The Eckert number (Ec) is a dimensionless number used in continuum mechanics. It expresses the relationship between a flow's kinetic energy and the boundary layer enthalpy difference, and is used to characterize heat dissipation. It is named after Ernst R. G. Eckert. It is defined as where * u is the local flow velocity of the continuum, * cp is the constant-pressure local specific heat of the continuum, * is the difference between wall temperature and local temperature.