The Twirl tool 
rotates processed pixels around the center of the cursor into a spiral.
Using the Twirl Tool(hover the mouse over the picture to see the original image)
The basic tool settings are shown in the Tool Options panel above the Image Window or by right-clicking on the image. To display the full list of parameters, press the tool icon in the Tool Options panel or use the F5 key. To specify the parameter settings, enter a numerical value in the parameter’s field or use the slider.
Size (20-500). The size of the brush.
Hardness (0-100). The softness of the tool’s edge. The effect is strongest in the center of the brush and lighter at the edge. Increasing the value intensifies the effect at the edge of the brush.
Strength (1-100). The strength of the effect. The higher the value, the stronger the changes are.
Rate (0-100). Frequency of application of deformations.
Clockwise. When the check-box is enabled, the twirling is clockwise, when it's disabled, the twirling is counterclockwise.
Click the Default button to reset all settings to their default values.