Tangential Velocity Distribution Research Articles

A case study on morphological aspects of distinct magnetized 3D hybrid nanoparticles on fluid flow between two orthogonal rotating disks: An application of thermal energy systems

The consolidation power of different nanomaterials such as metallic nanoparticles and metallic-oxides nanoparticles in a new-fangled and energetic hybrid material should give rise to fascinating properties that combine the advantages of each of the nanocomponents. In this paper, developed an MHD-hybrid model for the thermal energy system with seven different types of nanoparticles. For this purpose, we simulate the thermal conductivity and viscosity hybridized nanocomponents modeled based on the shape and size factor of each nanoparticle. The effect of morphology for Metallic and non-Metallic nanoparticles on flow and heat transfer rate has been investigated through hybrid nanofluids flow. Mathematical modeling of the concerning problem is done in the form of the partial differential structure under the boundary layer theory. The intrinsic features of capitalized induced particles along with base fluid are presented by empirical relations and utilized during the formulation of work. These hybrid nanofluids flow passing through the two orthogonal moving up/down porous disks. Thermal enhancement performance is analyzed through variation of shape and size of the nanoparticles with convective conditions. A stable system of nonlinear differential equations is obtained by applying suitable transformation on governing partial differential equations. Consequences of pertinent parameters on axial velocity, radial velocity, tangential velocity, and temperature distribution are elaborated. Important results of non-dimensional parameters with different types of hybrid nanofluids are examined through porous orthogonal disks. We achieved that the carbon nanomaterial has significant results on thermal performance. Novel results are obtained on thermal conductivity and viscosity associated with the shape/size of the nanoparticles. Shear stress increases with the increase of values of MHD. For the injection case, the Nusselt number shows significant results. If we increase the size of the nanoparticles then Skin friction also increases. This research set a strong foundation in the field of nano-biomedical devices, and engineering nanotechnology oriented electronic computers.

Parametric study on stability and morphology of liquid cone in flow focusing

A parametric study on the stability and morphology of the liquid cone in a flow focusing process is carried out through experimental and numerical methods. For the numerical simulations, we solve the Navier-Stokes equations coupled with a diffuse interface method. A scaling analysis which considers the competition between the viscous shear stress and the interfacial tension force is proposed, showing the effect of flow rates, geometrical parameters and liquid physical properties on the cone instability. The experimental and numerical results validate the scaling law and further show the effects of parameters on the cone morphology. We study the flow fields inside the liquid cone, with emphatic focus on the recirculation flow pattern which occurs at relatively high viscosity ratio between the focusing and the focused liquids. The occurrence of recirculation flow is close related to the tangential velocity distribution at both sides of the cone interface, and the change of flow rates and geometrical parameters is found to significantly affect the size of the recirculation flow. This study is expected to give a guidance to the optimization of process parameters in flow focusing system, which would contribute to the formation of a stable cone-jet structure and the production of microdroplets with high throughput.

Magnetoviscous effects on revolving ferrofluid due to an immersed rotating rod in the presence of gravitational force

In the present investigation, the effects of the rotating magnetic field, magnetization body force, and magnetic torque on revolving ferrofluid due to an immersed rotating rod are considered. The impact of the rotation of the rod and gravitational force are taken into deliberation in the present physical model. A similarity transformation is used to transform the governing partial differential equations into a set of nonlinear-coupled differential equations in dimensionless form. The numerical solution of the transformed nonlinear-coupled differential equations is obtained using COMSOL Multiphysics software in a framework of the finite element method. Results for radial, tangential, and axial velocity distributions are presented for different values of ferromagnetic interaction number, effective magnetization number, the volume concentration of particles, gravitational number, and speed of the rotation of the immersed rod. Coefficients of skin friction on the surface of the disk and wall of the rod are also computed for different values of considered physical parameters. Present results show that magnetic torque creates an additional resistance on the velocity distributions.

Evolution from conical to cylindrical fire whirl: An experimental study

This paper presents the first experimental effort on the evolution of the flow field from conical to cylindrical fire whirl, by using a small-scale rotating screen facility with finely controlled imposed circulation (Γ) under a fixed heat release rate of 4.0 kW. Stereo particle image velocimetry (SPIV) technique was employed to measure the instantaneous and mean velocity fields. Two-celled vortex structure and central recirculation zone are found to form and move downwards with increasing Γ in the plume region of cylindrical fire whirl. Within the mean flame height, the mean vortex core radius decreases slightly with Γ for conical fire whirl, while expands linearly after the onset of cylindrical fire whirl. The radial profiles of tangential velocity have self-similarity within the mean flame height for both conical and cylindrical fire whirls. In the plume region of the cylindrical fire whirl, the radial distribution of tangential velocity is similar to that of the Rankine vortex, and the decay of maximum tangential velocity and the expansion of the vortex core are faster than those of the conical fire whirl. With increasing Γ, the unimodal profile of axial velocity is found to change into the plateau profile and the wakelike profile in the plume region of the conical fire whirl and the transition location advances upstream steadily. For both conical and cylindrical fire whirls, the centerline axial velocities of certain levels and the mean flame height have consistent variation trends with Γ. Within the mean flame height for cylindrical fire whirl, the centerline axial velocity falls sharply at the axial position where the radial profile of axial velocity changes from the plateau to the wakelike profile. The height of this axial position is found to decrease steadily with the increase of Γ.

Study on energy distribution characteristics of cyclone in Laval nozzle

Supersonic separator is a device for dehydrating and separating heavy hydrocarbons in natural gas. Laval nozzle and cyclone in the separator have a great influence on the separation efficiency. At present, there are few studies on the energy distribution characteristics of the cyclone, and the law of the influence of cyclone on subsonic and transonic flow fields is not clear. Based on numerical simulation, the paper studies the influence of gas-liquid density on the separation performance of the separator, studies the energy distribution characteristics of methane flow in Laval nozzle under subsonic and transonic velocities, and deduces the energy equation containing axial kinetic energy term and radial kinetic energy term in the nozzle. The results show that the gas-liquid density has some effects on the separation efficiency of the separator. The distribution of tangential velocity and tangential kinetic energy in the nozzle is similar before the cyclone along the axis, but after the cyclone, the distribution of tangential velocity and tangential kinetic energy is significantly different. The proposal of tangential kinetic energy has important guiding significance to the structure design of supersonic separator.

Studying coolant hydrodynamics in the area of a guide channel of fuel assembly with intensifier grids

The article presents the results of studies of the coolant flow in fuel assemblies behind the intensifier grids of FA-Square reactors of the PWR type. The aim of this work is to evaluate the effectiveness of using various designs of the intensifier grid for the flow mixing. To achieve this goal, a number of experimental studies are carried out on an aerodynamic stand with scale models of fragments of fuel assemblies with intensifier grids of various designs. Adjacent cells of the guide channel, the design feature of which is the different spatial orientation of turbulators installed on the intensifier grids, are selected as a representative area of research. The general flow pattern is represented by vector fields of tangential velocities, as well as by graphical dependences of the distribution of transverse velocities in the gaps between the rods of the research area. To evaluate the efficiency of using various intensifier grids’ designs for the coolant flow mixing, the parameters of intracellular vortex formation and intercellular mixing are analyzed. Analysis of the spatial distribution of tangential flow velocities allows studying and detailing the coolant flow pattern behind the mixing grids with various designs of deflectors. The accumulated database on the coolant flow in the FAKVADRAT is the basis for engineering justification of the PWR reactor core designs. The results of experimental studies are used to verify CFD codes of both foreign and domestic development, as well as the programs for detailed cell-based calculation of active zones in order to reduce conservatism in justifying thermal reliability.

Removal of coke powders in coking wastewater using a hydrocyclone optimized by n-value

Coke powders in the coking wastewater generated by petroleum refining industry needs to be removed to achieve water reuse for lack of water resources. This study developed a decoking hydrocyclone in the closed coking wastewater circulation treatment system to remove coke powders, which was highly efficient and environmentally friendly. Computational Fluid Dynamics (CFD) method was carried out to study the tangential velocity distribution index n-value to guide design of decoking hydrocyclone and experiment was conducted to verify the coke powders removal effect. It was found that the increase of n-value is conducive to the improvement of coke powders separation efficiency. A decoking hydrocyclone with a cone angle of 15° and an inlet size of 4 × 6 mm is the optimum hydrocyclone and the recovery efficiency of coke powders is stable at more than 90%. It is the first time for hydrocyclone successfully applied to the removal of coke powders in coking wastewater in the decoking process of petroleum refining industry, in which the separation efficiency of coke powders is considerably improved.

Effect of scavenge port angles on flow distribution and performance of swirl-loop scavenging in 2-stroke aircraft diesel engine

Swirl-Loop Scavenging (SLS) improves the performance of 2-stroke aircraft diesel engine because the involved swirl may not only benefit the scavenging process, but also facilitate the fuel atomization and combustion. The arrangement of scavenge port angles greatly influences in-cylinder flow distribution and swirl intensity, as well as the performance of the SLS engine. However, the mechanism of the effect and visualization experiment are rarely mentioned in the literature. To further investigate the SLS, Particle Image Velocimetry (PIV) experiment and Computational Fluid Dynamics (CFD) simulation are adopted to obtain its swirl distribution characteristics, and the effect of port angles on scavenging performance is discussed based on engine fired cycle simulation. The results illustrate that Reynolds Stress Turbulence model is accurate enough for in-cylinder flow simulation. Tangential and axial velocity distribution of the flow, as well as the scavenging performance, are mainly determined by geometric scavenge port angles αgeom and βgeom. For reinforcement of scavenging on cross-sections and meridian planes, αgeom value of 27° and βgeom value of 60° are preferred, under which the scavenging efficiency reaches as high as 73.7%. Excessive swirl intensity has a negative effect on SLS performance, which should be controlled to a proper extent.

A vortex-type solar updraft power-desalination integrated system

In this paper, the convection vortex theory is combined with the existing solar chimney power plant combined with desalination (SCPPCSD), and a solar vortex power desalination system (SVPDS) is proposed. In SVPDS, the strong cyclone column generated by the convection vortex is used to replace the solid chimney. The physical model and three-dimensional numerical model of SVPDS are built. The flow field distributions in the solar vortex power plant (SVPP) and SVPDS under no-load condition are compared and analyzed, and the distribution rules of each parameter along the radial and axial direction and output performance are obtained. The results show that the simulation field has strong rotation characteristics, and there is obviously a low pressure area in the center of SVPDS, which enables the system to continuously draw in surrounding air, thus forming a stable vortex flow field. The maximum negative pressure of vortex center in SVPDS is −126.98 Pa, and the hourly freshwater output is about 7.92136 ton/h. Due to the sucking effect of vortex, the radial distributions of temperature and negative pressure at different heights both decrease from the center to the surrounding. With the increase of height, the temperature of central airflow, the pressure difference between the vortex center and the external environment are both decreasing, and finally close to the external environment. The vortex core structure can be obviously seen in the center, and the tangential velocity distribution is more consistent with the distribution of the Rankine combined vortex. The tangential velocity slowly decreases with the increase of height and then transforms into axial velocity. The temperature, vortex center negative pressure and tangential velocity in SVPDS are all slightly smaller than those of SVPP. With the increase of solar irradiance, the freshwater output and the vortex center maximum negative pressure both increase significantly.

Study of magnetoviscous effects on ferrofluid flow

Present results show the effect of magnetic field-dependent viscosity on the flow of magnetic fluid due to a non-conducting rotating disk. Shliomis model has been used in the problem formulation. A similarity transformation has been used to reduce a set of partial differential equations into nonlinear coupled differential equations. The nonlinear coupled differential equations involved in the problem are solved numerically through mathematical modeling in COMSOL Multiphysics. The radial, tangential, and axial velocity distribution is presented for different values of the magnetic field-dependent viscosity parameter. Some theoretical results used in the model have verified mathematically. These theoretical results are useful to validate the Shliomis model for rotational motion. The results indicate that the Shiliomis model is more appropriate to study the ferrofluid flow due to an infinite rotating disk in comparison to the Rosensweig model.

Study of ferrofluid flow in a rotating system through mathematical modeling

This work investigates the ferrohydrodynamic flow between a rotating disk and a rod in order to optimize the use of ferrofluids for liquid seals in a rotating system. Rotational viscosity effects in the flow, due to the difference of rotation between the magnetic particles and fluid in the presence of a magnetic field, are considered in the present mathematical model. The magnetic field on the disk has been directed in the radial and tangential directions and its impact on the momentum and energy equations has been considered. Similarity transformation has been used to transform the equations of the developed mathematical model into a dimensionless form. The transformed system of equations has been solved numerically with the help of the COMSOL Multiphysics software in the framework of a finite element method. The results for radial, tangential, and axial velocity distributions along with heat transfer analysis have been presented in the presence of physical parameters involved in the problem. The radius of the rod and magnetization force plays a crucial role in the velocity distribution and heat transfer enhancement.

Flow characteristics of three typical granular materials in near 2D moving beds

The granular materials involved in industrial moving beds vary widely, and the corresponding flow characteristics differ. This paper compares the flow characteristics of three kinds of typical granular materials, namely, glass beads, corundum beads, and coarse sand. The repose, internal friction, and particle-wall friction angles of these materials are measured, and the flow characteristics of these materials in near 2D silos, in moving beds with aligned pipes and staggered pipes are studied by particle image velocimetry (PIV). Detailed results regarding the vertical velocity distributions, horizontal velocity distributions, local velocity field surrounding pipes, and dimensionless tangential velocity distribution around pipes of the three granular materials are revealed and compared. The mass flow index of silos, the kinetic energy correction factor in certain cross sections and average dimensionless tangential velocities around pipes are calculated to reveal the similarities and differences of flow characteristics for different granular materials in moving beds.

An improved CFD simulation for investigation of the sand particles flow behavior in the sand shooting process

The flow behavior of sand particles has been examined by computational fluid dynamics (CFD) and experimental validations in sand shooting process. To avoid over-estimating the drag force between gas and solid phases, the energy minimization multiscale model(EMMS)has been incorporated. An applicable value of grid size is determined by grid dependency study. Three specularity coefficients are simulated to get an insight into the influence on the flow hydrodynamics of sand particles. The specularity coefficient affects tangential velocity and volume distribution of sand particles. No slip wall boundary condition is in better agreement with experimental data. With validation of sand shooting experiment, agreement is achieved between experiment images and simulation results. A comparison between EMMS drag model and Gidaspow model has been discussed in terms of simulating particles flow behavior with different particle diameters. The EMMS drag model has an accuracy prediction especially for smaller particles and dense flow.

Improved installation of gas filtration at thermal power plants in the preparation of fuel for urban energy systems

In accordance with the concept of development and modernization of energy, improvement of energy supply systems of LLC Gazprom processing enterprises will be aimed at the creation of highly efficient energy complexes and gas saving through the introduction of new combined units based on gas turbine units (GTU), providing a minimum level of costs. Improving the infrastructure of power equipment of gas processing enterprises, including fuel treatment systems, determines the efficiency of its operation. The improved design of the cyclone filter is proposed for the modernization of the gas filtration line of the fuel treatment system in order to improve the reliability of both the infrastructure and the energy systems and complexes. The device can be used for separation of suspensions at the point of gas preparation of the KS and GDS, including for gas turbine and combined cycle power plants TPP. The results of bench tests of the proposed design of the cyclone filter and numerical studies of the aerodynamic parameters of the cyclone based on the methods of Computational Fluid Dynamics (CFD). The distributions of tangential and axial flow velocities in the annular space of the cyclone are obtained in the field experiment. Similar devices can also be used to increase the degree of purification from fine particles of PM10, PM2,5 atmospheric emissions of energy systems, due to the reduction of the size of the captured particles from the average values for

Turbulent Flow Measurements near the Discharge Port of a Screw Compressor

Mean flow and turbulence characteristics have been measured within the male and female rotors close to the discharge port of a double screw compressor at different radial positions, two axial positions from the exit port, Hp, and two radial planes, αp. Cycle-resolved axial and tangential mean flow measurements and their corresponding turbulent velocity fluctuations were made over a time window of 1° using a laser Doppler velocimetry, LDV, system. Measurements were performed through two transparent windows near the inlet of the discharge port inside the male and female working chambers. The results revealed a highly complex 3-D flow within the male and female working chambers, in particular, near the discharge port with two distinct flow zones 1 and 2 before and after the opening of the port, respectively. The flow in zone 1 was controlled by the rotor motion while in zone 2 was greatly influenced by the discharge process. In zone 2, both components of mean velocities were subjected to a sudden increase in velocity forming strong axial and tangential jet flows due to rapid change in pressure across the port as the flow is exposed into the discharge port. It was found that the flow structures have been affected considerably by the position of the discharge port, radial planes and radial positions. Axial and tangential RMS velocity distributions within both rotors were found to be relatively high and less affected by the flow changes of zones 1 and 2 with almost uniform distribution. The measured magnitudes of axial and tangential RMS velocities suggest it would be reasonable to assume the local turbulence to be isotropic for the modelling purposes. To authors’ knowledge, the results are unique, original and in great details not only to describe the flow structure, but also, they can be used in CFD codes to establish a reliable model of the flow and pressure distribution within twin screw machines.

Experimental and computational analysis of a cyclone separator with a novel vortex finder

Simulations and experimental methods were used to evaluate the performance of notched vortex finders in a cyclone separator with a tangential inlet. The vortex finder was cut obliquely. Four types of cyclone separators with different vortex finder structures were studied. One of the separators did not have a cut at the vortex finder, while the other separators had cuts located at 45°, 135°, and 225° opposite to the inlet of the separator. An unsteady Reynolds stress transport model (RSM) was implemented for the gas-phase flow field, and a discrete phase model (DPM) was adopted for the particle phase. Considering the asymmetric flow field in the separator with a tangential inlet, the distribution of axial velocity, tangential velocity, and radial velocity along the circumference were discussed, and the effect of the notched vortex finder on the flow field in the separator was shown in detail. The grade efficiencies of the four models were compared. The simulation results show that the separation performances of the cyclone separators with notched vortex finders were greatly improved over the separation performance of the original separator. When the cut position was located 225° opposite to the inlet, the separation performance of the cyclone separator improved most obviously. Experiments were carried out to confirm the advantages of notched vortex finders. The experimental results show that a separator with a notched vortex finder at 225° can remove particles greater than 3.5μm in diameter, while a normal separator can remove only particles greater than 8μm in diameter. Furthermore, the total separation efficiency of the original separator is 0.73, while the total separation efficiency of the improved separator is 0.76.

Effect of the particle injection position on the performance of a cyclonic gas solids classifier

This study investigates the effect of the particle injection position on particle classification performance of a cyclonic classifier. The Rankine-type vortex flow in the cyclonic classifier is divided into three characteristic regions from the wall to the center according to the tangential and axial velocity distribution. Three representative particle injection positions are selected within those regions. The particle flow and the particle residence time are investigated via the Reynolds stress and discrete phase models. The simulation result shows that particles injected in the near-wall region provide the highest separation efficiency but the lowest classification accuracy. The residence time of particles injected within the region of maximum tangential gas velocity is shorter, facilitating a rapid and efficient particle classification. The powder classification experiment result confirms the simulation result and the feasibility of this method to enhance the separation degree of particles in the vortex flow.

Tornado loss model of Oklahoma and Kansas, United States, based on the historical tornado data and Monte Carlo simulation

This paper introduces a new tornado loss assessment model for one-family and two-family wood frame residential buildings in the states of Kansas (KS) and Oklahoma (OK), United States. The model belongs to the group of Monte Carlo simulations and consists of five main modules: (1) tornado climatology; (2) tornado intensity and tornado track geometry; (3) exposure map; (4) fragility and vulnerability functions; and (5) financial module that is used to calculate the resulting damages. In addition, two analytical formulations of radial distribution of tangential velocity in tornado vortex were implemented in the tornado intensity module—Rankine Vortex (RV) and Modified Rankine Vortex (MRV) models. Using the MRV tornado model, the resulting mean aggregated annual expected losses for the return period of 1000 years are US$ 392,080,526.8 and US$ 641,281,336.0 for KS and OK, respectively. Although house prices in KS are higher than in OK, the higher occurrence of tornadoes in OK combined with the larger population of OK (i.e., larger density of houses) result in the increased tornado losses for OK. The losses derived using the MRV module are higher than the losses from the RV module due to the RV module underestimating the tornado tangential velocity. Furthermore, the losses predicted by the current model using the MRV formulation are less than the estimated losses from the previous version of the model (Romanic et al., 2016). The model is also tested for the case of a single tornado track positioned over suburban area of Oklahoma City, OK.

The Numerical Analysis of Hydrodynamic Characteristics of Ducted Propeller by using SST k-ω Model

Hydrodynamic characteristics of the four-blade ducted propeller are numerically simulated by CFD method. The hydrodynamic performance of the propeller is analyzed by the SST k-ω Model, including the external characteristic parameters such as thrust and torque. The forward velocity at the propeller surface of the ducted propeller, the distribution of the induced velocity along the propeller surface, and the relationship between the propeller thrust and the surrounding velocity field are analyzed. The pressure distribution on the inner wall of the conduct is complicated. The pressure in the front half of the inner wall is small and large in the rear half. Axial, radial and tangential velocity distributions of sections at different distances from the paddle surface are calculated. The velocities on the dorsal side of the propellers are significantly higher than that on the foliar side and lower near the conduit.

Design of Spiral Casing of Francis Turbine for Micro Hydro Applications

Spiral casing is an important component of Francis turbine for even distribution of kinetic and potential energy of water so as to achieve the required reaction for better performance of the runner. Optimal design and analysis of spiral configuration is challenging, especially when the turbine is operating in a low head range due to the necessity of a large cross-sectional area of the casing to accumulate the large flow. The main objective of this study is to design the best configuration of cross section of spiral casing which have a very minimal pressure loss and can provide required inlet flow condition for stay vanes. For this, spiral casing configurations following free-vortex theory with different cross sections i.e. circular, trapezoidal and square are designed and analysed numerically. Pressure, radial and tangential velocity distributions are compared for different cross section of spiral casing suitable for micro hydro applications. Considering the ease of manufacturing, flexibility of dimension adjustments and comparable performance with that of the circular spiral casing, trapezoidal casing is found to be an appropriate alternative for such applications.