Problem Of Liquid Flow Research Articles

Measuring the viscosity of films by thermomechanical analysis: application to metal organic precursor films of functional oxides

We have developed a new method to measure the viscosity of micrometric films by thermomechanical analysis with a hemispherical probe of millimetric diameter. The loading curve (displacement vs. time) recorded as the probe tip crosses the whole film at constant load until it touches the substrate is fitted to a theoretical curve shape that has been obtained after solving the problem of liquid flow under the probe tip. The method has been validated by measuring the viscosity of rosin films. It has been applied to analyze the thermal evolution of unstable liquid films that appear on Ba propionate, Ce(III) propionate and a low-fluorine precursor film of YBa2Cu3O6+x. During pyrolysis of the last two films, viscosity first diminishes due to heating and then it increases as solid oxide particles are formed inside the liquid.

Certain Exact Solutions to the Problem of Liquid Flow in Prismatic Tubes

Certain Exact Solutions to the Problem of Liquid Flow in Prismatic Tubes

A Pressure-based Compressible-Liquid Flow Model for Computation of Instantaneous Valve Closure in Pipes

A generalized, pressure-based compressible-liquid flow model is proposed for the isothermal low-speed flow of liquids. The flow model incorporates dedicated equations of state for liquids into the pressure-based solvers to simulate the compressible effects in liquids. The model’s capability to handle compressible liquid flow problems is evaluated against the well-established density-based water-hammer model. The isothermal flow problem of an instantaneous valve closure in an irrigation pipe and the associated flow transients are numerically solved using the proposed model by employing the Tait equation of state in conjunction with a segregated pressure-based solver algorithm. The transient flow problem is solved for a range of operating pressures, and the surge in pressure and variation of other flow properties and their interrelations are studied in detail. The proposed model could successfully capture the entire physics of the problem, including the compressible modeling of the liquid involved and could produce high accuracy numerical results. The results suggest that the pressure-based compressible-liquid flow model is a reliable and computationally inexpensive numerical tool for isothermal low-speed compressible liquid flow computations.

Acceleration of Gas Flow Simulations in Dual-Continuum Porous Media Based on the Mass-Conservation POD Method

Reduced-order modeling approaches for gas flow in dual-porosity dual-permeability porous media are studied based on the proper orthogonal decomposition (POD) method combined with Galerkin projection. The typical modeling approach for non-porous-medium liquid flow problems is not appropriate for this compressible gas flow in a dual-continuum porous media. The reason is that non-zero mass transfer for the dual-continuum system can be generated artificially via the typical POD projection, violating the mass-conservation nature and causing the failure of the POD modeling. A new POD modeling approach is proposed considering the mass conservation of the whole matrix fracture system. Computation can be accelerated as much as 720 times with high precision (reconstruction errors as slow as 7.69 × 10−4%~3.87% for the matrix and 8.27 × 10−4%~2.84% for the fracture).

Research of influence of random change of annular seal parameters on efficiency of centrifugal pump

Development of reliable methods of increasing of centrifugal pump efficiency is a very actual scientific and practical problem. One of ways to increase reliability and efficiency of centrifugal pump is an improvement of constructions of annular seals of running part and methods of their calculation. Now in engineering practice several approaches to research of complicated spiral flow of liquid in the small gaps of annular seals are used. Divergences in the conclusions of researchers are likely to be linked with assumptions that are accepted when solving nonlinear equations of non-stationary motion of liquid in the gap of annular seal. It is necessary to mark that divergences between the calculation values of hydrodynamic characteristics of annular seals and rotor-dynamic characteristics of pump that arise during exploitation are first of all possible to explain by the absence of account of possible change of geometrical parameters of the annular seals, caused by the accepted tolerances in the calculations. Using of probabilistic methods of calculation with existent statistical information got on the stages of design and operating of centrifugal pumps will allow to forecast reliability and efficiency of centrifugal pumps taking into account influence and changing of basic operating factors. Determination of influence of random change of annular seal parameters on flow-rate characteristics and volume efficiency of centrifugal pump is the goal of this research. Dependences to determinate the flow-rate of liquid through the annular seal are got by solving the problem of liquid flow in a cylindrical channel with taking into account the influence of random factors. Influence of random variations of basic geometrical and regime parameters of annular seal on efficiency pump is considered. It is shown on the example of cantilever pump with one impeller, that its efficiency can substantially (up to 1 %) decrease under exploitation. This decrease can be higher in case when pump has more stages.

Refined reconstruction of liquid–gas interface structures for stratified two-phase flow using wire-mesh sensor

Wire-mesh sensors (WMS), developed at HZDR [13,4], are widely used to visualize two-phase flows and measure flow parameters, such as phase fraction distributions or gas phase velocities quantitatively and with a very high temporal resolution. They have been extensively applied to a wide range of two-phase gas–liquid flow problems with conducting and non-conducting liquids. However, for very low liquid loadings, the state of the art data analysis algorithms for WMS data suffer from the comparably low spatial resolution of measurements and from boundary effects, caused by e.g. flange rings – especially in the case of capacitance type WMS. In the recent past, diverse studies have been performed on two-phase liquid–gas stratified flow with low liquid loading conditions in horizontal pipes at the University of Tulsa. These tests cover oil–air flow in a 6-inch ID pipe and water–air flow in a 3-inch ID pipe employing dual WMS with 32×32 and 16×16 wires, respectively. For oil–air flow experiments, the superficial liquid and gas velocities vary between 9.2m/s≤νSG≤15m/s and 0.01m/s≤νSL≤0.02m/s, respectively [2]. In water–air experiments, the superficial liquid and gas velocities vary between 9.1m/s≤νSG≤33.5m/s and 0.03m/s≤νSL≤0.2m/s, respectively [17,18]. In order to understand the stratified wavy structure of the flow, the reconstruction of the liquid–gas interface is essential. Due to the relatively low spatial resolution in the WMS measurements of approximately 5mm, the liquid–gas interface recognition has always an unknown uncertainty level. In this work, a novel algorithm for refined liquid–gas interface reconstruction is introduced for flow conditions where entrainment is negligible.

Analysis of flux flow and the formation of oscillation marks in the continuous caster

In the industrial process of continuous steel casting, flux added at the top of the casting mould melts and forms a lubricating layer in the gap between the steel and the oscillating mould walls. The flow of flux in the gap plays an essential role in smoothing the casting operation. The aim of the present work is to better understand the mechanics of flux flow, with an emphasis on such problems as how the flux actually moves down the mould, the physical parameters governing the consumption rate of the flux and the geometry of the lubricating layer. The problem considered is a coupled problem of liquid flow and multi-phase heat transfer. In the first part of the paper, the formation of the lubricating layer is analysed and a set of equations to describe the flux flow is derived. Then, based on an analysis of the heat transfer from the molten steel through the lubricating layer to the mould wall, a system of equations correlating the temperature field in the steel and flux with the geometry of the lubricating layer is derived. Subsequently, the equations for the flux flow are coupled with those arising from heat-transfer analysis and then a numerical scheme for the calculation of the consumption rate of flux, the geometry of the lubricating layer and the solidification surface of the steel is presented.

Increasing the efficiency of tubular supercentrifuges

with a conical rotor [3] and experimental studies carried out atMIKhMe using a VM-100 laboratory tubular centrifuge with a 100-ram-diameter perforated rotor. Three radial baffles, 20 mm high, which engaged the entire liquid layer along the radius of the rotor, were installed in the lower section of the rotor. The angular velocity of the liquid was measured by a hydrodynamic rotating vane using stroboscopy. Even at relatively high flow rates the liquid (water) lag did not exceed 1.5-2%, while for more viscous liquids lag was practically zero. The effectiveness of accelerating liquid at the inlet zone of the rotor was verified by experimental studies of the separation of an emulsion of dibutylphthalate-aqueous glycerine using a type $45-1 laboratory supercentrifuge. The capacity of rotors with radial baffles installed only at the liquid inlet zone was the same as for rotors with impellers along the entire length of the rotor for equivalent quality separation. It was shown earlier [4] that an increase (acceleration) of liquid angular velocity over the rotor velocity occurs during the flow of prerotated liquid in the smooth outlet channel from the wall to the axis of the rotor. A simple inlet device [5] was designed to utilize the acceleration phenomenon to increase centrifugal efficiency. This consists of low radial baffles and a disc installed in the lower section of the rotor (Fig. 1). These baffles impart an angular velocity to the liquid equal to the rotor velocity and the liquid, flowing around the disc, enters the main section of the rotor close to its walls. Moving toward the outlet, the liquid, in passing from a larger to a smaller radius, retains a part of the imparted peripheral velocity, which -esults in increasing angular velocity as the liquid approaches the discharge surface. In a smooth clarifying rotor with an inlet device all the liquid moving radially is subject to greater forces, since the discharge end radius is always smaller than the radius at the inlet to the separation zone of the rotor. In a separating rotor the light fraction flow is similar to that in a clarifying rotor when the feed is accelerated. The heavy fraction flow in a separating rotor is practically not accelerated. Therefore, acceleration, which is determined by the light fraction flow, is lower in a separating than in a clarifying rotor. An analytical solution of the problem of liquid flow in a smooth cylindrical rotor with acceleration is quite difficult, since one cannot neglect any of the liquid velocity components in making approximations. Preliminary experimental studies using a type VM-100 laboratory tubular centrifuge were therefore carried out to determine the profile of liquid angular velocities when using an inlet device. The expe riments were carried out over a wide range of varying throughput u sing liquids of varying viscosities at different angular velocities, heights, and radii of rotor liquid discharge. The disc dimensions