We present comprehensive numerical studies of the motion of a buoyant or anearly neutrally buoyant nano-sized ellipsoidal particle in a fluid filledcylindrical tube without or with the presence of imposed pressure gradient(weak Poiseuille flow). The Fluctuating hydrodynamics approach and theDeterministic method are both employed. We ensure that thefluctuation-dissipation relation and the principle of thermal equipartition ofenergy are both satisfied. The major focus is on the effect of the confiningboundary. Results for the velocity and angular velocity autocorrelations (VACFand AVACF), diffusivities, and drag and lift forces as functions of shape,aspect ratio, inclination angle, and proximity to the wall are presented. Forthe parameters considered, the boundary modifies the VACF and AVACF such thatthree distinct regimes are discernible --- an initial exponential decay,followed by an algebraic decay culminating in a second exponential decay. Thefirst is due to thermal noise, the algebraic regime is due to both thermalnoise and hydrodynamic correlations, while the second exponential decay showsthe effect of momentum reflection from the confining wall. Our predictionsdisplay excellent comparison with published results for the algebraic regime(the only regime for which earlier results exist). We also discuss the role ofoff-diagonal elements of the mobility and diffusivity tensor that enables thequantification of the degree of lift and margination of the NC in the vessel.Our study covers a range of parameters that are of wide applicability innanotechnology and in targeted drug delivery related to the health sciences.
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