Pyörreviskosimetria

Pyörreviskosimetria, also known as eddy viscosity measurement, is a technique used to determine the eddy viscosity of a fluid. Eddy viscosity is a concept used in fluid dynamics to account for the increased momentum transfer due to turbulent eddies in a flow. Unlike molecular viscosity, which arises from the random motion of molecules, eddy viscosity is a macroscopic property that represents the turbulent mixing of the fluid.

The principle behind pyörreviskosimetria involves inducing a controlled eddy motion in the fluid and then measuring the forces or stresses required to maintain this motion. This can be achieved through various experimental setups, such as rotating cylinders, oscillating plates, or by introducing a controlled disturbance into a flow. By analyzing the relationship between the induced motion and the resulting forces, the eddy viscosity can be calculated.

This technique is particularly useful in studying turbulent flows where direct measurement of individual eddy properties is challenging. Eddy viscosity is a crucial parameter in many computational fluid dynamics (CFD) models used to simulate turbulent phenomena. Understanding and accurately measuring eddy viscosity allows for more precise predictions of flow behavior, heat transfer, and mass transport in applications ranging from aerodynamics and hydrodynamics to chemical engineering and meteorology. The term "pyörreviskosimetria" is a Finnish term combining "pyörre" (eddy) and "viskosimetria" (viscometry).