Laminar or parabolic flow describes flow in a vessel that is faster near the center of the vessel and slower near the vessel wall. Flow is slower at the vessel wall due to the viscosity of blood. Assuming that the entire vessel is completly insonated by the Doppler beam the velocities from all regions would be represented in the Doppler signal. The Doppler signal would display a wide range of frequencies. The spread of frequencies within the Doppler spectrum is known as spectral broadening.
