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Why Do All Boats Make This Shape?

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From: minutephysics
Duration: 04:16

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This video is about the "Kelvin wake" shape of water wakes behind boats - we talk about mach angle, dispersion, superposition of many waves, and how these all lead to the pattern of a wake. We don't get into Froude number though...

REFERENCES
Boat Wake Wikipedia Page: https://en.wikipedia.org/wiki/Wake

Interactive Boat Wake Simulation: https://observablehq.com/@rreusser/dispersion-in-water-surface-waves

Feynman Lectures on Water Waves: https://www.feynmanlectures.caltech.edu/I_51.html#Ch51-S4

Building up a Boat Wake from V-Shaped Wakes: https://editor.p5js.org/aatish/full/bDiykicsC

Wave Dispersion: https://en.wikipedia.org/wiki/Dispersion_relation

Mach angle shock waves:
https://www.sciencedirect.com/topics/engineering/mach-angle

Ship Wakes - Kelvin or Mach Angle? Rabaud and Moisy Paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.214503

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Created by Henry Reich

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drspam
535 days ago
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Artist François Vogel Turns His Unaware Cat into a Wriggling Jellyfish

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Based on a recent cameo, François Vogel ’s cat actually might enjoy a dip in the ocean despite his feline instincts to avoid it. The Abyssinian has been stretched and distorted in a series of humous clips made by his French owner, including one that lengthens and spirals the cat’s legs like flowing jellyfish tendrils. The unsuspecting pet also is stretched across the dining room and launched into an expanding sea of fish that he slowly swims through.

Vogel, who lives and works in the Parisian suburb Meudon, used slit-scan photography and time displacement in After Effects to twist and warp his cat’s figure. Head to Instagram to see his extensive backlog of comical distortions that includes turning his daughter into a seagull. (via Laughing Squid)

 

 

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drspam
880 days ago
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San Francisco, California
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Rippling Waves of Bricks Formed Through Groundbreaking New Augmented Bricklaying Technique

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Image © Michael Lyrenmann. All images shared with permission

The teams at Gramazio Kohler Research and Icon.Ai recently collaborated on an architectural project that merges digital savvy with traditional craftsmanship to create a skillful new building technique. Completed in 2019, “Augmented Bricklaying” relies on digital markers to instruct bricklayers about where to spread mortar, how thick to layer it, and what the position of the next stone should be.

A custom-designed guidance system, the hybrid technique combats the limitations of both traditional and innovative digital approaches: robotic arms have restricted mobility and difficulty with pliable materials like mortar, while physical templates can be cumbersome and less accurate for masons. The new model “combines the advantages of computational design with the dexterity of humans, supporting an entirely new way of fabrication,” the Zurich-based team said in a statement.

To create the 225 square-meter structure, masons assembled 13,596 locally sourced bricks in varying rows. The differentiated mortar heights range from five to 30 millimeters and help to determine each brick’s rotation that spans -20° to +20°. “That way mortar, usually treated as secondary material in the design of fair-faced brick walls, became a defining element in the appearance of the facade,” the team said.

Because of the differed construction, the porous exterior appears as a wave or ripple. The patterned facade provides ventilation and allows sunlight to stream into the building, which produces an array of circles that shifts based on the time of day.  It will house KITRVS Winery’s processing and storage facility. The Greek vineyard overlooks the Thermaic Gulf of the Aegean Sea at the base of Mount Olympus.

Gramazio Kohler Research is the ETH Zurich’s chair of architecture and digital fabrication, and Icon.Ai is a subsidiary of the organization’s robotic systems labs. Keep up with Gramazio Kohler’s inventive projects on Instagram and Vimeo. (via designboom)

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Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Michael Lyrenmann

Image © Gramazio Kohler Research, ETH Zurich

Image © Gramazio Kohler Research, ETH Zurich

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drspam
880 days ago
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drspam
927 days ago
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this blog is fantastic
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Winners of the 2020 Underwater Photographer of the Year Contest (15 photos)

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The winners of this year’s Underwater Photographer of the Year contest were just announced, and the photographer Greg Lecoeur was named Underwater Photographer of the Year 2020 for his image of crabeater seals in Antarctica. More than 5,500 images were submitted by photographers from around the world. Prizes and commendations were handed out in categories including Wide Angle, Macro, Wrecks, Behavior, Portrait, Black and White, Compact, Up and Coming, Marine Conservation, and in British waters, Wide Angle, Living Together, Compact, and Macro Shots. UPY was once again kind enough to share some of this year’s honorees with us below, with captions written by the photographers.

Frozen Mobile Home: Category Winner and Underwater Photographer of the Year 2020. Massive and mysterious habitats, icebergs are dynamic kingdoms that support marine life. As they swing and rotate slowly through polar currents, icebergs fertilize the oceans by carrying nutrients from land that spark blooms of phytoplankton, fundamental to the carbon cycle. During an expedition in Antarctica Peninsula with filmmaker Florian Fisher and freediver Guillaume Nery, we explored and documented the hidden face of this iceberg where crabeater seals have taken up residence among icebergs that drift at the whim of polar currents. (© Copyright Greg Lecoeur / UPY2020)
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drspam
943 days ago
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lovely stuff.
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The collapse of a bubble underwater doesn’t seem like a very...

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The collapse of a bubble underwater doesn’t seem like a very important matter, but when it happens near a solid surface, like part of a ship, it can be incredibly destructive. This video, featuring numerical simulations of the bubble’s collapse, shows why. 

When near a surface, the bubble’s collapse is asymmetric, and this asymmetry creates a powerful jet that pushes through the bubble and impacts the opposite side. That impact generates a shock wave that travels out toward the wall. As the bubble hits its minimum volume, a second shock front is generated. Both shock waves travel toward the wall and reflect off it, generating high pressure all along the surface. (Image and video credit: S. Beig and E. Johnson)

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drspam
1124 days ago
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i don't know why i love this so much but i do.
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