It helps if you understand Bernoulli's theory which states that when a fluid enters a constriction or a Narrow passage - Pressure and Volume decreases while Velocity Increases. Like putting pressure on a hose pipe when watering your garden;the water comes out faster with less volume on the constriction but after the narrow passage the volume and pressure increases while the Speed/Velocity Decreases. Think of the turning Prop as that Narrow passage where Air Velocity is High but low pressure and Low Volume. As the Air moves further Rearwards the Velocity Decreases and the Volume Increases with Pressure. Therefore, Large Mass of Air at Low Velocity.

thank you very much my friend.