Amable Liñán: The art of scale separation in fluid-flow analysis

Abstract

Amable Liñán, the founder of the Spanish school of fluid mechanics, passed away in Madrid on November 8, 2025. A leading theoretician in combustion and fluid mechanics, he made exemplary use of perturbation methods to simplify the analysis of complex fluid-flow problems. The present manuscript reviews his contributions to combustion science and non-reactive fluid mechanics. Two representative examples of his purely fluid-mechanical work are discussed in detail to illustrate how the disparate time and length scales that characterize many fluid-flow problems can be exploited to simplify their description.