This video lesson considers situations in which friction affects the pressure loss of a flowing gas, such as natural gas in a pipeline. Rayleigh flows are 1D compressible flows with the addition/removal of heat. Fanno flows describe situations in which the effect of friction on 1D flows is considered. This lesson is part of the Ansys Innovation Course: Internal Compressible Flows. To access this and all of our free, online courses — featuring additional videos, quizzes and handouts — visit Ansys Innovation Courses at https://www.ansys.com/courses.