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Saffman-Taylor Viscous Fingering Calculator

The Saffman-Taylor instability (viscous fingering) occurs when a low-viscosity fluid displaces a higher-viscosity fluid in a porous medium or narrow Hele-Shaw cell.

Viscosity of the displaced fluid (e.g. 0.1 Pa·s for crude oil).

Viscosity of injecting fluid (0.001 Pa·s for water).

Displacement front propagation velocity.

Surface tension between the two immiscible fluids.

Gap thickness between parallel glass plates.

Calculated Result
12.89 mm

Dominant Finger Wavelength (λmax)

Instability Growth Rate (σmax)

4.78 s⁻¹

Viscosity Contrast Ratio (μ₂/μ₁)

100.0x (Unfavorable)

Hele-Shaw Permeability (b²/12)

8.333e-8 m²

Calculation Breakdown

  1. Viscous Fingering Instability ConditionDriving fluid is less viscous than displaced fluid (μ₁ < μ₂), causing adverse mobility ratio
  2. Fastest Growing Wavelengthλmax = 2π / kmax = 12.89 mm with growth rate 4.78 s⁻¹

What Is the Saffman-Taylor Viscous Fingering Calculator?

In 1958, P.G. Saffman and Sir Geoffrey Taylor identified that when a fluid of low viscosity pushes a fluid of higher viscosity, the planar interface is unstable.

A small advance of the low-viscosity fluid encounters less flow resistance, causing it to accelerate ahead and form fingers.

How Does the Saffman-Taylor Viscous Fingering Calculator Work?

Viscosity contrast drives the instability, while interfacial surface tension suppresses short-wavelength perturbations.

The balance between Darcy viscous forces and Laplace capillary pressure defines a unique fastest-growing wavelength λmax.

Saffman-Taylor Viscous Fingering Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

k_{max} = \sqrt{\frac{U (\mu_2 - \mu_1)}{3 \gamma k_{perm}}}, \quad \lambda_{max} = \frac{2 \pi}{k_{max}}, \quad k_{perm} = \frac{b^2}{12}

Saffman-Taylor linear stability analysis for fastest-growing viscous finger wavelength.

How to Use the Saffman-Taylor Viscous Fingering Calculator

  1. Enter fluid viscosities, interface velocity, interfacial tension, and cell gap width.
  2. Check dominant finger wavelength and growth rate.

Step-by-Step Example Calculation

Waterflooding Secondary Oil Recovery

Input Values:

moreViscousFluidPaS:0.08
lessViscousFluidPaS:0.001
interfaceVelocityMPerS:0.01
interfacialTensionNPerM:0.03
heleshawGapWidthMeters:0.001
Worked Steps: Predicts finger wavelength ~7.9 mm during water displacement.

Understanding Your Result

Higher velocity or higher viscosity contrast produces thinner, more numerous fingers, accelerating breakthrough.

Factors That Affect the Result

  • Adding polymers to the displacing water increases its viscosity (μ1), stabilizing the interface against fingering.

When Should You Use This Calculator?

  • Enhanced oil recovery (EOR) modeling, groundwater contaminant transport, and microfluidics.

Assumptions & Limitations

  • Linear stability analysis in a 2D Hele-Shaw cell with Darcy flow.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Classical Saffman-Taylor theoretical benchmark.

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