To apply a 2D fluid texture to an object
Maya creates a 2D fluid container (fluidTexture2DShape node) and a place2DTexture node.
The surface shader uses the color at the 0 position on the ramp. The Density values use the colors corresponding with the position on the ramp.
To apply a 3D fluid texture to an object
Maya creates a 3D fluid container (fluidTexture3DShape node). The fluid container functions as the placement node, so no place3DTexture node is created.
If Density is defined as Gradient, move the fluid container so you can see both the container and the geometry.
The surface shader uses the color at the 0 position of the ramp. The Density values use the colors corresponding with the position on the ramp.