雷诺数到底衡量什么，为什么它决定流动是层流还是湍流？
What does the Reynolds number actually measure, and why does it decide laminar versus turbulent flow?
雷诺数是惯性力与粘性力的比值，反映了流体“想乱跑”还是“被粘住”。数值小则粘性主导、分层平稳（层流）；数值大则惯性主导、出现涡团翻滚（湍流）。
The Reynolds number is the ratio of inertial to viscous forces—how much fluid 'wants to wander' versus 'is held back'. Low values mean viscosity dominates calm layering (laminar); high values mean inertia dominates with swirling turbulence.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
White，《流体力学》（第8版）
White, 'Fluid Mechanics' (8th ed.)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1911850W：Fluid mechanics（首版 1979
#雷诺数 #层流 #湍流
为什么高烟囱或高桥塔在风里会发出“嗡嗡”声甚至剧烈抖，卡门涡街是什么？
Why do tall chimneys or bridge towers hum or even shake violently in wind—what is a Karman vortex street?
风绕过后方两侧会交替甩出旋转涡，形成有节奏的卡门涡街，涡脱落的频率若接近结构自振频率就会共振抖得厉害。工程师用导流板或改变截面来打乱这种节奏。
Wind sheds alternating rotating vortices behind a body—a Karman vortex street—and if its frequency nears the structure's natural frequency, resonant shaking results. Engineers use fairings or changed cross-sections to break the rhythm.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
White，《流体力学》（第8版）
White, 'Fluid Mechanics' (8th ed.)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1911850W：Fluid mechanics（首版 1979
#卡门涡街 #涡激振动 #共振
离心泵为什么会发生“汽蚀”，它和泵入口压力低于液体汽化压力有什么关系？
Why does a centrifugal pump suffer cavitation, and how is it linked to inlet pressure dropping below vapor pressure?
当泵入口压力低到液体自身沸点以下，水会局部汽化产生气泡，流到高压区又瞬间溃灭，像小爆炸一样啃蚀叶轮。汽蚀会掉性能、吵闹并很快打坏泵。
When inlet pressure falls below the liquid's vapor pressure, local boiling forms bubbles that collapse violently in high pressure, pitting the impeller like tiny explosions. Cavitation kills performance, is noisy and quickly damages the pump.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Karassik、Messina、Paul & Heald，《泵手册》（第4版）
Karassik, Messina, Paul & Heald, 'Pump Handbook' (4th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787801643810（豆瓣书目条目: 泵手册）
#汽蚀 #离心泵 #汽化压力
飞机能飞起来，和“流过机翼上下表面的空气速度不一样”有什么关系？
How is an airplane's ability to fly related to air moving at different speeds over and under the wing?
机翼做成上面弯下面平，上面空气跑得更快、压力变低，下面压力相对高，就把机翼往上托。这个上下压力差就是升力，飞机才飞得起来。
The wing is curved on top and flatter below, so air moves faster above and pressure drops there while pressure stays higher below, pushing the wing up. This pressure difference is lift, and that is how planes fly.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Anderson，《空气动力学基础》（第6版）
Anderson, 'Fundamentals of Aerodynamics' (6th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787516504413（豆瓣书目条目: 空气动力学基础）
#机翼 #升力 #伯努利