Apparatus and methods are described for use in mixing of fluids or mixing ingredients into fluids by means of a static mixer assembly (i.e. without requiring moving mechanical parts, where fluid flow is used to achieve mixing). The static mixer assembly is a cylindrical tube with three pairs of fins extending inward from the inner wall of the tube. The central fins form a prow pointing upstream, with two pairs of flanking fins arranged to prevent unhindered fluid flow parallel to the central axis of the tube a peripheral region, while allowing unobstructed flow in a central region and extending to a peripheral region near the inner wall opposite the prow. The fins force fluid outwards along the inner walls from the prow towards the unobstructed peripheral region opposite the prow and additionally fluid spills over the inner edges of the fins into the central region. The resulting flow pattern provides excellent mixing with a low ratio of pressure drop to volumetric flow rate across the assembly. Ingredients inserted into the unobstructed peripheral region opposite the prow are rapidly homogenized into flowing fluid.