Flow Of Incompressible Liquid Research Articles

Microscale damper prototype: A preliminary study on suppressing air flow oscillations within microchannels

This research introduces a novel micro-damper designed to mitigate pressure and velocity oscillations from a piezoelectric micropump in microfluidic environments. Unlike existing research focusing on damping in incompressible liquid flows with methods like elastic films and PDMS membranes, this study proposes a novel micro-damper prototype. Integrated into a microdevice for particle granulometric separation and detection, the damper connects to a piezoelectric micropump outlet and to a focusing microchannel inlet, followed by a capacitive sensor for size-based particle counting. Preliminary analysis determined an optimal airflow velocity at w = 0.5 m/s for accurate focusing and counting under laminar conditions. The micro-damper, constrained by the piezoelectric pump’s geometry, features a 27 µm high and 1000 µm wide cross section. Its outlet supports two potential focusing microchannel inlet configurations of 30 µm or 40 µm. Distinctively, it incorporates two symmetrical backward micro-channels connecting to the atmosphere, allowing direct piezometric contact between the main flow and an infinite compliant volume. OpenFOAM simulations confirm the damper’s effectiveness in maintaining laminar outlet flow and suppressing micropump disturbances. Thus, the proposed micro-damper ensures optimal inlet conditions for subsequent microchannel processes, enabling stable particle separation and detection in controlled airflow samples.

Численный эксперимент в задаче о распространении малых возмущений в круглой трубе

Flow of viscous incompressible isothermal liquid in round pipe at moderate Reynolds numbers corresponding to laminar and turbulent modes is considered. The problem is solved in a non-stationary formulation, the spatial coordinate system of Euler is used. As a mathematical algorithm, quasi-hydrodynamic (QHD) equations are used. Within the framework of this algorithm, it was first shown that random perturbations of the input speed in the channel attenuate for small Reynolds numbers and lead to the formation of a turbulent mode for large Reynolds numbers.

Effect of paragliding wing dome shape on its aerodynamic characteristics

Double-membrane gliding parachutes (DGP) obtain their wide variety of application, including the solution of cargo transportation problems. This parachute is a flexible canopy, which shape is maintained by ram air. In terms of the aerodynamic performance calculation and analysis when operating, DGP is the most complex aero elastic system. The computation of DPG aerodynamic performance is only possible, utilizing the methods of nonlinear aerodynamics and the nonlinear theory of elasticity methods.This paper investigates the aerodynamic characteristics of stable geometric shapes for various gliding parachutes, taking into account their dome shape both chord-wise and span-wise. Notably, the volumetric parachute profile is modeled by its median surface. The research, conducted by the authors, showed that such an aero elastic model of DGP allows you to obtain results that reflect correctly the qualitative effects of detached and free streamline flow. To solve the problem about the airflow over a gliding parachute, considering its canopy curvature, the method of discrete vortices with closed frames is employed, which allows you to calculate the paragliding wing aerodynamic performance within a wide range of angles of attack. There is also a possibility of flow separation simulation. The ideal incompressible liquid flow over the median surface of a stable shape for a double-membrane gliding parachute is regarded. The parachute fabric porosity is not analyzed, since the upper and lower DGP panels are made of either the low permeable or non-porous fabric. In the separated flow past, the aerodynamic coefficients are identified by time averaging to its large values after computing. The DGP aerodynamic performance computation results are given at a different value of its dome shape, as in the free streamline flow as in the flow separation. The computed coefficients, that allow us to consider the influence of canopy dome shape on its aerodynamic characteristics, are obtained. The proposed technique can be used for operational estimates of aerodynamic forces while designing and planning a pipe experiment.

Numerical simulations of liquid-solid flows with free surface by coupling IMPS and DEM

Liquid-solid two-phase flow with free surface is a significant issue in nature and engineering fields. In present study, an in-house solver MPSDEM-SJTU based on a fully Lagrangian coupled method is developed to solve the problems of liquid-solid two-phase flows. The improved moving particle semi-implicit (IMPS) method is applied for the simulation of incompressible viscous liquid flows while the discrete element method (DEM) is used to model the interaction among the solid particles. The coupling strategy is based on the local averaging technique. Multiple time-step algorithm is adopted for those two methods to balance the stability and the efficiency. The free surface detection and the solid-fluid neighbor search are modified. A simulation of multi-balls collapse is conducted to verify the DEM program of the present solver. The distributions of solid balls at different instants are in good agreement with the experimental results. Then, this solver is applied for two typical problems of two-phase flows, including the two-phase dam-break and the liquid-solid flows in a rotating cylindrical tank. The flow front, flow patterns and the shape of solid beds all agree well with experimental observations.

РЕШЕНИЕ ЗАДАЧИ В РАБОЧЕЙ ЗОНЕ. ЧИСЛЕННЫЙ РАСЧЕТ МОДЕЛИ НИЖНЕКАМСКОГО РЕАКТОРА ДЛЯ ПОЛУЧЕНИЯ СТИРОЛА (ЧАСТЬ 3)

Heterogeneous catalytic processes conducted in axial or radial type reactors with a still catalytic layer are some of the most important elements of the chemical technology. The attention of scientists and manufacturers to the investigation and application of these contact units deals with the following advantages: a highly developed surface of a phase separation, a possibility to provide a high flow velocity and hence to decrease sizes and a material consumption, a construction simplicity and a reliability of an exploit. Improving an operation of contact units may be achieved by refining present technologies, catalysts, disperse system structures and by creating new ones. Nevertheless, in some cases large scale hydrodynamic heterogeneities in a working zone of the unit cancel out efforts to increase an efficiency of chemical, heat/mass transfer and other processes. The exploration of reasons of the hydrodynamic heterogeneities formation requires an investigation of liquid and gas motion physics features in granular layers. A practice of a chemical reactors exploitation reveals that technical and economical indicators of an industrial process are as a rule lower than the calculated ones, derived on a stage of the process design. Now it can be considered proven that one of the reasons affecting the reactor output is the heterogeneity of a reagents flow in a granular catalyst layer. The article deals with a mathematical modeling of an incompressible liquid flow in flat and radial contact units with the still granular layer and a creation of numerical realization methods for the model We propose a cycle of articles dealt with a model of a real reactor that consists of three parts: a distributing manifold, a collecting manifold and a working zone, where the still layer of a granular catalyst is loaded. An input and an output are made with a Z-shaped scheme. We consider processes and their equations in each reactor zone in detail.

Determining the structure of a laminar detachable current in an open cavity

The paper reports a three-dimensional numerical solution to the test problem about a viscous incompressible liquid flow in the closed square-shaped cavity with a movable upper face. Disadvantages in a mathematical statement of the problem about a flow of fluid in a closed cavity have been identified. A finite element method was applied in order to investigate numerically the structure of a circulating detachable laminar movement of viscous incompressible fluid in an open cavity considering the external flow. The profiles of vorticity, the thickness of a boundary layer, the constituents of velocity components in different cross-sections of the cavity, in the boundary layer, as well as in the blending layer, have been given.Typically, studying laminar currents in cavities employs a model of the cavity with a movable wall. However, such a statement of the problem imposes a restriction on the flow pattern in the form of a straight line of the flow that connects the upper corners of the cavity, which results in the distorted structure of vorticity formation in the cavity in general. Within the framework of the current study, the problem statement that overcomes the specified disadvantage has been proposed. The movement of fluid in a cavity occurs due to the shear stress of the external flow in a channel above the cavity, which rules out the straightness of the flow line, which connects the cavity's corner points. Reliability of the reported results has been confirmed by comparing certain parameters to known experimental data by other authors. The study's scientific result in the form of the vorticity structure of a viscous incompressible laminar flow in an open cavity with a channel is interesting from a theoretical point of view. As regards the practical point of view, the identified structure of the flow makes it possible to define the conditions to control a flow in the cavity and, therefore, allows determining the conditions for optimizing the aerodynamic forces acting on a cavity. The applied aspect of the obtained scientific result is the possibility to employ it for a flow over industrial facilities: buildings, inter-carriage space in a railroad train, etc.

On the Linear Instability of Incompressible Polymeric Liquid Flows with Strong Discontinuity

The temporally growing particular solutions of linearized equations of an incompressible polymeric liquid with strong discontinuities were constructed.

On a hydrodynamic permeability of a system of coaxial partly porous cylinders with superhydrophobic surfaces

The paper considers a Stokes–Brinkman’s system with varying viscosity that describes the continuous flow of viscous incompressible liquid along an ensemble of partially porous cylindrical particles using the cell approach. The analytical solution for the considered system was derived and analyzed for a particular case of Brinkman’s viscosity which illustrates the presence of superhydrophobic surfaces in a porous system. Some numerical validation of the derived results are done and the hydrodynamic permeability of the porous system was calculated and analyzed depending on geometrical and physicochemical parameters. Our analysis of the problem shows that the bigger the impermeable core the less the coefficient of hydrodynamic permeability what agrees with the physical process of the filtration. In addition, the bigger the specific permeability of porous layer the greater the hydrodynamic permeability of the porous medium.

Slipping and tangential discontinuity instabilities in quasi-one-dimensional planar and cylindrical flows

An analytical linear theory of instability of an electron beam with a nonuniform directional velocity (slipping instability) against perturbations with wavelengths exceeding the transverse beam size is offered. An analogy with hydrodynamic instabilities of tangential discontinuity of an incompressible liquid flow is drawn. The instability growth rates are calculated for particular cases and in a general form in planar and cylindrical geometries. The stabilizing effect of the external magnetic field is analyzed.

Conservative Allen–Cahn–Navier–Stokes system for incompressible two-phase fluid flows

A new phase-field model for immiscible incompressible two-phase liquid flows has been developed. The model consists of a conservative Allen–Cahn equation with a space-time dependent Lagrange multiplier and a modified Navier–Stokes equation. Even though most phase-field methods for the multiphase flows preserve total mass, the bulk phase concentrations tend to shift from equilibrium concentration values of a double-well potential. The proposed model has a good feature which avoids mass spreading to the bulk phases. To validate the new system, the deformation of a drop from the initial circular shape in shear flow is presented and compared with other numerical results.

Nanoparticle deposition in granular filters at Reynolds numbers higher than unity

The influence of the inertia of a viscous incompressible liquid flow on the viscous drag and diffusion deposition of particles in model granular filters at Reynolds numbers higher than unity, Re > 1, has been considered. The granule drag forces and particle-collection efficiencies in isolated layers with square and hexagonal packings of granules have been calculated. The influence on each other of approaching monolayers of granules on pressure drop and nanoparticle deposition has been studied. It has been shown that, at Re > 1, the collection efficiency dramatically increases due to the effect of interception.

On the role of electron impact in an atmospheric-pressure microwave discharge in liquid n-heptane

The role of electron impact in the dissociation of n-heptane in an atmospheric-pressure microwave discharge in liquid n-heptane was investigated using a self-consistent two-dimensional model. The model includes the Navier–Stokes equations for a two-phase subsonic flow of incompressible liquid and compressible gas, the heat conduction equation, Maxwell’s equations for the microwave field, the Boltzmann equation for plasma electrons, and the balance equations for the electron density and weight fraction of n-heptane in the gaseous and liquid phases. It is shown that the effect of electron impact is negligible at times longer than 10–3 s.

ЧИСЛЕННЫЙ МЕТОД РЕШЕНИЯ ОДНОЙ НЕЛОКАЛЬНОЙ ЗАДАЧИ ТРУБОПРОВОДНОГО ТРАНСПОРТА ВЯЗКИХ ЖИДКОСТЕЙ

Х.М. Гамзаев, Азербайджанский государственный университет нефти и промышленности, г. Баку, Азербайджан E-mail: xan.h@rambler.ru. K.M. Gamzaev Azerbaijan State Oil and Industry University, Baku, Azerbaijan E-mail: xan.h@rambler.ru

Validation of magnetic resonance concentration measurements with adiabatic wall temperature measurements

Adiabatic wall temperature measurements were obtained in a high subsonic Mach number airflow experiment and compared with concentration measurements near the surface from a low-speed liquid flow experiment. Excellent agreement between the temperature and concentration measurements validates the investigation of turbulent mixing phenomena in compressible gas flows through the study of incompressible liquid flows with magnetic resonance techniques.

Instability of plane-parallel flow of incompressible liquid over a saturated porous medium.

The linear stability of plane-parallel flow of an incompressible viscous fluid over a saturated porous layer is studied to model the instability of water flow in a river over aquatic plants. The saturated porous layer is bounded from below by a rigid plate and the pure fluid layer has a free, undeformable upper boundary. A small inclination of the layers is imposed to simulate the riverbed slope. The layers are inclined at a small angle to the horizon. The problem is studied within two models: the Brinkman model with the boundary conditions by Ochoa-Tapia and Whitaker at the interface, and the Darcy-Forchheimer model with the conditions by Beavers and Joseph. The neutral curves and critical Reynolds numbers are calculated for various porous layer permeabilities and relative thicknesses of the porous layer. The results obtained within the two models are compared and analyzed.

Frequency Spectrum of Exact Solutions of the Two-Dimensional Hydrodynamic Equations

We show that the discrete frequency spectrum of a plane hydrodynamic flow of ideal incompressible liquid with localized trajectories of the liquid particles can contain only one, two, or an infinite number of harmonics.

General and approximate solutions of the boundary layer equation for radial flow of incompressible liquid

Non-linear partial differential equation for description of a laminar, incompressible, Newtonian radial flow in half-subspace is derived taking into account free slipping at a border. The boundary layer approximation is used and the equation with one free parameter for a steam function is obtained. The general solution for one value of this parameter is found and analysed. Some approximate solutions of the special form are constructed.

Моделирование взаимодействия с преградой потока несжимаемой жидкости методами VOF и SPH

Моделирование взаимодействия с преградой потока несжимаемой жидкости методами VOF и SPH

Prediction and Evaluation of Time-Dependent Effective Self-diffusivity of Water and Other Effective Transport Properties Associated with Reconstructed Porous Solids

We reconstructed pore structures of three porous solids that differ from each other in morphology and topology of pore space. To achieve this, we used a stochastic method based on simulated annealing and X-ray computed microtomography. Simulated annealing was constrained by the following microstructural descriptors sampled along the principal and diagonal directions: the two-point probability function for the void phase and the lineal-path functions for both void and solid phases. The stochastic method also assumed the isotropic pore structures in accordance with a recent paper (Capek et al. in Transp Porous Media 88(1): 87–106 (2011)). With the exception of the solid with the widest pores, we made tomographic volume images in high and low resolution, which enabled us to study the effect of resolution on microstructural descriptors and effective transport properties. A comparison of the two-point probability function and the lineal-path function sampled in the principal directions revealed that the pore structures derived from the tomographic volume images were slightly anisotropic, in opposition to the assumption of the stochastic method. Besides the anisotropy, other microstructural descriptors including the pore-size function and the total fraction of percolating cells indicated that the morphological and topological characteristics of the pore structures depended on the reconstruction method and its parameters. Particularly, the pore structures reproduced using the stochastic method contained wider pores than those obtained using X-ray tomography. Deviations between the pore structures derived from low- and high-resolution tomographic volume images were also observed and imputed to partial volume artefacts. Then, viscous flow of incompressible liquid, ordinary diffusion, Knudsen flow and self-diffusion of water in the reconstructed pore spaces were simulated. As counterparts, experimental data were measured by means of permeation and Wicke–Kallenbach cells and pulsed field gradient NMR. Deviations between the simulated quantities on the one hand and experimental data on the other hand were generally acceptable, which corroborated the pore-space models. As expected, the predictions based on the tomographic models of pore space were more successful than those derived from the stochastic models. The stationary effective transport properties, i.e. the effective permeability, the effective pore size and the geometric factor, were sensitive to a bias in long-range pore connectivity. Furthermore, the time-dependent effective diffusivity was found to be especially sensitive to relatively small morphological deviations between the real and reconstructed pore structures. It is concluded that the combined predictions of the effective permeability, the effective pore size, the geometric factor and time-dependent effective self-diffusivity of water are needed for the reliable evaluation of pore-space reconstruction.

Modeling Nonstationary Nonlinear-Viscous Liquid Flows Through a Pipeline

The process of nonstationary incompressible nonlinear-viscous liquid flow through a pipeline is considered. It is described by a parabolic-type one-dimensional nonlinear equation. The problem of determining the dependence of the pressure difference on time from the assigned volumetric flow rate in the given pipeline is formulated. Such a problem pertains to the class of inverse problems connected with the restoration of the dependence of the right-hand sides of parabolic equations on time. A computational algorithm for solving the problem has been suggested.