SELF-PORTRAITS OF BENOZZO GOZZOLI IN THE CHAPEL OF THE MAGI IN THE PALAZZO MEDICI RICCARDI IN FLORENCE

Created by Benozzo Gozzoli, the picturesque setting of the Magi Chapel (Chapel of the Magi) in the chapel of the Palazzo Medici Riccardi (1459–1460, Florence) includes about one hundred and fifty images of people, among which the artist himself is represented. In the Russian literature devoted to this fresco cycle, only one self-portrait of Benozzo is mentioned, which is dressed in a red cap, on which his name is indicated. He is among the escort of the youngest Magus, which mostly consists of the Medici, the unofficial rulers of the city, and their entourage. Meanwhile, on the opposite wall of the chapel, the master has painted himself again twice. This paper analyzes the three self-portraits in terms of the artist’s psychological features, of the growth of his artistic self-consciousness and of their compositional arrangement and the meanings conveyed through such variations

Temperature Profile of Thermal Impinging Flow Induced by Horizontally Oriented Rectangular Jet Flame Upon an Opposite Plate

The horizontally oriented jet flame induced by rectangular source impinging upon the opposite wall is actually common in the chemical industry, but the related studies are limited. In this paper, the computational fluid dynamics codes are carried out to investigate the temperature profile in thermal impinging flow of the horizontally oriented methane jet flame with rectangular source, which the rectangular orifice is 400 mm2 with three different aspect ratios (L/W = 1, 2, 4); besides, the jet velocities vary from 27.5 m/s to 125 m/s. As the horizontally oriented methane jet flame impinges on the vertical plate in front of the fuel orifice directly, the vertical temperature along the opposite plate is focused on. Results show that the temperature near the impingement point is the same for different jet velocities, but the temperature along the vertical direction is larger with increasing fuel jet velocity. Moreover, the orifice aspect ratio has a significant effect on the temperature, which increases with the aspect ratio at a given position for the momentum-controlled flame. The effective heat release rate on the basis of unburned fuel and ellipse flame shape hypothesis is put forward to correlate the temperature profile. Finally, a new correlation to illustrate the vertical temperature rising along the opposite plate is proposed in light of the orifice aspect ratio and fuel jet velocity, and the predictions obtained by the proposed model agree well with the numerical results, which is applicable for the horizontally oriented flame with rectangular source impinging upon the opposite wall.

The Sistine Mosaics of S. Maria Maggiore in Rome: Christology and Mariology in the Interlude between the Councils of Ephesus and Chalcedon

In the present re-reading of the Sistine mosaics of S. Maria Maggiore, which embraces the Old and New Testament scenes in their totality, it will be argued that the iconography is a visual manifestation of the Christology predominating in the Roman Episcopate during the interlude between the Councils of Ephesus and Chalcedon (AD 431 to 451). The fact that the Old Testament narration opens with the Life of Abraham and concludes, on the opposite wall, with the Battles of Joshua, including a distinct pictorial indication of the position of Rahab, the harlot of Jericho, who became the great-great-grandmother of King David, has led the present author to the suggestion that the lost panels concluding the cycle may have included at least one Davidic scene. Such a scene would have extolled the soteriological meaning of the human nature of Christ, “the Son of David, the Son of Abraham” (Mt 1:1), thoughts expounded by Leo the Great in his Tomus ad Flavianum, which laid the ground for the Chalcedonian Council. By the same token the thesis will be advanced that, on the triumphal arch, the matron in the blue maphorion, who sits on Christ’s left side, counterbalancing the Virgin in the Adoration of the Magi scene, may be a personification of the women in the genealogical line of Jesus Christ listed in the Gospel of Matthew (Mt 1:1-16). The two women counterpoised in the Adoration scene would thus exalt and substantiate the Gentile, non-Jewish, contribution to the lineage of Our Saviour. The divine providence expressed through these `extraneous´ links in His ancestry (the key figures of whom were the Gentile women Rahab and Ruth), in the story which led to the Descent of the Logos and the Birth of Christ, may have been the underlying, unifying theme in the vast decoration of the basilica.

Why, how and when MHD turbulence at low becomes three-dimensional

Magnetohydrodynamic (MHD) turbulence at low magnetic Reynolds number is experimentally investigated by studying a liquid metal flow in a cubic domain. We focus on the mechanisms that determine whether the flow is quasi-two-dimensional, three-dimensional or in any intermediate state. To this end, forcing is applied by injecting a DC current $I$ through one wall of the cube only, to drive vortices spinning along the magnetic field. Depending on the intensity of the externally applied magnetic field, these vortices extend part or all of the way through the cube. Driving the flow in this way allows us to precisely control not only the forcing intensity but also its dimensionality. A comparison with the theoretical analysis of this configuration singles out the influences of the walls and of the forcing on the flow dimensionality. Flow dimensionality is characterised in several ways. First, we show that when inertia drives three-dimensionality, the velocity near the wall where current is injected scales as $U_{b}\sim I^{2/3}$. Second, we show that when the distance $l_{z}$ over which momentum diffuses under the action of the Lorentz force (Sommeria & Moreau, J. Fluid Mech., vol. 118, 1982, pp. 507–518) reaches the channel width $h$, the velocity near the opposite wall $U_{t}$ follows a similar law with a correction factor $(1-h/l_{z})$ that measures three-dimensionality. When $l_{z}<h$, by contrast, the opposite wall has less influence on the flow and $U_{t}\sim I^{1/2}$. The central role played by the ratio $l_{z}/h$ is confirmed by experimentally verifying the scaling $l_{z}\sim N^{1/2}$ put forward by Sommeria & Moreau ($N$ is the interaction parameter) and, finally, the nature of the three-dimensionality involved is further clarified by distinguishing weak and strong three-dimensionalities previously introduced by Klein & Pothérat (Phys. Rev. Lett., vol. 104 (3), 2010, 034502). It is found that both types vanish only asymptotically in the limit $N\rightarrow \infty$. This provides evidence that because of the no-slip walls, (i) the transition between quasi-two-dimensional and three-dimensional turbulence does not result from a global instability of the flow, unlike in domains with non-dissipative boundaries (Boeck et al. Phys. Rev. Lett., vol. 101, 2008, 244501), and (ii) it does not occur simultaneously at all scales.

Effects of Pin-Fin Height on Flow and Heat Transfer in a Rectangular Duct

CFD simulations were performed to study the flow and heat transfer in a rectangular duct (Wd × Hd, where Wd/Hd = 3) with a staggered array of circular pin fins (D = Hd/4) mounted on the two opposite walls separated by Hd. For this array of pin fins, five different pin-fin height (H) combinations were examined, and they are (1) H = Hd = 4D (i.e., all pin fins extended from wall to wall), (2) H = 3D on both walls, (3) H = 2D on both walls, (4) H = 4D on one wall and H = 2D on the opposite wall, and (5) H = 3D on one wall and H = 2D on the opposite wall. The H values studied give H/D values of 2, 3, and 4 and C/D values of 2, 1, and 0, where C is the distance between the pin-fin tip and the opposite wall. For all cases, the duct wall and pin-fin surface temperatures were maintained at Tw = 313.15 K; the temperature and the speed of the air at the duct inlet were uniform at Tinlet = 343.15 K and U = 8.24 m/s; the pressure at the duct exit was fixed at Pb = 1 atm; and the Reynolds number based on the duct hydraulic diameter and duct inlet conditions was Re = 15,000. This CFD study is based on 3-D steady RANS, where the ensemble averaged continuity, compressible Navier-Stokes, and energy equations are closed by the thermally perfect equation of state and the two-equation realizable k-ε turbulence model with wall functions and with the low-Reynolds number model of Chen and Patel in the near-wall region. The usefulness of this CFD study was assessed by comparing predicted heat-transfer coefficient and friction factor with available experimental data. Results are presented to show how the flow induced by arrays of pin fins of different heights affects temperature distribution, surface heat transfer, and pressure loss.

Bubble transitions in strongly collapsed elastic tubes

The selection of long air bubbles propagating steadily in a strongly collapsed fluid-filled elastic tube is investigated experimentally in a benchtop model of airway reopening. Localized regions of strong collapse are likely in the lung, because collapsing fluid-elastic instabilities promote extensive deformation of the airway cross-section beyond the point of opposite wall contact. We find that radical changes in the reopening mechanics occur at this point. We build on the recent identification by Heap & Juel (Phys. Fluids, vol. 20, 2008, article no. 081702) of three different steadily propagating bubbles (asymmetric, double-tipped and pointed) that are selected successively for increasing values of the capillary number (Ca, ratio of viscous to surface tension forces) in tubes initially collapsed beyond the point of opposite wall contact. The asymmetric bubble is also observed in less collapsed tubes for small values of Ca, and we show that it bifurcates super-critically from the usual parabolic-tipped bubble as Ca increases. We also characterize the mechanisms underlying the discontinuous transitions between asymmetric and double-tipped bubbles, and double-tipped and pointed bubbles. In particular, we find that the tube must reopen to a critical height for double-tipped bubbles to be selected. The length of the precursor fingers in the double-tipped bubble decreases with Ca, and the bubble loses stability to pointed bubbles when this length is less than the height of the tube at the point where the fingers merge. By contrast with the asymmetric and double-tipped bubbles, the pointed bubble infiltrates the most collapsed part of the tube to yield the rapid reopening of the airway at low pressure, with the potential to reduce ventilation-induced lung damage.