For Computational Fluidic Dynamics (CFD) analysis, different types of software are available such as ANSYS, COMSOL, GAMBIT and ABAQUS. ANSYS FLUENT is a very influential CFD software that enables the researchers to execute advanced and fast simulation as the performance of product is optimized. In this research work, the capabilities of ANSYS FLUENT have been investigated through the fluidic simulation of nano scale channels. Here, the simulation of three straight shaped and one curvilinear nano channel has been performed to analyze the precision of simulation with the aspect ratio of smaller dimensions (radius, length). The accurate dimensions have been determined for various shapes of channels. For straight circular channel, the radius of 124.9 µm and length of 900 µm are the dimensions found for error free simulations with 7.20 aspect ratio. While for straight crossed channel, the radius of 5.1 mm and length of 100 mm are the accurate dimensions for error free simulations with 19.60 aspect ratio. Width and depth are determined as 180 µm with 180 µm length in case of straight square channel for error free simulations with 1.0 aspect ratio. Finally, in case of curvilinear channel for error free simulations, the radius and length are found 22 and 209.1 µm respectively with 9.50 aspect ratio. None of the channels is found fit for simulation in nanometer range. Even in micrometer range, the simulations of these channels have acquired errors. Moreover, it has been observed that the aspect ratio is different for different geometries of microchannels for error free simulation.