Search results

The purpose of the present study is to develop a new numerical framework that can predict the supersonic base flow more accurately, including the development of axisymmetrically separated shear layer and recompression shock. To this end, two aspects are improved and combined, i.e. a newly self-adaptive turbulence eddy simulation (SATES) turbulence modeling method and a high-order discretization numerical scheme. Furthermore, the performance of the new numerical framework within a general-purpose PHengLEI software is assessed in detail.

Satisfactory prediction of the supersonic separated shear layer with unsteady wake flow is quite challenging. By using a unified turbulence model called SATES combining high-order accurate discretization numerical schemes, the present study first assesses the performance of newly developed SATES for supersonic axisymmetric separation flows. A high-order finite differencing-based compressible computational fluid dynamics (CFD) code called PHengLEI is developed and several different numerical schemes are used to investigate the effects on shock-turbulence interactions, which include the monotonic upstream-centered scheme for conservation laws (MUSCL), weighted compact nonlinear scheme (WCNS) and hybrid cell-edge and cell-node dissipative compact scheme (HDCS).

Compared with the available experimental data and the numerical predictions, the results of SATES by using high-order accurate WCNS or HDCS schemes agree better with the experiments than the results by using the MUSCL scheme. The WCNS and HDCS can also significantly improve the prediction of flow physics in terms of the instability of the annular shear layer and the evolution of the turbulent wake.

The small deviations in the recirculation region can be found between the present numerical results and experimental data, which could be caused by the inaccurate incoming boundary layer condition and compressible effects. Therefore, a proper incoming boundary layer condition with turbulent fluctuations and compressibility effects need to be considered to further improve the accuracy of simulations.

The present study evaluates a high-order discretization-based SATES turbulence model for supersonic separation flows, which is quite valuable for improving the calculation accuracy of aeronautics applications, especially in supersonic conditions.

For the first time, the newly developed SATES turbulence modeling method combining the high-order accurate WCNS or HDCS numerical schemes is implemented on the PHengLEI software and successfully applied for the simulations of supersonic separation flows, and satisfactory results are obtained. The unsteady evolutions of the supersonic annular shear layer are analyzed, and the hairpin vortex structures are found in the simulation.

This study aims to explore the relationship among five types of power (expert, referent, legitimate, reward and coercive power), two dimensions of cooperative behavior (specific investments and communication) and three types of alliance performance (alliance stability, income increase and cost decrease) in contract farming. By investigating the dyadic perspectives of companies and contract farmers, the authors examine how power use influences cooperative behavior, which further enhances alliance performance.

The authors construct a theoretical model grounded on resource dependence theory (RDT). Data from 202 companies and 462 farmers in China are used to test the proposed hypotheses using structural equation modeling.

The authors' results show that the five types of power play different roles in cooperative behavior. On the one hand, farmers' expert, reward and coercive power enhance the company's specific investments; farmers' expert power enhances the company's communication but farmers' coercive power harms the company's communication. Also the company's specific investments enhance communication that is positively related to alliance ability, income increase and cost decrease. On the other hand, the company's expert, referent and legitimate power enhance farmers' communication, while the company's coercive power harms farmers' communication; the company's reward and coercive power enhance farmers' specific investments. Moreover, farmers' communication is positively related to alliance ability, income increase and cost decrease, but farmers' specific investments do not significantly influence such.

This study contributes to the literature on contract farming supply chain management by examining the relationships among power use, cooperative behavior and alliance performance from the dyadic perspective of companies and farmers. These findings have practical implications for agricultural companies and farmers promoting cooperative behavior and alliance performance through appropriate power use in contract farming supply chains.