Lockhart-Martinelli Two-Phase Pressure Drop Calculator
Calculate frictional pressure gradient and total pressure drop for simultaneous two-phase gas-liquid pipe flow using the classical Lockhart-Martinelli method with Chisholm multipliers.
Pipe Geometry & Flow Length
Liquid & Gas Phase Flow Rates
Two-Phase Pressure Drop & Multipliers
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Frequently Asked Questions
What is the physical meaning of the Martinelli parameter X?
The Martinelli parameter X represents the ratio of frictional pressure gradient if the liquid phase were flowing alone in the pipe to the pressure gradient if the gas phase were flowing alone: X = sqrt((dP/dL)L / (dP/dL)G). Large X (> 10) indicates a liquid-dominant flow, whereas small X (< 0.1) denotes a highly dispersed gas/vapor-dominant regime.
Why does two-phase pressure drop vastly exceed single-phase liquid drop?
In two-phase flow, fast-moving gas drags and shears the slower liquid film along the pipe wall, generating violent interfacial waves and turbulent eddy dissipation. The Chisholm two-phase multiplier Phi_L^2 frequently amplifies the nominal single-phase liquid pressure drop by factors of 10× to over 100×.
What is liquid holdup and why does it differ from input volume fraction?
Because gas is much lighter and less viscous than liquid, it travels faster through the pipe (phase slip). As a result, the liquid "slips" behind, accumulating in the pipe cross-section so that the in-situ liquid holdup (alpha_L) is substantially greater than the volumetric inlet liquid fraction (lambda_L).