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อัปเดต 2026-09-07
Friction models
DW · HW · CW
Three head-loss models: Darcy–Weisbach (DW), Hazen–Williams (HW), and exact Colebrook–White (CW). Chosen per project.
Darcy–Weisbach is the general, physically-grounded model (any fluid, any regime). Hazen–Williams is an empirical water-only fit common in fire and municipal work. Colebrook–White is the exact implicit turbulent friction relation.
ค่าที่ต้องกรอก
| ค่า | คำอธิบาย |
|---|---|
| Friction model | 'DW' | 'HW' | 'CW' — set in Project Settings. |
คำนวณอย่างไร
Darcy–Weisbach needs a friction factor f. In the turbulent regime we solve the exact implicit Colebrook–White relation (fixed-point iteration); the marching engine uses the explicit Swamee–Jain approximation. Hazen–Williams is a direct empirical head-loss formula with no explicit f.
สมการ
Colebrook–White (exact, implicit)
ε = absolute roughness. Solved iteratively for f — the "CW" option.
Swamee–Jain (explicit)
A closed-form approximation to Colebrook (within ~1%) — used inside the marching kernel where an iteration per segment is costly.
Hazen–Williams (water, SI)
C = roughness coefficient (≈100–150). Empirical, water-only, turbulent — the "HW" option; fire paths use it per NFPA-13.
ข้อควรระวัง
noteHazen–Williams is only valid for water in turbulent flow — the engine keeps it loud outside that envelope.
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