1 Foundation of Fluid Mechanics
11
needs to record the velocity information of any fluid particle passing through
a fixed space point. Therefore, it represents the spatial distribution of the
fluid particle velocity at any time, so it is called the flow field method. The
velocity records of fluid particles passing through any space point at any time
are measured directly, and the acceleration values obtained by definitions and
laws are measured indirectly. Imaginably speaking, this method can also be a
“stand by and wait for rabbits” mode of work.
This method leads to the concept of streamline, i.e., a specific curve passing
through any point at a certain time in the flow field. The velocity direction
of the fluid particles at each point on the curve is parallel to the tangent
direction of the curve at that point (as shown in Fig. 1.11). At some point,
the streamline equation at any point in the flow field is
dx
u
=
dy
v
=
dz
w
Streamline is a curve reflecting the instantaneous velocity direction of the
flow field. Compared with pathlines, streamlines are curves composed of
different particles at the same time. According to the definition of streamlines,
streamlines have the following properties:
Fig. 1.11 Streamlines in the flow field represented by the Euler method
11
needs to record the velocity information of any fluid particle passing through
a fixed space point. Therefore, it represents the spatial distribution of the
fluid particle velocity at any time, so it is called the flow field method. The
velocity records of fluid particles passing through any space point at any time
are measured directly, and the acceleration values obtained by definitions and
laws are measured indirectly. Imaginably speaking, this method can also be a
“stand by and wait for rabbits” mode of work.
This method leads to the concept of streamline, i.e., a specific curve passing
through any point at a certain time in the flow field. The velocity direction
of the fluid particles at each point on the curve is parallel to the tangent
direction of the curve at that point (as shown in Fig. 1.11). At some point,
the streamline equation at any point in the flow field is
dx
u
=
dy
v
=
dz
w
Streamline is a curve reflecting the instantaneous velocity direction of the
flow field. Compared with pathlines, streamlines are curves composed of
different particles at the same time. According to the definition of streamlines,
streamlines have the following properties:
Fig. 1.11 Streamlines in the flow field represented by the Euler method