Dispersionkertoimen

Dispersionkertoimen, or dispersion coefficient, is a quantitative measure of the spreading out of particles, substances, or wave energy as they move through a medium. It is a key parameter in fields such as hydrology, atmospheric science, and optical physics, where it describes how substances or waves diffuse due to random motion or refractive index variations.

In groundwater hydrology, the dispersion coefficient combines mechanical dispersion, resulting from velocity variations in a porous matrix, with molecular diffusion. It appears in the advection–dispersion equation, which models solute transport in aquifers. The coefficient is typically expressed in metres squared per second and is often split into longitudinal and transverse components to reflect anisotropic spreading. Engineers estimate it from field tracer tests or laboratory measurements to predict contaminant plume evolution.

Atmospheric scientists use dispersion coefficients to describe how pollutants or aerosols spread in the turbulent boundary layer. The coefficient is influenced by wind speed, stability class, and terrain roughness. Dispersion models, such as Gaussian plume models, incorporate these coefficients to estimate ground-level concentrations downwind of emission sources.

In optical physics, the dispersion coefficient characterizes wavelength-dependent propagation speeds of light in optical fibers or waveguides. Chromatic dispersion, in particular, determines pulse broadening in fiber‑optic communications. The coefficient is measured in picoseconds per nanometer per kilometre and is critical for designing dispersion‑managed transmission systems.

The dispersion coefficient is related to but distinct from the diffusion coefficient; the former accounts for large‑scale spreading phenomena, while the latter reflects microscopic random motion. It is often derived from the second spatial moment of the concentration or intensity distribution and is central to both theoretical analyses and practical applications in environmental engineering, meteorology, and photonics.