Sekoitusindeksi

Sekoitusindeksi is a dimensionless quantity used to quantify the degree of mixing in multiphase or multi-component systems. It is commonly applied in chemical and process engineering, but also used in environmental studies and polymer processing. In many contexts it ranges from 0 to 1, where 0 indicates no mixing and values approaching 1 indicate near-complete or well-distributed mixing.

A typical definition relates the index to the concentration variance within a control volume. One common form is MI = 1 − (σ/σ0), where σ is the standard deviation of a concentration field at a given time and σ0 is the initial standard deviation before mixing began. Another common variant expresses MI as MI = 1 − Var(c)/Var(c0). Different definitions exist, and some use concentration histograms, spatial averaging, or visual assessments, so the exact formula can vary between applications.

Calculation and measurement are usually based on experimental data or simulation results. In experiments, samples are taken across a cross-section or control volume and analyzed for concentration, or tracer imaging and image analysis are used. In computational fluid dynamics, the index can be computed from the simulated concentration field. The choice of sampling locations, averaging domain, and time window strongly influences the resulting value.

Applications include evaluating mixing performance in stirred tank reactors, pipe and duct flows, and polymer blends, as well as assessing dispersion and remediation in environmental engineering. Limitations include dependence on the chosen measurement scale, potential sensitivity to noise, and the fact that MI captures only overall dispersion (variance) rather than spatial pattern details. When used, the definition should be stated explicitly.