← Notedeck
All engines
·
流体·热力
en
zh-CN
zh-TW
ja
ko
fr
de
es
pt-BR
tr
it
ar
流体·热力
12
engines
雷诺数 · 层流与湍流
Reynolds number · laminar vs turbulent
Re=ρvL/μ · 惯性/黏性 · 层流<2300/湍流>4000
Re = ρvL/μ, the ratio of inertial to viscous forces sets the flow regime
伯努利原理 · 流速越大压强越小
Bernoulli's principle · faster flow, lower pressure
P+½ρv²+ρgh=常数 · 流速↑压强↓ · 管道收缩
P + ½ρv² + ρgh = constant along a streamline
文丘里效应 · 用压强测流量
Venturi effect · measuring flow by pressure
连续性 A₁v₁=A₂v₂ · 喉部压降 · 流量计
Converging–throat–diverging tube: narrow throat → fast flow → low pressure
Hagen–Poiseuille laminar flow
Hagen–Poiseuille laminar flow
Q=πΔPr⁴/8μL · 抛物速度剖面 · r⁴ 依赖
Volumetric flow in a pipe: Q = πΔP·r⁴ / (8μL) — the fourth-power radius law
Aerodynamic drag · the v² law
Aerodynamic drag · the v² law
F=½ρv²C_dA · v² 依赖 · 形状阻力系数
Drag force F_d = ½·ρ·v²·C_d·A — speed squared, shape through C_d
机翼升力 · L = ½ρv²C_LA
Airfoil lift · L = ½ρv²C_LA
L=½ρv²C_LA · 攻角 C_L(α) · 失速
Lift from airspeed, air density, wing area and angle of attack — with the stall
斯托克斯沉降 · v_t = 2r²(ρ_p−ρ_f)g / 9μ
Stokes settling · v_t = 2r²(ρ_p−ρ_f)g / 9μ
终端速度 v=2r²(ρp−ρf)g/9μ · r² 依赖 · 力平衡
Terminal velocity of a small sphere in a viscous fluid — where drag balances net weight
Mach number & Mach cone
Mach number & Mach cone
M=v/√(γRT) · 亚/跨/超/高超音速 · 马赫锥
Speed of sound a=√(γRT) depends only on temperature; M=v/a sets the flow regime
Capillary action & meniscus
Capillary action & meniscus
h=2γcosθ/ρgr · 1/r 依赖 · 浸润/非浸润弯月面
h = 2γcosθ / (ρgr) — surface tension lifts the column, the height scales as 1/r
Entropy change ΔS
Entropy change ΔS
ΔS=Q/T · 等温 nR·ln(V₂/V₁) · 第二定律
Reversible heat transfer ΔS = Q/T · isothermal gas expansion ΔS = nR·ln(V₂/V₁)
Fourier's law of heat conduction
Fourier's law of heat conduction
Q/t=kAΔT/L · 热阻 R=L/kA · 温度梯度
Steady conductive heat rate Q/t = k·A·ΔT / L
Otto-cycle thermal efficiency
Otto-cycle thermal efficiency
η=1−1/r^(γ−1) · 压缩比 · PV 图 · 递减收益
Idealized gasoline engine · η = 1 − 1/r^(γ−1)