No abstract

No abstract

No abstract

Under the background of "Internet +", increasing manufacturers sell standard products through retail channels and sell customized products in electronic channel. The competition about dual-channel supply, relationship between production cost and delivery time and the influences of online market acceptance, product customization attribute value, price and delivery time on online customization and traditional retail markets are considered, based on the decision variables of the price of custom and standard products and the guaranteed delivery time, the Stackelberg models are constructed respectively for the manufacturer-led and retail-led supply chain under decentralized system and the overall profits maximization of the supply chain is modeled under centralized system, the existence and uniqueness of the optimal solutions is proved by the optimization theory. The optimal decisions, market demands and enterprises profits under different systems are compared through numerical examples, the relation between the sensitivity coefficients and the optimal enterprises profits are obtained through the parameters sensitivity analysis. The idea of model construction and relevant conclusions are of reference and significance for manufacturing enterprise management practices.

Steady incoming flow past a circular cylinder has been a classical problem in fluid mechanics owing to its extensive practical applications in e.g. offshore engineering. In this study, large-eddy simulations are performed for flow past a circular cylinder at the Reynolds number (Re) of 3900. Particular focuses are on the comparisons of different numerical methods and computational domain patterns. The case Re = 3900 is computed with both OpenFOAM and Nektar++, which are based on the conventional finite volume method and the highorder spectral/hp element method, respectively. It is found that the computational cost for the Nektar++ model is only less than 10% of that for the OpenFOAM model. In addition, both circular and C-shaped domains are tested for the OpenFOAM and Nektar++ models. It is found that a circular domain is required for the OpenFOAM model to minimise the footprint of mesh non-orthogonality on the simulated flow, while the Nektar++ model does not have strict requirements for the orthogonality of the mesh. The present findings regarding the computational cost and the domain/mesh patterns are expected to be applicable to the numerical modelling of bluff-body flows in general. Based on Nektar++ and the circular domain, additional simulations are performed at Re = 1000 and 7000. For the three Re values investigated, the Strouhal number, hydrodynamic forces and the streamwise and spanwise vorticity fields are examined and compared.

The transition from the primary (Ká rmá n) and two-layered vortex streets to the secondary vortex street in the far wake of a thin rectangular cylinder is examined through direct numerical simulations. It is found that at Reynolds numbers of 110 and 120 the secondary vortices are induced by the hydrodynamic instability of the two parallel shear layers (without vortex merging), whereas at Reynolds numbers above 130 the secondary vortices are formed from direct merging of the two-layered vortices. In summary, depending on the Reynolds number either hydrodynamic instability or vortex merging may be the physical cause for the secondary vortex street.

No abstract