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control volume

 Definition/Summary The initial use of control volumes for fluid analysis is largely credited to Ludwig Prandtl at the beginning of the 20'th century according to Vincenti (1990). When first introduced, the control volume was "an imagined spatial volume having certain characteristics and introduced for purposes of analysis" of fluid mechanics. The concept was later expanded to aid in thermodynamic analysis. A control volumes is defined as a region of three dimensional space selected for the purposes of analysis and on which specific fundamental physical laws can be applied. Around this volume of space is a control surface. That surface is an imaginary, infinitely thin 2 dimensional surface. The purpose of the control surface is to aid in identifying mass and energy which act on the control volume. Typically, the control volume concept is only applied to fluid mechanics or thermodynamics and only applied to analytical situations. Per Gerhart and Gross (1985), there are both "differential formulations" and "finite control volume formulations", the difference being that differential equations are applied to the differential formulation such that the fluid obeys the physical laws at all points within the volume. In comparison, the finite CV formulation considers all mass within a control volume to have the same properties including velocity or temperature for example. When applying control volumes to fluid dynamics, flow is allowed to enter or leave the volume, resulting in changes to momentum, kinetic energy and other physically measurable properties internal to the volume. When applying control volumes to thermodynamics, this flow influences the internal energy of the volume and other properties of the fluid's physical state. Heat and work are also accounted for when they are found to cross the control surface. Gerhart, P. M. and R. J. Gross, 1985, 'Fundamentals of Fluid Mechanics' Addison-Wesley publishing Co. Vincenti, W. G. 1990, 'What Engineers Know and How They Know It' The Johns Hopkins University Press

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 tiny-tim @ 03:08 AM Feb6-10 Someone asks a question about control volume, and as soon as they post it, the words "control volume" are underlined, they see it, wonder why it's there, click on the link, and come to this page. That's Greg's autolinking … the server automatically links posts to the Library.

 CFDFEAGURU @ 08:51 AM Jan15-10 tiny-tim, What is autolinking? Matt

 tiny-tim @ 03:48 PM Jan14-10 the present title, "First Law of Thermodynamics as Applied to a Control Volume". is never going to get any autolinking! … perhaps "control volume" would be a better title?