Piston-cylinder cell assemblies experience inhomogeneous pressure distribution upon pressurization due to the variable compressibilities of the cell components. This results in the sample experiencing a pressure lower than expected, given the applied force of the piston. Although the effect is generally compensated for by applying a ‘friction’ correction, there have been wide variations in the corrections applied for some of the harder cell materials. We have determined friction correction factors for a range of cell assemblies commonly used in our laboratory relative to select well-characterized phase equilibria. Single-sleeve NaCl cells require, using the piston-in technique, very small corrections of the order −0.05 GPa for 12.7 mm diameter, and less for larger diameter assemblies. Four separate calibrations of the single sleeve 12.7 mm BaCO3 cell show that it requires a correction of −9%. This factor is entirely independent of temperature and pressure within the range 1000 to 1600°C and 1.5 to 3.2 GPa. This result is in contrast to the results of Fram and Longhi (1992) who claim that the correction for BaCO3 cells is highly dependent on pressure. For the assemblies included in this study there is an increase in the pressure correction required in the order of 12.7 mm diameter NaCl-pyrex −3%; 19 mm talc-pyrex −3.6%; 12.7 mm BaCO3 −9% and 12.7 mm BaCO3-silica glass −13%.

Wind-tunnel measurements were used to study the characteristics of the unsteady separation bubbles on a NACA 0015 aerofoil with simulated two-dimensional leading-edge glaze ice accretions. The unsteadiness present in the iced-aerofoil flowfield was determined using measurements of the time-dependent aerofoil surface pressure distribution at Reynolds number of 1.0 × 106. Additionally, the unsteady flow features were investigated through the power spectrum of the stream-wise velocity fluctuations using a hot-wire anemometry. The results showed that the highest value of root-mean-square fluctuation of the surface pressure consistently occurred upstream of the mean shear-layer reattachment location. Spectral analysis of stream-wise velocity fluctuations near reattachment location revealed evidence of the regular frequency at Strouhal numbers of 0.5-0.63. Moreover, the low-frequency oscillations associated with shear-layer flapping was also identified in the wake velocity spectra on the order of 10 Hz that resulted in Strouhal numbers of 0.0186-021.

In this paper the pressure distribution of the gaseous flow in a microchannel is studied via a lattice Boltzmann equation (LBE) method. With effective relaxation times and a generalized second order slip boundary condition, the LBE can be used to simulate rarefied gas flows from slip to transition regimes. The Knudsen minimum phenomena of mass flow rate in the pressure driven flow is also investigated. The effects of Knudsen number (rarefaction effect), pressure ratio and aspect ratio (compression effect) on the pressure distribution are analyzed. It is found the rarefaction effect tends to the curvature of the nonlinear pressure distribution, while the compression effect tends to enhance its nonlinearity. The combined effects lead to a local minimum of the pressure deviation. Furthermore, it is also found that the relationship between the pressure deviation and the aspect ratio follows a pow-law.

In the present paper an experimental investigation of drag reduction on in-line tubebundles with a configuration of seven by seven with a pitch ratio of 1.44 has beenperformed. Two longitudinal grooves are placed on the external surface of the circularcylinders as a passive control. The experiment is carried out using a subsonic windtunnel. The pressure distributions for various azimuthal angles along the tubes aremeasured using a multi-channel differential pressure. Drag forces are also determinedusing a combined wire-strain gauge balance. The pressure drops are deduced from theresulting drag forces. The results obtained show an unexpected reduction in the pressuredrop for the tube bundles. A reduction of 36.5% in the pressure drop for a Reynolds numberof 1.33 × 104 is found compared to the configuration without grooves. Somecorrelations for the pressure drop are proposed.

The pressure distributions around a square cylinder in a crossflow were experimentally studied in a wind tunnel. The subject of study was conventional, but the results presented new findings. The experiments were performed by using a home-made linear pressure scanner. The ranges of Reynolds number and incidence angle were 2 × 104 - 9.4 × 104 and 0° - 45°, respectively. According to the topological flow patterns, the flows around the square cylinder at incidence showed three characteristic regimes: The subcritical, supercritical, and wedge flows. A critical incidence angle αcri = 15° separated the regimes of subcritical and supercritical modes. The results of current study provided information regarding the effects of the topological flow patterns on surface pressure distribution, drag, and lift characteristics. The pressure distributions, drag, and lift presented different characteristics in different characteristic flow regimes and had close correlations with the flows. At the critical incidence angle 15° which separated the subcritical and supercritical regimes, the surface-averaged pressure coefficient on each face displayed local extreme value—The drag coefficient attained a minimum of 1.6, the lateral force coefficient reached a maximum of 0.9. The appearance of the minimum drag at the critical incidence angle was attributed to the reduction of wake width which was induced by two surface flow phenomena: (1) reattachment of the separated boundary layer on the lateral surface facing windward at the critical incidence angle and (2) flow pattern change on the lateral surface facing leeward.