The revolving impeller carries the fluid with it, inside the converter casing.
The fluid is rotating around the axis of the converter.
This is known as the Rotary flow.
At the same time, centrifugal force moves the fluid outwards, away from the converter axis.
During torque multiplication, the shape of the converter case makes the fluid flow in a circular motion, through the impeller, turbine and stator.
This is known as the Vortex flow.
Combining these 2 fluid flows produces a progressive circular, or spiralling motion.
This is known as the Spiral flow.
In a stalled converter, fluid flows at high velocity from the revolving impeller through the stationary turbine and stator.
This results in a fast moving vortex flow and high torque multiplication.
When the turbine starts to rotate and increases in speed, the centrifugal force on the fluid in the turbine opposes the high velocity flow from the impeller.
This reduces vortex flow and torque multiplication.
At coupling point, the vortex flow of fluid is slight and there is no torque multiplication.
The converter now acts as a fluid coupling.
During acceleration or hill climbing, torque needed by the drive shaft can exceed the engine output torque. As a result, the turbine slows, causing an increase in vortex flow. This again causes torque multiplication.
The converter automatically adjusts its output, within design limits, to meet drive shaft requirements.
