Regardless of whether the propeller is turning to go ahead or astern, what is the water flow pattern in the propeller's arc of rotation called?

Regardless of whether the propeller is turning to go ahead or astern, what is the water flow pattern in the propeller's arc of rotation called?

• A. SCREW
• B. CURRENT
• C. FLOW
• D. SUCTION

Answer: (D)

As the propeller blades move through the water, they pull water toward themselves on the face that meets the water first, creating a region of lower pressure. That inward, low-pressure flow pattern around the arc of rotation is called suction. It appears whether the propeller is turning to move the boat ahead or backward, because the blade motion always produces that inward flow toward the blade in its rotation path. The other terms are more generic and don’t describe this specific inward, low-pressure flow that the blade causes.

As the propeller blades move through the water, they pull water toward themselves on the face that meets the water first, creating a region of lower pressure. That inward, low-pressure flow pattern around the arc of rotation is called suction. It appears whether the propeller is turning to move the boat ahead or backward, because the blade motion always produces that inward flow toward the blade in its rotation path. The other terms are more generic and don’t describe this specific inward, low-pressure flow that the blade causes.