In order to investigate the effect of processing parameters on permeability of structure, electrospun nanofibrous webs were produced based on Taguchi method. Afterwards, the SEM images of webs were obtained. Fiber diameter distribution and orientation in webs were obtained using image analysis technique. Moreover, porosity and thickness of webs were measured using experimental techniques. The effect of processing parameters on fiber diameter and orientation, porosity and air permeability of structures was investigated. A Matlab-based program capable of producing ?brous structures with various ?ber diameters, porosities, thicknesses and 3D fiber orientations was developed. The obtained parameters from SEM images were then implemented into the simulation code to generate 3D virtual nanofibrous structures. Fluid flow was simulated by numerically solving incompressible creeping Newtonian flow through the 3D pore space of virtual structures and air permeability was calculated. The results were compared with experimental data as well as some of well-known analytical and empirical models. The results indicated that applied voltage, feed rate, collector speed and solution concentration affect fiber diameter and air permeability of nanofibrous webs. It was found that increasing solution concentration from 12% to 15% increases air permeability, beyond which it reduces. Increase in applied voltage from 10 to 14 decreases air permeability; afterward further increase in applied voltage increases air permeability. It was established that increase in feed rate from 0.2 to 0.3 results in increasing air permeability, beyond which it reduces. The lowest air permeability was observed when the collector speed was set to 800 rpm. The results indicated that permeability of web is strongly dependent on porosity of structure. It was found that at low fiber diameters, the fluid flow is in slip flow regime. The greater the slip velocity, the closer the streamlines to the ?ber surface. This means that the greater the slip velocity, the lesser the in?uence of the ?bers on the ?ow ?eld. Therefore, permeability of a nanofibrous webs is greater than that of fibrous webs with micron fiber diameters. The results indicated that permeability of nanofibrous webs containing fibers of 100 and 1000 can respectively be modeled using analytical models of Ogorodnikov and Tomadakis and Robertson.
