The role of computational fluid dynamics (CFD) in hair science.

The use of computational fluid dynamics (CFD) as a virtual prototyping tool is widespread in the consumer packaged goods industry. CFD refers to the calculation on a computer of the velocity, pressure, and temperature and chemical species concentrations within a flowing liquid or gas. Because the performance of manufacturing equipment and product designs can be simulated on the computer, the benefit of using CFD is significant time and cost savings when compared to traditional physical testing methods. CFD has been used to design, scale-up and troubleshoot mixing tanks, spray dryers, heat exchangers and other process equipment. Recently, computer models of the capillary wicking process inside fibrous structures have been added to CFD software. These models have been used to gain a better understanding of the absorbent performance of diapers and feminine protection products. The same models can also be used to represent the movement of shampoo, conditioner, colorants and other products through the hair and scalp. In this paper, we provide an introduction to CFD and show some examples of its application to the manufacture of consumer products. We also provide sonic examples to show the potential of CFD for understanding the performance of products applied to the hair and scalp.