Let us consider isolated unconfined and confined Au nanoparticles in water medium at room temperature (25 o C) and atmospheric pressure being irradiated by plane wave laser as shown in Figure . While for nanospheres, orientation does not matter, the angles θ and ϕ defines the orientation of a nanorod with respect to the incident laser, Figure (b). As shown in Figure (c), the Au nanoparticle absorbs parts of the incident laser to heat up and the resulting hotter fluid around the particle flow upward due to buoyancy. Since in practical scenarios the nanoparticles are confined, spherical and hemispherical enclosures were assumed as simplistic micro-scale confinements. The confinement size and the hydrodynamic boundary conditions on the confining walls influences the temperature field, flow patterns and strength. At LSPR wavelength of the incident light, the absorption and subsequent heat dissipation is maximum. The electric field of the electromagnetic radiation excites electrons into higher energy levels and the excited electrons thermalize rapidly to produce a hot free electron gas. The oscillation of this electron gas inside the metal heats up the metal lattice through electron phonon collisions. The electron-phonon thermal relaxation time is of the order of picoseconds . When the laser irradiation is continuous or the pulse duration is long enough relative to the relaxation time, the hot electron cloud has enough time for the thermal equilibrium with the lattice to establish. So the laser heating can be modelled by the energy balance equation without taking in to consideration the series of rapid phenomena of subnanosecond timescale. In the present work, nanosecond laser pulses have been considered for the direct implementation of equation . Most of the previous works have appropriately assumed the convective contribution to be negligible and used the Fourier's conduction equation . The validity of this assumption is obvious from the value of the Grashof number (