Pulsations

Pulsations are periodic changes in a quantity that recur over time, such as pressure, brightness, or flow. They can be regular or irregular and may be simple or complex. Key descriptors include period, frequency, amplitude, and phase, which together define the pulsation pattern.

In astronomy, pulsating stars physically oscillate in radius and luminosity. They exhibit radial or non-radial modes, with classes such as Cepheids, RR Lyrae, and Delta Scuti. Periods span minutes to months, and the regularity of pulsations makes these stars useful as distance indicators and probes of stellar structure.

Biology and medicine use the term pulsatility to describe rhythmic processes such as the heartbeat, arterial pulses, and episodic hormone release. Pulsatile blood flow and heartbeats provide essential cues for diagnosis and assessment of cardiovascular and endocrine function.

In engineering, pulsations arise from pumps, valves, or turbines and produce pressure and flow fluctuations that can cause noise and fatigue. Mitigation strategies include dampers, accumulators, and flow conditioning, which reduce amplitude and smooth the signal.

Pulsations are analyzed with time-domain plots and frequency-domain tools such as Fourier transforms or wavelets, enabling identification of dominant periods and modes. Models range from simple harmonic oscillators to damped, multi-mode systems.