Direct numerical or large-eddy simulations of the majority of spatially inhomogeneous turbulent flows require turbulent inflow boundary conditions. A potential implication is that any results computed may be strongly influenced by the prescribed instantaneous inlet velocity profiles. Such profiles are practically never available, and a usual practice is to generate synthetic inflow data satisfying certain statistical properties, which may, for example, be known from experimental data or empirical correlations. The present paper describes a new method for generating turbulent inflow data based on digital filters that is capable of reproducing specified statistical data. Two variants of the approach are presented: a simple method in which the Reynolds stresses and a single length scale are prescribed, and a more detailed approach that is able to reproduce the complete Reynolds-stress tensor as well as any given, locally defined, spatial and temporal correlation functions. The application of the methods to a plane jet flow and to a developing wall boundary layer serve to demonstrate the applicability of the approach.

8Fouling by asphaltene, which constitutes the densest, most polar fraction of crude oil, poses a serious 9 problem for the oil production industry. In order to obtain a fundamental understanding of asphaltene 10 deposition it is necessary to determine both the thermodynamics and kinetics that govern this process. In 11 recent years, there have been numerous studies of the kinetics of asphaltene adsorption, however, a 12 consensus on the model that best describes asphaltene adsorption remains elusive. In this paper the 13 adsorption of asphaltene from solution in toluene onto a gold surface is investigated using a quartz crystal 14 microbalance inside a flow cell. The kinetics of adsorption depends on the state of asphaltene in solution 15 and the adsorption behaviour alters with long-time aging of asphaltene solutions. A model is developed 16 that links the kinetics of asphaltene adsorption to the bulk solution properties in terms of coexisting 17 monomer and multimer states. A large portion of deposited asphaltene is effectively irreversibly bound 18 and not easily removed by rinsing with toluene. The model suggests that asphaltene-asphaltene 19interactions play an important role in the formation of irreversibly bound deposits, which could lead to 20 fouling problems. 21 22

The rheology of submicron thick polymer melt is examined under high normal pressure conditions by a recently developed photobleached‐fluorescence imaging velocimetry technique. In particular, the validity and limitation of Reynold equation solution, which suggests a linear through‐thickness velocity profile, is investigated. Polybutene (PB) is sheared between two surfaces in a point contact. The results presented in this work suggest the existence of a critical pressure below which the through‐thickness velocity profile is close to linear. At higher pressures however, the profile assumes a sigmoidal shape resembling partial plug flow. The departure of the sigmoidal profile from the linear profile increases with pressure, which is indicative of a second‐order phase/glass transition. The nature of the transition is confirmed independently by examining the pressure‐dependent dynamics of PB squeeze films. The critical pressure for flow profile transition varies with molecular weight, which is consistent with the pressure‐induced glass transition of polymer melt. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 708–715

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Shock tube experiments are a primary means of obtaining ground test data for the hypersonic regime. Accurate characterisation of the test gas is crucial to understanding experimental results. However, characterisation of the flows produced behind the shockwave has historically proven challenging. This paper applies a methodology to calculate the shocked test gas properties using the experimentally recovered shock speed profile. Static pressure, Pitot pressure and heat transfer predictions are found to closely match the experimental data for a range of shock trajectories with both Argon and Air test gases. Thermochemical variations in the test gases are found to depend strongly upon variations in shock speed along the tube, and it is shown that characterisation of the test gases requires accommodating the influence of wave effects associated with the varying shock speed. Tube diameter is found to influence test time significantly, and also the magnitude of nonuniformities in the test gas. Location and number of shock timing stations in experimental facilities are found to play a vital role in the ability to accurately characterise the test gas of a given experiment.

Microviscosity of PAO 8 measured from the fluorescence anisotropy of Nile red ηA compared to the corrected area-averaged viscosity from friction η* and high-pressure rheology η.

Shock tubes are a crucial source of experimental data for the aerothermodynamic modelling of atmospheric entry vehicles. Notably, many chemical-kinetic and radiative models are validated directly against optical measurements from these facilities. Typically, the incident shock speed at the location of the experimental measurement is taken to be representative of the test slug; however, the shock velocity can vary substantially upstream of this location. These variations have been long posited as a source of disagreement with computational predictions, although a definitive link has proved elusive. This work describes a series of experiments which aim to isolate and confirm the importance of the shock deceleration effect. This is achieved by generating different shock trajectories and comparing the post-shock trends in atomic oxygen emission and electron density. These trends are shown to be directly linked to the upstream shock speed variations using a recently developed numerical tool (LASTA). The close agreement of the comparisons confirms the importance of shock speed variation for shock tube experiments; these findings have direct and potentially critical relevance for all such studies, both past and present.

A new equation for the convective heat loss from the sensor of a hot-wire probe is derived which accounts for both the potential and the viscous parts of the flow past the prongs. The convective heat loss from the sensor is related to the far-field velocity by an expression containing a term representing the potential flow around the prongs, and a term representing their viscous effect. This latter term is absent in the response equations available in the literature but is essential in representing some features of the observed response of miniature hot-wire probes. The response equation contains only four parameters but it can reproduce, with great accuracy, the behaviour of commonly used single-wire probes. The response equation simplifies the calibration the angular response of rotated slanted hot-wire probes: only standard King’s law parameters and a Reynolds-dependent drag coefficient need to be determined.