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From 2D to 4D: How to deeply understand fluid dynamics through three-dimensional particle tracking technology?
In the study of fluid mechanics, particle tracking velocity measurement (PTV) has become an important measurement technology. This technology measures the velocity and trajectory of neutrally buoyant particles suspended in fluid flows. Unlike the Euler method of particle image velocity measurement (PIV), PTV tracking relies on the movement of the observed object, forming a Lagrangian perspective. With the advancement of technology, PTV has developed from 2D to 3D, and now even further to 4D, allowing us to more fully understand the dynamic behavior of fluids.
Through three-dimensional particle tracking technology, researchers can obtain instantaneous velocity and vorticity distribution, thereby obtaining detailed flow information in two or three dimensions of space.
The evolution of PTV technology
Traditionally, 2D PTV is measured in a thin laser plane slice. This method requires particle density to ensure that each particle can be tracked independently. With the emergence of 3D PTV, researchers are no longer limited to plane measurements, but can capture the movement of particles randomly distributed in three-dimensional space through three-dimensional images. This technique was originally developed to study fully turbulent flows and is now widely used in fields as diverse as structural mechanics, medicine, and industrial settings.
The 3D PTV method uses a three-dimensional configuration of multiple cameras to simultaneously record the fluid tracking particles in the flow and obtain their instantaneous positions in the three-dimensional space.
Core technology of 3D PTV
3D PTV uses two to four digital cameras to simultaneously record the flowing particles according to specific angle configurations. These cameras capture light that is scattered or fluorescently emitted from the fluid. Particles within the flow field are illuminated by lasers or other light sources. This reduces the exposure time of the moving optical target, thus "freezing" the particles in each image frame. Location. This technology is capable of providing a data density of more than 10 velocity vectors per cubic centimeter, providing powerful data support for comprehensive analysis of flow.
4D PTV: Breaking the limitations of time and space
With the emergence of time-resolved three-dimensional particle tracking technology (4D-PTV), researchers can not only track the movement of flowing particles in space, but also obtain their movement trajectories over time. This is a unique advantage for the Lagrangian description of turbulence. The development of this method allows researchers to perform statistical analyzes to better understand the underlying mechanisms of complex dynamic behavior in fluids.
The introduction of 4D-PTV makes it possible to study the behavior of different fluids under different conditions, opening new doors for industrial applications and scientific research.
Progress in real-time image processing technology
With the continuous advancement of technology, real-time image processing has gradually become an important aspect of 3D PTV. Developers have begun to explore white light illumination, rather than relying solely on lasers, which can significantly reduce measurement costs and improve the safety environment. Advances in these technologies will undoubtedly enable researchers to conduct efficient fluid flow studies in a variety of environments.
Future challenges and prospects
Although PTV technology has made significant progress, many challenges still exist in the face of the growing demand for fluid mechanics applications. For example, how to improve the accuracy and efficiency of measurement in more complex flow environments, how to further reduce costs to facilitate wider application, etc., are all issues that need to be explored in depth in the future.
How will the evolution of 3D and 4D PTV technology change our understanding and application of fluid dynamics?
