FLOW / 007
Pressure Drop Calculator
Estimate fully developed internal-flow pressure loss using Darcy-Weisbach, Reynolds number and a smooth/rough-pipe friction-factor approximation, with optional minor-loss coefficient K.
Pressure drop is only as good as the friction model behind it.
For laminar circular-pipe flow, f = 64/Re. For turbulent flow this tool uses the explicit Swamee–Jain approximation to the Colebrook relation. In the transitional band it provides a blended engineering estimate and flags the uncertainty.
Calculate Re. Re = ρUD/μ.
Estimate Darcy f. Laminar or roughness-dependent turbulent correlation.
Apply Darcy-Weisbach. Major loss = f(L/D)ρU²/2.
Add minor losses. ΣK·ρU²/2 when fittings/components are represented by K-values.
Use the hand calculation to challenge the CFD, not just to produce another number.
Align pressure definitions, reporting stations, flow rate, roughness and local-loss scope before deciding the CFD is wrong.