| |
The smoke
particles shown in the flow photographs serve to mark the trajectory followed
by the fluid elements. At any given instant, the speed of the element
is tangential to the "streamline" shown by the smoke trail. This is
illustrated in the top diagram.
No fluid elements in the flow cross a
streamline and a group of such streamlines can form a streamtube as shown in
the lower diagram. The area of cross-section, A, of this tube will change with
location in the flow, however, the total quantity of fluid crossing any cross-section
in unit time remains constant. This implies that the velocity of
the flow must change if the fluid is incompressible.
The fluid elements
must obey Newton's laws of motion, and valuable insights can be gained as
to how they move in the fluid by using these ideas and energy conservation concepts. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
