月曜日のたわわ その５８４ 『お姉さんのおともだち』

月曜日のたわわ　その５８４　『お姉さんのおともだち』

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Electrodynamics Hydrodynamics quantum mechanics penetration depth

 

  These three quantities — the skin depth, the viscous penetration depth, and the thermal penetration depth — share the same mathematical structure.  Each describes how far an oscillatory disturbance can penetrate into a dissipative medium. In electromagnetics, the skin depth measures how deeply a time-harmonic field penetrates into a conductor.
  In fluid mechanics, the viscous penetration depth gives the thickness of the oscillatory viscous layer near a vibrating boundary.
  In heat transfer, the thermal penetration depth describes how far a periodic temperature variation can propagate into a medium. In all three cases, the penetration depth is determined by the competition between diffusivity and oscillation frequency, and scales as

《Physical Hydrodynamics》, §4.5.4 Oscillating flows in a viscous fluid

“ In Physical Hydrodynamics (§4.5.4), the oscillatory viscous boundary-layer problem is explicitly described as analogous to the skin effect in electrical conduction and to the penetration of seasonal temperature variations into the ground.”

熊野本宮大社新茶祭

 熊野本宮大社

紀伊國熊野本宮大社舉行新茶祭，境內的茶田裡，身穿白衣、緋紅袴，並繫著紅色襷帶的巫女們，正在採摘當地特產「音無茶」的新芽。

熊野本宮大社的主祭神即為熊野大神家津美御子。