Herwig, HeinzHeinzHerwigSchmandt, BastianBastianSchmandt2020-05-132020-05-132013-08-30Fluid Dynamics Research 5 (45): 055507 (2013)http://hdl.handle.net/11420/6141Internal and external flows are characterized by friction factors and drag coefficients, respectively. Their definitions are based on pressure drop and drag force and thus are very different in character. From a thermodynamics point of view in both cases dissipation occurs which can uniformly be related to the entropy generation in the flow field. Therefore we suggest to account for losses in the flow field by friction factors and drag coefficients that are based on the overall entropy generation due to the dissipation in the internal and external flow fields. This second law analysis (SLA) has been applied to internal flows in many studies already. Examples of this flow category are given together with new cases of external flows, also treated by the general SLA-approach. © 2013 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.en0169-598320135Elsevier ScienceTechnikIngenieurwissenschaftenJournal Article10.1088/0169-5983/45/5/055507Other