A static mixer, also known as a motionless mixer, is an inline device composed of fixed geometric elements housed within a pipe or duct that promotes the blending of fluids—such as liquids, gases, slurries, or multiphase mixtures—without any moving parts, utilizing the kinetic energy from the process flow (typically driven by pumps or blowers) to divide, recombine, and redistribute the streams for homogenization of concentration, temperature, and velocity profiles.[1][2]

These mixers operate on fundamental principles of flow manipulation, including stream division (splitting the flow into multiple substreams), radial mixing (transferring material between the pipe’s center and walls), and shear generation, which enable effective mixing in both laminar (low Reynolds number, Re < 2000) and turbulent (high Reynolds number, Re > 2000) flow regimes.[3][1] In laminar flow, mixing relies primarily on repetitive division and recombination, often requiring 12–24 elements for complete homogenization, while turbulent flow benefits from enhanced radial diffusion, achieving uniformity with as few as 1.5–4 elements; the process ensures predictable droplet or bubble sizes in dispersions, with 80% of particles typically within ±20% of the average size after four elements.[3][2]