0


EDITORIAL

J. Fluids Eng. 1999;121(1):1-2. doi:10.1115/1.2822003.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

ANNOUNCEMENTS

J. Fluids Eng. 1999;121(1):3-4. doi:10.1115/1.2822008.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Fluids Eng. 1999;121(1):5-33. doi:10.1115/1.2822013.

Manufacturing processes that can create extremely small machines have been developed in recent years. Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than 1 mm but more than 1 micron, that combine electrical and mechanical components and that are fabricated using integrated circuit batch-processing techniques. Electrostatic, magnetic, pneumatic and thermal actuators, motors, valves, gears, and tweezers of less than 100-μm size have been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity and sound, as actuators for linear and angular motions, and as simple components for complex systems such as micro-heat-engines and micro-heat-pumps. The technology is progressing at a rate that far exceeds that of our understanding of the unconventional physics involved in the operation as well as the manufacturing of those minute devices. The primary objective of this article is to critically review the status of our understanding of fluid flow phenomena particular to microdevices. In terms of applications, the paper emphasizes the use of MEMS as sensors and actuators for flow diagnosis and control.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):34-43. doi:10.1115/1.2822007.

The present study deals with the noninvasive measurement of concentration in the intermediate shallow turbulent wake region using a video-imaging technique. The flow depths considered in the present study are small compared to the width of the channel and the generated wakes are categorized as shallow. On the basis of the observed behavior, the waves are classified as deep-shallow wakes and shallow-shallow wakes. The topology of the dye concentration distribution in the near and intermediate wake region indicates that the vortex structure tends to be preserved when the flow depth is relatively high and the dominant eddy structures are similar to that noticed in conventional two-dimensional wakes. In shallow-shallow wakes, the conventional Karman vortex street appears to be annihilated or intermittent. The lateral concentration distribution at several axial stations covering the first thirty body widths are considered for analysis. The instantaneous concentrations are observed to be several times higher than the corresponding mean values. Attempts are also made to determine the paths traversed by the vortex cores and the vortex core convection velocity. The axial variation of the wake half-width with depth of flow is also examined. A model is developed to predict the spread of the wake with downstream distance from the test body. A friction length scale is introduced in the model to account for the influence of depth and bed friction on the development of the wake.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):44-51. doi:10.1115/1.2822009.

Materials exposed in the marine environment, including those protected by antifouling paints, may rapidly become colonized by microfouling. This may affect frictional resistance and turbulent boundary layer structure. This study compares the mean and turbulent boundary layer velocity characteristics of surfaces covered with a marine biofilm with those of a smooth surface. Measurements were made in a nominally zero pressure gradient, boundary layer flow with a two-component laser Doppler velocimeter at momentum thickness Reynolds numbers of 5600 to 19,000 in a recirculating water tunnel. Profiles of the mean and turbulence velocity components, including the Reynolds shear stress, were measured. An average increase in the skin friction coefficient of 33 to 187 percent was measured on the fouled specimens. The skin friction coefficient was found to be dependent on both biofilm thickness and morphology. The biofilms tested showed varying effect on the Reynolds stresses when those quantities were normalized with the friction velocity.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):52-56. doi:10.1115/1.2822010.

A facility capable of generating steady and oscillating flows was constructed and experiments were conducted to investigate the pressure-drop characteristics of regenerators packed with wire screens. Both the velocity and pressure-drop across the regenerator were measured. To accurately determine the correlation between pressure-drop and velocity, the experiments covered a wide range from very low to very high Reynolds numbers, Reh . The steady flow results reveal that a three-term correlation with a term proportional to Reh −1/2 in addition to the Darcy-Forchheimer two-term correlation will fit best to the data. This Reh −1/2 term accounts for the boundary layer effect at intermediate Reynolds number. The results also show that the correlation for oscillating flows coincides with that for steady flows in 1 < Reh < 2000. This suggests that the oscillating flows in the regenerators behave as quasi-steady at the frequency range of less than 4.0 Hz, which is the maximum operable oscillating flow frequency of the facility.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):57-64. doi:10.1115/1.2822011.

Mean pressure gradient affects the turbulence mainly through the modulation of the mean rate of strain. Modification of the turbulence structure feeds, in turn, back into the mean flow. Particularly affected is the near wall region (including the viscous sublayer) where the pressure gradient invalidates the conventional boundary-layer “equilibrium” assumptions and inner-wall scaling. Accurate predictions of such flows require application of advanced turbulence closures, preferably at the differential second-moment level with integration up to the wall. This paper aims at demonstrating the potential usefulness of such a model to engineers by revisiting some of the recent experimental and DNS results and by presenting a series of computations relevant to low-speed external aerodynamics. Several attached and separated flows, subjected to strong adverse and favorable pressure gradient, as well as to periodic alternation of the pressure gradient sign, all computed with a low-Re-number second-moment closure, display good agreement with experimental and DNS data. It is argued that models of this kind (in full or a truncated form) may serve both for steady or transient Reynolds-Averaged Navier-Stokes (RANS, TRANS) computations of a variety of industrial and aeronautical flows, particularly if transition phenomena, wall friction, and heat transfer are in focus.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):65-72. doi:10.1115/1.2822014.

An experimental work and a physical analysis dedicated to the study of a low density jet subjected to a time varying crossflow with high acceleration/deceleration levels are presented in this paper. Relevant nondimensional numbers are derived and show that unsteady effects associated with the presence of the jet in the acceleration field have noticeable consequences on the flapping of the jet. The Schlieren technique is applied in the test section of a square duct to obtain time resolved images of the jet. Analysis of the results is focused on the influence of the unsteady effects on the global dynamic behaviour of the jet in the near field. The interaction between the jet and the crossflow is analysed in three contrasted situations corresponding to different values of the jet outlet velocity U0 . We predict and observe an increase of the jet deflection during the acceleration phase and a competition between drag and acceleration during the deceleration. This competition is particularly clear for the two lowest ejection velocities of the jet and we have shown that the jet is initially deflected upstream the nozzle. The influence of exit jet injection angle is finally considered. We show that upstream or downstream injections induce a very strong modification of the mixing process of the jet fluid with the pulsed crossflow.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):73-79. doi:10.1115/1.2822015.

This study presents the applications of a turbulence probability density function (pdf) equation to compute an axisymmetric turbulent free jet flow. In view of the difficulty of solving this pdf equation directly by conventional numerical methods, an approximate moment method is applied. The Calculated triple velocity correlations appearing in the second-order moments equation are calculated and compared with measured values and with those estimated by moment-closure models. The results reveal that the pdf approach gives consistency in the higher-order moments and radial budget of third moments of velocity, and that the neglect of the mean-strain production, the rapid part of the pressure correlation and the dissipation are responsible for deviations between moment-closure models and experiments. Therefore, pdf methods appear to be more suitable than conventional moment-closure models in terms of revealing turbulence structure.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):80-85. doi:10.1115/1.2822016.

Recently the authors introduced a length scale which effectively collapsed the near field centerline development of velocity and mass fraction for variable density axisymmetric jets whose initial conditions correspond to those of fully developed turbulent pipe flow. The new length scale incorporated the initial mass, momentum, and turbulence intensity per unit area to capture the Reynolds number dependence of near field development for the velocity and scalar distributions observed in low Reynolds number turbulent jets. The presents paper extends the analysis for a constant density jet to the intermediate and self-similar far fields further downstream using a dynamic length scale based on the local centerline turbulence intensity. The normalized mean velocity distributions of an air jet collapse over the entire flow distance investigated velocity distributions of an air jet collapse over the entire flow distance investigated velocity distributions of an air jet collapse over the entire flow distance investigated when the axial distance is normalized by the proposed length scale, thus scaling the virtual origin shift and effectively incorporating the Reynolds number dependence.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):86-92. doi:10.1115/1.2822017.

An experimental study is performed to investigate the relationship between an unsub-merged water jet impinging onto a horizontal surface and radius of hydraulic jump. Experiments are undertaken over a wide range of pipe Reynolds numbers for which the pipe flow is laminar. The laminar impinging jet produced a smooth circular hydraulic jump, at which the film thickness experienced a sudden increase in thickness. Effects of various parameters on a stable and stationary hydraulic jump are studied. The impingement point radius ri , is taken as a characteristic length of the film flow, and correlations are obtained for radius of hydraulic jump in terms of various dimensionless parameters.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):93-101. doi:10.1115/1.2822018.

Existing data on transient turbulent jet injection in to large chambers demonstrates self-similar behavior under a wide range of conditions including compressibility, thermal and species diffusion, and nozzle under expansion. The Jet penetration distance well downstream of the virtual origin is proportional to the square root of the time and the fourth root of the ratio of nozzle exit momentum flow rate to chamber density. The constant of proportionality has been evaluated by invoking the concept of Turner that the flow can be modeled as a steady jet headed by a spherical vortex. Using incompressible transient jet observations to determine the asymptotically constant ratio of maximum jet width to penetration distance, and the steady jet entrainment results of Ricou and Spalding, it is shown that the penetration constant is 3 ± 0.1. This value is shown to hold for compressible flows also, with substantial thermal and species diffusion, and even with transient jets from highly under-expanded in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under expanded nozzles. Observations of transient jet injection have been made in a chamber in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under-expanded nozzles it was found that at high nozzle pressure ratios, depending on the jet injection angle, the jet penetration can be consistent with a penetration constant of 3. At low pressure ratios the presence of the wall noticeably retards the penetration of the jet.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):102-105. doi:10.1115/1.2821988.

Vortex breakdown is a significant phenomenon in science and technology. In spite of extensive research, the question of the underlying mechanisms for vortex breakdown still lacks a definite answer. The uncertainty of the governing principles for vortex breakdown is revealed by the common use of a variety of different parameters to describe the degree of swirl. In this paper, a theoretical discussion on the suitability of three kinds parameters was conducted, and it was found that one appears to be the natural one if the flow is primarily a swirling channel flow, but if the jet character of the flow is dominant, another one appears to be the most suitable. CFD simulations were performed for a channel with an annular inlet considerably smaller than the channel width. For this case the jet character of the flow should predominate and it was found that the parameter, which theoretically appeared to be best suited for jet flows, indeed was less dependent of the detailed inflow geometry than the others.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):106-111. doi:10.1115/1.2821989.

In this paper results are presented from experiments in which the pressure loss in single-phase pipe flow is studied when radial inflow occurs. Experiments have been carried out with pipes which have different perforation geometries so as to be able to investigate the effect of perforation geometry on the pressure loss. Data analysis of these experiments, as well as analysis of experiments carried out by other groups, yields a pressure loss model which accurately describes pressure losses in single-phase pipe flow with radial inflow through perforations in the pipe wall. The experimental data is subsequently used to establish a numerical value of a parameter which is used in a model description. This leads to the formulation of an effective friction factor for pipe flow with radial inflow.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):112-117. doi:10.1115/1.2821990.

One-dimensional models for predicting the damage induced by pressure transients in piping systems conveying liquids have been proposed and analysed recently. However, such works have been concerned mainly with the adequacy of the constitutive equations adopted for different pipe materials and with the numerical techniques used for approximating the solution of the resulting mathematical problems. In the present paper the suitability of the simplifying low Mach number assumption adopted in the modeling is investigated. The analysis is carried out based on the eigenvalue problem associated to the governing equations, without appealing to any specific mechanical behavior of the pipe material. Numerical results obtained for the most used pipe materials show that this simplifying assumption is adequate for metallic tubes, but may fail when plastic tubes are considered.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):118-125. doi:10.1115/1.2821991.

The aerodynamic effects of trailing edge ejection on mixing losses downstream of cooled gas turbine blades were experimentally investigated and compared with an already existing one-dimensional theory by Schobeiri (1989). The significant parameters determining the mixing losses and, therefore, the efficiency of cooled blades, are the ejection velocity ratio, the cooling mass flow ratio, the temperature ratio, the slot thickness ratio, and the ejection flow angle. To cover a broad range of representative turbine blade geometry and flow deflections, a General Electric power generation gas turbine blade with a high flow deflection and a NASA-turbine blade with intermediate flow deflection and different thickness distributions were experimentally investigated and compared with the existing theory. Comprehensive experimental investigations show that for the ejection velocity ratio μ = 1, the trailing edge ejection reduces the mixing losses downstream of the cooled gas turbine blade to a minimum, which is in agreement with the theory. For the given cooling mass flow ratios that are dictated by the heat transfer requirements, optimum slot thickness to trailing edge thickness ratios are found, which correspond to the minimum mixing loss coefficients. The results allow the turbine aerodynamicist to minimize the mixing losses and to increase the efficiency of cooled gas turbine blades.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):126-132. doi:10.1115/1.2821992.

A research pump intended for both flow visualization studies and direct measurement of hydrodynamic radial and axial forces has been developed. The impeller and the volute casing are constructed from Plexiglas which facilitates optical access for laser velocimetry measurements of the flow field both inside the impeller and in the volute casing. The pump housing is designed for flexibility allowing for each interchange of impellers and volute configurations. The pump rotor is supported by three radial magnetic bearings and one double acting magnetic thrust bearing. The magnetic bearings have been calibrated to characterize the force versus coil current and air gap relationship for each bearing type. Linear calibration functions valid for rotor eccentricities of up to 2/3 of the nominal bearing clearances and force level of ±58 N (13 lbf ) and ±267 N (60 lbf ) for the radial and axial bearings, respectively, were found. A detailed uncertainty analysis of the force calibration functions was conducted such that meaningful uncertainty bounds can be applied to in situ force measurements. Hysteresis and eddy current effects were quantified for each bearing such that their effect on the in situ force measurements could be assessed. By directly measuring the bearing reaction forces it is possible to determine the radial and axial hydraulic loads acting on the pump impeller. To demonstrate the capability of the magnetic bearings as active load cells representative hydraulic force measurements for a centered 4 vane 16 degree log spiral radial flow impeller operating in a single tongue spiral volute casing were made. At shut-off a nondimensional radial thrust of 0.084 was measured. A minimum nondimensional radial thrust of about 0.007 was observed at the nominal design flow. The nondimensional radial thrust increased to about 0.019 at 120 percent of design flow. The nondimensional axial thrust had a maximum at shut-off of 0.265 and decreased steadily to approximately 0.185 at 120 percent of design flow. Two regions of increasing axial thrust, in the flow range 75 to 100 percent of design flow, were observed. The measurements are compared to radial and axial force predictions using classical force models. The direct radial force measurements are compared to a representative set of radial force measurements from the literature. In addition, the directly measured radial force at design flow is compared to a single representative radial force measurement (obtained from the literature) calculated from the combination of static pressure and net momentum flux distribution at the impeller exit.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):133-138. doi:10.1115/1.2821993.
Abstract
Topics: Pumps , Leakage flows
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):139-147. doi:10.1115/1.2821994.

In this two-part paper, time-accurate solutions of the Reynolds-averaged Navier-Stokes equations are presented, which address through model problems, the response of turbulent propeller-blade boundary layers and wakes to external-flow traveling waves. In Part 1, the Massachusetts Institute of Technology flapping-foil experiment was simulated and the results validated through comparisons with data. The response was shown to be significantly more complex than classical unsteady boundary layer and unsteady lifting flows thus motivating further study. In Part 2, the effects of frequency, waveform, and foil geometry are investigated. The results demonstrate that uniquely different response occurs for low and high frequency. High-frequency response agrees with behavior seen in the flapping-foil experiment, whereas low-frequency response displays a temporal behavior which more closely agrees with classical inviscid-flow theories. Study of waveform and geometry show that, for high frequency, the driving mechanism of the response is a viscous-inviscid interaction created by a near-wake peak in the displacement thickness which, in turn, is directly related to unsteady lift and the oscillatory wake sheet. Pressure waves radiate upstream and downstream of the displacement thickness peak for high frequency flows. Secondary effects, which are primarily due to geometry, include gust deformation due to steady-unsteady interaction and trailing-edge counter-rotating vortices which create a two-layered amplitude and phase-angle profile across the boundary layer.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):148-154. doi:10.1115/1.2821995.

Simulations of the flow field and temperature distribution in a low grade vertical continuous cooling sugar crystallizer were carried out by numerically solving the Navier-Stokes equations in a cylindrical coordinate system. The model results indicate highly nonuniform massecuite cooling, primarily due to the massecuite’s large Prandtl number, and significant short-circuiting of flow between inlet and outlet. Modifications to the crystallizer design are proposed and demonstrated to be successful in improving the performance of the vessel.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):155-162. doi:10.1115/1.2821996.

In the present study, particle growth on individual fibers within a fibrous medium is examined as flow conditions transition beyond the Stokes flow regime. Employing a numerical model that solves the viscous, incompressible Navier-Stokes equations, the Stokes flow approximation used in past research to describe the velocity field through the fibrous medium is eliminated. Fibers are modeled in a staggered array to eliminate assumptions regarding the effects of neighboring fibers. Results from the numerical model are compared to the limiting theoretical results obtained for individual cylinders and arrays of cylinders. Particle growth is presented as a function of time, angular position around the fiber, and flow Reynolds number. From the range of conditions examined, particles agglomerate into taller and narrower dendrites as Reynolds number is increased, which increases the probability that they will break off as larger agglomerations and, subsequently, substantially reduce the hydraulic conductivity of the porous medium.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):163-170. doi:10.1115/1.2821997.

A method for efficient solid particle removal from liquids using microporous tubes with flow swirl and flow interruption is presented. Experiments were performed using particle laden water obtained from an actual field project of high pressure water jet paint stripping. The flow rate, orientation, flow interruption, and swirl index were varied, and their effect on performance observed and measured as a function of time. Flux rate increases of a factor of 20 over a conventional microporous tube cross flow filtration were generated. Flux rates were found to increase both with increasing swirl and with moderate increases in the shear exerted on the tube wall. Results of independent testing by the US Navy at Port Hueneme of a small field unit demonstrate high flux rate performance with high permeate quality and turbidity removal.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):171-178. doi:10.1115/1.2821998.

Measurements of particle and fluid velocities are reported for a turbulent, liquid-solid, sudden expansion flow flowing in the direction of gravity and laden with solid particles, at loadings equal to 1, 2, 3, 4, and 5 percent per volume. The measured two-phase flow velocities are compared to the characteristics of the corresponding single phase flow. Forces and flow mechanisms affecting particle dispersion in the various flow regimes are identified and it is indicated that there exist regions where the transverse Saffman lift force attains high values and controls particle dispersion. A consistent correlation between the mean reattachment point and the volumetric particle loading is indicated. All the two phase flows examined reattached upstream the corresponding mean reattachment location measured for the single phase flow. Increasing particle concentration affected locally the flow behaviour, with most obvious consequences within the recirculation zone and the near wall region.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):179-184. doi:10.1115/1.2821999.

The present work investigates the mechanics of particle collisions submerged in a liquid using a simple pendulum experiment. Particle trajectories for different particles in water are measured using a high-speed digital camera and the magnitude of the collision is recorded using a high-frequency-response pressure transducer at the colliding surface. The particle deceleration occurs at distances less than half a particle diameter from the wall. The measured collision impulse increases with impact velocity and particle mass. Comparisons are drawn between the measured pressures and the predictions of basic impact mechanics assuming a perfectly elastic collision. A control-volume model is proposed that accounts for the fluid inertia and viscosity. When a particle approaches a planar surface or another particle, the fluid is squeezed prior to contact, reducing the initial kinetic energy and decelerating the particle. The pressure profile is integrated over the surface of the particle to obtain a force that is a function of the initial particle Reynolds number, Reo , and the ratio of the densities of the particle and fluid phases, ρp /ρf . The model predicts a critical Stokes number at which the particle reaches the wall with zero velocity. Comparisons between the proposed model and the experimental measurements show qualitative agreement.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):185-190. doi:10.1115/1.2822000.

An analytical study is performed on the dynamics and hydrodynamic stability of liquid-vapor mixtures in the bubbly-flow range in reciprocating motion through a horizontal channel. The perturbation technique is applied on the one-dimensional conservation equations for laminar flow and on the thermodynamic equation of state. The Laplace transform is operated on the linearized equations from which a transfer function is derived, relating the flow rate change due to a change in pressure drop along the channel. The resulting characteristic equation is analyzed to determine the dynamic behavior of the two-phase flow in reciprocating motion and the conditions for neutral stability under which self-induced oscillations occur. The natural frequency of the physical system is derived, which can be used to predict the resonance that will occur in forced vibrations. Results can be applied to systems such as car suspensions (shock absorbers) in which oil is susceptible to cavitation, resulting in bubbly flow due to vibrations. Conditions under which resonance occurs in the two-phase system are determined. Resonance leads to severe oscillations and noise generation, as experienced in shock absorbers in car suspensions.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):191-197. doi:10.1115/1.2822001.

An experimental study on flow around two similarly-sized, adjacent air bubbles confined in a 1000 mm vertical, square channel (100 × 100 mm2 ) with downward flow of water was conducted. The bubbles were D = 11.7 mm in major diameter, ellipsoidal in shape (0.4 ml volume) and 12 mm apart. The Reynolds and Eötvös numbers were 1950 < ReD < 2250, 11 < Eo < 11.5 such that the bubbles oscillated. Velocity measurements were taken using Digital Particle Image Velocimetry, Complemented by Laser Induced Fluorescence. Simultaneously, a second CCD camera recorded the shadow image of the bubble pair’s motions. Visualization revealed that the bubbles move out of phase and do not collide nor coalesce. The velocity data revealed the dynamic interaction of two wake-flow velocity fields with a jet-like flow in-between. From the DPIV data, estimates of the vorticity, Reynolds-stress and turbulent kinetic energy (TKE) distributions confirmed the spatio-temporal nature of the flow. Details will be presented.

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):198-204. doi:10.1115/1.2822002.

The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):208-210. doi:10.1115/1.2822005.
Abstract
Commentary by Dr. Valentin Fuster
J. Fluids Eng. 1999;121(1):210-212. doi:10.1115/1.2822006.

The operating principles, as well as the technical aspects of the implementation of a new computer-controlled pressure standard are presented. The instrument can have dual use: either as a pressure source or as a pressure sensor. The device is intended mostly for use in problems where small differential pressures are of interest, i. e., 0–2.5 KPa and high accuracy is desired. Such a pressure range encompasses, for example, most of the pressure measurement applications in subsonic wind-tunnel testing. The device interfaces to a PC and is ideal for fully-automated pressure transducer calibration applications. The accuracy of the pressures produced or measured by the device is 0.08 percent F. S. (Full Scale).

Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In