Як розрахувати Poiseuille Law
Що таке Poiseuille Law?
Poiseuille's law quantifies laminar flow through cylindrical pipes. It shows how flow rate depends on pressure, pipe dimensions, and fluid viscosity.
Формула
The calculator applies Q = (π × ΔP × r⁴) / (8 × η × L)
- Q
- (π × ΔP × r⁴) / (8 × η × L) — (π × ΔP × r⁴) / (8 × η × L)
- L
- L value — Variable used in the calculation
Покрокова інструкція
- 1Enter pressure difference, pipe radius, length, and dynamic viscosity
- 2The calculator applies Q = (π × ΔP × r⁴) / (8 × η × L)
- 3Results show volumetric flow rate
Розв'язані приклади
Введення
ΔP = 1000 Pa, r = 1 mm, L = 1 m, η = 0.001 Pa·s (water)
Результат
Q ≈ 0.39 mL/s
Surprisingly slow
Поширені помилки
- ✕Forgetting to use radius, not diameter, in the r⁴ term
- ✕Confusing dynamic viscosity (Pa·s) with kinematic viscosity (m²/s)
Часті запитання
Why is flow proportional to r⁴?
Small radius changes dramatically affect flow; doubling radius increases flow 16×, which is why plumbing uses large pipes.
How does viscosity affect flow?
Higher viscosity reduces flow; thick oils flow much slower than water at the same pressure difference.
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