3D Modeling and Simulation of Fancy Fabrics in Weft Knitting

Weft knitted fancy fabrics are widely used in knitted garment design. Due to the complexity of the structures, their modeling and simulation needs to be solved in three-dimensional (3D) CAD developments. In this paper, 3D loop geometrical models of weft knitted fancy structures, including tuck stitch, jacquard stitch, transfer stitch and fleecy stitch, were developed based on an improved model of plain loop, and their central axes as some 3D space curves were achieved by using Non-Uniform Rational B-Splines (NURBS). The 3D visual simulation programme was written in C++ programming language using OpenGL, which was a function library of 3D graphics. Some examples of weft knitted fancy fabrics were generated and practical application of 3D simulation was discussed.

Monte Carlo study of the universal area distribution of clusters in the honeycomb O(n) loop model

We investigate the area distribution of clusters （loops） in the honeycomb O（n） loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method.

Dynamical Study of a Constant Viscous Dark Energy Model in Classical and Loop Quantum Cosmology

Dynamical behaviors and stability properties of a flat space Friedmann-Robertson-Walker universe filled with pressureless dark matter and viscous dark energy are studied in the context of standard classical and loop quantum cosmology. Assuming that the dark energy has a constant bulk viscosity, it is found that the bulk viscosity effects influence only the quintessence model case leading to the existence of a viscous late time attractor solution of de- Sitter type, whereas the quantum geometry effects influence the phantom model case where the big rip singularity is removed. Moreover, our results of the Hubble parameter as a function of the redshift are in good agreement with the more recent data.

Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor

Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.

Experiments and simulations of gas-solid flow in an airlift loop reactor

The hydrodynamics in a gas-solid airlift loop reactor was investigated systematically using experimental measurements and CFD simulation. In the experiments, the time averaged parameters, such as solid frac- tion and particle velocity, were measured by optical fiber probe. In the simulation, the modified Gidaspow drag model accounting for the interparticles clustering was incorporated into the Eulerian-Eulerian CFD model with particulate-phase kinetic theory. Predicted values of solid fraction and particle velocity were compared with experimental results, validating the drag model and the simulation. The results show that the profiles of particle velocity and solid fraction are uniform in annulus. However, the core-annulus structure appears in other three regions （draft tube region, bottom region and particle diffluence region）, which presents the similar heterogeneous feature of aggregative fluidization usually occurred in nor- mal fiuidized beds. Simulated profiles of particle residence time distribution indicate that the airlift loop reactor should be characterized by near perfect mixing.