pulsation

Pulsation broadly refers to a rhythmic, often periodic, variation of a quantity associated with an object or system. The variation can be in radius, volume, pressure, temperature, luminosity, or other properties, and is typically characterized by its period (or frequency) and amplitude.

In physiology, the term is closely linked to the arterial pulse, the rhythmic expansion of arteries caused by heartbeats. The pulse rate provides information about heart rate and cardiovascular status; pulse strength conveys stroke volume and vascular tone.

In astronomy, pulsating stars such as Cepheids and RR Lyrae vary regularly in brightness due to cyclic expansions and contractions of their outer layers. The period–luminosity relation of Cepheids enables distance measurement in astronomy.

In fluid mechanics and engineering, pulsations are fluctuations in flow rate or pressure, often caused by pumps, valves, or turbulence. Pressure pulsations can induce vibration and fatigue, so dampers and compliant components are used to mitigate them.

In physics, pulsation can be self-excited (as in some stellar pulsations) or driven by an external force; it is related to, but distinct from, traveling waves, since the entire body may contract and expand in a coherent manner.

Measurements rely on appropriate sensors: electrodes or photoplethysmography for physiological pulses, photometry or spectroscopy for stellar pulsations, pressure transducers for flow pulsations.