Manifold (fluid mechanics)

In engineering, a manifold is a structure or machine element that splits a flow of fluid or gas from one channel into multiple channels or, vice versa, collects flow from multiple channels into one. Both this noun sense of the word and the general-vocabulary adjective sense come from roots meaning "many" and "-fold", expressing the idea of multitude, which in the case of manifolds in engineering applies to their theme of multiple inputs or outputs (inlets or outlets).

Common form factors for manifolds include a set of pipes that merge into one; a block of metal with various cross-holes drilled to connect to a common larger hole inside; or a casting with various cored passages that connect. The common area (trunking area) inside the manifold, to which the various branches connect, is often called a plenum, with the branch holes called ports or passages. The original sense of the term plenum refers specifically to positive-pressure spaces (plenum chambers), although the broader sense refers to such a space at any pressure (for example, the plenum of an inlet manifold contains a partial vacuum—the manifold vacuum—and the plenum spaces of HVAC systems may be designed to operate at either positive or negative pressures).

Various types of Engineering Manifolds include:

• Exhaust manifold, an engine part which collects the exhaust gases from multiple cylinders into one pipe
• Hydraulic manifold, a component used to regulate fluid flow in a hydraulic system, thus controlling the transfer of power between actuators and pumps
• Inlet manifold or "intake manifold", an engine part which supplies the air or fuel/air mixture to the cylinders
• Manifold (scuba), in a scuba set, connects two or more diving cylinders
• Manifold chemistry, an apparatus used in chemistry to manipulate gases