A fluid jet becomes unstable when the perturbation wavelength exceeds the jet perimeter due to the interplay of interfacial energy and surface tension. This instability occurs because longer wavelengths can lead to greater variations in pressure and velocity, disrupting the jet's coherence. The balance between inertial forces and surface tension is crucial; when the wavelength is too long, surface tension cannot effectively stabilize the jet. Additionally, the geometry of the jet influences how perturbations propagate and grow. Understanding these dynamics is essential for applications in fluid dynamics and engineering.
