Occurrence of flow separation within the boundary-layer is primarily attributed to the growth of adverse pres-sure gradient within the boundary-layer. Such a separating boundary-layer can, however,...

A generally admitted fact about the nanofluids is the expedition of heat transfer process in comparison to pure fluids. The calculation of enhanced rate of heat transfer depends strongly upon the nanofluid modeling. Following the experimental evidence most of the researchers assume the nanofluid to be a homogeneous mixture. However, this is a severe condition that results in under-prediction of heat transfer rates. Due to the ongoing convection phenomena the nanoparticle concentration is actually non-homogeneous within the boundary-layer because of the presence of concentration gradients. The objective of this study is to calculate the heat transfer enhancement in 3-D boundary-layer when the working fluid is a nanofluid. The rotating disk geometry, which perhaps serves as the bench mark for the 3-D boundary-layers, have been chosen for the purpose here. The non-homogeneous nanofluid modeling has been utilized and a percent increase in Nusselt number has been calculated. Detailed analyses of flow and heat transfer phenomena for nanofluids have been conducted under the influence of several physical parameters.

Theoretical investigation of a turbulent boundary layer formed over a uniformly moving sinusoidal-shaped wavy plate is presented. The primary objective of this study is twofold: first to report the theoretical treatment of the considered flow and second to investigate and quantify the potential impacts of the surface non-flatness on the turbulent boundary-layer characteristics. Boundary-layer characteristics, such as the boundary-layer thickness, momentum thickness, coefficient of skin friction, and the shape factor, have been formulated into the form of the similarity variables. Theoretical modeling is based on the boundary-layer assumption imposed on the Reynolds-averaged Navier–Stokes equations. Numerical solution is obtained due to the Keller-Box method after implementing the mixing-length turbulence model. Significant contribution of surface waviness in enhancing the momentum transport across the boundary layer is noted, in accordance with the laminar flow. However, such enhancement is much pronounced in the turbulent boundary layer in comparison to the laminar one. Momentum transport is seen to be strengthened by almost 23% in comparison to a flat plate case. Local and average coefficient of skin-friction and the other boundary-layer characteristics are computed for various values of the amplitude-to-wavelength ratio parameter to express its impactful role on the overall flow phenomenon.