aircraft is in a high 'g' maneuver.

flapper valves.

Explanation:

According to my research on Aircraft Fuel Tanks, I can say that based on the information provided within the question many fuel tanks incorporate flapper valves. Like mentioned in the question these are implemented to prevent fuel from flowing away from the boost pump or tank outlet. This can happen when the aircraft is experiencing high gravity force/pressure.

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answer; they are called (pebbling);