David Z. Saltz

Boundary conditions for a two pressure two-phase flow model

Abstract New closures for two pressure two-phase flow in the context of unstable fluid mixing have been proposed recently by the authors. Here we examine the physical basis for the models, the nature of the boundary conditions at the edges of the mixing layer, and an algorithm for the numerical solution of the two-phase flow equations. Physically, the closures describe chunk mix, in which the flow is dominated by coherent structures of size comparable to the mixing zone thickness. The closed form solution previously introduced for the incompressible limit is reviewed and extended. Sufficient boundary conditions for the compressible equations are found from drag and buoyancy laws proposed by others, with coefficients fit to two sets of independent experiments. These laws complete the closure of the two-phase flow equations. A postulate of stationary center of mass, previously introduced at a numerical level, is here related to a weak notion of self similarity and is solved analytically for the ratio of the growth rates of the two sides of the mixing zone in the self similar case.

Live Media: Interactive Technology and Theatre

In the past century, film, radio, and video technologies gave rise to new forms of dramatic expression and a global entertainment industry. In the past decade, interactive media technologies have been producing an artistic and cultural revolution of similar, if not greater, proportions. Interactive media are giving birth to new art forms, and the practice and history of theatre has a great deal to contribute to these new forms. As I have argued elsewhere, the way that current digital artists valorize the concept of “interactivity” relates closely to the way theatre and performance artists have long valorized the concept of “liveness.” Digital artists strive to define interactive experiences in much the same way, and perhaps for many of the same reasons, as did creators of Happenings and environmental theatre in the 1960s (Saltz, “Interaction”).

Renormalization group solution of two-phase flow equations for Rayleigh-Taylor mixing

Abstract We obtain the exact solution of a recently proposed two-phase flow model of the Rayleigh-Taylor mixing zone, in the incompressible, large time scaling limit. The scaling limit equations are the renormalization group equations for this problem. Our results show that the large time behavior of the incompressible Rayleigh-Taylor mixing layer is determined by a renormalization group fixed point. Our solution allows independent pressures in each fluid. The pressures do not equilibrate dynamically, implying that distinct pressures for each phase is an intrinsic aspect of this problem.

Two-phase flow analysis of unstable fluid mixing in one-dimensional geometry

A two-phase flow model for an acceleration-driven compressible fluid mixing layer is applied to an initially planar/cylindrical/spherical fluid configuration. A conservative form of the one-dimensional compressible equations is derived under the assumption that the fluid concentration is continuous. With a hyperbolic conservation law for the concentration gradient, the model supports traveling discontinuities in this quantity. The primary examples of this wave type are the moving boundaries of a finite mixing layer, which determine the instability growth rate. Constitutive laws for interfacial averages, previously derived for planar incompressible mixing, are reinterpreted and shown to be applicable to other one-dimensional mixing problems of interest. The equations of motion for an incompressible mixing layer in planar, cylindrical, or spherical geometry are solved exactly, up to a history integral of a function of the edge trajectories, and without assuming incompressible flow outside the layer. Full so...

Using the noninteracting cluster theory to predict the properties of real vapor

We examine the nonideal behavior of real vapor in the context of the theory of noninteracting molecular clusters. The vapor is treated as a perfect mixture of clusters, which in equilibrium attain a distribution in size determined by formation energies ΔGi, where ΔGi is the energy required to form a cluster of i molecules from i molecules in bulk saturated liquid. A theory for the ΔGi gives an equation of state that captures the nonideal behavior of the vapor; conversely, equation of state data provide a validation of the theory. In this paper, we compare the predictions of this equation of state to experimental data. Utilizing the ΔGi proposed by Dillmann and Meier and based on Fisher’s droplet model, we compute the vapor compressibility along the saturation curve for several nonpolar substances and obtain excellent agreement with experiment. We also compute the third virial coefficient for these substances and observe correct qualitative behavior; in the case of benzene and n‐octane, for which some data...

When is the Play the Thing?—Analytic Aesthetics and Dramatic Theory

When the Prague semiotician Jiri Veltrusky maintains that ‘in theater, the linguistic sign system, which intervenes through the dramatic text, always combines and conflicts with acting, which belongs to an entirely different sign system’, he makes explicit a commonplace premise: that the performance and the play constitute two distinct and parallel sign systems. This premise underlies the standard distinction between the dramatic text and the performance text, and forms the basis of what I will call the ‘two-text’ model of the play/performance relationship. The difference between a play and its performance is a difference between the ‘languages’ in which the two ‘texts’ are ‘written’: a play is a text constructed of linguistic signs, and a performance, a text constructed of theatrical signs.

Editorial Comment: Performance and Cognition

The announcement for this special issue cast a very wide net, inviting papers exemplifying “New Paradigms” for scholarship in theatre and performance studies. The call observed that scholars “are growing restless or disenchanted with critical and theoretical paradigms that have dominated the field since the 980s. The field appears to be at a crossroads, with no clear consensus about what rigorous scholarship should look like.” The pool of submissions we received, however, suggested that a consensus of sorts does seem to be emerging among a large and diverse group of scholars. We received an outpouring of papers espousing cognitive approaches rooted in scientific research—thus this special issue on “Performance and Cognition” was born.

Media, Technology, and Performance

Toward the end of the 1980s, digital technology began to make significant inroads into mainstream culture. Computers grew in power and acquired the ability to drive and manipulate visual and sound media, even as they steadily decreased in size and cost. A disparate group of artists emerging from the worlds of electronic music, video art, performance art, and theatre—such as George Coates Performance Works, Troika Ranch, Laurie Anderson, Stelarc, David Rockeby, IRCAM (Institut de Recherche et Coordination Acoustique/Musique), Robert Lepage’s Ex Machina, Jeffrey Shaw’s ZKM Institute for Visual Media, and Granular Synthesis—began to integrate new digital technologies into live performance. In the heady period prior to the bursting of the dot-com bubble at the end of 1990s, champions

From Semiotics to Philosophy: Daring to Ask the Obvious

From the late 1960s through the 1980s a steadily-expanding group of international scholars joined forces to develop a comprehensive and unified semiotic theory of theatre. The semiotic wave had largely subsided by the early 1990s, leaving in its wake a profound, and largely justified, scepticism about universal, essentialist, and ahistorical theoretical models. It is possible, however, to ask basic philosophical questions about the ‘nature’ of theatre and performance without falling into the trap of universalizing or essentializing what are, in fact, historically and/or culturally specific practices and biases. In this essay, I advocate an open-ended and dialogic process that characterizes the work of many contemporary philosophers, in both the analytic and continental traditions, and in particular those who have been inspired by the late-Wittgensteinian notion of philosophy as a kind of conceptual therapy.

The Reality of Doing

Theatre scholar Bernard Beckerman defines theatre as a show of “illusion” that displays “people pretending to do something. Whatever they do is a representation of some other action.”1 This definition makes explicit a view that many theatre and performance theorists take for granted. In particular, the dichotomy between stage action and “real” action is integral to semiotic theories of theatre, according to which stage action stands to real action as a signifier to a signified. As theatre semiotician Keir Elam writes: “What converts objects, people and action into signs on stage … is the removal of the performance from praxis. This may seem self-evident and commonplace, but upon this simple act of severance rests the whole power of theatrical semiosis, indeed its very existence.”2