Russell Keanini - Academia.edu (original) (raw)

Papers by Russell Keanini

Geological Society of America Abstracts with Programs

Heat Transfer: Volume 4, 1999

This paper describes the first phase of a two-part project designed to develop a new anemometry m... more This paper describes the first phase of a two-part project designed to develop a new anemometry method for use in high temperature liquid metal flows. The device will incorporate a dual-cantilever, PZT-driven touch sensor housed within a sealed, temperature resistant ceramic Pitot tube. Due to differing cantilever lengths, the device’s unloaded spectral response exhibits two distinct peaks, each corresponding to the cantilevers’ resonant frequencies. The principal of operation is based on the fact that pressure-induced forces on each cantilever produce resonant frequency shifts which can then be correlated with applied pressures. The first project phase has focused on development and testing of the dual cantilever touch-sensor and its supporting electronics. Two new concepts have been introduced in designing the touch sensor — use of a dual cantilever for simultaneous force measurement, and simultaneous detection of associated pressure-induced resonant frequency shifts. Here, we des...

Fluids Engineering, 1999

Particle transport associated with quasistatic second-order streaming flow in wavy-walled channel... more Particle transport associated with quasistatic second-order streaming flow in wavy-walled channels is theoretically investigated. Small amplitude tangential oscillations of both walls drive steady second-order streaming, while superposed, large-amplitude oscillations of one wall produce the time-dependent, quasisteady flows of interest. Short-time transport is characterized by collective particle motion in the direction of large-scale boundary displacement and by filamentary motion in the opposite direction, both consistent with transport in traveling waves [E. Moses and V. Steinburg, Phys. Rev. Lett. 60, 2030 (1988)]. Long time or asymptotic transport is characterized by particle agglomeration toward, or repulsion from, moving elliptic points. Under certain conditions, collective, periodic motion on the periphery of central cells also occurs. These characteristics correspond respectively to attraction or repulsion to or from period-1 elliptic points and attraction toward limit cycl...

Journal of visualized experiments : JoVE, Dec 4, 2017

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases ... more An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are hi...

Reviews of Geophysics, 2017

Low-magnitude subcritical stresses from superimposed sources likely drive most mechanical weather... more Low-magnitude subcritical stresses from superimposed sources likely drive most mechanical weathering at and near Earth's surface Weathering by subcritical cracking and concomitant regolith production and erosion are climate-dependent regardless of the stressing process Climate's influence on subcritical cracking varies with magnitude of the applied stress and with rock mechanical properties

Journal of Materials Processing Technology, 2016

Abstract Vibrational finishing processes are finding increased application in the finishing of hi... more Abstract Vibrational finishing processes are finding increased application in the finishing of high end components. Despite the growing popularity of vibrational finishing, and due to limited suitable process instrumentation, understanding of underlying physical processes remains largely anecdotal and empirical, and system-independent process control remains unrealized. In this paper, particle image velocimetry (PIV) is proposed as a versatile, non-intrusive, readily available diagnostic for both studying fundamental features associated with vibrational finishing, as well as for developing system-independent control strategies. With regard to fundamental processes, PIV is used to measure surface media velocity fields and find that in our experimental system, the media flow field consists of: (i) a weak, random component having repeatable statistical properties which are sensitive to, and indicative of, changing process parameters and media selection, superposed on, (ii) a dominant, non-random component which is insensitive to changes in process parameters. Importantly, from a potential process control standpoint, it is shown that a filtered version of the random velocity component offers a system-independent, parameter-sensitive indicator of process conditions.

Physical Review E, 2000

Second-order streaming in a thin fluid layer driven by one or two opposed, tangentially oscillati... more Second-order streaming in a thin fluid layer driven by one or two opposed, tangentially oscillating wavy walls is theoretically investigated. In contrast to the well-studied problem of oscillatory flow past a stationary boundary, the present problem is subject to a nonhomogeneous second-order boundary velocity condition. A combination of steady Reynolds stresses and boundary forcing thus drives the streaming flow; indeed, under most conditions, boundary-forced flow dominates Reynolds-stress-driven flow. The first part of the paper examines parametric effects on second-order flow structure. Under low-Reynolds-stress conditions and during single-boundary forcing, flow structure remains essentially independent of all parameters, including the Stokes layer thickness, the fluid layer thickness, and the forcing wave form. Three approximations to the full secondorder solution, valid under low-Reynolds-stress conditions, are used to explain these results. In the case of dual-boundary forcing, no corresponding universal behaviors are observed; flow structure exhibits sensitivity to all problem parameters. The second part of the paper investigates particle transport during quasistatic second-order streaming. Here, slow, superposed, large-amplitude oscillations of one wall produce the timedependent, quasisteady flows of interest. Collective particle motion in the direction of large-scale boundary displacement and filamentary motion in the opposite direction, features consistent with transport in traveling waves ͓E. Moses and V. Steinberg, Phys. Rev. Lett. 60, 2030 ͑1988͔͒, characterize short-time transport. Long-time or asymptotic transport, in contrast, is characterized by particle attraction or repulsion to or from period-one elliptic points and attraction toward limit cycles on the Poincaré map.

27th Aerospace Sciences Meeting, 1989

International Journal of Computational Methods and Experimental Measurements, 2013

A series of fi ve full-scale, nearly conventional, curtain wall specimens was tested in the UNC C... more A series of fi ve full-scale, nearly conventional, curtain wall specimens was tested in the UNC Charlotte Structures Laboratory. Specimens were subjected to quasi-static, uniform, out-of-plane loading to failure under displacement control. The tests were performed to obtain complete resistance curves, including the nonlinear behavior of the specimens up to 'ultimate failure'. Ultimate failure was defi ned as mullion fracture or signifi cant breach of the curtain wall system when viewed as the protective barrier between building occupants and the external blast load. Representative load-defl ection and loadstrain resistance curves are presented. The energy absorbed by the curtain wall system up to three different limit states-fi rst cracking of glass, fi rst yield of mullions, and fracture/breach of the system (ultimate failure)-and maximum mullion end rotations are computed from the experimental results. Ultimate energy absorption capacity-the recoverable linear strain energy plus the nonlinear energy due to formation of damage mechanisms-and maximum mullion end rotations are essential for reliable and economical design of blast resistant curtain walls. To this end, a simplifi ed methodology is presented for analytically approximating curtain wall resistance functions that can be input to an energy expression that models nonlinear structural dynamic behavior due to an 'impulsive' loading. The blast resistance of a curtain wall can then be approximated using this procedure. It is shown that a nearly conventional curtain wall, a conventional system with two modifi cations-use of laminated glass lites that are structurally glazed (wet-glazed) to a conventional framing system with structural silicone sealanthad nearly 14 times the ultimate energy absorption capacity and nearly four times the blast resistance as the fully conventional system.

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2002

During ground-tests of most production rocket engines over the last 30 years, large asymmetric tr... more During ground-tests of most production rocket engines over the last 30 years, large asymmetric transient side loads coming from the nozzle and related steady-state vibrational loads within the nozzle have been measured.

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2012

High-fidelity numerical experiments and theoretical modelling are used to study the dynamics of a... more High-fidelity numerical experiments and theoretical modelling are used to study the dynamics of a sounding-rocket-scale rocket, subject to altitude-dependent random wind and nozzle side loads and deterministic aerodynamic loading. This paper completes a series of studies that showed that Ornstein–Uhlenbeck (OU) rotational dynamics arise when random nozzle side loads dominate wind and aerodynamic loading. In contrast to the earlier work, this paper elucidates that under conditions where aerodynamic, wind and nozzle side loads are comparable, the rocket behaves as stochastic Brownian oscillator. The Brownian oscillator model allows straightforward interpretation of the complex rotational dynamics observed: three dynamical regimes—each characterized by differing balances between nozzle-side-load-induced torques, spring-like aerodynamic torques and mass flux damping torques—characterize rocket ascent. Further, the paper illuminates that in the limit where wind and aerodynamic loads are ...

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2006

Three stochastic-based methods are proposed for solving unsteady scalar transport problems in bou... more Three stochastic-based methods are proposed for solving unsteady scalar transport problems in bounded, single-phase domains. The first (Method I), a local solution appropriate to problems having Dirichlet conditions, adapts a well-known local stochastic solution of a backward Fokker-Planck equation to scalar transport. Method II, a local solution applicable to Dirichlet, Neumann and/or mixed initial boundary value problems (IBVPs), and representing a time-dependent extension of a recently reported heuristic steady solution, provides a straightforward addition to the limited collection of techniques available for Neumann and mixed problems. This approach is shown to be equivalent to a long-standing, rigorous low-order solution and, in addition, allows development of a probabilistic-based analytical solution to Neumann problems, stated in terms of an exit probability. Method III, a global solution, likewise suitable for Neumann and mixed IBVPs, follows by combined application of domain boundary Taylor expansions and Method I. This approach is shown to be computationally equivalent to a global version of Method II.

Plant Physiology, 1988

The growth equation for the rate of water uptake is augmented with a transpiration term. The obta... more The growth equation for the rate of water uptake is augmented with a transpiration term. The obtained augmented growth equations are used to develop methodology which employs the pressure probe to measure transpiration rates from single plant cells. Experiments are conducted on the sporangiophores of Phycomyces blakesleeanus to demonstrate this technique.

Metallurgical and Materials Transactions B, 2001

This article reports an experimental and theoretical investigation of mercury dissolution from de... more This article reports an experimental and theoretical investigation of mercury dissolution from dental amalgams immersed in neutral (noncorrosive) and acidic (corrosive) flows. Atomic absorption spectrophotometric measurements of Hg loss indicate that in neutral flow, surface oxide films formed in air prior to immersion persist and effectively suppress significant mercury release. In acidic (pH 1) flows, by contrast, oxide films are unstable and dissolve; depending on the amalgam's material composition, particularly its copper content, two distinct mercury release mechanisms are initiated. In low copper amalgam, high initial mercury release rates are observed and appear to reflect preferential mercury dissolution from unstable Sn 8 Hg (␥ 2) grains within the amalgam matrix. In high copper amalgam, mercury release rates are initially low, but increase with time. Microscopic examination suggests that this feature reflects corrosion of copper from grains of Cu 6 Sn 5 (Ј) and consequent exposure of Ag 2 Hg 3 (␥ 1) grains; the latter serve as internal mercury release sites and become more numerous as corrosion proceeds. Three theoretical models are proposed in order to explain observed dissolution characteristics. Model I, applicable to high and low copper amalgams in neutral flow, assumes that mercury dissolution is mediated by solid diffusion within the amalgam, and that a thin oxide film persists on the amalgam's surface and lumps diffusive in-film transport into an effective convective boundary condition. Model II, applicable to low copper amalgam in acidic flow, assumes that the amalgam's external oxide film dissolves on a short time scale relative to the experimental observation period; it neglects corrosive suppression of mercury transport. Model III, applicable to high copper amalgam in acidic flow, assumes that internal mercury release sites are created by corrosion of copper in Ј grains and that corrosion proceeds via an oxidation-reduction reaction involving bound copper and diffusing hydrogen ions. The models appear to capture the correct time dependence of each dissolution mechanism and to provide reasonable fits to the experimental data.

Metallurgical and Materials Transactions B, 2007

Journal of Applied Physics, 2010

It is well known that the dynamic performance of a rocket or launch vehicle is enhanced when the ... more It is well known that the dynamic performance of a rocket or launch vehicle is enhanced when the length of the divergent section of its nozzle is reduced or the nozzle exit area ratio is increased. However, there exists a significant performance trade-off in such rocket nozzle designs due to the presence of random side loads under overexpanded nozzle operating conditions. Flow separation and the associated side-load phenomena have been extensively investigated over the past five decades; however, not much has been reported on the effect of side loads on the attitude dynamics of rocket or launch vehicle. This paper presents a quantitative investigation on the influence of in-nozzle random side loads on the attitude dynamics of a launch vehicle. The attitude dynamics of launch vehicle motion is captured using variable-mass control-volume formulation on a cylindrical rigid sounding rocket model. A novel physics-based stochastic model of nozzle side-load force is developed and embedded in the rigid-body model of rocket. The mathematical model, computational scheme, and results corresponding to side loading scenario are subsequently discussed. The results highlight the influence of in-nozzle random side loads on the roll, pitch, yaw, and translational dynamics of a rigid-body rocket model.

Journal of Applied Physics, 2013

This paper presents a study of the internal stress distribution and its stress transfer mechanism... more This paper presents a study of the internal stress distribution and its stress transfer mechanism of composite anchors for carbon fiber-reinforced polymer (CFRP) tendons. One set of static tensile test for composite anchor was introduced and carried out. Three zones designated as tension zone, holding zone and compression zone respectively were divided to analyze the stress distribution separately based on some assumptions. Test and analysis results show that the tensile stress and its variation on the steel tube surface will reflect the internal stress distribution of composite anchor. Peak tensile stress exists in the tension zone test points indicates the bonding failure occurs between adhesive and CFRP tendons. The radial clamping action of wedge could effectively enhance the anchoring effect. The obvious decrease of stress curve in the compression zone indicates the bonding damage of entire composite anchor occurs.

Inverse Problems in Engineering, 1996

This paper describes an inverse technique for imaging multi-dimensional optically opaque phase ch... more This paper describes an inverse technique for imaging multi-dimensional optically opaque phase change boundaries and associated near-melt solid phase temperature fields. The algorithm confines calculations to the solid region immediately surrounding the melt interface, uses a coarse, spatially limited finite element mesh, and is capable of determining phase boundaries in nonlinear, heterogeneous, anisotropic materials. Upwind differencing is introduced to circumvent instabilities associated with large grid Peclet numbers while first order regularization is used to enhance solution stability. Since all a priori unknown boundary heat fluxes are determined by the inverse procedure and ad hoc assumptions are eliminated, the technique is non-problem-specific and portable. Algorithm performance is examined using a simple analog welding experiment. In cases where the fusion boundary is known and fixed in the inverse code, and for initial heat flux guesses that differ by up to four orders of magnitude from the characteristic flux magnitude, average relative error between predicted and actual solid temperature distributions is approximately 7.4%. In the more general case where the interior melt shape is unknown, and over a wide range of initial parameter specifications, average relative error between predicted and actual interior boundaries is less than 3% while corresponding average relative temperature error is less than 8%.

International Journal of Heat and Mass Transfer, 1993

A finite element-based simulation of the plasma arc welding process is presented. The simulation ... more A finite element-based simulation of the plasma arc welding process is presented. The simulation determines the weld pool's three-dimensional capillary surface shape, the approximate solid-liquid phase boundary, and calculates the pool's three-dimensional flow and temperature fields. The simulation is first used to examine the effect of ambient temperature and plate speed on pool shape. Pool flow is then studied. The Row's qualitative features are primarily determined by jet shear and the~ocapi~la~ty while buoyancy is of secondary importance.