External flow

In fluid mechanics, external flow is a flow that boundary layers develop freely, without constraints imposed by adjacent surfaces.[1][2] It can be defined as the flow of a fluid around a body that is completely submerged in it. Examples include fluid motion over a flat plate (inclined or parallel to the free stream velocity) and flow over curved surfaces such as a sphere, cylinder, airfoil, or turbine blade, water flowing around submarines, and air flowing around a truck;[3] a 2000 paper analyzing the latter used computational fluid dynamics to model the three-dimensional flow structure and pressure distribution on the external surface of the truck.[3] In a 2008 paper, external flow was said to be "arguably is the most common and best studied case in soft matter systems.[4]

The term can also be used simply to describe flow in any body of fluid external to the system under consideration.[5][6]

In external co-flow, fluid in the external region occurs in the same direction as flow within the system of interest; this contrasts with external counterflow.[1]

References
  1. Jendoubi, S.; Strykowski, P. J. (September 1, 1994). "Absolute and convective instability of axisymmetric jets with external flow". Physics of Fluids. 6 (9): 3000–3009. Bibcode:1994PhFl....6.3000J. doi:10.1063/1.868126.
  2. Lebedev, V. V.; Turitsyn, K. S.; Vergeles, S. S. (November 20, 2007). "Dynamics of nearly spherical vesicles in an external flow". Physical Review Letters. 99 (21): 218101. arXiv:cond-mat/0702650. Bibcode:2007PhRvL..99u8101L. doi:10.1103/PhysRevLett.99.218101. PMID 18233260. S2CID 17517230.
  3. Roy, Subrata; Srinivasan, Pradeep (2000). "External Flow Analysis of a Truck for Drag Reduction". SAE Transactions. 109: 808–812. JSTOR 44650820.
  4. Speck, Thomas; Mehl, Jakob; Seifert, Udo (April 28, 2008). "Role of External Flow and Frame Invariance in Stochastic Thermodynamics". Physical Review Letters. 100 (17): 178302. arXiv:0712.0232. Bibcode:2008PhRvL.100q8302S. doi:10.1103/PhysRevLett.100.178302. PMID 18518344. S2CID 2743850.
  5. Chiu, Y-H.; Etheridge, D. W. (April 1, 2007). "External flow effects on the discharge coefficients of two types of ventilation opening". Journal of Wind Engineering and Industrial Aerodynamics. 95 (4): 225–252. doi:10.1016/j.jweia.2006.06.013.
  6. Chew, J. W.; Green, T.; Turner, A. B. (February 18, 2015). "Rim Sealing of Rotor-Stator Wheelspaces in the Presence of External Flow". Turbo Expo: Power for Land, Sea, and Air. American Society of Mechanical Engineers. doi:10.1115/94-GT-126. ISBN 978-0-7918-7883-5. S2CID 110218328.
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