*Article* **Appearance of a Solitary Wave Particle Concentration in Nanofluids under a Light Field**

**Abram I. Livashvili <sup>1</sup> , Victor V. Krishtop 2,\*, Polina V. Vinogradova <sup>1</sup> , Yuriy M. Karpets <sup>1</sup> , Vyacheslav G. Efremenko <sup>1</sup> , Alexander V. Syuy <sup>3</sup> , Evgenii N. Kuzmichev <sup>4</sup> and Pavel V. Igumnov <sup>4</sup>**


**Abstract:** In this study, the nonlinear dynamics of nanoparticle concentration in a colloidal suspension (nanofluid) were theoretically studied under the action of a light field with constant intensity by considering concentration convection. The heat and nanoparticle transfer processes that occur in this case are associated with the phenomenon of thermal diffusion, which is considered to be positive in our work. Two exact analytical solutions of a nonlinear Burgers-Huxley-type equation were derived and investigated, one of which was presented in the form of a solitary concentration wave. These solutions were derived considering the dependence of the coefficients of thermal conductivity, viscosity, and absorption of radiation on the nanoparticle concentration in the nanofluid. Furthermore, an expression was obtained for the solitary wave velocity, which depends on the absorption coefficient and intensity of the light wave. Numerical estimates of the concentration wave velocity for a specific nanofluid—water/silver—are given. The results of this study can be useful in the creation of next-generation solar collectors.

**Keywords:** nanofluid; nonlinear dynamics; colloidal suspension; solitary wave; Burgers–Huxley equation
