Longitudinal Strain Rate
Estimate interval longitudinal normal strain rate from velocity gradients along a supplied flow transect; not transverse or tensor shear strain.
Description
Longitudinal strain rate describes stretching or compression along a flowline.
Longitudinal strain rate describes stretching or compression along a flowline. It can be estimated from the spatial gradient of along-flow velocity.1
Estimate interval longitudinal normal strain rate from velocity gradients along a supplied flow transect; not transverse or tensor shear strain.
When to use Longitudinal Strain Rate
Use this for the following task: Estimate interval longitudinal normal strain rate from velocity gradients along a supplied flow transect; not transverse or tensor shear strain.
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 Longitudinal 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 alongFlowDistancesM, alongFlowVelocitiesMPerYear using the field table, then run the tool.
- Read intervalLongitudinalStrainRatesPerYear. 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 |
|---|---|---|---|
| alongFlowDistancesM | Along flow distances m | list of number; each entry: number | Required |
| alongFlowVelocitiesMPerYear | Along flow velocities m per year | list of number; each entry: number | Required |
Pair velocities with strictly increasing along-flow distances. Compute one signed rate per adjacent interval.2
ε̇xx = Δu/Δx This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| intervalLongitudinalStrainRatesPerYear | Interval longitudinal strain rates per year | list of number |
{
"input": {
"alongFlowDistancesM": [
0,
100,
300
],
"alongFlowVelocitiesMPerYear": [
10,
20,
60
]
},
"output": {
"intervalLongitudinalStrainRatesPerYear": [
0.1,
0.2
]
}
}Limitations and assumptions
Positive rates indicate extension in the chosen coordinate direction. The tool does not compute a complete strain tensor.
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 Shear Strain Rate Depth for this operation: Estimate epsilon_xz=half du/dz with z positive upward from depths increasing downward and negligible dw/dx; distinct from along-flow normal strain or a constitutive Glen prediction. For a complementary task, use Incompressibility Principal Strain Checker for this operation: Audit incompressibility through the trace of three principal normal strain rates and report the closure value; no eigenvectors or full tensor are inferred.
Further background: Ice rheology.
References
-
Ice rheology — PISM
-
Longitudinal Strain Rate — tool.io
Similar or alternative tools
- Shear Strain Rate Depth
Estimate epsilon_xz=half du/dz with z positive upward from depths increasing downward and negligible dw/dx; distinct from along-flow normal strain or a constitutive Glen prediction.
- Incompressibility Principal Strain Checker
Audit incompressibility through the trace of three principal normal strain rates and report the closure value; no eigenvectors or full tensor are inferred.