The flow of liquid argon inside convergance-divergance nanopores as asymmetric nanopores is investigated by the use of molecular dynamics. The investigation is divided into two major parts. The first part deals with the fluid flow induced by an external force inside a conical nanopore and the second part deals with the thermal creep flow. In the first part, the geometrical effects of a rough asymmetric conical nanochannel on the mass flux of a simple liquid flow are studied. Both static and dynamic driving forces are applied to each fluid atom to form a so-called “acceleration or force driven flow”. The mean-zero time-dependent periodic dynamic force is applied to induce a net flow as a ratchet. The results show that when the static driving forces are strong enough, there is a symmetry break-down between mass fluxes in divergent and convergent channels. Thus, by applying a dynamic force a net mass flux is induced (toward the convergent direction). In this paper the effects of three different geometrical parameters are investigated. Simulation results indicate that (i) if the radiuses of the two sides of the channel are kept constant, there is a certain length in which the net flux induced by ratchet motion has a maximum value; (ii) when the length and the radius of the smaller area of the channel are kept constant, increasing the other side radius generally increases the flux in ratchet motion and (iii) increasing channel length in constant apex angle increases the flux in ratchet motion. The simulation results are justified with molecular principals to provide a better understanding of flow in such nanochannels. The results can be applicable in designing and optimizing nanofluidic devices such as thermocapillary pumps, ion-pumps and Brownian pumps. As mentioned earlier the phenomenon of thermal trairation (or creep) of a liquid inside a channel is investigated too. As the thermal creep phenomenon is a new field in scientific studies, the author tries to clarify the mechanisms of liquid thermal creep phenomenon in the thesis. It is shown that the main reason for this phenomenon is the fluid layering effect near the wall which has a temperature gradient along itself. It is shown that this effect could lead to an unbalance of the fluid pressure near the wall. This heterogeneity produces a surface force near the wall to drive the flow. It is shown that this force is affected by the amount of thermal gradient, diameter of the nanopore and the solid-fluid intermolecular strength. The more thermal gradient, the shorter diameter of the nanopore and the stronger solid-fluid intermolecular interaction can intensify the thermal creep effect. It is shown that it is possible to design thermal nanopumps via the effect of the thermal creep. The author proposed four layouts to pump the liquid. Two of them are by the use of nanotubes and the others are by the use of conical nanochannels. It is shown that by using conical nanochannels we can pump the liquid continuously even the thermal gradient is symmetric along the channel. In such case it is not necessary to construct the nanochannel with two different materials which is practicaly difficult to make. Keywords Asymmetric nanochannels, molecular dynamics, ratchet effect, liquid thermal creep, thermal nanopumps.