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水力学
12
engines
Moody chart · Darcy friction factor
Moody chart · Darcy friction factor
f vs Re与ε/D · 层流64/Re · 湍流Swamee-Jain
Friction factor f from Reynolds number and relative roughness · Swamee-Jain
Pipe head loss · Darcy-Weisbach
Pipe head loss · Darcy-Weisbach
达西hf=f·L/D·v²/2g · +局部ΣK·v²/2g
Major friction loss plus minor fitting losses, both from the velocity head
Hydraulic & energy grade lines
Hydraulic & energy grade lines
测压管水头线HGL · 能量线EGL · 沿管高程+v²/2g
Elevation, HGL and EGL plotted along a pipe under friction
Hardy-Cross · pipe-loop balancing
Hardy-Cross · pipe-loop balancing
环校正ΔQ=−Σ(KQ|Q|)/Σ(2K|Q|) · 迭代平衡
Iterative loop correction ΔQ until the head loss around the loop → 0
Pump & system curves — operating point
Pump & system curves — operating point
H=H0−aQ² ∩ Hs+bQ² · 工况点Q*/H*
Where the pump curve meets the system curve, the pump runs
NPSH — cavitation check on the suction side
NPSH — cavitation check on the suction side
NPSHa=(Patm−Pvap)/γ−hs−hf · <NPSHr气蚀
NPSHa must stay above the pump's required NPSHr, or the pump cavitates
Open-channel flow · Manning's equation
Open-channel flow · Manning's equation
曼宁Q=(1/n)A·R^⅔·S^½ · 水力半径 · 弗劳德数
Uniform flow: pick the channel, read A, P, R, V, Q and the Froude number
Specific energy · E–y diagram
Specific energy · E–y diagram
E=y+q²/2gy² · E-y图 · 临界水深yc · 缓/急流
E = y + q²/(2g y²): read the critical depth, minimum energy and the two alternate depths
Hydraulic jump · conjugate depths
Hydraulic jump · conjugate depths
共轭水深y2/y1=½(√(1+8Fr1²)−1) · 能量损失 · 跃型
y2/y1 = ½(√(1+8Fr1²) − 1): read the sequent depth, energy loss and jump type
Weir flow · discharge measurement
Weir flow · discharge measurement
矩形Q=⅔Cd√2g·L·H^1.5 · 三角堰H^2.5 · 量测
Head over the crest sets the flow rate · rectangular & V-notch weirs
Orifice discharge (Torricelli)
Orifice discharge (Torricelli)
托里拆利v=√2gh · Q=Cd·A·√2gh · 缩脉Cc/Cv/Cd
Ideal velocity, actual discharge, coefficients and the jet trajectory
Water hammer (Joukowsky surge)
Water hammer (Joukowsky surge)
儒可夫斯基Δp=ρaΔv · 波速a · 临界关阀2L/a
Pressure rise from valve closure and the wave that travels the pipe