Understanding Schlieren

Schlieren techniques are one of my favorite forms of flow visualization. They cleverly make the invisible visible through an optical set-up that’s sensitive to changes in density. They’re great–as seen in the examples here–for seeing local buoyant flows like the plumes that rise from a candle, or for making gases like carbon dioxide visible. They’re also excellent for visualizing shock waves.

In this video, physicist David Jackson explains how one particular flavor of schlieren–one using a spherical mirror–works. There are lots of other possible schlieren set-ups, too, though each one has its quirks. (Video and image credit: All Things Physics; submitted by David J.)

#DIYFluids #flowVisualization #fluidDynamics #physics #schlierenPhotography #science

PS5 vs. Xbox Series X Airflow Testing: Cooling Design Efficiency & Flow Paths

https://peertube.gravitywell.xyz/w/vkwjkxeknzaswzQi5HVvhB

“Soap Bubble Bonanza

This video offers an artistic look at a soap bubble bursting. The process is captured with high-speed video combined with schlieren photography, a technique that makes visible subtle density variations in the air. The bubbles all pop spontaneously, once enough of their cap drains or evaporates away for a hole to form. That hole retracts quickly; the acceleration of the liquid around the bubble’s spherical shape makes the retracting film break into droplets, seen as falling streaks near the bottom of the bubble. The retraction also affects air inside the bubble, making the air that touched the film curl up on itself, creating turbulence. Then, as the film completes its retraction, it pushes a plume of the once-interior air upward, as if the interior of the bubble is turning itself inside out. (Video and image credit: D. van Gils)

#flowVisualization #fluidDynamics #fluidsAsArt #physics #schlierenPhotography #science #soapBubbles

Imaging a New Era of Supersonic Travel

Supersonic commercial travel was briefly possible in the twentieth century when the Concorde flew. But the window-rattling sonic boom of that aircraft made governments restrict supersonic travel over land. Now a new generation of aviation companies are revisiting the concept of supersonic commercial travel with technologies that help dampen the irritating effects of a plane’s shock waves.

One such company, Boom Supersonic, partnered with NASA to capture the above schlieren image of their experimental XB-1 aircraft in flight. The diagonal lines spreading from the nose, wings, and tail of the aircraft mark shock waves. It’s those shock waves’ interactions with people and buildings on the ground that causes problems. But the XB-1 is testing out scalable methods for producing weaker shock waves that dissipate before reaching people down below, thus reducing the biggest source of complaints about supersonic flight over land. (Image credit: Boom Supersonic/NASA; via Quartz)

#aircraft #flowVisualization #fluidDynamics #physics #schlierenPhotography #science #shockwave #supersonic #supersonicFlight

Schlieren microscopy of daphnia + a dragonfly larva done in Rudi Strickler’s lab, visualizing microscopic currents. Rudi studies the hydrodynamic senses of plankton and how these tiny currents are used in mating and behavior. I had so much fun in his lab. #SciArt #schlierenphotography

Observe Airflow Using Smartphone And Background-Oriented Schlieren https://hackaday.com/2022/07/17/observe-airflow-using-smartphone-and-background-oriented-schlieren/ #backgroundorientedschlieren #schlierenphotography #digitalcamerashacks #cellphonehacks #photograph #schlieren #density #science #camera #optics #fluid #image #phone

Helicopter is Full of Compressed Air

[Tom] likes to build little helicopters and decided to build one that runs on compressed air. (Video, embedded below.) Turns out it was a little harder than he thought. Originally, he was trying for a compressed air quadcopter. He'd already worked with an air turbine, but putting on a vehicle that can lift itself into the air turns out to have a lot of hidden gotchas.

[Tom] went through a lot of design considerations to arrive at the helicopter design. He considered counter-rotating props, but there were a host of problems involved. He finally settled on a single prob with a tail rotor that resides on the far end of a long boom to allow the resulting lever arm to reduce the work required of the tail rotor.

Some of the best parts of this build are the test setups. We liked the test rig he has for testing the thrust of a propeller. It allowed him to understand that his quadcopter design wasn't feasible with the props he had on hand. His schlieren photography setup was interesting, too, and provided some cool photos of the airflow.

In the end, the results were somewhat disappointing. However, you sometimes learn more from your failures than your successes. Also, an astute Hackaday reader might have some advice on how to make the flying machine better. We feel like it is very close.

We've seen [Tom] working on this in one form or another for a while. Some of his air-powered designs are quite sophisticated.

#dronehacks #airturbine #helicopter #schlieren #schlierenphotography