Results Of Fluid Flow Simulation Research Articles

Non-uniform knot (NUK) SIAC post-processing of flow fields produced through unstructured grid adaptation and optimization

As the finite element method (FEM) and the finite volume method (FVM), both their traditional and high-order variants, continue their proliferation into various applied engineering disciplines, adaptive mesh refinement and optimization strategies have increased in their importance when solving real-world computational fluid mechanics applications. The post-processing and visualization of the resulting flow fields present two significant analysis and visualization challenges. The first challenge is the handling of elemental continuity, which is often only C0 continuous (in continuous Galerkin methods) or piecewise discontinuous (in discontinuous Galerkin methods). The second challenge is that, depending on the flow regime and the geometric configurations for which adaptive meshing strategies are used, the meshes generated are often highly anisotropic. The (uniform knot) line-SIAC (L-SIAC) filter has been proposed as a way of handling elemental continuity issues in an accuracy-conserving manner with the added benefit of casting the data in a smooth context even if the representation is element discontinuous. In this paper, we demonstrate that the state-of-the-art adaptive L-SIAC filter, designed for mildly anisotropic meshes, suffers degradation in the quality of the post-processed solution when applied to the types of highly anisotropic meshes produced through adaptive mesh refinement and optimization. Hence, a new Non-Uniform Knot (NUK) L-SIAC filter is proposed that automatically conforms to the underlying mesh anisotropy. We demonstrate that the new filter behaves similarly to the adaptive L-SIAC filter when applied to uniform and mildly anisotropic meshes, and furthermore we show the superiority of the NUK L-SIAC filter when applied to highly anisotropic meshes. The newly formulated filter is applied to 2D canonical scalar fields and used to visualize 2D and 3D fluid flow simulation results.

Upgrading recycling of Al–7 wt%Si alloys using electromagnetic force in directional solidification

The highly reactive chemical nature of aluminum makes it production energy-intensive or essentially impossible to extract alloying elements from Al-based liquids. Using molten salt fluxing and electrolysis processes can effectively refine coarse Al scraps. However, the generation of toxic gases and hazardous dross during these processes can cause significant environmental protection challenges and result in notable social concerns. Therefore, the primary recycling of post-consumer Al in industries currently proceeds mainly in a cascade manner, which is not sustainable when considering the Al cycle trends in the coming decades. Herein, we develop a novel process to separate primary Al from the crystallizing liquid when a constant electromagnetic force (EMF) is applied. Using this technique, we successfully upgraded Al–7mass%Si (hereafter, unless specified otherwise) alloy to approximately Al–3.6%Si in directional solidification. The separation mechanism was discussed in terms of the electrical properties of the respective phases during solidification. Fluid flow simulation results were applied to elucidate the separation behavior in the alloy. The upper and lower limits to separate the crystallizing alloy into an Al-rich and Si-rich areas were determined when the controlling factors were clarified, which made it possible to scale up the present laboratory-based setup to an industrial level. Moreover, the energy consumption of the process was slightly higher than that required for remelting only. Using the EMF technique to separate the crystallizing alloy into Al-rich and Si-rich regions did not produce hazardous dross or toxic gases. This energy-saving and eco-friendly process can provide a breakthrough to overcome the “dead metal” crisis and thus realize sustainability by upgrading recycling of post-consumer hypoeutectic Al–Si casting alloys.

4D petroelastic model calibration using time-lapse seismic signal

In the last two decades, 4D seismic monitoring has become a widely used technique for oil and gas field production. Modeling studies are a standard for defining reservoir monitoring plans, optimizing survey design, and justifying the expense of data acquisition. Discrepancies between 4D seismic data and synthetic results can be analyzed through petroelastic modeling of reservoir simulations. However, assuming that a history match is available and that the reservoir model and fluid-flow simulation results can be trusted, characterization of pressure and fluid changes in the field remain challenging. A workflow is proposed to adjust the 4D petroelastic model (PEM) to better fit 4D seismic attributes with the dynamic behavior of the reservoir. The input data for 4D inversion consist of multiple broadband 4D-compliant processed base and monitor surveys recorded in a highly depleted clastic field offshore Africa. The broadband inversion results greatly reduce the background noise level, enhance the signal-to-noise ratio, and improve the definition of 4D signals. Due to various production effects all over the field, a new global calibration workflow to speed up the 4D petroelastic model adjustment is proposed. The combination of good 4D seismic inversions and a well-calibrated PEM is expected to have a significant impact on the reservoir monitoring. During the calibration process, reservoir model discrepancies with 4D seismic attributes can be identified, suggesting some updates of the reservoir model. In addition, when further monitors are considered, the calibrated 4D PEM provides more reliable predictability.

Investigating NMR-based absolute and relative permeability models of sandstone using digital rock techniques

Absolute permeability determines fluid production capacity, and relative permeability determines the produced fluid types, and their accurate calculations are critical for evaluating hydrocarbon-bearing formations. In oil/gas fields, the nuclear magnetic resonance (NMR) logging tool has been widely used due to its unique advantage of directly detecting the rock pores. However, this tool cannot measure absolute permeability or relative permeability directly. There exist many approaches for estimating NMR-based permeabilities, but most of them lack the basic understandings of fluid flow characteristics in micro-pores. To investigate NMR-based absolute and relative permeability models of sandstone , we suggest three types of pores, i.e., non-flowing bound water pores , slow-flowing free water pores, and fast-flowing free water pores, and incorporate them into the permeability calculations. The digital rock technique was utilized to study fluid flow mechanisms. Lattice Boltzmann method (LBM) was applied on two constructed three-dimensional digital rocks to calculate fluid flow velocity field distributions and absolute permeabilities. From the fluid flow simulation results, it was found that bound water exists not only in small pores but also in medium-sized pores and big pores. By comparing the permeability values of digital rocks with various porosities, we demonstrated that fast-flowing free water pores have the highest contribution to absolute permeability. Five relative permeability calculation models were investigated, where we found that the best link between the T 2 spectrum and relative permeability curve was the pore size distribution index. The obtained results indicated that the traditional Coates model combined with the spectral bulk volume irreducible method and the Brooks-Corey model are high-precision models for calculating the NMR-based absolute and relative permeabilities in sandstone reservoirs. • Three fluid flow velocity-based types of pores were investigated. • Fluid flow characteristics and their impacts on permeability were analyzed. • The three-dimensional spatial distribution of bound water was studied. • The accuracies of five relative permeability calculation models were compared.

SIMULATION OF WATER DROPLET IMPINGEMENT ON A HEATED SURFACE- SINGLE AND DOUBLE DROPLETS

The present numerical work is concerned with the single drop and double drops impingement on a heated surface. Fluid flow and heat transfer coefficients were modeled using a volume of fluid (VOF) code. The stainless –steel thin plate surface is uniformly heated to reach a constant temperature at (50C°), this was done by using relatively thicker plate underneath the heated plate. The thick plate is made of high conductivity aluminum alloy 2mm thickness. Relatively a lower temperature water drop is used for cooling to ensure that drop temperature remains below the boiling point of water. The drop –plate initial impingement distances were varied in the range (10-60) cm which represent an impact velocity in the range (1.4-3.4) m/s. The single drop fluid flow simulation results are compared with that in the literature, while the heat transfer fluid flow results are represented as instantons heat transfer coefficient variation as alternative to values of heat flux on the surface. Double drops impingement results are then presented and its features are compared to the single drop. Results show that the flow characteristics for the double drops are similar to the single drop at small distances with smaller coverage areas during impingement with lower heat removal rates. As distances increase rebound and splash occurs leading to bigger coverage areas during impingement with relatively smaller heat coefficients compared to the single drop one. The present results shows the same behavior for drop deformation when compared with M.pasandideh-Fard et al. [1] numerical results with an agreement of 90 % and 95 % in calculations the spread factor and impact velocities respectively. The calculated average heat coefficients show acceptable values with that given in literature.

Systematic assessment of the anode flow field hydrodynamics in a new circular PEM water electrolyser

In this work, we investigated the key underlying flow characteristics of a circular unit cell proton exchange membrane (PEM) water electrolyser. In particular, we focused on investigating anode flow field design using computational fluid dynamics (CFD) tool. Transient, 3D single phase fluid flow simulation results were presented, and in-house experiments were conducted for validation against CFD simulation data identifying key performance parameters of the PEM water electrolyser: uniform water distribution, pressure drop and hydraulic retention time. The effects of the water flow rate, inlet and outlet sizing and different number of inlet and outlet configurations were considered. The main observation from the study was discussed to provide insight into the factors affecting the flow pattern. Among the studied flow field design cases, it was found that the average pressure drop decreased with increase in number of inlets, also flow profile can be grouped into different set, depending on number of inlets. The correlation between pressure drop and mean velocity profile for different inlet and outlet configurations provides a useful basis to properly design the high performance PEM water electrolyser.

Research on Fluid Flow and Permeability in Low Porous Rock Sample Using Laboratory and Computational Techniques

The paper presents results of fluid flow simulation in tight rock being potentially gas-bearing formation. Core samples are under careful investigation because of the high cost of production from the well. Numerical simulations allow determining absolute permeability based on computed X-ray tomography images of the rock sample. Computational fluid dynamics (CFD) give the opportunity to use the partial slip Maxwell model for permeability calculations. A detailed 3D geometrical model of the pore space was the input data. These 3D models of the pore space were extracted from the rock sample using highly specialized software poROSE (poROus materials examination SoftwarE, AGH University of Science and Technology, Kraków, Poland), which is the product of close cooperation of petroleum science and industry. The changes in mass flow depended on the pressure difference, and the tangential momentum accommodation coefficient was delivered and used in further quantitative analysis. The results of fluid flow simulations were combined with laboratory measurement results using a gas permeameter. It appeared that for the established parameters and proper fluid flow model (partial slip model, Tangential Momentum Accommodation Coefficient (TMAC), volumetric flow rate values), the obtained absolute permeability was similar to the permeability from the core test analysis.

Numerical modeling of fluid flow in a fault zone: a case of study from Majella Mountain (Italy)

We present the preliminary results of a numerical model of fluid flow in a fault zone, based on field data acquired at the Majella Mountain, (Italy). The fault damage zone is described as a discretely fractured medium, and the fault core as a porous medium. Our model utilizes dfnWorks, a parallelized computational suite, developed at Los Alamos National Laboratory to model the damage zone and characterizes its hydraulic parameters. We present results from the field investigations and the basic computational workflow, along with preliminary results of fluid flow simulations at the scale of the fault.

Investigation on formation of equiaxed zone in low carbon steel slabs

The effects of liquid flow in mold and superheat on the formation of equiaxed zone in continuously cast low carbon steel slabs were discussed in present work. According to the fluid flow simulation results, “washing effect” was found out to bring about numerous equixed nuclei by detaching the dendrite arms at the solidification front in mold, and then the detached dendrites were remelted during sedimentation when the temperature in liquid pool was higher than remelting point. Based on the simulation results of liquid flow combining with the observation of equiaxed zone ratios and composition measurements varied with superheat, a formation mechanism of equiaxed zone was suggested for continuously cast slabs.

Virtual reality aided visualization of fluid flow simulations with application in medical education and diagnostics

Medical education, training and preoperative diagnostics can be drastically improved with advanced technologies, such as virtual reality. The method proposed in this paper enables medical doctors and students to visualize and manipulate three-dimensional models created from CT or MRI scans, and also to analyze the results of fluid flow simulations. Simulation of fluid flow using the finite element method is performed, in order to compute the shear stress on the artery walls. The simulation of motion through the artery is also enabled. The virtual reality system proposed here could shorten the length of training programs and make the education process more effective.

Failure analysis of overhead flow cooling systems of a light naphtha separator tower at a petrochemical plant

In the present research, root causes of fouling in overhead cooling flow of a naphtha separator tower at a petrochemical company in southern Iran were studied. For this purpose, chemical properties of the various deposits present in distinct points inside the cooling systems were analyzed using the Thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) methods. The overhead cooling systems consisted of an air cooler, a drum and a heat exchanger. The results revealed that the vast majority of these deposits had non-organic origin and could be produced by corrosion. To investigate the causes of corrosion, sulfur and chloride content of the fluid at input and output of some process equipments were measured via analytical methods. The results indicated that the fluid temperature reached to 92–94°C in some parts of air cooler exchanger in naphtha overhead flowing system. Within this temperature range, sulfur and chloride compounds were condensed on the wall of the air cooler tubes causing corrosion in these regions. The results of fluid flow simulation inside the heat exchanger showed that the accumulation of corrosion products on the back of the first baffle was the reason for complete fouling of the heat exchanger box after almost 2month. To prevent the fouling deposition and corrosion in overhead flow line, inhibitors were utilized. To investigate the performance of this treatment method, corrosion coupons were also installed at three points along overhead line. The results of XRD analyses showed that the main source of the fouling deposits was produced from a combination of almost 64% corrosion product and 36% dehydro carbon materials.

Ultrasound Open Channel Flow-Speed Measurement Based on the Lateral Directional Echo Observations

Conventional ultrasonic flowmeters have a problem in measuring the small open channel fluid flow. To solve this problem, a lateral observation technique using a single transmitter/receiver transducer attached at the bottom of the pipe was proposed. Pulse echo signals scattered from the particles in the medium were repetitively recorded with a constant time interval. From the slope of the correlation peak amplitude with the variation in pulse echo excitation time, the flow speed of the medium was estimated. The method has an advantage in that the variation in flow speed in the vertical depth direction is directly measured with a minimum measurement space. Moreover, the fluctuations caused by the turbulent water can be avoided compared with the case of a conventional method based on the time estimation method. Bubbles were generated by an aspirator and flour powder was mixed with water as scatterers in the imitated drainage water. The flow speed of water was measured with respect to the inflowing fluid volume. Moreover, vertical flow speed profiles were measured and compared with fluid flow simulation results. The results showed that the precision of the measured flow speed was satisfactory and tolerant against the turbulence of the water flow medium.

Fluid dynamics based modelling of the Falcon concentrator for ultrafine particle beneficiation

Enhanced gravity separators are widely used in mineral beneficiation, as their superior gravity field enables them to separate particles within narrow classes of density and size. This study aims to shed light on the Falcon concentrator’s ability to separate particles within size and density ranges lower than usual, say 5–60 μm and 1.2–3.0 s.g. respectively. As differential particle settling is expected to be the prevailing separation mechanism under such conditions, this study presents the workings of a predictive Falcon separation model that embeds phenomenological fluid and particle flow simulation inside the Falcon’s flowing film. Adding to the novelty of modelling the Falcon concentrator using a fluid mechanics approach, one point of practical significance within this work is the derivation of the Falcon’s partition function from fluid flow simulation results.

Numerical simulation of molten metal flow under vacuum condition in high pressure and low pressure die casting process

The vacuum analysis algorithm was developed to simulate the total system of high pressure die casting process including vacuum vent, cavity and plunger area. The various vacuum degrees (760, 650, 500, 250 and 60 mmHg) were artificially applied in cavity. The filling behaviours of molten metal under the applied vacuum conditions were simulated and compared with those of experiment. The filling amount in cavity was increased with the increase of applied vacuum pressure during partial shot experiments. The simulated filling behaviours of molten metal were relatively well agreed with those of experiment. Through the results of fluid flow simulation, the relationship of filling length and filling velocity with the variation of vacuum pressure was analysed respectively. And it applied to a real die casting product and the internal gas quantity of product was significantly reduced by modification of vacuum gate system.

Fluid flow simulation in a double L-bend pipe with small nozzle outlets

The results of fluid flow simulation in a double L-bend pipe with small nozzle outlets are presented in this paper. The pipe geometry represents a sparger for a mixing process in a tank. The flow simulation was performed with a commercially available computational fluid dynamics package, Star-CD. The effects of the L-bend and small nozzle outlets on the velocity and pressure distributions in the pipe are discussed. The discussion will lead to an improved design of the sparger with the objective of obtaining a uniform fluid discharge from the nozzle outlets.

Fourier spectral method on ensemble architectures

The direct simulation of three-dimensional, unsteady fluid flows, is performed on some of the most powerful parallel computers presently available: Connection Machine-2, Intel i860 and the NCUBE/2. A Fourier pseudospectral method and second-order timestepping scheme is used. Implementation, performance analysis and experimental timings are given. Results of fluid flow simulations on meshes up to 2563 show sustained rates of 520 MFLOPS on the 64 K-node CM-2, 484 MFLOPS on the 1 K-node NCUBE/2 and 103 MFLOPS on the 32-node Intel i860.