An orifice plate is a commonly used device in fluid mechanics and engineering to measure the flow rate of a liquid or gas within a pipeline. It consists of a thin, flat plate with a precisely machined hole, known as an orifice, in the center. When inserted into a pipeline, the orifice plate creates a constriction that causes the fluid to accelerate as it passes through the smaller opening. This acceleration leads to a pressure drop across the plate, which is proportional to the flow rate of the fluid.