Hydrostatic Mode Research Articles

Resolving nonhydrostatic effects in oceanic lee waves

With increased computing power, the horizontal grid-spacing of regional ocean models is decreasing to the point where they can directly simulate lee waves. Although oceanic lee waves can be inherently nonhydrostatic, such as in the abyssal ocean or in the Gulf Stream, regional ocean models are frequently run in hydrostatic mode to avoid the computational expense of solving the nonhydrostatic pressure. However, the effects of the nonhydrostatic pressure and the numerical error on the accuracy of the simulated lee waves is not immediately obvious. To quantify these effects, this paper presents hydrostatic and nonhydrostatic simulations of an idealized lee wave over both linear and nonlinear height and varying length bathymetry utilizing a range of horizontal grid-spacings. We present an analysis of the numerical error arising from the discrete linear, stratified Euler equations to identify the numerically induced physics in lee wave simulations. As expected for the second-order accurate model, the numerical error in the lee wave drag decreases quadratically with respect to horizontal grid refinement, although the error arises from two primary sources. The first is related to discretization of the kinematic bottom boundary condition, which acts to decrease the lee wave drag. The second is related to discretization of the nonhydrostatic pressure, which acts to increase the drag. Together, the results offer a regional ocean modeler several cautionary notes for calculating and interpreting properties of simulated lee waves, namely, that a hydrostatic model can produce the correct form drag due simply to numerical error, and attempting to employ a nonhydrostatic model to correct for this error can require prohibitively fine grid resolution.

Analytical Study of Non-Recessed Conical Hole Entry Hybrid/Hydrostatic Journal Bearing with Constant Flow Valve Restrictor

The present work studies the analysis of a non recessed hole entry conical hybrid/hydrostatic journal bearing adjusted for constant flow valve (CFV) restriction. The paper provides effectiveness between the conical bearings with hole entry operating in hybrid and hydrostatic mode. The Reynolds formulae, for the flow of fluid through the mating surfaces of a conical journal and bearing, are numerically worked out in both the modes considering the finite element analysis (FEA) and the necessary boundary preconditions. Holes in double row are marked on conical bearing circumference to accommodate the CFV restrictors, the angular distance between two holes are 30o apart from the apex. Qualitative features of the conical journal bearing system with hole entry have been elaborated to analyze bearing performance for radial load variation Wr = 0.25-2. Numerical results obtained from the present study indicate that load carrying capacity of conical bearing, operating in hydrostatic mode, is enhanced by the maximum pressure, direct fluid film damping and direct film stiffness coefficients vis-a-vis corresponding hybrid mode. 

On pressure perturbations caused by a moving heat source of the frontal type (hydrostatic mode)

The problem of perturbations of the surface pressure caused by a moving nonstationary frontal heat source (localized along one horizontal coordinate) is considered. Pressure disturbances are associated with internal gravity waves (IGWs). It is shown that when a source moves in a finite-height atmospheric layer (atmospheric waveguide) when a discrete set of vertical IGW modes is excited, there are three types of temporal variation of surface pressure at a fixed observation point. These types correspond respectively to the time signal with amplitude modulation, the signal with frequency modulated Doppler type and the signal that occurs only after passing through the source. Each type is implemented for specific values of the oscillation frequency of the source and the Mach number (the ratio of the speed of the source to the phase velocity of the IGW). At Mach numbers less than one, an oscillating source always excites wave precursors disturbances observed before the source arrives. The movement of the source in a semi-infinite atmosphere leads to additional excitation of waves that transfer energy to the upper layers of the atmosphere.

Comparative characteristics of hydrostatic conical hole-entry journal bearing with CFV, orifice and capillary restrictors

ABSTRACTThe present comparison is mainly based on the type of restrictor employed in the conical journal bearing with hole-entry in hydrostatic mode. It suggests efficient restrictor to be used in the subjected conical journal bearing. To find the characteristics, Reynolds's equation is applied to the fluid present in the space between conical journal and bearing, the flow equations for various restrictors have been presented using FEM. Different parametric characteristics have been obtained for the range of eccentricity ratio () = 0.1–0.7. The outcome of the comparative characteristics depict the significant variations in the restrictor-based conical hole-entry journal bearing performances in hydrostatic mode which may be useful for the bearing designer to precisely design the conical hole-entry journal bearing. Comparatively, the constant flow valve fitted hydrostatic conical journal bearing with hole-entry may be recommended based on the present study.

On Pressure Perturbations Caused by a Moving Heat Source of Frontal Type (Hydrostatic Mode)

The problem of surface-pressure perturbations caused by a moving nonstationary heat source (localized along one horizontal coordinate and periodic along the other) is considered. Pressure perturbations are associated with internal gravity waves (IGWs). It is shown that, during the source movement throughout a finite-height atmospheric layer (atmospheric waveguide), when a discrete set of vertical IGW modes is excited, there may be three types of time surface-pressure variations at a fixed observation point. A time amplitude-modulated signal; a Doppler frequency-modulated signal; and a signal that occurs only after the passage of the source correspond to these three types, respectively. Each of these types is implemented for certain source oscillation frequencies and Mach numbers (ratio between the movement rate of source and the phase velocity of IGWs). At $$M < 1$$ , a nonstationary source always excites wave precursors—disturbances observed before the source arrival. The movement of the source in a semi-infinite atmosphere leads to additional generation of waves that transport energy into the upper atmospheric layers.

Seasonal range test run with Global Eta Framework

Abstract. Global Eta Framework (GEF) is a global atmospheric model developed in general curvilinear coordinates and capable of running on arbitrary rectangular quasi-uniform spherical grids, using stepwise (Eta) representation of the terrain. In this study, the model is run on a cubed-sphere grid topology, in a version with uniform Jacobians (UJ), which provides equal-area grid cells, and a smooth transition of coordinate lines across the edges of the cubed-sphere. Within a project at the Brazilian Center for Weather Forecasts and Climate Studies (CPTEC), a nonhydrostatic version of this model is under development and will be applied for seasonal prediction studies. This note describes preliminary tests with the GEF on the UJ cubed-sphere in which model performance is evaluated in seasonal simulations at a horizontal resolution of approximately 25 km, running in the hydrostatic mode. Comparison of these simulations with the ERA-Interim reanalyses shows that the 850 hPa temperature is underestimated, while precipitation pattern is mostly underestimated in tropical continental regions and overestimated in tropical oceanic regions. Nevertheless, the model is still able to well capture the main seasonal climate characteristics. These results will be used as a control run in further tests with the nonhydrostatic version of the model.

Electro‐active polymer transduction for distributed netted sensing

The Naval Undersea Warfare Center in Newport, RI is developing an electro‐active polymer‐based sensing node for use in a persistent distributed underwater surveillance system. Persistence demands extreme energy conservation measures. The node will resemble a jellyfish in form, complete with tentacles housing a volumetric array of light‐weight piezoelectric polyvinylidene fluoride trifluoroethylene (PVDF‐TrFE) copolymer cylindrical hydrophones designed for an ultra‐low power acoustic receiver. Each cylinder has conductive silver electrodes on the inside and outside surfaces, a length of 2.5 cm, an outside diameter of 11 mm, a 1 mm wall thickness, and a mass less than 2 g. Operating in the hydrostatic mode, the hydrophone sensitivity is typically ‐195 dB//1 V/μPa and is stable with both hydrostatic pressure (50 to 1000 psi) and temperature (‐1 to 35°C). [Work supported by the Office of Naval Research.]

Proline-coated column for the capillary electrochromatographic separation of amino acids by in-column derivatization.

With 3-trimethoxysilylpropyl chloride as the spacer, a proline-coated capillary column was prepared for the capillary electrochromatographic (CEC) separation of amino acids by in-column derivatization. Nine standard mixtures, including aspartic acid, glutamic acid, valine, phenylalanine, alanine, isoleucine, leucine, tyrosine, and tryptophan, were injected. o-Phthalaldehyde (OPA), OPA/2-mercaptoethanol (2-ME) and OPA/N-acetylcysteine (NAC) in borate buffer were tested as the derivatizing agent. Among them, OPA (50 mM) in borate buffer (pH 9.5, 50 mM) gave the best performance. The formation of isoindole could be detected by UV detection. The sandwich-type injection was carried out in hydrostatic mode (10 cm) with the program R(10 s)S(10 s) R(10 s)W(10 min) with R, S, and W being the reagent, sample, and waiting times. Mesityl oxide, benzyl alcohol, and acetone showed some interaction with the column. A current monitoring method was used instead of the determination of the electroosmotic flow (EOF). The direction of EOF was from anode to cathode even under acidic condition lower than the pI value (6.31) of the bonded group due to some unreacted silanol groups. Some parameters including pH, nature, and concentration of the mobile phase and the effect of organic modifier with regard to the CEC separation were investigated. With the proline-coated column (75 (50) cm x 75 microm ID) the best separation was performed in phosphate buffer (pH 4.00, 100 mM) with an applied voltage of -15 kV. The established method was also compared with those precolumn derivatized prior to the separation with proline-coated column as well as with in-capillary derivatization and separation with a bare fused-silica column.

An Improved Analytical Model for Time-Dependent Shearing Deformation in Area-Array Interconnects

An improved time-dependent analytical model is developed for predicting the maximum shearing displacement in an area-array electronic assembly under global thermal mismatch loading. The thermal loads are assumed to be uniform within the component and substrate, with both step-function and sinusoidal temperature histories being considered. The time-dependent effects in the array’s shear deformation are introduced in an approximate manner by modeling the interconnect material (solder) as a temperature-independent linear viscoelastic material. The viscoelastic constitutive law used for the solder is that of a three-parameter viscoelastic standard solid in distortion and an elastic solid in the hydrostatic mode. In the authors’ previous work the steady-state shear force in the joints was assumed to vary sinusoidally with a frequency-independent amplitude. This assumption has been relaxed in the present study, leading to improved accuracy. All results have been derived as closed-form correction factors to be applied to the easily calculated unconstrained shear displacement to obtain the maximum shear displacement. All the correction factors depend on prescribed geometric and material parameters of the component, substrate, and joints. The results have been presented in the form of dimensionless plots to aid in the analysis or design process, thereby providing convenient alternatives or supplements to time-consuming and expensive finite element analyses of entire assemblies.

A new positive‐definite regularization of incompressible Navier–Stokes equations discretized with Q1/P0 finite element

AbstractA new regularization method is proposed for the Galerkin approximation of the incompressible Navier–Stokes equations with Q1/P0 element, by newly introducing a square‐type linear form into the variational divergence‐free constraint regularized with the global pressure jump (GPJ) method. The addition of the square‐type linear form is intended to eliminate the hydrostatic pressure mode appearing in confined flows, and to make the discretized matrix positive definite and then non‐singular without the pressure pegging trick. Effects of the free parameters for the regularization on the solutions are numerically examined with a 2‐D driven cavity flow problem. Furthermore, the convergences in the conjugate gradient iteration for the solution of the pressure Poisson equation are compared among the mixed method, the GPJ method and the present method for both leaky and non‐leaky 3‐D driven cavity flows. Finally, the non‐leaky 3‐D cavity flows at different Re numbers are solved to compare with the literature data and to demonstrate the accuracy of the proposed method. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Comparison of stratocumulus cloud modeling with satellite observations and in situ measurements

As part of the European Cloud and Radiation Experiment campaign, we conducted studies with the regional atmospheric modeling system in order to simulate stratocumulus clouds observed on April 18, 1994, over Brittany (France). This three‐dimensional model was used in its non hydrostatic mode, with bulk microphysical and radiative transfer parameterizations. The first initialization employed data provided by the European Center for Medium‐range Weather Forecasts (ECMWF) and radiosoundings obtained at the Guipavas ground station. The model outputs were then compared with the corresponding NOAA‐AVHRR (advanced very high resolution radiometer) satellite image and aircraft data collected in situ during the experiment. The relative differences between modeled and actual microphysical quantities (i.e., mixing ratio of water vapor, liquid water content, or liquid water path) were found to be less than 25% along the airplane trajectory; this disagreement was as large as 200% elsewhere in the experimental domain, principally because cloud cover was underestimated. The development of a simple time‐to‐space analysis made it possible to force the mesoscale model with satellite images combined with vertical profiles and tridimensional data of the ECMWF, leading to a more accurate spatial distribution of clouds over a large domain and diminishing these errors to 10%.

Porous lead zirconate titanate ceramics for hydrophones

Abstract Passive sonar arrays of the last generation need a large number of hydrophones. To obtain simple and low cost devices, new active materials working in an hydrostatic mode are investigated. In this context, porous LZT ceramics whose characteristics are very promising are highlighted.

U.S. Navy 0–3 piezocomposite transducers

Interest in 0–3 piezoelectric composite materials for use in hydrophone applications has grown considerably in recent years. Designs which require operation in the hydrostatic mode with a large hydrostatic voltage coefficient gh, are desired to increase free-field voltage sensitivity and meet the ever increasing demands placed on hydrophone performance. U.S. Navy scientists at the Naval Research Laboratory, Underwater Sound Reference Detachment, have investigated the utilization of 0–3 piezocomposite for sonar applications and have developed various hydrophone configurations based on specific program requirements. The requirements of the programs, such as a lightweight, low-profile, and high receive sensitivity, demanded unique designs and the need for utilizing the unique characteristics of 0–3 composite materials. The hydrophones presented in this discussion used a 0–3 composite known at NRL simply as piezorubber or PZR. This material consists of lead titanate particles embedded in a neoprene elastomeric matrix. This discussion will cover the development, including problems and solutions, fabrication, and testing of two unique 0–3 composite hydrophones.

Versatility of capillary electrophoresis of anions with a high mobility chromate electrolyte

Capillary ion electrophoresis (Waters' trade name: Capillary Ion Analysis) is a capillary electrophoretic technique which is optimized for the rapid analysis of low molecular-mass inorganic and organic ions. Indirect UV detection at 254 nm was used throughout. An electroosmotic flow modifier was added to the chromate electrolyte and a negative power supply was used. Analysis of anions in a variety of samples with differing matrices was investigated. Examples discussed include trace level anions in power plant water (ng/ml) and μ/ml level of anions in intermediate and concentrated sulfonated dyes. Anion analysis using this technique is rapid (less than 5 min), with little sample preparation required. The same electrolyte composition, with only minor variations, was used for all samples. Both hydrostatic mode of injection for ppm level analysis and electromigration mode of injection for trace level analysis was used.

Composite piezoelectric materials for transduction

In order to optimize the detection of acoustical signals in a hydrostatic mode for future applications, new transduction materials which combine active ferroelectric materials with other inert phases such as polymers were developed. These new composite piezoelectric materials exhibit hydrostatic piezoelectric coefficients that far exceed what the conventional lead-zirconate-titanate (PZT) ceramics can offer. The particular concept of 0–3 composites is discussed in detail as a typical example of recent accomplishment in this area of new materials technology. The dielectric and piezoelectric properties of some 0–3 composite samples are given as a function of temperature and pressure. The acoustic performance of a prototype hydrophone array is also presented to demonstrate the potential of these materials for future transducer applications.

A review on the development of piezoelectric composites for underwater acoustic transducer applications

For future sonar transducer applications that emphasize the detection of acoustical signals in a hydrostatic mode, new piezoelectric composite materials have been developed. Ceramic-polymer composites having '1-3' and '0-3' connectivity patterns are shown to exhibit much higher sensitivities than conventional PZT ceramics. Glass-ceramic composites are free of aging, and have potential applications in standard transducers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The hydroacoustic behavior of piezoelectric composite materials

Abstract Piezoelectric composites that contain both ceramic and polymeric phases, and non-ferroelectric glass-ceramic composites have recently been developed. These materials exhibit attractive piezoelectric properties for applications in hydrophones that operate in a hydrostatic mode. Prototype hydrophones were developed using a porous PZT ceramic, a “0–3” and a “1–3” ceramic-polymer composite and a glass-ceramic sample. The test results on the acoustical performance of these devices are presented to demonstrate the potential of these new materials for underwater acoustical applications.

Deviatoric and hydrostatic mode interaction in hard and soft tissue

It has been established that many hard and soft tissues have anisotropic material symmetries. These materials are contrasted with traditional structural metals which have isotropic material symmetry. It is noted here that the deviatoric and hydrostatic modes interact with each other in a general anisotropic elastic material. In the special case of isotropic, linear elastic, materials these modes are non-interactive. As a consequence of the interaction of these modes encountered in anisotropic materials, the decomposition into hydrostatic and deviatoric modes, and deviatoric mode concepts such as the von Mises effective stress are not appropriate for anisotropic materials in general. The implications of this observation for the presentation of computationally generated stress contours for hard and soft tissues are discussed. It is also pointed out that the mode coupling and mode interaction raise the question of whether anisotropic living tissues respond directly to stress or to some other physical quantity such as strain or strain energy, in view of the recent hypothesis concerning the proliferation and ossification of cartilage.

Evaluation of new piezoelectric composite materials for hydrophone applications

Polymer-ceramic composites with different connectivity designs have been developed. The piezoelectric d and g coefficients of these composites in hydrostatic mode were characterized as a function of pressure, temperature, and frequency. All composite samples exhibited piezoelectric properties greatly improved over those of conventional piezoelectric ceramics. However, the introduction of soft polymer matrix caused the composite properties to be highly pressure-dependent. The effect of reinforced polymer matrix on the temperature and pressure dependences of the piezoelectric coefficients was also investigated. Prototype hydrophones containing the composite samples were designed and evaluated for their free-field voltage sensitivity. The potential use of polymer-ceramic composites for underwater acoustic applications is discussed.

Hydrogen motion in single-crystal palladium hydride as studied ultrasonically

The attenuation of ultrasonic waves has been investigated in single-crystal ${\ensuremath{\alpha}}^{\ensuremath{'}}$-phase palladium hydride (Pd${\mathrm{H}}_{0.64}$) over the temperature range of 77-300 K. The longitudinal and two independent transverse waves were propagated along the [110] crystal axis. These correspond to the elastic constants ${C}_{L}=\frac{1}{2}({C}_{11}+{C}_{12}+2{C}_{44})$, ${C}^{\ensuremath{'}}=\frac{1}{2}({C}_{11}\ensuremath{-}{C}_{12})$, and ${C}_{44}$. Attenuation peaks were observed for all three modes. At 10 MHz the maxima occurred at approximately 190 K for ${C}_{L}$ and ${C}^{\ensuremath{'}}$, and 180 K for ${C}_{44}$. The peaks are attributed to a stress-induced ordering of hydrogen pairs and complexes, and vacancy pairs and complexes, on the hydrogen sublattice. The relative magnitudes of the peaks are well accounted for in terms of hydrogen-hydrogen, hydrogen-vacancy, and vacancy-vacancy interactions at nearest- and next-nearest-neighbor positions. A simple nearest-neighbor interaction is shown to be inadequate to explain the results. The gradients of the hydrogen-vacancy interaction energies at nearest- and next-nearest-neighbor sites are deduced, with the main uncertainty having to do with the selection of an anelastic critical temperature in the theoretical expression. Using 50 K for the critical temperature we find 5.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}11}$ and 3.8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}11}$ N for the absolute value of the gradients at nearest- and next-nearest-neighbor sites, respectively. The three measured attenuation peaks were found to satisfy a Cauchy-type relationship. Such a relationship suggests a central-force description of the interactions among hydrogen atoms and vacancies. The existence of a hydrostatic mode of relaxation is shown for the first time for this system. The relaxation rate for this mode is approximately the same as that for ${C}_{L}$ and ${C}^{\ensuremath{'}}$, while the ${C}_{44}$ mode relaxes approximately twice as fast. Plots of the attenuation times the temperature versus inverse temperature are asymmetric. Such asymmetry was previously observed in internal-friction measurements and attributed to the existence of an anelastic critical temperature. Our data, taken at higher frequencies and thus higher temperatures, can be fitted using an anelastic critical temperature, but the value is considerably higher than that deduced from the internal-friction experiments. The difference suggests that the asymmetry is not due to a critical temperature, but has some other origin.