Glen Flow Law Strain Rate
Evaluate signed scalar Glen shear strain rate A·E·sign(tau)|tau|^n; A units follow n, and shear tensor strain rate differs by a factor two from engineering shear rate.
Description
Glen-type ice rheology relates stress to nonlinear deformation rate.
Glen-type ice rheology relates stress to nonlinear deformation rate. Scalar tensor shear and engineering shear rates use different conventions.1
Evaluate signed scalar Glen shear strain rate A·E·sign(tau)|tau|^n; A units follow n, and shear tensor strain rate differs by a factor two from engineering shear rate.
When to use Glen Flow Law Strain Rate
Use this for the following task: Evaluate signed scalar Glen shear strain rate A·E·sign(tau)|tau|^n; A units follow n, and shear tensor strain rate differs by a factor two from engineering shear rate.
Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
How to use Glen Flow Law Strain Rate and understand its results
- Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
- Enter signedShearStressesPa, rateFactorPerYearPaToMinusN, glenExponent, enhancementFactor using the field table, then run the tool.
- Read signedShearStrainRatesPerYear. Interpret flags, units, ordering and placeholder values using the rules below.
- Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| signedShearStressesPa | Signed shear stresses pa | list of number; each entry: number | Required |
| rateFactorPerYearPaToMinusN | Rate factor per year pa to minus n | number | Required |
| glenExponent | Glen exponent | number | Required |
| enhancementFactor | Enhancement factor | number | Required |
Require nonempty signed stresses and positive rate factor, exponent and enhancement. Evaluate each stress preserving sign; a zero stress returns zero rate.2
ε̇ = A E sign(τ)|τ|^n This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| signedShearStrainRatesPerYear | Signed shear strain rates per year | list of number |
{
"input": {
"signedShearStressesPa": [
-2,
0,
2
],
"rateFactorPerYearPaToMinusN": 0.1,
"glenExponent": 3,
"enhancementFactor": 2
},
"output": {
"signedShearStrainRatesPerYear": [
-1.6,
0,
1.6
]
}
}Limitations and assumptions
Rate-factor units depend on n and the year convention. Engineering shear rate is twice the tensor shear rate; temperature dependence is not fitted.
Constants and empirical coefficients are supplied rather than calibrated. Check units and observational applicability before interpreting the model. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.
Alternative or Complementary methods
Choose Weertman Basal Sliding Law for this operation: Evaluate a supplied Weertman-type power sliding law C·sign(tau)|tau|^p/N^q; coefficient is unit-specific and zero/negative effective pressures lie outside the model. For a complementary task, use Deformation Rate Glen N Exponent for this operation: Fit n and apparent A from positive stress/strain observations in log space; fitted A absorbs enhancement and calibration, unlike a forward Glen-law prediction.
Further background: Ice rheology.
References
-
Ice rheology — PISM
-
Glen Flow Law Strain Rate — tool.io
Similar or alternative tools
- Weertman Basal Sliding Law
Evaluate a supplied Weertman-type power sliding law C·sign(tau)|tau|^p/N^q; coefficient is unit-specific and zero/negative effective pressures lie outside the model.
- Deformation Rate Glen N Exponent
Fit n and apparent A from positive stress/strain observations in log space; fitted A absorbs enhancement and calibration, unlike a forward Glen-law prediction.