CFD Analysis of Single and Multiphase Flow Characteristics in Elbow

Introduction: We examined the viability of pairing wire-obtained flow pressure data with computational fluid dynamic (CFD) analysis for accurate patient-specific 3D reconstruction of flow through cerebral vessels—an approach that provides comprehensive velocity data and other flow parameters to assist the preventative diagnosis of cerebral stenosis. Methods: Two physical phantom models of a cerebral stenosis—differing in regard to vascular morphology at and around the stenosis—were prepared, filled with physiological saline and connected individually to a flow pump (Vascular Simulations LLC Left Heart Replicator) applying pulsatile flow. Pressure measurements were taken upstream of the stenosis by microcatheter-guided wires to define an inlet boundary condition for CFD analysis. Pressure and velocity at 2 cm proximal to stenosis, the stenosis inlet, the stenosis outlet, and 2 cm distal to stenosis were measured to validate the CFD simulated flow. Results: Excellent agreement was observed between CFD and wire-measured time-dependent flow pressure, with the expected pulsatile behavior observed at each location. Between the two methods, differences in maximum systolic pressures ranged between |0.73±0.72|% and |3.90±0.74|%. Differences in minimum diastolic pressures ranged between |1.79±1.33|% and |9.08±1.42|%. Velocity data from wire measurements lacked pulsatile behavior and showed differences ranging between |2.93±5.20|% and |120.10±2.91|% from CFD-obtained measurements, which did show correct pulsatile behavior. Larger discrepancies were strongly associated with areas of higher CFD predicted velocities (r=0.86). Conclusion: Guidewire flow measurements provided CFD analysis with accurate inlet boundary conditions and validated CFD simulation results. CFD analysis allowed for detailed visualization of key flow parameters that may be difficult to physically measure—such as velocity—that are relevant for understanding risk factors associated with cerebral stenosis on a case-by-case basis.

The Solar energy is renewable energy resources which is available in plenty in our country. So far many research works is carried out in the field of solar energy like solar ponds, solar cells, solar heaters, solar chimney etc. There are many effective methods to tap the solar energy. Solar chimney power generation is one of the latest methods of producing high energy output from sun. In solar chimney the electricity is generated by rotating the turbine at the base of the chimney by the warm rising air through the chimney. In solar chimney; the power is generated by the principle of buoyancy. In Buoyancy driven Solar Engine, atmospheric air inside the chimney gets heated by hot sunlight and it rises up. The rising warm air is converged through the convergent nozzle, producing kinetic energy at the throat of the convergent nozzle. A wind turbine was installed at the entrance of the air for generating electricity. Height of the chimney and the solar absorbers are the important parameters which decides the velocity of air flowing through the wind turbine. In this paper the velocity of air at convergent throat is obtained by mathematical calculations for 1.5 meter chimney height and 1 square meter solar absorber area. The Computational fluid dynamics (CFD) analysis of buoyancy driven solar engine (BDSE) is done for the same chimney parameters. Finally a pilot model experimental setup of BDSE is made and the results obtained from the experimental set up is compared and with the results of theoretical design and CFD analysis.

CFD Simulations of Abnormal Flow in Horizontal Pipes for Offshore Hydrocarbon Transport

Background: Fractional flow reserve (FFR) is used to evaluate the need for percutaneous coronary intervention (PCI) in cases of moderate stenosis of the coronary artery. Recently, diagnostic imaging support with computational fluid dynamics (CFD) analysis has been garnering attention. This study defines the relationship between FFR conducted for cardiac catheterization and CFD analyses conducted using coronary computed tomography (CT) for moderate stenosis, in addition to considering whether wall pressure (WP) and wall shear stress (WSS) can be used to evaluate ischemia.Methods and Results: Cases in which FFR was measured via coronary CT and cardiac catheterization was performed within 3 months were collected retrospectively. In the CFD analysis, WP and WSS were calculated and compared with FFR. Three groups were created to compare results of CFD analysis and FFR values according to the location of the stenosis: the right coronary artery, the left anterior descending artery, and the left circumflex artery. There was a correlation between FFR and WSS according to CFD analysis for moderate stenosis of the coronary artery, with a cut-off value for treatment able to be calculated.Conclusions: The results of this study suggest that ischemia can be evaluated by conducting CFD analysis (WSS) using coronary CT.

Pumping efficiency and rotordynamic stability are paramount to subsea multiphase pump operation since, during the life of a well, the process fluid transitions from a pure liquid to a mixture of gas in the liquid to just gas. Circumferentially grooved seals commonly serve as balance pistons in pumps while also restricting secondary flow. Prior experimental results obtained with a grooved seal operating with a mixture of air and mineral oil show the seal rotordynamic force coefficients vary significantly with the gas volume fraction (GVF). This paper, complementing an exhaustive experimental program, presents a computational fluid dynamics (CFD) analysis to predict the leakage and dynamic force coefficients of a circumferentially grooved seal supplied with air in an oil mixture with a GVF varying from 0 to 0.7. The test seal has 14 grooves, an overall axial length of 43.6 mm, and radial clearance of 0.211 mm. The 127 mm diameter rotor spins at constant angular speed (Ω = 3500 rpm). The mixture enters the seal at a supply pressure (Pin) of 2.9 bar(a), and the seal exit pressure (Pout) is 1 bar(a). The CFD two-phase flow simulations utilize the Euler–Euler multiphase model to predict the mass flowrate and the pressure field as a function of the operating conditions. Using a multi-frequency shaft orbit motion method, the CFD simulations deliver the variations of reaction force on the rotor with respect to the excitation frequency. For a pure liquid condition (GVF = 0), both the CFD and experimental results produce constant stiffness, damping, and added mass coefficients. The experimental and CFD results demonstrate the seal rotordynamic force coefficients are quite sensitive to the GVF. When introducing a small amount of air into the oil (GVF = 0.1), the direct damping coefficient increases by approximately 10%. For operation with a mixture with inlet GVF > 0.1, the cross-coupled stiffness coefficients develop strong frequency-dependent characteristics. In contrast, the direct damping coefficient has a negligible variation with excitation frequency. The CFD predictions, as well as the experimental results, evidence that air injection in a liquid stream can significantly change the seal rotordynamic characteristics, and thus can affect the rotordynamic stability of a pump. An accurate CFD analysis provides engineers to design reliable grooved seals operating under two-phase flow conditions.

Passive cooling of the PBMR spent and used fuel tanks

Modeling and experimental analysis of packed column for SO2 emission control process

This research has focused on optimizing operating parameters of a multi-lamp In-duct UVC air disinfection system through Computational Fluid Dynamics (CFD) analysis. The efficacy of the system has highly dependent on proper system design to ensure both effective disinfection and minimal energy consumption. In this study five configurations with varying numbers of Ultraviolet-C (UVC) lamps (3, 6, 9, 11, 13) of wavelength 254nm has been investigated through CFD analysis. The velocity and irradiation profiles corresponding to different lamp configurations has been studied to optimize number of lamps. Further orientation profile has been explored at the original vertical position, 30-degree rotation, 60-degree rotation, and horizontal position to optimize position of lamps within duct. The 13 lamps arrangement yields maximum germicidal action has been evidenced from velocity and irradiation profiles. The orientation profiles has revealed that a uniform vertical arrangement of lamps offers best position for achieving the maximum UV dose. Standard deviation calculations for UV dose distribution across different orientation positions has confirmed that a vertical arrangement provide an uniform dose distribution. In comparision to earlier studies, optimized 13-lamp configuration has resulted in a more than 60% increase in average uv dose, superior dose uniformity, and higher germicidal efficacy than conventional configurations.

The objective of this paper is to present the performance comparison of 2D Computational Fluid Dynamics (CFD) analysis with experimental analysis of 0.6 m impulse turbine with fixed guide vanes for both 0.6 and 0.7 hub to tip ratio (H/T). Also the comparison of 2D CFD analysis of the said turbine with different values of H/T ranging from 0.5 to 0.7. A 2D-cascade model was used for CFD analysis while uni-directional steady flow was used for experimental analysis. The blade and guide vane geometries are based on 0.6 m rotor diameter, with optimum profile, and different H/T of 0.5, 0.6 and 0.7. It was concluded from 2D CFD analysis that 0.5 H/T ratio performances was higher than that of 0.6 and 0.7 H/T at peak efficiency and the operational flow range for 0.5 H/T was found to be wider than that of 0.6 and 0.7 H/T ratio.

PurposeWind loading calculations are currently performed according to the ASCE 7 standard. Values in this standard were estimated from simplified models that do not necessarily take into account relevant flow characteristics. Thus, the standard does not have provisions to handle the majority of rooftop photovoltaic (PV) systems. Accurate solutions for this problem can be produced using a full-fledged three-dimensional computational fluid dynamics (CFD) analysis. Unfortunately, CFD requires enormous computation times, and its use would be unsuitable for this application which requires real-time solutions. To this end, a real-time response framework based on the proper orthogonal decomposition (POD) method is proposed.Design/methodology/approachA real-time response framework based on the POD method was used. This framework used beforehand and off-line CFD solutions from an extensive data set developed using a predefined design space. Solutions were organized to form the basis snapshots of a POD matrix. The interpolation network using a radial-basis function (RBF) was used to predict the solution from the POD method given a set of values of the design variables. The results presented assume varying design variables for wind speed and direction on typical PV roof installations.FindingsThe trained POD–RBF interpolation network was tested and validated by performing the fast-algebraic interpolation to obtain the pressure distribution on the PV system surface and they were compared to actual grid-converged fully turbulent 3D CFD solutions at the specified values of the design variables. The POD network was validated and proved that large-scale CFD problems can be parametrized and simplified by using this framework.Originality/valueThe solar power industry, engineering design firms and the society as a whole could realize significant savings with the availability of a real-time in situ wind-load calculator that can prove essential for plug-and-play installation of PV systems. Additionally, this technology allows for automated parametric design optimization to arrive at the best fit for a set of given operating conditions. All these tasks are currently prohibited because of the massive computational resources and time required to address large-scale CFD analysis problems, all made possible by a simple but robust technology that can yield massive savings for the solar industry.

This paper reports the findings of a mixing study involving a variety of “aerodynamic ramp” fuel injectors. Computational fluid dynamics analysis was employed to study various spanwise injector spacings, injector yaw angless, injector transverse angles, and dynamic pressure ratios. The resulting data were studied to determine the impact of each change on performance. One configuration was also tested on a coarser grid; grid convergence was considered acceptable. Analyses prove that neither spanwise injector displacement nor yaw is necessary for the formation of strong streamwise vortices. In general, the elimination of spanwise injector displacement and yaw reduces losses. Centerward displacement and yaw enhance penetration but reduce mixing; the converse is also true. Increasing the transverse angle of centerline injectors improves both penetration and mixing but strengthens shocks and enhances losses; increasing the dynamic pressure ratio produces a similar effect. INTRODUCTION The design of fuel injectors for supersonic combustion engines is among the most formidable tasks facing high-speed aerodynamicists. Achieving mixing adequate for combustion in an environment with millisecond residence times is only the first of many challenges the designer must meet. Drag, thermal degradation, and even machinability are all unavoidable factors in the design of a successful supersonic combustion engine. Because intrusive injectors tend to increase drag, reduce pressure recovery, promote thermal degradation, and complicate fabrication, many researchers have turned their attention to flush-mounted injectors. Direct comparisons between flush-mounted injectors and leading intrusive designs have demonstrated the viability of flush-mounted injectors for efficient fuel mixing. ’ Furthermore, flush-mounted injectors are * Research Scientist, Member AIAA. ’ Aerospace Engineer, Senior Member AIAA. particularly advantageous in combined-cycle systems and engine-off portions of supersonic flight, because the injectors are essentially invisible to the flow when not fueled. By contrast, intrusive injectors carry a substantial drag penalty, especially in unfueled flight modes (for example, during ejector or rocket modes or unpowered cruise). For these reasons flush-mounted injectors are strong contenders for the fueling systems of any supersonic combustion engine design. The advantages of flush-mounted fuel injectors have been known for many years, and various researchers have investigated a great number of flush-mounted injector designs.’ Of particular interest are those research programs which consider the performance of a group of flush-mounted injectors, arranged in such a manner as to allow the injectors to interact favorably with each other. One such design was originally conceived as an “aerodynamic ramp,” an attempt to mimic the geometry, and therefore the performance, of a swept-ramp injector with fluid from nine low-angled, flush-mounted fuel injectors arranged in three columns of three injectors each.3 (See Fig. 1.) Subsequent analysis indicated that, while the design showed considerable promise as a scheme for fuel injection and mixing, its performance was in fact quite different from that of an actual ramp injector.” Computational fluid dynamics (CFD) analysis of the same design provided a great deal of insight into the details of the jet interactions and into the dependence of injector performance upon these details.5 One outcome of the above-mentioned CFD analysis was a list of suggestions for design modifications and possible improvements. With these suggestions as a starting point, work is underway to improve the aerodynamic ramp. Early efforts in this research program were reported in Refs. 6 and 7, and support two conclusions. First, a design process based on the CFD analysis has indeed led to a number of Copyright

The increasing global demand for sustainable energy solutions has driven research into pico-hydropower systems as an efficient and environmentally friendly method for harnessing renewable energy. This study focuses on the optimization of free-flow water turbine applications using Computational Fluid Dynamics (CFD) analysis. Free-flow turbines, which operate in rivers or channels without the need for large-scale infrastructure, offer significant advantages in terms of cost, ecological impact, and ease of deployment. The research employs advanced CFD techniques to evaluate and enhance the performance of a turbine under various conditions. Key design parameters, including water flow rates of 2 L/s, water heads of less 5 m, turbine diameters of 0.75 m and 1 m, nozzle sizes at 10 mm, 12 mm and 15 mm and the pipe diameters setting of 0.75 inch and 1 inch. Optimization algorithms are integrated with CFD simulations to identify the most efficient configurations. The findings reveal the critical role of hydrodynamic optimization in improving the energy conversion efficiency of pico-hydropower turbines. The results identified the 1 m turbine with 0.75 inch pipe size at 12 mm nozzle diameter give the optimal design, achieving a maximum power out at 100 W with 5 m and 3 m water head. The optimized turbine design demonstrated a significant improvement in performance compared to existing models, validating the potential of CFD as a powerful tool for innovation in hydropower technology.

The actual underlying mechanisms of acute type A aortic dissection (AAAD) are not well understood. The present study aimed to elucidate the mechanism of AAAD using computational fluid dynamics (CFD) analysis. We performed CFD analysis using patient-specific computed tomography imaging in 3 healthy control cases and 3 patients with AAAD. From computed tomography images, we made a healthy control model or pre-dissection model for CFD analysis. Pulsatile cardiac flow during one cardiac cycle was simulated, and a three-dimensional flow streamline was visualized to evaluate flow velocity, wall shear stress and oscillatory shear index (OSI). In healthy controls, the transvalvular aortic flow was parallel to the ascending aorta. There was no spotty high OSI area at the ascending aorta. In pre-dissection patients, accelerated transvalvular aortic flow was towards the posterolateral ascending aorta. The vortex flow was observed on the side of the lesser curvature in mid-systole and expanded throughout the entire ascending aorta during diastole. Systolic wall shear stress was high due to the accelerated aortic blood flow on the side of the greater curvature of the ascending aorta. On the side of the lesser curvature, high OSI areas were observed around the vortex flow. In all pre-dissection cases, a spotty high OSI area was in close proximity to the actual primary entry site of the future AAAD. The pre-onset high OSI area with vortex flow is closely associated with the future primary entry site. Therefore, we can elucidate the mechanism of AAAD with CFD analysis.

A computational fluid dynamics (CFD) analysis is conducted on the flow of Newtonian and non-Newtonian fluids in annuli including the effect of inner pipe rotation. A practical numerical model is proposed that accurately estimates the annular frictional pressure losses with and without the inner pipe rotation. Experiments are conducted at a 91 ft. long flow loop using various fluids that can be characterized as Yield Power Law (YPL). A commercial CFD software is used to validate the proposed numerical approach. A comprehensive comparison of the proposed model, CFD results, experimental results, the published experimental results and most widely used models from the literature is presented. The experimental setup simulates horizontal wellbore applications, which are increasingly prevalent due to recent shale plays. Today, since most drilling fluids show YPL behavior, YPL fluids with a wide range of rheological properties are used as test fluids in this study. The numerical model is coupled with a stability criterion that determines the onset and offset of the transitional flow between laminar and turbulent regions. The velocity profiles of a wide range of diameter ratios, Taylor and Reynolds numbers are presented. Various degrees of eccentricity are analyzed in terms of pressure profile and flow stability with the proposed method. The results from the experiments show significantly reduced pressure drops in fully eccentric annuli compared to concentric geometry. An increase in pressure loss is observed as the pipe is rotated while it is eccentric. The comparisons between the models indicate that the slot approximation can result in large errors especially when the diameter ratio is low. A 3D wellbore can be evaluated with grids using the proposed numerical method and the local stability criterion, which leads to accurate pressure loss estimations. Grid analysis can show the flow state profile and the pressure loss profile of a wellbore, which has potential to optimize operations in real-time or in the design phase. This study contributes to a better understanding of flow in annuli. The results obtained from this study are useful to predict the transition and the annular frictional pressure loss profiles more accurately than existing methods. Potential applications include risk avoidance and optimized operations.

Mechanical Heating Ventilation and Air-Conditioning (HVAC) systems account for 60% of the total energy consumption of buildings. As a sector, buildings contributes about 40% of the total global energy demand. By using passive technology coupled with natural ventilation from wind towers, significant amounts of energy can be saved, reducing the emissions of greenhouse gases. In this study, the development of Computational Fluid Dynamics (CFD) analysis in aiding the development of wind towers was explored. Initial concepts of simple wind tower mechanics to detailed design of wind towers which integrate modifications specifically to improve the efficiency of wind towers were detailed. From this, using CFD analysis, heat transfer devices were integrated into a wind tower to provide cooling for incoming air, thus negating the reliance on mechanical HVAC systems. A commercial CFD code Fluent was used in this study to simulate the airflow inside the wind tower model with the heat transfer devices. Scaled wind tunnel testing was used to validate the computational model. The airflow supply velocity was measured and compared with the numerical results and good correlation was observed. Additionally, the spacing between the heat transfer devices was varied to optimise the performance. The technology presented here is subject to a patent application (PCT/GB2014/052263).