In this paper, unsteady flow and heat transfer of water flow in a backward-facing step under pulsating nanofluid blowing are studied numerically. Attention is focused to examine the impact of this type of blowing and its pertinent parameters on the heat transfer performance and to detect possible non-equilibrium between the base fluid and the nanoparticles inside the flow field. To this aim, the Eulerian-Eulerian two-phase model is adopted. This approach consists of separate equation sets for the base fluid and the nanoparticles. So, it provides details of the flow field for each of the constituents, separately. Computations are undertaken for different cases and the consequences of the frequency, amplitude, and the mean velocity of the pulsating blowing as well as the type, diameter, and the volume fraction of the nanoparticles therein on the heat transfer characteristics are analyzed. It is found that in addition to thermal conductivity of the blown nanoparticles, their penetration into the water flow is an important trait that has a momentous role on the heat transfer rate. In the current Eulerian-Eulerian simulation, temperature distributions of the base fluid and the nanoparticles are similar but the corresponding velocity fields are quite distinct. This reveals a kind of non-equilibrium between the base fluid and the nanoparticles inside the flow that invalidates equilibrium approaches (e.g., the single-phase model or the two-phase mixture model) for the description of the problem.

The present study investigates the hydromagnetic pulsating nanofluid flow in a porous channel with thermal radiation. In this work, we considered water as the base fluid and silver (Ag), copper (Cu), alumina (Al2O3) and titanium dioxide (TiO2) as nanoparticles. The Maxwell-Garnetts and Brinkman models are used to evaluate the effective thermal conductivity and viscosity of the nanofluid. The governing equations are solved analytically and the influence of various parameters on velocity, temperature and heat transfer rate has been discussed through graphical results. From the results, it is found that the rate of heat transfer enhances with an increase of nanoparticle volume fraction. Further, the heat transfer rate is higher for silver nanoparticles as compared with copper, alumina and titanium dioxide.

Turbochargers are widely used in Diesel engines as a means of increasing the output power. Most of them are fitted with radial or mixed flow turbines. In applications where high boost pressure is required, radial turbines are replaced with mixed flow turbines with positive rotor inlet blade angle so that they can achieve a maximum efficiency at a lower value of blade speed to isentropic expansion velocity ratio than the usual 0.7 (for radial turbines). This study, performed with the ICEM and CFX softwares of ANSYS, presents a numerical performance prediction of a mixed flow turbine for a wide range of rotational speeds and pressure ratios. The influence of the clearance between the rotor tip blades and the casing on the turbine performances is also investigated. A simulation of the turbine under pulsed inlet flow conditions is also presented.