Laminar separation bubbles in two and three dimensional incompressible flow.

PhDA theoretical and experimental study is made of the closed 'bubbles` of separated flow formed when a laminar boundary layer separates from an aerofoil surface and, after undergoing transition to turbulence, subsequently re-attaches. Attention is mainly confined to the so-called 'short' type of bubble, which is distinguished from the 'long' type by its relatively slight overall effect upon the pressure distribution. In Part I, a semi-empirical theory for the prediction of the growth and bursting of two-dimensional short bubbles is developed. The existing data concerning short bubbles are re-examined, with particular emphasis upon the conditions governing re-attachment. A criterion for the determination of turbulent re-attachment is proposed, and approximate quadrature methods developed for the calculation of the momentum thickness in the separated region. These results, together with am empirical formula for the determination of the position of transition, are combined with a simplified model of the pressure distritbution in the bubble region to predict the re-attachment position. It is found that, for a given imposed pressure distribution, there exists a Reynolds number at separation below which re-attachment is impossible. This is associated with the phenomenon of short bubble bursting. The predictions of the theory are in reasonable quantitative agreement with experiment. Part II deals with bubbles in three-dimensional flow. Experiments are described in which separation bubbles were produced using an apparatus closely simulating conditions near the leading-edge of a swept wing of infinite span. Measurements of surface pressure, mean velocity and turbulence level are presented, from which it is deduced that the bubble structure is similar to that of two-dimensional bubbles, apart from the existence of cross-flows in the shear-layer and a strong spanwise flow in the reverse-flow vortex. An extension of the two-dimensional bursting theory by means of the independence principle is in reasonable agreement with measured bursting parameters.Ministry of Technolog

The administrative, social and economic structure of the Durham bishopric estates, 1500-1640

A study designed to elucidate some of the special features and problems of ecclesiastical land ownership, through the medium of one of the leading English bishoprics, during a period of social and economic stress, coinciding with a phase of crisis and readjustment in the history of the Church. In spite of its palatinal jurisdiction Durham is found to be little different from the other bishoprics in terms of its temporalities. After a description of the bishopric estates and the manner of their administration, attention is turned to the phenomenon of an income which remained fairly static in an inflationary age, amidst conditions auguring growth. The bulk of the thesis is devoted to an examination of the resultant failure of the Bishops of Durham to become the improving landlords demanded by logic. Explanations are found in: the inadequacy of the antique administrative machinery as an instrument of improvement; the abandonment of entrepreneurial activity; the entrenchment of the tenantry behind beneficial conditions of tenure; the requirements of the patronage system made necessary by the Bishops' important, socio-political role, which put them at a disadvantage in management terms; the exploitation by powerful interests emanating from the State-Church relationship; the impediments to effective husbanding and regulation of resources inherent in the system of episcopal succession and the behaviour patterns characteristic of the episcopate; and the short comings of the counter-measures taken to arrest the administrative and economic defects. Overall it is clear that however desirable the efficient administration and improvement of the temporalities might have been, fulfilment of these twin objectives was rendered impossible by the power of the several countervailing considerations. In conclusion it is suggested that the Durham experience was fairly representative in its exposure to conditions which allowed for variation in detail within a framework of basic similarities

Radical-cation salts of BEDT-TTF with lithium tris(oxalato)metallate(III)

The first radical-cation salts in the extensive family (BEDT-TTF)x[(A)M(C2O4)3]·Guest containing lithium as the counter cation have been synthesized and characterised

Influence of wave phase difference between surface soil heat flux and soil surface temperature on land surface energy balance closure

The sensitivity of climate simulations to the diurnal variation in surface energy budget encourages enhanced inspection into the energy balance closure failure encountered in micrometeorological experiments. The diurnal wave phases of soil surface heat flux and temperature are theoretically characterized and compared for both moist soil and absolute dry soil surfaces, indicating that the diurnal wave phase difference between soil surface heat flux and temperature ranges from 0 to π/4 for natural soils. Assuming net radiation and turbulent heat fluxes have identical phase with soil surface temper- ature, we evaluate potential contributions of the wave phase difference on the surface energy balance closure. Results show that the sum of sensible heat flux (H ) and latent heat flux (LE ) is always less than surface available energy (Rn − G0) even if all energy components are accurately measured, their footprints are strictly matched, and all cor- rections are made. The energy balance closure ratio (ε) is extremely sensitive to the ratio of soil surface heat flux amplitude (A4) to net radiation flux amplitude (A1), and large value of A4/A1 causes a significant failure in surface energy balance closure. An experimental case study confirms the theoretical analysis

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are reported, including a 4:1 salt with the meso stereoisomer of the dinuclear [Fe2(oxalate)5 ]4- anion in which both cation and anion have chiral components linked together by hydrogen bonding, and a semiconducting salt with triiodide

Generation and Structure of Solitary Rossby Vortices in Rotating Fluids

The formation of zonal flows and vortices in the generalized Charney-Hasegawa-Mima equation is studied. We focus on the regime when the size of structures is comparable to or larger than the deformation (Rossby) radius. Numerical simulations show the formation of anticyclonic vortices in unstable shear flows and ring-like vortices with quiescent cores and vorticity concentrated in a ring. Physical mechanisms that lead to these phenomena and their relevance to turbulence in planetary atmospheres are discussed.Comment: 3 pages in REVTeX, 5 postscript figures separately, submitted to Phys. Rev.

Modus Vivendi Beyond the Social Contract: Peace, Justice, and Survival in Realist Political Theory

This essay examines the promise of the notion of modus vivendi for realist political theory. I interpret recent theories of modus vivendi as affirming the priority of peace over justice, and explore several ways of making sense of this idea. I proceed to identify two key problems for modus vivendi theory, so conceived. Normatively speaking, it remains unclear how this approach can sustain a realist critique of Rawlsian theorizing about justice while avoiding a Hobbesian endorsement of absolutism. And conceptually, the theory remains wedded to a key feature of social contract theory: political order is conceived as based on agreement. This construes the horizontal tensions among individual or group agents in society as prior to the vertical, authoritative relations between authorities and their subjects. Political authority thereby appears from the start as a solution to societal conflict, rather than a problem in itself. I argue that this way of framing the issue abstracts from political experience. Instead I attempt to rethink the notion of modus vivendi from within the lived experience of political conflict, as oriented not primarily toward peace, but political survival. With this shift of perspective, the idea of modus vivendi shows us, pace Bernard Williams, that the “first political question” is not how to achieve order and stability, but rather: what can I live with