what is control volume ,system in fluid mechnics?why we need these twoapproaches whats difference between them

Question

explain with an example.in which mass,energy remains constant?while deriving reynolds transport theorm we consider CV remains constant,moving and deforming.. i heard CV is fixed always .is it true?

Answer 1

fluid mechanics, a control volume is a mathematical abstraction often employed by scientists and mathematicians in the process of creating mathematical models of physical processes. Generally, a control volume can be thought of as an arbitrary volume in which the mass and the enclosed energy of the fluid remains constant. As fluid moves, this implies that the mass that enters the control volume is the same amount that the one that leaves it.Thats why in deriving reynold's transport theorm we consider cv remains constant

Answer 2

n fluid mechanics, a control volume is a mathematical abstraction often employed by scientists and mathematicians in the process of creating mathematical models of physical processes. Generally, a control volume can be thought of as an arbitrary volume in which the mass and the enclosed energy of the fluid remains constant. As fluid moves, this implies that the mass that enters the control volume is the same amount that the one that leaves it.Thats why in deriving reynold's transport theorm we consider cv remains constant