Solution-blown nanofiber mats from fish sarcoplasmic protein

In the present work, solution-blowing was adopted to form nanofibers from fish sarcoplasmic proteins (FSPs). Nanofiber mats containing different weight ratios (up to 90/10) of FSP in the FSP/nylon 6 blended nanofibers were formed from formic acid solutions, and compared to electrospun fibers made from the same solutions. The nanofiber mats produced by the two methods were characterized in terms of FSP content, fiber diameter distribution, fiber mat porosity, and mass of the fibers collected. The mechanical strength of the solution-blown fibers was also measured. Overall, fibers made by the two techniques were similar, but with some exceptions. The fiber diameter of the electrospun fibers was slightly smaller than those made using solution-blowing, however in both cases the fiber diameter increased with increasing FSP content. Interestingly, for uniform fibers the stretchability of the fibers increased with increasing FSP content, indicated by an increased strain at rupture. Moreover, the mechanical tests showed that up to 50% of nylon 6 could be replaced with FSP without compromising the mechanical properties, compared to pure nylon 6 nanofibers. Comparison of the yield showed that the production rate of solution-blowing was increased 30-fold in relation to electrospinning. Overall, this study reveals FSP as an interesting biopolymeric alternative to synthetic polymers, and the introduction of FSP to nylon 6 provides a composite with controlled properties

Random field sampling for a simplified model of melt-blowing considering turbulent velocity fluctuations

In melt-blowing very thin liquid fiber jets are spun due to high-velocity air streams. In literature there is a clear, unsolved discrepancy between the measured and computed jet attenuation. In this paper we will verify numerically that the turbulent velocity fluctuations causing a random aerodynamic drag on the fiber jets -- that has been neglected so far -- are the crucial effect to close this gap. For this purpose, we model the velocity fluctuations as vector Gaussian random fields on top of a k-epsilon turbulence description and develop an efficient sampling procedure. Taking advantage of the special covariance structure the effort of the sampling is linear in the discretization and makes the realization possible

Shapes, contact angles, and line tensions of droplets on cylinders

Using an interface displacement model we calculate the shapes of nanometer-size liquid droplets on homogeneous cylindrical surfaces. We determine effective contact angles and line tensions, the latter defined as excess free energies per unit length associated with the two contact lines at the ends of the droplet. The dependences of these quantities on the cylinder radius and on the volume of the droplets are analyzed.Comment: 26 pages, RevTeX, 10 Figure

Capillary filling with pseudo-potential binary Lattice-Boltzmann model

We present a systematic study of capillary filling for a binary fluid by using a mesoscopic lattice Boltzmann model for immiscible fluids describing a diffusive interface moving at a given contact angle with respect to the walls. The phenomenological way to impose a given contact angle is analysed. Particular attention is given to the case of complete wetting, that is contact angle equal to zero. Numerical results yield quantitative agreement with the theoretical Washburn law, provided that the correct ratio of the dynamic viscosities between the two fluids is used. Finally, the presence of precursor films is experienced and it is shown that these films advance in time with a square-root law but with a different prefactor with respect to the bulk interface.Comment: 13 pages, 8 figures, accepted for publication on The European journal of physics

Friction Coefficient of an Intact Free Liquid Jet Moving in Air

Here, we propose a novel method of determining the friction coefficient of intact free liquid jets moving in quiescent air. The middle-size jets of this kind are relevant for such applications as decorative fountains, fiber-forming, fire suppression, agriculture, and forensics. The present method is based on measurements of trajectories created using a straightforward experimental apparatus emulating such jets at a variety of initial inclination angles. Then, the trajectories are described theoretically, accounting for the longitudinal traction imposed on such jets by the surrounding air. The comparison of the experimental data with the theoretical predictions shows that the results can be perfectly superimposed with the friction coefficient Cfd = 5Red−1∕2±0.05, in the 621 ⩽ Red ⩽ 1289 range, with Red being the Reynolds number based on the local cross-sectional diameter of the jet. The results also show that the farthest distance such jets can reach corresponds to the initial inclination angle 훼 = 35◦ which is in agreement with already published data

Theoretical and Experimental Investigation of Forward Spatter of Blood from a Gunshot

A theoretical model predicting forward blood spatter patterns resulting from a round nose bullet gunshot wound is proposed. The chaotic disintegration of a blood layer located ahead and aside of the bullet is considered in the framework of percolation theory. The size distribution of blood drops is determined which allows for the prediction of a blood spatter cloud being ejected from the rear side of the target where the bullet exits. Then, droplet trajectories are numerically predicted accounting for gravity and air drag which is affected by the collective aerodynamic interaction of drops through air. The model predicts the number and area of individual stains, as well as the stain distribution as a function of distance from the region of origin. The theoretical predictions are compared with experimental data acquired in this work from 9 mm Luger copper full metal jacket bullets fired from a handgun. The agreement between the predicted and experimentally measured parameters are found to be good

Spreading of Carbopol Gels

This work aims to study flows within a wedge at the inclination angles in the 5°–20° range. Flow within a wedge occurs when a Carbopol solution is pulled horizontally by a moving conveyer belt through the wedge apex opening at different speeds. The upper side of the wedge is fixed at the exit by a pivot joint about which it could rotate. At the wedge entrance, a force gauge is placed so that it is pushing at the upper side of the wedge to keep it at a predetermined position (and thus at a predetermined inclination angle). The gauge measures the restraining force required to counteract the pressure buildup on the flowing Carbopol solution side and to keep the upper side of the wedge at its position. Visualization through the transparent vertical sides of the wedge was used to track seeding particles inside the solution to reconstruct the velocity profile and in particular to reveal plug flow regions characteristic of the yield stress liquids