A baffle includes a body member having a first surface, a second opposed surface, and an outer peripheral edge. An aperture may be formed through the body member so as to define an inner peripheral edge. The inner peripheral edge is distorted so as to be non-planar. An apparatus includes a first conduit having a first end, a second end, and a first channel extending therebetween. At least one baffle is disposed in the first channel and includes a body member having a first surface, a second opposed surface, and an outer peripheral edge. At least one aperture may be formed through the body member to define an inner peripheral edge. The inner peripheral edge is distorted so as to be non-planar. A second conduit may be disposed inside the first conduit and extend through the aperture in the baffle. The apparatus may, for example, be configured as an ultraviolet light reactor, a heat exchanger, or a static mixer.