Drag estimation on wedge-shaped protuberances in high-speed flows

A semi-empirical method is developed to estimate drag on wedge-shaped projections in hypersonic flow. Force balance measurements from gun tunnel tests directly measure total drag on blunt wedges, where the boundary layer and the entropy layer are weakly coupled. Detailed flowfield analysis from numerical simulations provides estimated locations of peak pressure ratio and skin friction. Schlieren images are used for detecting incipient separation in incoming flows with laminar and turbulent boundary layers. Test results indicate the presence of local hotspots at reattachment points of strong detached shocks on the wedge compression ramp, and of primary and secondary vortical structures around lateral faces. Total drag is found to decrease with decreasing bluntness but increasing slenderness in wedges tend to increase skin friction drag

The Polish wage inequality explosion

This paper presents and analyses the sharp increase in hourly wage inequality after 1998 in Poland. The increase was similar in magnitude to the much-studied increase in British wage inequality during the 1980s. Using data from the Polish Labour Force Survey, we find this increase to be associated with rising wage differentials and within-group variances at both the upper and lower ends of the wage distribution. These increases are associated with differences in wage-setting patterns between the public and private sector as well as with the rapid increase in demand for educated labour. One important difference between the sectors is the lack of an impact of local labour market conditions, or wage curve, clearly evident in private sector wages, on public sector wages. Copyright (c) 2007 The Authors Journal compilation (c) 2007 The European Bank for Reconstruction and Development .

Computational methodology for investigating the transient interaction between a reaction control jet and a hypersonic crossflow

A computational methodology has been developed to investigate the transient start of a Reaction Control (RC) jet into a hypersonic cross flow. The method uses the rhoCentral-Foam solver, which forms part of the OpenFOAM Computational Fluid Dynamics (CFD) package. Results have been compared to analytical solutions and previous simulations of a one-dimensional shock tube, a two-dimensional wedge, a diamond airfoil and a forward step. Further evidence of validation has been gained by comparing results with experimental data for a two-dimensional jet issuing into a quiescent atmosphere, and the steady interaction between a three-dimensional RC jet and a hypersonic cross flow. This work extends the scope of validation data available for rhoCentralFoam in open literature. Results show that the rhoCentralFoam solver performs well, and is able to capture all relevant flow structures. Shock properties, velocity and density fields were well predicted, but accuracy was decreased in some cases when predicting temperature and pressure fields. Overall, the numerical scheme is suitable for investigating the transient interaction between an RC jet and a hypersonic cross flow