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P. Liu
new concepts and mathematical models. As the famous master of fluid
mechanics in the world, German scientist Prandtl said, “I only came up
with mathematical equations after I believed I had a deep understanding
of the nature of physics. The use of the equation is to say the size of the
quantity, which is not intuitive, and it also proves whether the conclusion
is correct.” Flow visualization and measurement technology itself is also the
primary means of solving practical engineering problems. It can be said that
every theoretical breakthrough in the development of fluid mechanics and
its application in engineering almost starts from the observation of the flow
phenomenon. Such as the Reynolds transition experiment in 1880, the Mach
shock phenomenon test in 1888, the concept of the boundary layer proposed
by Prandtl in 1904, and the analysis of the vortex street around the cylinder
in 1912. All are based on the results of flow visualization and measurement.
The in-depth analysis of the flow phenomenon is the key to establish and
verify new concepts and discover new laws.
It should be pointed out that in recent decades, due to the urgent
need for engineering practice and the rapid development of modern optics,
laser technology, computer technology, electronic technology, and information processing technology, it has brought vigor and vitality to the flow
visualization and measurement technology. There is considerable progress,
especially in the ability to display the spatial flow and flow internal structure, as well as the quantitative extraction and analysis of flow information.
Three-dimensional, unsteady complex flow quantitative display and measurement information can be obtained simultaneously. The flow visualization
and measurement methods that have appeared so far are often divided into
two categories, conventional and computer-aided. The former is called the
conventional method, and the latter is called the method of combining flow
visualization and measurement with computer image processing. Among the
conventional methods, the wall surface tracking method, the wire method,
the tracer method, and the optical method are included.
1. Conventional flow visualization technique
(1) Wall surface tracking method
The method is to coat a thin layer of material on the surface and produce a
certain visible flow pattern on the surface when it interacts with the fluid. It
is used to qualitatively or quantitatively display the flow characteristics of the
surface, such as laminar flow, turbulence and transition position, separation
P. Liu
new concepts and mathematical models. As the famous master of fluid
mechanics in the world, German scientist Prandtl said, “I only came up
with mathematical equations after I believed I had a deep understanding
of the nature of physics. The use of the equation is to say the size of the
quantity, which is not intuitive, and it also proves whether the conclusion
is correct.” Flow visualization and measurement technology itself is also the
primary means of solving practical engineering problems. It can be said that
every theoretical breakthrough in the development of fluid mechanics and
its application in engineering almost starts from the observation of the flow
phenomenon. Such as the Reynolds transition experiment in 1880, the Mach
shock phenomenon test in 1888, the concept of the boundary layer proposed
by Prandtl in 1904, and the analysis of the vortex street around the cylinder
in 1912. All are based on the results of flow visualization and measurement.
The in-depth analysis of the flow phenomenon is the key to establish and
verify new concepts and discover new laws.
It should be pointed out that in recent decades, due to the urgent
need for engineering practice and the rapid development of modern optics,
laser technology, computer technology, electronic technology, and information processing technology, it has brought vigor and vitality to the flow
visualization and measurement technology. There is considerable progress,
especially in the ability to display the spatial flow and flow internal structure, as well as the quantitative extraction and analysis of flow information.
Three-dimensional, unsteady complex flow quantitative display and measurement information can be obtained simultaneously. The flow visualization
and measurement methods that have appeared so far are often divided into
two categories, conventional and computer-aided. The former is called the
conventional method, and the latter is called the method of combining flow
visualization and measurement with computer image processing. Among the
conventional methods, the wall surface tracking method, the wire method,
the tracer method, and the optical method are included.
1. Conventional flow visualization technique
(1) Wall surface tracking method
The method is to coat a thin layer of material on the surface and produce a
certain visible flow pattern on the surface when it interacts with the fluid. It
is used to qualitatively or quantitatively display the flow characteristics of the
surface, such as laminar flow, turbulence and transition position, separation