Transparent Flows

Transparent flow research pertains to shock waves, entrainments, and turbulent flows, among other phenomena. For example, an important shock wave application is the study of how a shock wave move through various mediums, whether air, water, or a solid substances. This research is critical to understanding how shock waves alter the mechanical, electrical, and thermal properties of solids, a necessary component to understanding the equation of state of any material. Each type of transparent flow research has a unique set of challenges to overcome through proper setup and camera selection.

High-speed imaging gives research scientists a close look into:

  • Efficiency of wind turbines
  • Combustion plumes
  • Atmospheric turbulence
  • Refractive Index Gradients (RIG)
  • Schlieren and shadowgraphy imaging

Understanding Transparent Flows Research Goals

When imaging transparent flows it is important to understand the subject area of interest for an event. This will assist in determining the imaging technique necessary for researchers to gather appropriate and accurate data. 

Some common areas of interest are: 

  • Meterology – Air flows and interaction with other gas or particles
  • Thermal Studies – Properties of heat transfer
  • Epidemiology – Particle transmission via liquid or air movement
  • Hydrodynamics – Fluid flows and interaction with another fluid
  • Ballistics & Range – Motion of air or liquid from pressure
  • Aerodynamics – Interaction of an object with air
  • Wind Tunnels – Subsonic, transonic, supersonic, and hypersonic levels for research

Challenges & Solutions

Transparent flow imaging has a unique set of challenges that come with extreme high-speed imaging. Each of these difficulties can be resolved by ensuring that both the correct tool (Phantom camera) and correct imaging techniques are used to produce accurate and clear high-speed imaging. Three of the most common are shape and form characterization, reduced light testing, and complex set-ups.

Challenge 1: Shape and Form Characterization – These two, hard to image, characteristics require different types of lighting during high-speed imaging. Shape can be seen by using a uniform field of light, either bright field or dark field, which keeps the lines at the edge of the flow thin with high contrast. Form requires strategically placed lighting that creates a gradient across the subject. This gradient allows for the observation of the shadowing or pattern across the subject. Regardless of the method being used it is important that the camera in use can create quality images through high dynamic range and low noise capabilities.  

Challenge 2: Reduced Light Testing – Some techniques used in transparent flow imaging reduce the amount of light that reaches the camera sensor. For example, Schlieren imaging seeks to visualize the change in air movement.  This is accomplished by relying on a bend in light and a knife edge, before it reaches the sensor. The airflow becomes visual to the high speed camera but at the same time the amount of available light is reduced.  To work more efficiently in light starved environments it is important that a high-speed camera with high light sensitivity is used. 

Challenge 3: Complex Set-ups – The method being used to image the flow may require not only a particular camera but also unique environments or specialized equipment. Variables such as wind tunnels, large surface areas, microscopes, or specialized mirrors will all affect the setup and the type of Phantom camera that is needed to gather data.  

CAMERAS