Equilibrium mass transfer coefficients for a dilute species diffusing between laminar counter flowing streams derived from the corresponding eigenvalue problem for the advection–diffusion equation

The turbulent flow over backward-facing step (BFS) is numerically investigated by using FLUENT® code. Both uniform and non-uniform velocity profiles are used as inlet boundary condition. Five different Reynolds averaged Navier–Stokes (RANS) turbulence models are employed. The Std. k–ω model shows the best agreement with the experimental data among the models used under the conditions considered in this study. The results show that using a uniform velocity profile has a negative effect on predictions if the domain is not sufficiently extended upstream from the inlet. To eliminate this effect, the domain should be extended upstream by about 10Dh from the inlet. However, results show that this extension causes absorption effects of inlet parameters such as inlet turbulence intensity.

The effect of inlet velocity profile on entropy generation and hydrothermal performance of a pin-fin heatsink with biologically prepared silver/water nanofluid coolant: Two-phase mixture model

Numerical solutions of a 2D stator compressor cascade at one inlet Mach number (0.7) and four values of incidence (49°, 51°, 53° and 55°) are obtained. Reynolds averaged, thin layer, compressible Navier Stokes equations are solved by using a multi block, parallel algorithm. Finite differencing approach and LU - ADI splitting technique are used. BaldwinLomax turbulence model is applied. Computational pressure distribution and boundary layer results obtained with uniform inlet velocity profiles are compared well with the available experimental data. Rotor wake effects are simulated by defining non-uniform inlet velocity profiles. Steady non-uniform inlet velocity profiles with various shift locations along the tangential direction are tested. Unsteady computations are also performed with moving non-uniform inlet velocity profiles and it is shown that the amplitude of the normal force oscillations are higher at lower frequencies.

A numerical investigation is presented of Brillouin gain in SBS-suppressing optical fibers with non-uniform acoustic velocity profiles. The equation determining the acoustic displacement in response to the electrostriction caused by the pump and Stokes waves reduces to the non-homogeneous Helmholtz equation for fibers with a uniform acoustic velocity profile. In this special case the acoustic displacement and subsequently the Brillouin gain are calculated using a Green's function. These results are then used to validate a finite-element solution of the same equation. This finite element method is then used to analyze a standard large mode area fiber as well as fibers incorporating four different acoustic velocity profiles with 5% variation in the acoustic velocity across the core. The profiles which suppress the peak Brillouin gain most effectively exhibit a maximum acoustic gradient near the midpoint between the center and boundary of the fiber core. These profiles produce 11 dB of suppression relative to standard large mode area fibers.

Previous work on stability of fluid-conveying cantilever pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces drop out of the system’s dynamics since the force of fluid shear on the wall is precisely balanced by pressure drop in the conveyed fluid. The effect of shear has therefore not been ignored in these studies. However, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed non-uniform profile such as would be encountered in real fluid flows. A modified equation of motion was derived to account for the reduced momentum carried by the sheared fluid. Numerical analysis was carried out to determine a number of velocity profiles over the Reynolds number range of interest and a simple set of curve fits was used when finer discretization was required. Stability analysis of a pipe conveying fluid with these profiles was performed, and the results were compared to a uniform profile. The mass ratio, β, is the ratio of the fluid mass to the total system mass. At β = 0.2, the non-uniform case becomes unstable at a critical velocity, ucr, that is 5.4% lower than the uniform case. The critical frequency, fcr, is 0.36% higher than the uniform case. A more sensitive region exists near β = 0.32. There, the nonuniform velocity ucr is 23% lower than the uniform case and the non-uniform critical frequency fcr is 49% of the uniform case.

A uniform inlet velocity profile is widely used in the numerical simulations of fluid flow and heat transfer in ducts for both incompressible and compressible flows. In incompressible flows, the calculated fluid pressure at the inlet edge is extremely high and affects the calculation of the average pressure. In compressible flows, the fluctuation of pressure in the flow direction results in the fluctuation in the velocity. This has motivated this study to numerically investigate a physically realistic velocity profile at the inlet of a pipe rather than using a uniform velocity profile. The numerical simulations were based on the control volume-based power law scheme and the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The continuity and momentum equations for a flow in a pipe with the rounded inlet corner were solved to obtain a physically realistic inlet velocity profile. The obtained inlet velocity profile was expressed by a simple expression in the range of Reynolds number from 100 to 2000. Using this velocity profile, both the incompressible and compressible flows in a pipe were numerically investigated. The results resolved the previously observed inconsistencies in the pressure that were previously observed in the numerical simulations with uniform inlet velocity profiles.

Reviewed by: The Visual Turn: Classical Film Theory and Art History Jennifer Wild Dalle Vacche, Angela , ed. The Visual Turn: Classical Film Theory and Art History. New Brunswick, NJ: Rutgers University Press, 2002. Pp. 279. Students of Film Studies and Art History have long recognized the centrality of Walter Benjamin's essay "The Work of Art in the Age of Mechanical Reproduction" and are accustomed to considering its place in the canon of theoretical writing on the image and on image technologies. Inattentive readers of The Visual Turn: Classical Film Theory and Art History, would, however, be mistaken in assuming that it is solely canonical impulse that has led Angela Dalle Vacche to open her collection of essays with a discussion of Benjamin's classic text. Dalle Vacche invokes a portion of this oft-quoted essay in calling attention to Benjamin's close reading of art historical texts, namely those of Aloïs Riegl —a figure who becomes a "present absence" looming over The Visual Turn and shaping its own dialectical organization.1 Riegl is not the only parental figure hovering over these pages. From Lessing to Wagner to Warburg to Andrew, Dalle Vache introduces discursive strains and disciplinary maps that allow her to pay homage to writers and critics while also expanding her own art historical frame of reference. What emerges is a nuanced view of the art-historical drives of film theory, and a clear understanding that the interdisciplinary study of cinema and painting is actually a "classic" critical paradigm out of which a new interdisciplinary field is swiftly developing. Not only do the contributions to Dalle Vacche's volume offer ample evidence that "the project of viewing film through the lens of art history has a history of its own" (x), as Donald Crafton remarks in the foreword. They also present a sustained argument concerning the extent to which Film Studies has always used art history unwittingly as a "conceptual tool," a move that posits canonical film theorists as distanced readers of classic texts in the history and theory of art. Inasmuch as painting can be considered the popular doxa for art history (3), the project of The Visual Turn involves casting the image as the doxa for the comparative analysis of film and painting. For readers expecting a work that places the cinema under the rubric of mechanical reproduction and considers it against a backdrop of significant art-historical movements and dates, or within a history of the film industry [End Page 149] and the cultural events that shaped it, this book is not a satisfying choice. Rather, Dalle Vacche's desire is not unlike Riegl's, whose aim, she asserts, was to "handl[e] art historical periods by trying to figure out their organizing principles, or, at least, their basic representational formula" (4). Several of The Visual Turn's bi-partite sections demonstrate how what is now known as classical film theory has in fact understood its object of analysis through an organization of certain formal principles including, for instance, the close-up (Béla Balázs and Jacques Aumont), the frame of the image (André Bazin), and montage (Gilles Deleuze). By pairing Heinrich Wölfflin's "Linear and Painterly" with an excerpt from The Movement Image, wherein Deleuze organizes montage styles into "American" and "Soviet" schools, The Visual Turn cleverly and efficiently identifies an agency internal to Deleuze's formal project—Deleuze's Kunstwollen, so to speak—that amounts to a theory of the image from within formal art historical methods. The Visual Turn proceeds by establishing a diachronical interface between paired authors, including Erwin Panofsky ("Style and Medium in the Motion Pictures") and Thomas Y. Levin ("Iconology at the Movies: Panofsky's Film Theory"), Rudolf Arnheim ("Painting and Film") and Ara H. Merjian ("Middlebrow Modernism: Rudolf Arnheim at the Crossroads of Film Theory and the Psychology of Art"), and Sergei Eisenstein ("El Greco") and Pietro Montani ("The Uncrossable Threshold: The Relation of Painting and Cinema in Eisenstein"). This approach underscores the importance of the problematics of reception that are posed by now classic essays that place film and painting in an overt dialectical relation, or that implicitly do so when a classic film...

In the present paper, numerical investigations are carried out in a newly proposed propulsive system Aerial Coanda high-efficiency orienting jet nozzle (ACHEON), which supports thrust vectoring and its application to prototype unmanned aerial vehicles (UAVs). The ACHEON system is presently being proposed for propelling a new vertical and short takeoff (V/STOL) airplane in the European Union. This system is powered by two axial electric turbofans and uses the Coanda effect (attachment of the jet to a curved surface) to achieve precise control of the thrust angle. The present study investigates the thrust vectoring efficiency of this newly patented nozzle and its integration with UAV aircraft. This study numerically investigates the 3D effects on this new machine and proposes remedies to solve the associated problems. Further, swirling effects generated by electric turbofans were studied in great detail. The effect of uniform and nonuniform velocity profiles were investigated on thrust vectoring eff...

Three-dimensional numerical investigations have been carried out for flow past surface mounted finite-height square cylinder using Open Source Field Operation and Manipulation (OpenFOAM). Unsteady wake behaviour has been studies for different values of angle of incidence (α) varying from 0o to 45o at fixed Reynolds number equal to 150. Uniform and non-uniform velocity profiles have been considered at inlet. Unsteady wake oscillations have been examined using Hilbert Huang transformation. Transverse velocity signal in the wake has been decomposed into component signals and frequency variation of each decomposed signals has been presented in Hilbert spectra. Appearance of frequency modulations in the spectra has been related with nonlinear oscillations in the wake. Frequency distribution corresponding to each value of α has been presented in marginal spectra. Wake nonlinearity has been quantified in terms of degree of stationarity. Variation in mean drag coefficient with change in values of α has also been reported.

We extend fluorescence correlation spectroscopy to systems that undergo translation or laminar flow in a sample cell. We include theoretical and experimental results; we consider uniform and nonuniform velocity profiles. Concentration correlation analysis extracts microscopic rate parameters from measurements of the spontaneous concentration fluctutations, which occur even at equilibrium. Fluorescence is one of the most sensitive means of monitoring these fluctuations. Analysis of flowing or translating systems (1) offers a method of measuring number concentrations of selected species, for example, of aggregates or polymers, (2) provides a nonperturbing velocity probe, (3) sometimes allows one to circumvent photolytic degradation, (4) has proved extremely helpful in testing and aliging apparatus for fluorescence correaltion measurement and in verifying theoretical analyses, and (5) may be required for interpretation of results obtained on systems in motion, even though that motion is undesired or initially unsuspected. We include both theoretical and experimental results for combined Poiseuille flow and diffusion in the geometry which is of most practical interest. Theoretical expressions for the much simpler cases of nondiffusive Poiseuille flow as well as uniform flow or translation with or without diffusion constitute limiting cases which are displayed explicitly.

Particle inhalation and deposition in a human nasal cavity from the external surrounding environment

Previous analytical work on stability of fluid-conveying pipes assumed a uniform velocity profile for the conveyed fluid. In real fluid flows, the presence of viscosity leads to a sheared region near the wall. Earlier studies correctly note that viscous forces do not affect the dynamics of the system since these forces are balanced by pressure drop in the conveyed fluid. Although viscous shear has not been ignored in these studies, a uniform velocity profile assumes that the sheared region is infinitely thin. Prior analysis was extended to account for a fully developed nonuniform profile such as would be encountered in real fluid flows. A modified, highly tractable equation of motion was derived, which includes a single additional parameter to account for the true momentum of the fluid. This empirical parameter was determined by numerical analysis over the Reynolds number range of interest. The stability of cantilever pipes conveying fluid with two types of non-uniform velocity profile was assessed. In the first case, the profile was a function of Reynolds number and transition to turbulence occurred before the onset of flutter instability. This case had stability properties similar to the uniform velocity case except in specific narrow regions of the parameter space. The second case required that the Reynolds number be such that the flow was always laminar. For this case, lower fluid velocity was required to achieve instability, and the oscillation frequency at instability was considerably lower over much of the parameter space, compared to the uniform case.

Dynamics of pipes conveying fluid with non-uniform turbulent and laminar velocity profiles

The heyday of classical film theory is predominantly understood to have been concerned with ontological and formal matters and with promoting film as an art. Pursuing the shapes and contours of the new medium, many writers on cinema from the 1920s heralded cinema as a ‘universal language’. Examining the ‘universal language’ thesis, one finds a remarkable variety to the various arguments. By undertaking a close prospect of just one version of the ‘universal language’ thesis by a single writer, Bela Balazs, this essay intends to complicate the enterprise of 1920s ‘classical film theory’. Tracing back the messy trail of reception and production and returning to the heart of Balazs's output, one finds a universal language which is neither truly universal, nor technically a language. Balazs's writings on cinema and language form the basis of a Janus-faced philosophy caught between future and past, film theory and human history, between an anthropology of the person and a prescription for various peoples. Re-examining Balazs and interrogating the ‘universal language thesis’ draws attention to the various modes, functions and addressees of what is called ‘classical film theory’ and to the need for new historiographical paradigms which take material matters of production and reception into account. At the same time, Balazs serves as an example for what unites many of the 1920s classical film theorists: the tension between the universal and the nationally specific and between their proposed theories and implied histories of film.

A method is presented of designing very wide angle axisymmetric diffusing ducts which achieve uniform outlet velocity profiles. The aim was to concentrate the major part of the diffuser pressure rise on a small portion of the duct boundary with zero or favorable pressure gradients on the remainder of the boundary. With an optimum location and design of gauze the diffusers are capable of giving a very uniform outlet velocity profile in a short overall length, when working with thin inlet boundary layers and some, although recognizably moderate, pressure recovery. One diffuser tested (diffuser C) produced uniform outlet velocity profiles in approximately 1.5 inlet diameters compared with the 10 diameters required for a sudden enlargement having comparable performance.