In a wide range of operations in the petroleum industry, co-current flow of two immiscible liquids commonly occurs; therefore, an in-depth knowledge regarding these phenomena is highly necessary to predict the flow behavior during production and transportation of oil in pipeline systems. To this end, numerous researchers have applied different experimental techniques for the characterization of liquid-liquid flows in horizontal and inclined pipes. For reliable design methods, this paper reviews some of the existing experimental techniques and their applications, strengths, and limitations and gives some direction for future studies. Two main aspects of these approaches have been abundantly discussed, with an emphasis on the second one: the first section focuses on fluid physical properties and geometrical and operational variables of liquid-liquid flow experimental systems; the second one reviews the main two-phase immiscible liquid-liquid characterization methods used for flow pattern identification, velocity, and phase distribution measurements, including optical-based, irradiation, electrical, and thermal methods.
Experimental and numerical results of airflow and heat transfer in the vicinity of oblique shock-wave incidence on a flat plate are presented. Sharp and blunted leading edge of flat plates is conceded.
The main results of experimental studies of hypersonic flow over a cylindrical obstacle are presented in this paper.
The model of the air intake considered in this paper represents folding edges compressing the flow with a cowl on top of them. Such a configuration is not typical for air intakes applied practically. However, the results presented here may be used for different configurations of air intakes.
The flow over a pair of wedges fixed on a sharp and blunted plate is studied. It is observed that even a small bluntness of the plate can significantly alter the flow structure and cause local blocking of the channel. A similar effect causes the decrease of Reynolds number.
The results of studying gas flow near a sharp wedge mounted both on sharp and blunt plates are presented. The data on the flow over a wedge mounted on the axisymmetric body (a cone or a cylinder) when the wedge dimensions are small as compared to the body curvature radius are also provided. The primary focus is on the flow structure and heat transfer in the region of the shock wave interference with the boundary layer. The flow over a wedge with a sharp leading edge is considered in this paper.
Because of the phenomenon of kinetic energy in accumulating supercooled water, crystallization may arise due to both single intensive mechanical action and multiple pulses of low intensity. The results of experimental studies on crystallization of supercooled water have revealed a connection between the parameters of the intermolecular interaction and macroscopic phenomena accompanying the crystallization of the supercooled liquid. A mathematical model of the crystallization and stability criterion of a supercooled liquid when it hits the surface of the aircraft is developed. Numerical and experimental evaluation of the physical parameters characterizing the crystallization of the supercooled liquid in relation to the problem of icing is presented
Heat transfer in the separation zone (particularly in the reattachment zone) can increase multiple times. We discuss the effect of blunt leading edges on the internal flows in air intakes and channels.
The results of smoke visualization of unsteady subsonic gas flows intended for subsequent image processing by smoke image velocimetry (SIV) method for obtaining instantaneous velocity vector field dynamics are presented.
Investigation of material flow in the solid-state friction stir welding (FSW) is quite a complex process. It can be carried out either by experimentation or numerical simulation. However, compared to experimentation, numerical simulation is inexpensive, efficient and convenient, but quite challenging to model. The challenging issue in modeling FSW is to deal with the large deformations of the work piece material. The Lagrangian simulations of FSW show that the severely distorted finite elements are caused due to the large deformation of the workpiece material, which makes the Lagrangian approach inappropriate for modeling FSW. A good alternative is to study it in a smooth particle hydrodynamics (SPH) environment. SPH formulations are used to overcoming the shortcoming of Lagrangian formulations due to their continuous regimes. The basic idea of the SPH approach is that the mesh is obliged to follow material flow. Thereby the excessively distorted elements can be avoided as in Lagrangian formulations. In this paper, we fulfill this aim by using a SPH method. On the basis of the simulation results, it is concluded that the material motion characteristics on the top surface and through the depth (volume) of friction stir welds have been made for the advancing and retreating sides. The motion trends are consistent with the reported published experimental evidence.
Particle image surface flow visualization (PISFV) consists of measuring the velocity field of thin oil-film movement on the model surface in external gas flow. Surface streamlines and wall shear stress (skin-friction) field can be calculated from this velocity field. Surface streamlines are restored from velocity direction distribution. To calculate the shear stress field it is necessary also to know the velocity value, oil-film thickness, and oil dynamic viscosity in each point of the model surface. Particle distribution inside the oil layer and the oil rheology can affect the accuracy of skin-friction measurements. The aim of the present work is to investigate the opportunity of wall shear stress field measurement by the PISFV method. Flat plate in the subsonic flow with a known surface wall shear stress is used to test the method. A linear relationship between the measured oil (particle) shift and shear stress values in a wide range of oil thicknesses and oil shifts suggests the possibility of skin-friction measurements
The phenomenon of hysteresis in axisymmetrical supersonic air flow over a circular cavity with the shape of a rectangular cutout on a cylindrical body with a conical tip is demonstrated. Photographs and a video clip of shadow patterns of the flow over a cavity during the continued variation of the cavity length are presented. The plot of the corresponding pressure change at the rear cavity wall has a typical form of the hysteresis loop. The presented experimental data will be useful to validate computational technologies, intended to simulate separated flows in cavities
All aircrafts are objects with multiple operation modes. Therefore, studying the aerodynamic characteristics of the simplest hypersonic air intake in different operation modes, as well as showing the effect of the laminar–turbulent transition on its aerodynamic characteristics, is of great interest. These problems are discussed in this paper based on the numerical simulation results.
This paper discusses flow and heat transfer behavior in the simplest hypersonic air intake based on the numerical analysis of full perfect viscous gas dynamics equations. The simplest air intake is assumed to operate under the design conditions corresponding to the laminar flow.
This article describes the features of the development of supersonic viscous gas flow and the behavior of aerodynamic characteristics in relation to the fundamental problem parameters using an example of channels with a simple configuration.
Flow structure and aerodynamic characteristics of a double-wedged airfoil at transonic velocities, as well as the peculiarities of transition from subsonic to supersonic flow regime, are discussed in this paper. The interest in this airfoil is caused by the fact that it is considered to be an optimal airfoil from the viewpoint of wave drag within the framework of ideal gas theory. Its aerodynamics was actively investigated both theoretically and experimentally in 1950s–1960s.
The Rayleigh problem for a compressible fluid is considered in the present paper. The purpose of this work is to study the effect of compressibility of a medium in motion on the flow structure and aerodynamic parameters of the streamlined surface.
The paper presents a brief introduction in the materials and methods of the panoramic diagnostics of shear stresses, induced by the flow on the model surface, by liquid crystals. Two mechano - optical effects in liquid crystals with helicoidal supermolecular structure (texture transition from con-focal to planar liquid crystal texture and shift of the selective reflection peak of initially planar texture), which form the bases of experimental techniques, are considered. The optical response of liquid crystals manufactured at ITAM was investigated by the spectral and colorimetric methods. Some results obtained under sub-sonic velocities give evidence of wide possibilities of the technique.
In the present study, bubble dynamics in potential flow is considered. The computational approach is based on the boundary element method (BEM) accelerated both via the fast multipole method (FMM) and the heterogeneous computing architecture (multicore CPUs and graphics processors). The dynamics of exited high-order surface modes of bubble and the transfer of energy between surface modes, which can lead to bubble self-propulsion, are studied.
Mass conservation is a key issue for accurate streamline construction. We introduce a mass conservative streamline tracking method using dual stream functions over tetrahedral domains. A set of exact dual stream function solutions for mass conservative linear momentum vectors have been evaluated and are presented here together with their computer graphics renderings. The local behavior of streamlines is described by stream function maps which display the transformed tetrahedra in a two-dimensional "mass flux space," where all streamlines are normal to the plane of the map. The map can be used to determine how faces of a tetrahedron are connected by the streamlines. The mass conservative streamline tracking method uses the intersections of the exact dual stream functions as the streamline segments in tetrahedra and connects the segments to generate streamlines in the domain of the velocity fields. The method can be used to draw streamlines for the velocity fields of steady flows given at discrete locations in three dimensions.
