Tracer Particle Spreading Device for Boundary Layer Flow Visualization
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Solution Overview
Problem
Conventional methods for flow visualization in near-wall areas of boundary layers on flat plates face challenges in uniformly distributing tracer particles due to hysteresis effects and insufficient momentum exchange, limiting the accuracy of flow visualization experiments.
Innovation Solution
A tracer particle spreading device comprising a tracer particle generator, smoke storage box, and wall-surface particle distribution box, which includes a fume and oil storage tank, micro pump, heating tube, nozzle, smoke guiding tubes, and a wall-surface particle distribution box with a rectifier plate and particle spreading slits angled at 15°, ensuring even distribution of tracer particles into the near-wall area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If tracer particles are spread directly in the upstream incoming flow of the experiment section, then the particle spreading method is simple, but the tracer particles cannot uniformly enter the near-wall area due to hysteresis action and lack of momentum exchange
Solution Approach 1:
The device divides the particle spreading process into two stages: first spreading particles in the mainstream flow, then using a rectifier plate to redirect them into the near-wall boundary layer. This segmentation allows particles to be introduced easily while ensuring uniform distribution in the target area.
Solution Approach 2:
The rectifier plate acts as an intermediary element that mediates between the mainstream flow and the near-wall boundary layer. It redirects tracer particles from the high-speed mainstream into the low-speed boundary layer region, enabling uniform particle distribution without direct injection into the boundary layer.
2Measurement precision
If a probe is placed inside the boundary layer for contact measurement, then single-point measurement can be performed, but the probe interferes with the flow in the near-wall area and affects measurement accuracy
Solution Approach 1:
The patent replaces mechanical contact measurement probes with an optical measurement system. Tracer particles are introduced into the flow field and tracked using image acquisition equipment, eliminating the need for physical probes that would interfere with the boundary layer flow while enabling non-intrusive measurement.
Solution Approach 2:
Instead of directly measuring flow parameters with probes, the system uses tracer particles as proxies to visualize and infer flow characteristics. The particles copy the flow behavior, allowing indirect measurement of velocity vectors and turbulence structures without disturbing the actual flow.
3Manufacturing precision
If tracer particles are introduced directly into the boundary layer, then near-wall flow visualization can be achieved, but the device complexity increases due to the need for specialized injection systems
Solution Approach 1:
The rectifier plate serves multiple functions: it redirects particles into the boundary layer, distributes particles uniformly across the near-wall area, and maintains particle concentration. This multi-functionality eliminates the need for complex specialized injection systems while achieving the desired particle distribution.
Solution Approach 2:
The device changes the flow direction parameter of particles by using the rectifier plate at a specific angle (15-30 degrees). This parameter change redirects particles from horizontal mainstream flow into the vertical near-wall boundary layer, achieving effective particle distribution without complex injection mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device enables uniform distribution of tracer particles in the near-wall area, enhancing the accuracy of flow visualization experiments by reducing interference and improving the observation of velocity vectors and turbulence structures within the boundary layer.
Implementation Method 1
Fume and oil are pressurized by the micro pump
Implementation Method 2
the pressurized fume and oil flow into the heating tube to be heated and vaporized
Implementation Method 3
an axial flow fan is mounted in an inner wall surface of the fume storage tank, and the flow speed of the particles is adjusted by a rotation speed of the axial flow fan
Implementation Method 4
a smoke is ejected through the nozzle to form tracer particles
Data Source
AI summary
A tracer particle spreading device for a boundary layer flow visualization experiment based on a flat plate includes a tracer particle generator, a smoke storage box, and a wall-surface particle distribution box. Fume and oil are pressurized by a micro pump and flows into a heating pipe to be heated and vaporized, and then is ejected from a nozzle to form tracer particles. The tracer particles enter the smoke storage box via a smoke guiding tube. An axial flow fan is mounted on a wall surface of the smoke storage box. The tracer particles enter a cavity of the wall-surface particle distribution box via the smoke guiding tube, and the tracer particles are rectified by a rectifying plate and ejected from a spreading slit. An outlet of the spreading slit is at an angle of 15° with respect to an experiment flat plate.