Optical Gas Flow Diagnostics
Optical Gas Flow Diagnostics
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Stanford Applied Plasma Physics & High-Intensity Radiation Engineering (SAPPHIRE) Lab | Experimental Fluid Systems
Stanford Applied Plasma Physics & High-Intensity Radiation Engineering (SAPPHIRE) Lab | Experimental Fluid Systems
Designed and built a noninvasive optical diagnostic system using Schlieren and shadowgraph imaging techniques to visualize density, gradients, and mixing in concentric CO₂ and nitrogen flows. By routing a laser through precision optics to map refractive index changes, the setup enabled high-contrast imaging of fluid dynamics and mixing layers without physically disturbing the flow field.
01 | Problem Statement | Invisible Boundary Challenges
01 | Problem Statement | Invisible Boundary Challenges
Problem: Critical fluid boundaries, gas flows, and mixing layers are inherently invisible to standard camera sensors.
Challenge: Physical sensors block, drag, and deform the fluid dynamics they attempt to measure.
Engineering Goal: Construct a non-invasive, high-speed optical system to visualize gas density gradients from a concentric CO2/nitrogen flow tube.
02 | Analysis & Design Process | Optical Physics & Mechanics
02 | Analysis & Design Process | Optical Physics & Mechanics
Density-Driven Refraction: Local density changes caused by flow of CO₂ and nitrogen alter the gas's refractive index, deflecting the collimated laser beam at different angles.
Optical Path: A laser beam is routed through mirrors, lenses, and an iris, then focused onto a knife-edge and imaged with a camera.
Schlieren Technique: A knife-edge partially blocks the focused beam, converting first-order refraction angles into bright-and-dark contrast.
Shadowgraph Technique: Removing the knife-edge projects deflected beams directly onto the sensor, mapping second-order density fluctuations.
03 | Manufacturing & Testing | Testing & Flow Visualization
03 | Manufacturing & Testing | Testing & Flow Visualization
Schlieren results: Clearly imaged turbulence and uneven flow at the gas outlet, exposing invisible flow characteristics.
Shadowgraph Comparison: Same flow appeared smoother with less fine-scale detail, confirming Schlieren's higher sensitivity to small fluctuations.
Alignment Control: Achieved repeatable, high-contrast Schlieren images by isolating ambient light, correcting imperfections in the laser beam, and keeping dust off the image filter.
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