A fluid is directed toward a surface of an optical element based on a first flow pattern, the surface of the optical element including debris and the fluid directed based on the first flow pattern moving at least some of the debris to a first stagnation region at the surface of the optical element; and the fluid is directed toward the optical element based on a second flow pattern, the fluid directed based on the second flow pattern moving at least some of the debris to a second stagnation region on the surface of the optical element, the second stagnation region and the first stagnation region being different locations at the surface of the optical element. Directing the fluid toward the surface of the optical element based on the second flow pattern removes at least some of the debris from the first stagnation region.