Theoretical Analysis of Cu-H2O, Al2O3-H2O, and TiO2-H2O Nanofluid Flow Past a Rotating Disk with Velocity Slip and Convective Conditions

The nanofluids can be used in the subsequent precise areas like chemical nanofluids, environmental nanofluids, heat transfer nanofluids, pharmaceutical nanofluids, drug delivery nanofluids, and process/extraction nanofluids. In short, the number of engineering and industrial applications of nanofluid technologies, as well as their emphasis on particular industrial applications, has been increased recently. Therefore, this exploration is carried out to analyze the nanofluid flow past a rotating disk with velocity slip and convective conditions. The water-based spherical-shaped nanoparticles of copper, alumina, and titanium have been considered in this analysis. The modeled problem has been solved with the help of homotopic technique. Convergence of the homotopic technique is shown with the help of the figure. The role of the physical factors on radial and tangential velocities, temperature, surface drag force, and heat transfer rate are displayed through figures and tables. The outcomes demonstrate that the surface drag force of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2 has been reduced with a greater magnetic field. The radial and tangential velocities of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2, and pure water have been augmented via magnetic parameter. The radial velocity of the water-based spherical-shaped nanoparticle of Cu has been augmented via nanoparticle volume fraction, whereas reduced for the Al2O3 and TiO2 nanoparticles. The tangential velocity of the water-based spherical-shaped nanoparticles of Cu, Al2O3, and TiO2 has reduced via nanoparticle volume fraction. Also, the variations in radial and tangential velocities are greater for slip conditions as compared to no-slip conditions.

Anisotropy of Unstably Stratified Near-Surface Turbulence

Classic Monin–Obukov similarity scaling states that in a stationary, horizontally homogeneous flow, in the absence of subsidence, turbulence is dictated by the balance between shear production and buoyancy production/destruction, whose ratio is characterized by a single universal scaling parameter. An evident breakdown in scaling is observed though, through large scatter in traditional scaling relations for the horizontal velocity variances under unstable stratification, or more generally in complex flow conditions. This breakdown suggests the existence of processes other than local shear and buoyancy that modulate near-surface turbulence. Recent studies on the role of anisotropy in similarity scaling have shown that anisotropy, even if calculated locally, may encode the information about these missing processes. We therefore examine the possible processes that govern the degree of anisotropy in convective conditions. We first use the reduced turbulence-kinetic-energy budget to show that anisotropy in convective conditions cannot be uniquely described by a balance of buoyancy and shear production and dissipation, but that other terms in the budget play an important role. Subsequently, we identify a ratio of local time scales that acts as a proxy for the anisotropic state of convective turbulence. This ratio can be used to formulate a new non-dimensional group. Results show that building on this approach the role of anisotropy in scaling relations over complex terrain can be placed into a more generalized framework.