| CPC E21B 34/16 (2013.01) [E21B 34/14 (2013.01); E21B 34/066 (2013.01); E21B 34/10 (2013.01); E21B 2200/05 (2020.05)] | 20 Claims |

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1. A system comprising:
a tubing string deployable in a wellbore to transport a wellbore fluid; and
a flow valve couplable to the tubing string, the flow valve comprising:
a flapper positionable to control the wellbore fluid transportable through the tubing string, the flapper being adjustable between an open position and a closed position; and
a flow tube positionable in the tubing string, the flow tube comprising a downhole end having a curvature to slow a closure rate corresponding to adjusting the flapper from the open position to the closed position, wherein the curvature of the downhole end corresponds to a roulette curve.
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