Subdomain method for unsteady flow of ZnO − SAE50 nano-lubricant through expanding/contracting walls in an asymmetric porous horizontal channel.

The laminar time-dependent fluid flow of an engine oil (Zinc Oxide−Society of Automotive Engineers 50 alias ZnO − SAE 50 nano-lubricant) through a rectangular channel is presented. The channel is made up of permeable walls that can expand or contract. It is also under the impact of thermal radiation and magnetic field is dominant enough to be ignored. The lower and upper walls of the channel bear different permeabilities and temperatures. Hence, a system of governing nonlinear partial differential equations is setup by means of conversation laws and aforementioned assumptions. By the implementation of suitable similarity transformations and conservation of mass, the equations for momentum, and energy are reduced to relatively simpler system of ordinary differential equations. The resulting system is solved by employing a semi analytical technique named as Subdomain Method (SDM). The results are further supported by another numerical scheme (a duos of shooting method along with Runge-Kutta-Fehlberg algorithm). The functioning of flow and temperature profiles under the variation in significant physical parameters is demonstrate upon the description of graphs and tables. Thorough discussions and concluding results are also presented at the end of the manuscript. • The flow of ZnO-SAE50 nanolubricant inside a rectangular channel with expanding and contacting permeable walls is considered. • Nanoparticles volume fraction affects the flow and temperature profiles. • The rate of heat transfer at the walls is affected by imposed thermal radiation and the presence of magnetic field. • Subdomain Method can be used to solve problems related to the flows inside expanding contacting channels. • The flow is only due to suction or injection. [ABSTRACT FROM AUTHOR]