Showing papers on "Volume of fluid method published in 1988"

Enhanced pressure measurement flow control system

Abstract: The present invention provides a system for measuring flow of a fluid through a line. In the system, a region (15) of fluid along the line is isolated from pressure effects outside of the region. A source region (12) contains a measurement gas in communication with the isolated region, such that the source means and the isolated region together define a fixed volume, and such that a change in volume of fluid in the isolated region produces a complementary change in the volume of the source means with a resulting change in the pressure of the measurement gas contained in the source region. Further provided is a reservoir (11) in communication with the source means for containing a known volume of measurement gas, and means (25) for pumping measurement gas from the reservoir. The pressure of the measurement gas in the reservoir and the source region is monitored. This pressure data is then analyzed to determine the volume of fluid in the isolated region.

Continuous cyclic peritoneal dialysis system and method

Abstract: A continuous cycle peritoneal dialysis system which includes a source (14) of dialysis fluid, and an inflow line (34) and outflow line (35) connected to a catheter (26) implanted in the peritoneal cavity (28). A fill pump (B) pumps dialysis fluid from the source to the catheter during a fill cycle. A drain pump C pumps fluid from the catheter to a drain during a drain cycle. A function of a volume of the dialysis fluid in the peritoneal cavity is detected by a manometer (D). A process controller (A) controls the fill and drain pumps in response to signals from a high fluid level detector (50) and a low fluid level detector (52) on a fluid column tube (48) to pump a calibrated fill volume of fluid into the cavity and a calibrated drain volume of fluid out of the cavity continuously in alternating fill and drain cycles in a manner that the fluid flows through the cavity generally with zero dwell time. In the process, an inflow volume of dialysis fluid pumped into the cavity is metered (36b) and an outflow volume of fluid pumped out of the cavity is metered (44b) to determine the amount of fluid removed from the patient by comparing the inflow and outflow volumes.

Apparatus for dispensing fluid materials

Abstract: Apparatus and method for dispensing fluid material whereby the fluid is discharged from a nozzle onto a workpiece. Delivery of fluid to the nozzle is controlled by a metering valve located in close proximity to the nozzle. The flow of dispensed fluid is sensed by a pressure transducer disposed to sense the pressure drop across the nozzle. The pressure transducer generates a feedback signal which can be applied by way of a closed loop control system to an electropneumatic servovalve which operates a double-acting air cylinder the pressure drop across the nozzle thereby controlling the flow of dispensed fluid in accordance with a driving signal. Where the dispenser is carried by a robot, the driving signal can be correlated to the relative speed between the workpiece and the nozzle to accurately control the amount of fluid per unit length contained in a bead deposited on the surface of the workpiece. Due to the rapid response of the system such precise control is possible even during relatively rapid changes in the relative speed between the nozzle and the workpiece. Also disclosed are means for insuring that the volume of fluid dispensed over a predetermined interval corresponds to a desired setpoint thereby correcting for changes in the intrinsic viscosity of the dispensed fluid as may be caused by changes in its temperature.

Finite Element Characteristic Advection Model

Abstract: For advection‐dominated transport processes, the traditional numerical techniques for solving the advection‐diffusion equation fail because of numerical oscillations. Fractional step solutions, in which the advection and diffusion processes are treated in separate steps, have been proposed as one way of overcoming this problem. Here a solution to the advection step based on the method of characteristics on a fixed grid is used. Interpolation is achieved with the finite element technique. Linear and quadratic elements are evaluated in terms of artificial diffusion, phase, and other errors. It was found that linear interpolation creates too much numerical diffusion, while the quadratic scheme is reasonably accurate, but under certain conditions generates spurious extrema. A method retaining the accuracy of the quadratic interpolation and eliminating its shortcoming is suggested. Boundary conditions and source loadings are considered in detail. An application of the model to salinity distribution resulting f...

Remapping on the staggered mesh

Abstract: The staggered mesh of von Neumann and Richtmyer provides a natural pattern of data storage for Lagrangian fluid dynamics. However, the solution of the advection equation, a necessary step for continuous rezone codes, leads to problems for fields stored on the nodes of the mesh, and in particular for the material velocities. In this paper, we describe a new scheme for advecting nodal quantities that is exactly conservative, computationally efficient and consistent in the sense of truncation error with the advection of cell-centered quantities. 5 refs.

Baroclinic instability of three-layer flows Part 2. Experiments with eddies

Abstract: The stability of eddies with three-layer stratification is examined experimentally. When the difference in density between the upper two layers is much greater (or less) than that between the lower two layers baroclinic instability on two different lengthscales (the Rossby radii associated with the upper and the lower interfaces) is possible. The vortices are created using modifications of two techniques described by Griffiths & Linden (1981) in their study of two-layer eddies.‘Constant-flux’ eddies are generated by the release of a constant flux of buoyant fluid from a small source positioned at the surface of a two-layer fluid. In a second variation of this experiment, the source is positioned at the interface between two layers and fluid of intermediate density is injected. As the horizontal lengthscale increases, the vortices evolve from a stable to an unstable state. It is showns that the size at which the vortices become unstable may be significantly altered by the presence of a second interface. The results agree qualitatively with the conclusions of a linear stability analysis of quasi-geostrophic three-layer flow in a channel (Smeed 1988), but it is necessary to examine the effects of horizontal shear and Ekman dissipation to explain the experimental results.‘Constant-volume’ eddies are produced by the release of a volume of buoyant fluid, initially contained within a cylindrical barrier, at the surface of a two-layer fluid. After the barrier is removed, the buoyant fluid spreads a distance of the order of the Rossby radius. Similarly, vortices are created by releasing a volume of fluid of density intermediate between the initial two layers. Within a few rotation periods the vortices become unstable to disturbances similar to those observed in two-layer experiments. Qualitative agreement is found between the observed wavelength and the fastest growing mode predicted by the linear stability theory (Smeed 1988). When the disturbances reach large amplitude a change in lengthscale is often observed.

Progressive fluid deformation in low Reynolds number flow past a falling cylinder

Abstract: A new laboratory technique is outlined by which the flow of a very viscous fluid can be made visible and finite strains and fluid rotations in the flow can be measured. The technique involves the emplacement of a pattern of grid lines in a plane through the fluid before the flow begins. The grid lines are in fact formed by placing an ‘‘unfixed’’ photocopy in contact with a surface of the fluid, thereby transferring carbon particles from the photocopying paper on to the fluid, and then bringing that surface of the fluid into contact with another similar volume of fluid. The carbon particles are therefore embedded within the working volume of fluid. Use of the technique, and some of the results that can be obtained, are demonstrated by the example of flow about a falling cylinder.

Volumetric, self-resetting, hydraulic fuse

Abstract: A hydraulic fuse or cut-off device divides fluid flow into: (i) a primary fluid stream; and (ii) a secondary fluid stream having a substantially constant, but small ratio of flow to said primary stream The secondary stream exerts pressure on a timing piston which thereby monitors the entire flow and causes the fuse to cut-off when a predetermined volume of fluid has passed through the device The fuse includes a regulating piston for building inlet pressure to a value sufficient to develop the power necessary to drive the timing piston Greater simplicity of the component parts and decreased sensitivity to contamination results from the use of a small fluid orifice to control the secondary stream This is achieved by fitting the regulating piston with an inwardly directed flange, just touching the peripheral surface of a slightly tapered, central pin--whereby the taper of the pin causes the orifice to be created as the regulating piston is caused to slide as a result of the primary fluid flow

Numerical simulation of plume-advection over a hill with coupled models. Part I: Numerical solution of the transport-equation

Abstract: Four numerical methods suitable for the calculation of transport are compared on a linear two-dimensional advection equation It is found that a mass-compensation algorithm which removes negative values has also a beneficial effect on the accuracy of schemes which are of higher order but are not positive It is shown by numerical experiments, that the upstream spline advection scheme combined with a mass compensation is prefereable for some applications rather than other high accurate positive schemes like the flux-corrected transport scheme

Variable displacement port plate

Abstract: An improved hydraulic apparatus is disclosed which may function as either a hydraulic pump or hydraulic motor A port plate (18) is provided with a high pressure arcuate prot (82) which permits the full range of rotation of the port plate to be used in linearly adjusting the rate of fluid flow into the cylinders (22) of the cylinder block (20) The invention provides a maximum range of adjustability of the volume of fluid flow passing through the cylinders

Large Eddy Interaction with Propagating Flames

Abstract: In this report, we describe work in progress on a long-range project to model combustion within a moving piston. While the ultimate goal is a three-dimensional simulation of the interaction between vortex stretching, flame propagation and large-scale eddy formation, the current project is aimed at a 2-D calculation of the effect of varying fuel inlet placement and inclination angles on flame propagation in a swirling fluid. The equations of motion are the equations of zero Mach number combustion, which describe viscous, uniformly compressible flow. At the core of the hydrodynamic calculation is the random vortex method, originally designed for high Reynolds number turbulent flow. At the center of the flame algorithm has been a volume of fluid advection scheme to track the motion of the burning fluid. While this will probably remain the main ingredient on the combustion side, we are currently studying a new algorithm that is proving particularly useful for the analysis of specialized combustion phenomena requiring highly accurate schemes.

Process and device for apportioning a primary volume of fluid into a given number of secondary volumes in predetermined proportions

Abstract: A process and device for apportioning a primary volume of fluid into a number of secondary volumes in predetermined proportions by means of a receiving chamber for the primary volume of fluid, the bottom of which has ports (6) for discharge of the fluid arranged in the same horizontal plane and connected to discharge pipes (8). The discharge pipes are fitted with cocks (19) which permit synchronization of the start of flow of the fluid in the pipes (8), the end of the flow being determined by the subdivision of the free surface of the fluid (20) by the discharge ports.