Introductory FLUENT Notes Fluent User Services cente ANSYS LUENT v6. 3 December 2006 wwfluentusers. com FLUENT What is Turbulence? Unsteady, irregular(aperiodic)motion in which transported quantities (maSs, momentum, scalar species) fluctuate in time and space Identifiable swirling patterns characterize turbulent eddies Enhanced mixing(matter, momentum, energy, etc. )results fluid properties and velocity exhibit random variations Statistical averaging results in accountable, turbulence related transport mechanisms This characteristic allows for turbulence modeling Contains a wide range of turbulent eddy sizes(scales spectrum) The size/velocity of large eddies is on the order of mean flow a Large eddies derive energy from the mean flow Energy is transferred from larger eddies to smaller eddies In the smallest eddies, turbulent energy is converted to internal energy by vIscous dissipation C 2006 ANSYS. nc All ANSYS, Inc. Proprietar© 2006 ANSYS, Inc. All rights reserved. 6-2 ANSYS, Inc. Proprietary Fluent User Services Center www.fluentusers.com Introductory FLUENT Notes FLUENT v6.3 December 2006 What is Turbulence? ◆ Unsteady, irregular (aperiodic) motion in which transported quantities (mass, momentum, scalar species) fluctuate in time and space ⚫ Identifiable swirling patterns characterize turbulent eddies. ⚫ Enhanced mixing (matter, momentum, energy, etc.) results ◆ Fluid properties and velocity exhibit random variations ⚫ Statistical averaging results in accountable, turbulence related transport mechanisms. ⚫ This characteristic allows for turbulence modeling. ◆ Contains a wide range of turbulent eddy sizes (scales spectrum). ⚫ The size/velocity of large eddies is on the order of mean flow. ◼ Large eddies derive energy from the mean flow ⚫ Energy is transferred from larger eddies to smaller eddies ◼ In the smallest eddies, turbulent energy is converted to internal energy by viscous dissipation