Mixing device

A method of mixing a fluid within a container comprising:

• providing a container;
• locating a mixing apparatus within the container, the mixing apparatus comprising
• a shaft;
• a blade attached to the shaft, wherein the blade includes a variable pitch angle, the variable pitch angle is configured to create axial fluid flow, and radial fluid flow within the container,
• wherein the variable pitch angle is about 60 degrees proximate to the shaft, the variable pitch angle is about 40 degrees at a location between the shaft and an end of the blade, and the variable pitch angle is about 20 degrees near the end of the blade, such that the change in pitch angle from proximate the shaft to near the end of the blade is about 40 degrees;
• a hub located at a proximal end of the shaft;
• and
• a first rib having a convex shape in relationship with a leading side of the blade and a second rib having a concave shape in relationship to the leading side of the blade;
• rotating the mixing apparatus within the container, wherein rotating the mixing apparatus creates an axial flow vector and a radial flow vector combining to create a complex flow;
• and mixing a quantity of the fluid within the container.