Showing papers on "Volume of fluid method published in 1992"
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TL;DR: In this paper, the dynamics of a thin film of Newtonian fluid coating the inner surface of an elastic circular tube is analyzed and nonlinear evolution equations for the film thickness and wall position are derived using lubrication theory, but an accurate representation of the curvatures of both the liquid and wall interfaces is employed which is valid for thick films.
Abstract: The dynamics of a thin film of Newtonian fluid coating the inner surface of an elastic circular tube is analysed. This problem is motivated by an interest in the closure of small airways of the lungs either by formation of a liquid bridge, the collapse of the airway wall or a combination of both processes. Liquid bridge formation is due to the destabilization of the liquid film that coats the inner surface of airways, while wall collapse can be due to either the high surface tension of the air–liquid interface or the flexibility of the wall.Nonlinear evolution equations for the film thickness and wall position are derived using lubrication theory, but an accurate representation of the curvatures of both the liquid and wall interfaces is employed which is valid for thick films. These approximations allow closure to be predicted. In addition, these approximations are justified by comparison with rigid-wall results obtained by solving the full Navier–Stokes equations and because fluid inertia only becomes important in the very late stages of closure. The linear stability of these equations is examined using normal-mode analysis for infinitesimal disturbances and the nonlinear stability is investigated by solving the governing equations numerically using the method of lines. Solutions show that there is a critical film thickness, strongly dependent on fluid and wall properties, above which unstable waves grow to form liquid bridges. The critical film thickness decreases with increasing surface tension or wall compliance since waves grow faster. Even for relatively stiff airways, the volume of fluid in the liquid lining required for closure can be approximately 70% of the volume for the rigid-tube case. Wall damping is an important effect only when the airway is sufficiently compliant. Airway closure occurs more rapidly with increasing unperturbed film thickness, surface tension and wall flexibility and decreasing wall damping.
147 citations
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TL;DR: In this paper, the authors analyzed the flow of viscous fluid from a point or line source on an inclined plane using the equations of lubrication theory in which surface tension is neglected.
Abstract: The flow of a viscous fluid from a point or line source on an inclined plane is analysed using the equations of lubrication theory in which surface tension is neglected. At short times, when the gradient of the interfacial thickness is much greater than that of the plane, the fluid is shown to spread symmetrically from the source, as on a horizontal plane. At long times, the flow is predominantly downslope, with some cross-slope spreading for the case of a point source. Similarity solutions for the long-time behaviour of the governing nonlinear partial differential equations are found for the case in which the volume of fluid increases with time like tα, where α is a constant. The two-dimensional equations appropriate to a line source are hyperbolic in the self-similar regime and the similarity profile is found analytically to end abruptly at a downslope position which increases like t(2α+1)/3. Inclusion of higher-order terms in the analysis resolves this frontal shock into a boundary-layer structure of width comparable to the thickness of the current. Owing to the term representing cross-slope spreading, the mathematical structure of the equations is considerably more complex for flow from a point source and the similarity form is found numerically in this case. Though the downslope and cross-slope extents of the current again increase with time according to a power-law if α > 0, they also depend on a power of In t if α = 0. The leading-order near-source structure is shown to be that of steady flow from a constant-flux source of strength given by the instantaneous flow rate. For sources with α > 1, the contact line advances at all points on the perimeter of the flow and the entire plane is eventually covered by the flow; for sources with 0 < α < 1, only a portion of the contact line is advancing at any time and only that part of the plane with |y| [les ] cx3α/(4α+3) is eventually covered, where x and y are the downslope and cross-slope coordinates and c is a constant. The theoretical spreading relationships and planforms are found to be in good agreement with experimental measurements of constant-volume and constant-flux flows of viscous fluids from a point source on a plane. At very long times, however, the experimental flows are observed to be unstable to the formation of a capillary rivulet at the nose of the current.
145 citations
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TL;DR: In this article, the role of compressional tectonics in driving regional fluid flow in the later stages of thrusting in a foreland basin is quantified using two-dimensional numerical models.
Abstract: Deep groundwater flow can be driven by several mechanisms in sedimentary basins. In the case of evolving foreland basins, large-scale compression and thrusting could develop abnormally high pressures in the foreland sag that would initiate transient fluid flow. The so-called tectonic “squeegee” effect is thought to have caused basin-wide migration of ore-forming brines and hydrocarbons (Oliver, 1986). Two-dimensional numerical models are developed here to quantify the role of compressional tectonics in driving regional fluid flow in the later stages of thrusting in a foreland basin. Poroelasticity theory coupled with regional groundwater flow form the basic elements of the mathematical model. We use the mathematical model to predict deformation and pressure dissipation in the unfaulted and nonfolded part of a foreland basin in front of a thrust belt as it is subjected to an instantaneous loading event. Sets of numerical experiments show that overpressure zones develop along the leading edge of the thrust belt near the loading front. Stress-induced flow rates of the order of centimeters to meters per year are possible soon after compression of the foreland, and transient flow fields dissipate in about 103 and 104 years. Longer transients can exist in very low permeability strata. Large overpressures may be unable to buildup under conditions of gradual thrusting, as fluid pressures may dissipate too quickly. The general features of tectonically driven flow are also explored through a sensitivity study to consider effects of permeability, fault and stratigraphic heterogeneity, loading magnitude, and variations in rock compressibility. The sensitivity study is based mostly on numerical experiments. As these solutions suffered from stability problems in cases where bulk rock compressibility exceeded 10−9 Pa−1, some simple scaling arguments are used to extend the numerical results for squeezing of soft shale. One basin-specific application to the Ouachita orogen suggests that tectonic squeezing could have caused transient flow systems with relatively large flow velocities in basal Cambro-Ordovician aquifers. The volume of fluid expelled, however, is probably only a small fraction of the total brine volume needed to have formed the huge Mississippi Valley-type lead-zinc ore deposits fringing the northern margin of the Arkoma Basin on the Ozark Uplift.
134 citations
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01 Jul 1992
TL;DR: Fluids in motion numerical solutions to partial differential equations computer-based analysis procedures and tools describing flow problems in engineering building a mesh setting the fluid flow parameters obtaining a solution and analyzing the results some case studies.
Abstract: Fluids in motion numerical solutions to partial differential equations computer-based analysis procedures and tools describing flow problems in engineering building a mesh setting the fluid flow parameters obtaining a solution analyzing the results some case studies modelling flows with additional complexity acquiring CFD technology.
128 citations
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TL;DR: In this paper, three momentum advection methods are reviewed and a new one is proposed, which is called cell-centered and its relationship to the other two methods is discussed.
121 citations
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TL;DR: In this paper, a microburst is modeled by releasing a volume of fluid that is slightly heavier than the ambient fluid, allowing it to fall onto a horizontal surface, where vortexicity develops on the sides of this parcel as it descends and causes it to roll up into a turbulent vortex ring which impinges on the ground.
Abstract: A microburst can be modeled by releasing a volume of fluid that is slightly heavier than the ambient fluid, allowing it to fall onto a horizontal surface. Vorticity develops on the sides of this parcel as it descends and causes it to roll up into a turbulent vortex ring which impinges on the ground. Such a model exhibits many of the features of naturally occurring microbursts which are a hazard to aviation. In this paper this model is achieved experimentally by releasing a volume of salt water into fresh water from a cylindrical dispenser. When care is taken with the release the spreading rate of the surface outflow is measurable and quite repeatable despite the fact that the flow is turbulent. An elementary numerical approximation to this model, based on inviscid vortex dynamics, has also been developed. A scaling law is proposed which allows experiments with different fluid densities to be compared with each other and with the numerical results. More importantly the scaling law makes it possible to compare the model results with real microbursts.
112 citations
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01 Jan 1992TL;DR: Numerical simulation is numerical modelling and simulation of flow circumstances, including numerical experiments by the computer, which may have several important advantages over physical measurements on a laboratory model.
Abstract: Very fast development of computing enabled also the development of numerical fluid dynamics. It is numerical modelling and simulation of flow circumstances, including numerical experiments by the computer. Such procedure may have several important advantages over physical measurements on a laboratory model. It is of great importance that fluid properties (density, viscosity, compressibility, etc.) may be simply and arbitrarily changed, numerical experiment does not disturb the flow, plane flows can simply be simulated what may not be the case with laboratory experiments. The numerical experiment also has its own drawbacks and disadvantages, known to all numerical procedures, since the numerical solution represents a result of a discrete equation systems, which are not completely identical to basic physical laws of mechanics of continua. Discretisation often changes quantitatively and qualitatively the behavior of equations and thus also the solutions. Numerical simulation has also similar limitations like a laboratory experiments, since the solutions are individual discrete values only, not the functions of the flow fields.
66 citations
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TL;DR: In this article, the authors carried out numerical computations of water impact on a two-dimensional flat-bottomed body using a volume-of-fluid method based on a modified SOLA-VOF code.
30 citations
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15 Jun 1992
TL;DR: A fluid drop system for an aircraft for use in firefighting is described in this paper, which uses electronic control circuitry coupled with a hydraulic controller that opens and closes the fluid tank's door panels to rate-control fluid drops based on fluid volume remaining in the tank.
Abstract: A fluid drop system for an aircraft for use in firefighting is described. The preferred embodiment uses electronic control circuitry coupled with a hydraulic controller that opens and closes the fluid tank's door panels to rate-control fluid drops based on fluid volume remaining in the tank. The circuitry produces a command generated drop rate profile based upon manual drop rate and drop fraction selector controls. It does so by constant comparison of the instantaneous volume of fluid remaining in the tank with a predetermined, desired instantaneous remnant volume in accordance with a defined, declining-volume profile, e.g. one defining a constant drop rate. A stabilized feedback control circuit ensures that, at any instant of time, the opening in the tank's door panels releases a volume of fluid that will maintain the remnant tank volume equal to the desired tank volume. Such variable forces on the fluid as inertia, acceleration, declining mass and splashing automatically are compensated for by the feedback-based fluid drop rate control circuitry. External variables such as aircraft groundspeed, heat intensity, etc. may be taken into account, thereby to render highly controllable and accurate fluid drops for effective and efficient fire fighting operations.
19 citations
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11 May 1992
TL;DR: In this paper, a method and apparatus for apportioning a primary volume of fluid into a plurality of secondary volumes having a predefined mutual relationship, by means of a chamber for receiving the primary volume, having a bottom including fluid evacuation orifices, disposed in a common horizontal plane and connected to evacuation ducts provided with cocks, is presented.
Abstract: A method and apparatus for apportioning a primary volume of fluid into a plurality of secondary volumes having a predefined mutual relationship, by means of a chamber for receiving the primary volume of fluid having a bottom including fluid evacuation orifices (6) disposed in a common horizontal plane and connected to evacuation ducts (8) provided with cocks (19), enabling the beginning of fluid flow in the ducts (8) to be synchronized, with the end of said flow being determined by the free surface (26) of the fluid being fractioned by the evacuation orifices (6).
14 citations
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21 Apr 1992
TL;DR: In this paper, a measured amount of a first fluid is metered into a measure of a second fluid by a method where a fluid is confined within a first chamber and a plunger of a predetermined volume is mechanically moved into the chamber to displace a first measured amount.
Abstract: A measured amount of a first fluid is metered into a measured amount of a second fluid by a method where a fluid is confined within a first chamber and a plunger of predetermined volume is mechanically moved into the chamber to displace a first measured amount of fluid after which a second plunger is mechanically moved into a defined volume of the chamber to displace a second volume of fluid therefrom different from the first volume whereupon the first and second volumes can be mixed in predetermined proportions.
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08 Jul 1992
TL;DR: A flow control device for a fluid container comprises flow control means (2) which allow passage of fluid and limiting means (4, 5, 6) which prevent further outward flow of fluid once a predetermined total volume of fluid has passed through the fluid control means.
Abstract: A flow control device for a fluid container comprises flow control means (2) which allow passage of fluid and limiting means (4, 5, 6) which prevent further outward flow of fluid once a predetermined total volume of fluid has passed through the fluid control means (2). The device prevents re-use of the container if refilled with a counterfeit product.
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04 May 1992
TL;DR: A fluid regulating apparatus adapted operably to be connected to a source of fluid under pressure, the apparatus having a housing having an internal chamber and at least one passage interconnecting the chamber and the exterior of the housing, a mount for mounting the chamber of a housing in fluid receiving relation to the source, and an assembly mounted in the housing responsive to fluid pressure to reduce the fluctuation in the volume of fluid released from the chamber through the passage as the result of fluctuation of fluid pressure received from the source.
Abstract: A fluid regulating apparatus adapted operably to be connected to a source of fluid under pressure, the apparatus having a housing having an internal chamber and at least one passage interconnecting the chamber and the exterior of the housing; a mount for mounting the chamber of the housing in fluid receiving relation to the source of fluid under pressure; and an assembly mounted in the housing responsive to fluid pressure to reduce the fluctuation in the volume of fluid released from the chamber through the passage as the result of fluctuation in the fluid pressure received from the source.
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15 May 1992-JSME international journal. Series 2, Fluids engineering, heat transfer, power, combustion, thermophysical properties
TL;DR: In this paper, the authors developed a computer code for analyzing the two-dimensional turbulent flow with a free surface based on the volume fraction of fluid and compared the computed results with those of the experiments.
Abstract: In the design of a liquid metal fast breeder reactor, it is important to know the movement of a free surface in a tank. So we developed a computer code for analyzing the two-dimensional turbulent flow with a free surface based on the VOF (volume fraction of fluid) and compared the computed results with those of the experiments. The measurements of surface location were made by the technique of digital processing of video images, and the velocity distributions were measured by the particle trace method and laser deppler velocimeter. The flow patterns and the locations of the surface computed by this code agree with the measured values.
14 Jun 1992
TL;DR: In this article, an improved volume of fluid (VOF) technique has been used to test numerical simulation of breaking waves against a vertical wall seated on a structural foundation, where Laitone's second order solitary wave theory is used as the initial conditions.
Abstract: In this paper, an improved volume of fluid (VOF) technique has been used to test numerical simulation of breaking waves against a vertical wall seated on a structural foundation. Laitone's second order solitary wave theory is used as the initial conditions. When no foundation is present, the run up of a solitary wave on a vertical wall for a range of H/d agrees well with the experimental data. The phenomena of wave breaking, such as wave steepening, overturning and formulation of bores, have been successfully simulated by an improved VOF method. Very high intensity shock pressure and wave impact force on the vertical wall are also obtained.
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TL;DR: In this article, the authors describe phenomena of advection dispersion in subsurface flow by using Eulerian Lagrangian Finite Element Method with Galerkin formulation and weigthed residual method.
Abstract: In this paper the author will be describe phenomena of advection dispersion in subsurface flow by using Eulerian Lagrangian Finite Element Method Where Finite Element Method with Galerkin formulation and weigthed residual method is used to solve seepage and advection dispersion equation The problem of one dimensional and two dimensional rectangular wave are analyzed in this paper And the result of numerical analyses will be compared with analytical solutions The numerical results showed the very good agreement with the analytical solutions
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14 Apr 1992
TL;DR: In this article, a cylindrical piston free of engagement with the cylinder side wall is movable longitudinally into the cylinder so as to displace through the fluid outlet a volume of fluid corresponding to the volume of the piston accommodated in the chamber.
Abstract: Apparatus for generating a precision fluid flow comprises a cylinder (10) having side (14) and end (16, 17) walls forming a fluid-receiving chamber (18) having a fluid inlet and a fluid outlet. A cylindrical piston (60) free of engagement with the cylinder side wall is movable longitudinally into the cylinder so as to displace through the fluid outlet a volume of fluid corresponding to the volume of the piston accommodated in the chamber. The piston is formed of a material which is substantially insensitive to variations in temperature and pressure of the fluid in the chamber so that the piston rod is substantially dimensionally stable. The piston is moved relative to the chamber by a precision driving mechanism (70) either at a constant velocity to provide a constant volumetric flow of fluid through the outlet or at a variable velocity to provide a constant fluid pressure at the outlet.