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This paper discusses the high heat transfer demand from application prospects. Hybrid nanofluid is a well-known liquid with higher heat transfer capabilities. Here, the time-dependent flow of hybrid nanocomposite, by hybridizing the metal (Cu) and metallic oxide (Al2O3) and inserting them into water-based nanofluid, is examined. The flow takes place over the upper half of a parabolic surface. The modified Buongiorno model is used to express the physical phenomenon in mathematical equations form. The governing system of partial differential equations (PDEs) is reduced to a system of ordinary differential equations (ODEs) by applying certain transformations. Computation of the final equations has been done by a numerical scheme, known as the Keller-box method. The significance of dimensionless flow causing physical parameters is shown through graphs and tables. The findings reveal that among the hybrid nanofluids with two types of nanoparticles varying from 0% to 5%, a nanofluid having 5% of both nanoparticles is the one with the maximum surface drag force and heat transport rate, which are 41.8% and 22.7% higher to water, respectively. A higher amount of Al2O3 than Cu results in a suitable hybrid combination for application purposes to produce higher cooling rate with less surface drag. Also, the thickness of the surface, unsteadiness, nanoparticles suspension and power index of wall temperature enhance the heat transfer rate. Thin parabolic surfaces experience less drag and have larger boundary layer thicknesses (momentum, thermal and concentration) as compared to thicker parabolic surfaces. Also, the addition of copper slows down the hybrid fluid flow field, but alumina magnifies the mobility of hybrid fluid. [ABSTRACT FROM AUTHOR]

The article deals with 2D unsteady nanofluid flow past a vertical wedge along with nonlinear mixed convection. Brownian diffusion and thermophoresis effects are considered to model nanofluid flow. Convenient transformations are assumed to change the coupled nonlinear governing PDEs into ODEs. To analyze the problem, the solutions of transformed equations are numerically achieved via 'bvp4c', a MATLAB approach. Graphical presentation is adopted to see the impact of various influential parameters. Results reveal that nonlinear temperature and concentration convection parameters exhibit the same impact for velocity, temperature and concentration profile, though nonlinear convection parameter for temperature is more impactful than concentration. Velocity overshoot is observed for assisting flow situations. In nonlinear mixed convection flow, skin-friction coefficient, heat and mass transfer rates prominently change for favorable and adverse pressure gradient conditions. [ABSTRACT FROM AUTHOR]

This analysis is framed to take care of the high heat transfer demand from various application prospects and in this context nanofluid may be in consideration because nanofluids are well-known liquids with higher heat transfer capabilities. Here, a mixed convection flow of Molybdenum disulfide-water (MoS2-H2O) nanofluid on a moving vertical plate is examined when there are chemical reactions. Nanofluid problem is investigated using Tiwari and Das model, and numerically solved by "bvp4c" method. For the considered effects in the study, overshoots in temperature profile of nanofluid are observed. Momentum and thermal layer thicknesses become thinner with suction and thicker with blowing. Temperature overshoot is higher for blowing cases. Enhanced homogeneous–heterogeneous reactions lead to rise of the concentration boundary layer's thickness. Also, magnitude of surface-drag force decays and cooling rate enhances with MoS2-H2O nanofluid mixed convection. For weaker suction and for blowing, cooling of nanofluid is faster with larger volume fraction of nanoparticles, but contrast results are obtained for greater suction. Importantly, compared to the homogeneous reaction, the heterogeneous reaction exhibits more impactful influences on flow and heat-mass transport characters. [ABSTRACT FROM AUTHOR]

Separation control and formation of boundary layer Newtonian flow in a diverging permeable channel in Darcy-Forchheimer porous material having suction/injection are discussed. Self-similar equations from governing equations are acquired and existence conditions for boundary layer structure are derived using nature of velocity gradient inside boundary layer. It reveals that if sum of Darcy permeability parameter and twice of Forchheimer parameter exceeds 2, then the boundary layer flow always exists with all type of mass suction/injection and even without suction/injection. Also, if mass suction parameter goes beyond 2/2, then there is no matter what are the values of Darcy permeability parameter and Forchheimer parameter, a boundary layer exists inside the divergent channel. In addition, obtained numerical solutions are exhibited graphically. It reveals that thicknesses of velocity and thermal boundary layers reduce with Darcy and non-Darcy resistances of porous medium and fluid temperature also diminishes. The velocity and temperature reduce with increment of mass suction and contrary results are found for mass injection. [ABSTRACT FROM AUTHOR]

A model study of unsteady stagnation-point flow of most important nanoparticles, that is, carbon nanotubes suspended nanofluid towards shrinking/expanding sheet with convective boundary condition is demonstrated. Two types of carbon nanotubes, namely, single-wall and multi-wall nanotubes are carefully considered. Numerical solutions of converted equations from governing equation of the problem are obtained and those are graphically presented. Similar to without carbon nanotubes case, dual and unique solutions in specific ranges of velocity ratio parameter are achieved. Analysis disclosures that the condition on range where dual solutions exist is unaltered with solid-volume fraction and type of carbon nanotubes. The surface drag-force and heat transfer rate from wall are larger for single-walled carbon nanotubes nanofluid than multi-walled carbon nanotubes nanofluid. An increment in the parameter related to convective boundary condition generates high rate of heat transfer. After stability analysis, it is identified that in case of dual solutions, upper branch is stable and lower branch is unstable, while unique solution is always stable. [ABSTRACT FROM AUTHOR]

This paper deals with a detailed investigation of the effects of various metal oxide nanoparticles on unsteady stagnation point flow of a hybrid base fluid impinging on a flat surface. The 'single-phase' nanofluid model, i.e., the Tiwari and Das model, is considered for the study. We consider water and ethylene glycol in 1:1 ratio as the base fluid and four different types of metal oxides, namely, CuO, TiO 2 , ZnO and MgO as the nanoparticles. Using similarity transformations, the conservation equations are transformed into self-similar ordinary differential equations. Dual and unique similarity solutions are obtained for certain set of values of parameters. The analysis explores many important findings. Dual self-similar solutions exist up to a certain critical value of the decelerating unsteady parameter and the critical value is independent of the type of metal oxide nanoparticles considered. The strongest surface drag force is observed for the nanofluid with CuO nanoparticles, while the weakest is for the nanofluid with MgO nanoparticles. The heat transfer rate is highest for the nanofluid with CuO nanoparticles and lowest for the nanofluid with TiO 2 nanoparticles. Also, the boundary layer is thickest for the nanofluid with MgO nanoparticles. [ABSTRACT FROM AUTHOR]

This work is addressed to the study of MHD boundary layer couple-stress fluid flow considering the non-Fourier Cattaneo-Christov hyperbolic heat transfer model over a bidirectional movable surface. The group of continuous symmetry transformations is adopted to determine invariant solutions of governing equations for boundary layer fluid flow with heat transfer. Using Lie symmetry analysis, the governing equations having boundary conditions are converted into self-similar equations under a group of transformations only when initial prescribed velocity distributions are in linear form. The similar velocity and temperature profiles are obtained and the effects of the magnetic field and hyperbolic heat-flux are explored. The study revealed that the flow boundary layer thickness becomes thicker due to the increase of the couple-stress parameter, while the thermal boundary layer thickness becomes thinner for increasing relaxation time of heat-flux. The couple-stress parameter acts in the flow field in opposite style to the magnetic parameter. Also, for an increase in the couple-stress parameter and the thermal relaxation-time parameter, the higher wall heat transfer is exhibited. [ABSTRACT FROM AUTHOR]