Mohammad Danish

The Shear Thickening Fluid (STF) is a non- Newtonian fluid which comes under dilatant material, STF undergoes phase transition from a low to high viscosity when shear stress is applied on it. In this paper modelling and simulation tools are used to study the STF fluid interaction when subjected to applied shear stress. The Eulerian description used for the fluid flow and the model considered the Lagrangian description of the rigid particles. The numerical analysis inspects important guideline such as acceleration of the flow, particle dispersion and the base of Non-Newtonian fluid. The fluid particles interrelation of STF showed that the shape, arrangement, volume concentration, and size of the particles had a vital effect on the behavior of STF. By adding sand particles in non-Newtonian fluids and applying high shear strain rates showed improvement in the shear thickening effects.

To get better understanding of vortex shedding mechanism, we conducted numerical simulation on NACA 4418 hydrofoil at an angle of attack of 12° for 2D incompressible flow. The numerical method consists of transient, finite volume method using Transient SST turbulent model to capture the turbulent wake flows. At high Reynolds number the occurrence of 2D structures of shed vortices and the modulation of vortex-induced frequency are investigated. The lift, pressure and skin friction coefficients of hydrofoil were studied.

In this work, we investigate the influence of compressibility on vorticity-strain rate dynamics. Well-resolved direct numerical simulations of compressible homogeneous isotropic turbulence performed over a cubical domain of 1024³ are employed for this study. To clearly identify the influence of compressibility on the time-dependent dynamics (rather than on the one-time flow field), we employ a well-validated Lagrangian particle tracker. The tracker is used to obtain time correlations between the instantaneous vorticity vector and the strain-rate eigenvector system of an appropriately chosen reference time. In this work, compressibility is parameterized in terms of both global (turbulent Mach number) and local parameters (normalized dilatation-rate and flow field topology). Our investigations reveal that the local dilatation rate significantly influences these statistics. In turn, this observed influence of the dilatation rate is predominantly associated with rotation dominated topologies (unstable-focus-compressing, stable-focus-stretching). We find that an enhanced dilatation rate (in both contracting and expanding fluid elements) significantly enhances the tendency of the vorticity vector to align with the largest eigenvector of the strain-rate. Further, in fluid particles where the vorticity vector is maximally misaligned (perpendicular) at the reference time, vorticity does show a substantial tendency to align with the intermediate eigenvector as well. The authors make an attempt to provide physical explanations of these observations (in terms of moment of inertia and angular momentum) by performing detailed calculations following tetrads {approach of Chertkov et al. [“Lagrangian tetrad dynamics and the phenomenology of turbulence,” Phys. Fluids 11(8), 2394–2410 (1999)] and Xu et al. [“The pirouette effect in turbulent flows,” Nat. Phys. 7(9), 709–712 (2011)]} in a compressible flow field.