Cryopanel cooling with liquid nitrogen and its study by computer simulation

This paper is a review of applications of Finite Element Method (FEM) and Computational Fluid Dynamics (CFD) to evaluate design and performance of intravascular prosthetic devices used clinically today. This study is focused on devices such as stents, flow diverters and heart valves. A stent is a device with mesh which is placed in stenosed blood vessels to overcome flow constriction. Vascular injury and restenosis are two major drawbacks with stenting treatment. Flow diverter is a mesh structure similar to a stent which is passed across the aneurysm neck to divert blood flow from the aneurysm, allowing it to occlude over time. This technique has proven successful in many challenging aneurysm cases, post treatment hemorrhage is a serious problem reported. Mechanical heart valve is placed into the heart to replace malfunction valve. Structural failure of these valves has been reported in many patients. Numerical simulation of such devices can provide important insights about their failure. Finite element method and computational fluid dynamics are the most popular simulation techniques used for this purpose. Many researchers have studied such simulations on these prosthetic devices. It includes modeling of stent to study its mechanical behavior, modeling of deployment and expansion of flow diverter, simulation of heart valve closure etc. Studies on biological condition simulation such as blood flow simulation in human aorta, multidimensional modeling of carotid artery blood flow etc. are also discussed in brief. Similar simulations needs to be conducted on occlusion devices used for Ventricular Septal Defect, Patent Ductus Arteriosus, Atrial Septal Defect, Patient Foramen Ovale etc. to evaluate their performance and reduce their failure in future. We apply this for the first time to show ballooning of an aneurysm.

In the research and development of sports, Finite Element Methods (FEMs) and Computer Fluid Dynamics (CFD) are frequently used as tools to examine the transformation of a solid and the flow of a fluid, respectively. This chapter presents a simplified approach to understanding the FEM and CFD and their basic equations, providing the foundation for a theoretical understanding of the two methods. To facilitate an understanding of the application of the FEM to sports research, an analysis of the impact of landing on the human body is presented. Similarly, the application of CFD to sports research is illustrated through a flow analysis around spiked shoes. This chapter will not only enable students to study CFD but also introduce them to literature on the FEM and CFD with regard to other sports to encourage them to study further.

<div class="section abstract"><div class="htmlview paragraph">With the growing demand for electric vehicles (EVs), ensuring the safety and efficiency of battery systems is critical. This paper presents a methodology integrating 3D Finite Element Methods (FEM) and Computational Fluid Dynamics (CFD) to analyze battery systems, effectively mitigating thermal runaway phenomena. By combining FEM and CFD, our methodology provides a comprehensive approach to assess thermal management strategies within battery systems. This integration enables engineers to accurately simulate thermal behavior, predict hotspots, and optimize cooling strategies, thereby mitigating the risk of thermal runaway. Furthermore, our methodology minimizes the reliance on costly and time-intensive physical prototypes and testing. By leveraging virtual simulations, engineers can rapidly iterate through design modifications, assess their impact on thermal performance, and make informed decisions early in the development process. This article demonstrates the efficacy and accuracy of our methodology in analyzing battery systems for electric vehicles. Using Simcenter STAR-CCM+, temperature profiles were analyzed focusing on critical thresholds during the use of a battery pack in an extreme condition. In parallel, finite element analysis via Simcenter 3D indicated thermal stresses leading to catastrophic failure of battery packs. By looping this cycle, it is possible to iteratively define safe and efficient designs. Overall, our approach offers a significant advancement in battery development, facilitating faster and more cost-effective design iterations while ensuring enhanced safety and reliability of EV battery systems.</div></div>

Over recent years, ultrasonic atomization, especially with regard to liquid metals, has become an object of increased interest, mainly from industry, for additive manufacturing, but also from investigators, for research purposes. A strong correlation between the average particle size, distribution of particle sizes, and other process parameters like frequency and vibration amplitude was noted based on the analysis of available theoretical studies, simulations and experiments. The influence of parameters of the atomized fluid-like viscosity and surface tension on process parameters was also mentioned. The objective of this study is further research on the feasibility of using ultrasonic atomization to examine the properties of liquids, especially metals in liquid state. It attempts to close a gap in existing knowledge in searching for a new, possibly simple and cost-effective method to study the properties of liquid metals and further clarify the relationship between ultrasonic atomization parameters (amplitude, frequency, characteristics of metal being spilled on a vibrating surface) and obtained atomization results meant by average particle size and atomization time. Using numerical modeling (finite element method and computational fluid dynamics) as a methodology, combined with tests of using ultrasonic atomization as an instrument to determine properties of liquid metals, was considered as an introduction to a series of experiments. These tests were followed by real experiments that are also presented. At the first stage, numerical modeling was applied to a case of a specific liquid being spilled over a vibrating surface of different angles of inclination and specified, constant frequency and amplitude. The results of the simulation are in line with the current state of knowledge about ultrasonic atomization. Moreover, they can provide some more information on scalability, thus easing the comparison of the results of other experiments presented in the available literature. As a result, the relationship between fluid properties and the average size of atomized particles was demonstrated independently of the surface inclination angle. In the same way, the dependence of successful atomization on a sufficiently thin layer of a liquid was demonstrated. Thirdly, a correlation between the aforementioned layer thickness and the value of vibration amplitude has also been shown. Taking all the above into consideration, ultrasonic atomization can also be considered a research method and can be applied to study the properties of liquid metals. Further research, simulations and experimentation will be conducted to verify, develop and describe this method in full.

Axial-flux electrical machines are ideal candidates as in-wheel motors for electrical vehicles (EVs). Due to their characteristics of high power density and compact structure, thermal management is vital for them. Lowering the temperature of the stator windings can protect the insulation material from rapid degradation and reduce the extra copper losses by decreasing their electrical resistance. Contrary to the widely reported axial-flux permanent magnet synchronous machines, thermal modeling methods of axial-flux induction machines are rarely seen in previous literature. Hence, the present work aims at investigating their thermal response based on both the finite element method (FEM) and computational fluid dynamics (CFD) techniques. In addition, a test rig is built to validate the computed results of these two thermal models with the experimental measurement. The CFD conjugate heat transfer analysis is found to be more accurate than the FEM thermal analysis in predicting the temperature distribution of different components in the machine and the temperature rise of the airflow, with lower than 5 ∘C average errors deviating from the corresponding measured data at three rotation speeds. Additionally, the CFD simulation is able to capture the backflow occurring near the outlets of the casing that has been found during the experiments.

Ischemic heart disease remains a leading cause of mortality worldwide, which has promoted extensive therapeutic efforts. Stenting has emerged as the primary intervention, particularly among individuals aged 70 years and older. The geometric specifications of stents must align with various mechanical performance criteria outlined by regulatory agencies such as the Food and Drug Administration (FDA). Finite element method (FEM) analysis and computational fluid dynamics (CFD) serve as essential tools to assess the mechanical performance parameters of stents. However, the growing complexity of the numerical models presents significant challenges. Herein, we propose a method to determine the mechanical performance parameters of stents using a simplified FEM model comprising solid and shell elements. In addition, a baseline model of a stent is developed and validated with experimental data, considering parameters such as foreshortening, radial recoil, radial recoil index, and radial stiffness of stents. The results of the simplified FEM model agree well with the baseline model, decreasing up to 80% in computational time. This method can be employed to design stents with specific mechanical performance parameters that satisfy the requirements of each patient.

This study addresses the selection and application of composite materials for aerospace systems operating in extreme environmental conditions, with a particular focus on high-altitude pseudo-satellites (HAPS). This research is centered on the development of a 400 kg autonomous aerial vehicle (AAV) capable of sustained operations at altitudes of up to 30 km. KMU-3's microstructure, comprising high-modulus carbon fibers (5-7 µm diameter) in a 5-211B epoxy matrix, provides a high specific strength (1000-2500 MPa), low density (1.6-1.8 g/cm3), and thermal stability (-60 °C to +600 °C), ensuring structural integrity in stratospheric conditions. The mechanical, thermal, and aerodynamic properties of KMU-3-based truss structures were evaluated using finite element method (FEM) simulations, computational fluid dynamics (CFD) analysis, and experimental prototyping. The results indicate that ultra-thin KMU-3 with a wall thickness of 0.1 mm maintains structural integrity under dynamic loads while minimizing overall mass. A novel thermal bonding technique employing 5-211B epoxy resin was developed, resulting in joints with a shear strength of 40 MPa and fatigue life exceeding 106 cycles at 50% load. The material properties remained stable across the operational temperature range of -60 °C to +80 °C. An optimized fiber orientation (0°/90° for longerons and ±45° for diagonals) enhanced the resistance to axial, shear, and torsional stresses, while the epoxy matrix ensures radiation resistance. Finite element method (FEM) and computational fluid dynamics (CFD) analyses, validated by prototyping, confirm the performance of ultra-thin (0.1 mm) truss structures, achieving a lightweight (45 kg) design. These findings provide a validated, lightweight framework for next-generation HAPS, supporting extended mission durations under harsh stratospheric conditions.

Mechanical extraction is commonly used to extract oils from vegetable seeds and a single screw extruder has been successfully reported to separate oil and cake from <em>Jatropha curcas</em> seeds. In this study, a single screw extruder was designed and analyzed using Finite Element Method (FEM) and Computational Fluid Dynamics (CFD). Three different geometrical dimensions of screw extruder were designed and analyzed using FEM and CFD with software ANSYS POLYFLOW to study simulation of the flow and the behavior of <em>Jatropha</em> dough through of a single screw extruder. In a preliminary study, this study focused to simulate the velocity profile and local shear rate indie section with a power law model. The result obtained revealed that three important are as in designing a single screw extruder were gap area (clearance) in the range of 0.5-1.0 mm, chamber area (normal pitch) in the range 17-22 mm and root area.

PurposeThe purpose of this study was to investigate hemodynamics and coil distribution with changing coil stiffness and length using the finite element method (FEM) and computational fluid dynamics (CFD) analysis.MethodsBasic...

Coupled three-dimensional finite element analysis (3D-FEA) and computational fluid dynamics (CFD) software packages used to simulate heat transfer and airflow can be valuable tools for predicting and comparing the thermal performance of building enclosure components, assemblies, and systems when validated and used consistently. Today, the most commonly used tools are two-dimensional FEA (2D-FEA) programs that have been developed as part of efforts to establish uniform methods of evaluation to compare conduction-dominated heat transfer through building envelope elements, primarily fenestration systems. Increasingly, these tools are being used to predict in-service surface temperatures of building enclosure assemblies, particularly for the risk of interior condensation. However, these commonly used 2D-FEA tools have substantial limitations. They typically do not explicitly model radiation between objects or convective fluid flows, each of which can significantly affect heat transfer at element surfaces. They also cannot account for conditions that vary in three dimensions. As a result of these limitations, the computational tools most commonly used today cannot accurately predict surface temperatures that are significantly affected by convective currents, surface radiation, or three-dimensional variations in relevant factors. Coupled 3D finite element analysis and computational fluid dynamics (3D-FEA-CFD) software packages that can explicitly model convection, radiation and three dimensions are now commercially available, and more advanced analyses can be performed. Because many of these multiphysics packages were initially developed for mechanical applications, relatively little work has been done to evaluate their use in the study and design of building enclosure systems. The objective of this study is to develop and evaluate a practical methodology for using a 3D-FEA-CFD package to predict nighttime in-service building enclosure surface temperatures. The evaluation includes instrumentation and data collection from a test space, 3D-FEA-CFD simulation of the instrumented assemblies, assessment of basic simulation accuracy, comparison to 2D analysis results, and an analysis of sensitivity to selected simulation variables.

Cirrhosis is a severe and common digestive disease worldwide and is associated with a poor outcome. Portal hypertension (PHT) is a frequently encountered complication in cirrhotic patients [1–3]. Therefore, evaluation of portal pressure (PP) is urgently needed for the grading and staging of PHT. Direct measurement of PP is rarely performed due to significant invasiveness and potential complications. Hepatic venous pressure gradient (HVPG) is currently treated as the “gold standard” [1–4]. However, the invasiveness and technical difficulty greatly restrict its repeatable application. An index computed from computed tomography angiography (CTA) has recently demonstrated its diagnostic value compared with the “gold standard” [5, 6]. For instance, fractional flow reserve from coronary CTA showed good performance in the diagnosis of functional coronary stenosis in a multicenter randomized clinical controlled trial on 159 vessels in 103 patients [6]. On the basis of our previous study of noninvasive measurement of coronary stenosis by fractional flow reserve [7], this study, for the first time, introduces a novel noninvasive assessment of HVPG (HVPGni) and PP (PPni) computed from three dimensional (3D) hepatic portal venous models reconstructed from CTA to diagnose the severity of PHT in cirrhotic patients. The patient enrolled in the pilot study was a 50-year-old man who showed visible clinical manifestations of PHT, such as ascites and splenomegaly, and was diagnosed with cirrhosis in the decompensated stage. Approval was obtained from the ethical committees of Tongji Hospital and the participant gave written informed consent in advance. The CTA was performed with multi-detector CT scanners (GE Light-Speed Ultra, 120 kV, 220 mA). Original images were spilt into thin layers and exported into imaging control software MIMICS10.0. 3D hepatic portal venous models were reconstructed from surrounding tissues by different CT values, which were then meshed with 3D Flotran elements in the software ANSYS11.0. Given boundary conditions including average velocity of hepatic venous and portal venous flow were measured by color Doppler ultrasound (CDUS) (Philips iU22 x MATRIX Ultrasound System, convex array probe C5-2). Afterwards, finite element analysis and computational fluid dynamics were applied to compute the pressure distribution in the hepatic portal vein in vitro. Clinical data of the decompensated cirrhotic patient were calculated to test the feasibility and accuracy of the novel noninvasive assessment with the clinical diagnosis, CTA and CDUS as reference standards. The CTA images showed that the diameter of the portal vein was 1.6 cm while the normal diameter is ≤ 1.3 cm [2, 3]. Besides, the average velocity of portal venous flow was 12.5 cm/s, which was obviously slower than 22.62 cm/s in normal patients [1, 3, 4] and indicated severe PHT. According to the calculation by the novel assessment, HVPGni and PPni were computed as 65.2 Pa (Figure 1) and 3535.0 Pa (Figure 2), which generally corresponded to the diagnosis of PHT. Furthermore, the pressure and velocity distribution of different sections could be simultaneously obtained. Figure 1 Noninvasive assessment of hepatic ve- 702.835 1493.68 2284.52 3075.36 3866.2 nous pressure gradient in decompensated cirrhosis. Hepatic venous pressure gradient was calculated in vitro with the value of 65.2 Pa Figure 2 Noninvasive assessment of portal pressure in decompensated cirrhosis. Portal pressure was quantified in vitro as 3535.0 Pa and was generally consistent with the clinical diagnosis of portal hypertension The PHT is known as a frequent complication of cirrhosis worldwide which significantly reduces the patient's quality of life. The HVPG is currently considered as the “gold standard” to identify PHT. However, shortcomings, such as invasiveness and technical difficulty, limit its diagnostic worth greatly. In the pilot study, finite element analysis and computational fluid dynamics over the 3D hepatic portal venous model were applied, which potentially developed a novel noninvasive assessment of HVPGni and PPni to evaluate the severity of PHT. Besides, the novel assessment was successfully applied and the diagnostic performance of HVPGni and PPni was overall consistent with the clinical diagnosis, CTA and CDUS. This study introduces, for the first time, a novel noninvasive assessment of HVPGni and PPni computed from hepatic portal venous models, which might be a potential diagnostic tool to evaluate the severity of PHT, grading of cirrhosis and choice of treatment in the future. However, large randomized clinical controlled trials evaluated by both the novel assessment and invasive “gold standard” are needed before the application from bench to bedside.

A classification is given of methods for studying the process of interaction of soil environments with the tillage tools of soil-cultivating machines. The methods are divided into two groups: mathematical modeling and experimental research. Mathematical methods for studying soil interactions using numerical modeling methods that allow one to overcome the shortcomings of analytical and empirical approaches are considered in more detail. A classification, existing software, and an analysis of the possibilities of continuous and discrete numerical methods are given. Studies were performed using continual methods are analyzed: finite element method (FEM) and computational fluid dynamics (CFD). Also studies using discrete methods are considered: the discrete element method (DEM) and the smooth particle hydrodynamics (SPH). An analysis of existing studies has shown that the finite element method can be used for cohesive soils, making it possible to obtain both strength characteristics and data on the process of destruction and displacement of the soil massif. The computational hydrodynamics method can be effectively applied only to the study of the power characteristics of overmoistened soils. Attempts to extend this approach to a wider range of soils lead to significant errors. Discrete methods are most versatile and reliable. So the method of discrete elements allows to reliably assess both the power and quality characteristics of the tillage process. For example, the shape of the transverse profile, the degree of loosening (compaction) of the soil, the nature of mixing of the soil layers.

Damage to compressor blades is of critical importance2 in military aircraft engines. Irregular movements of throttle settings are mandatory requirement for pilots to perform various air combat maneuvers in military aircraft. It leads to excessive stresses on engine compressor blades in various flight regimes. Aircraft are also required to fly in varying atmospheric conditions ranging from negative temperature to over 50 degree Celsius in operations from deserts and tropics. The compressor blades are inspected exhaustively using non destructive inspection techniques during engine overhaul process. It is normally difficult and time consuming for service technicians to localize the damaged areas. A variety of non destructive inspections inspection methods like dye penetrant, eddy currents, magnetic particle testing and radiographic inspections are used that consume a large number of man machine hours increasing the cost of inspections. The possibilities of missing out internally damaged area due to micro cracks may still exist. Present research was focused on using computer simulation techniques such as Finite element methods (FEM) and Computational Fluid dynamics (CFD) to predict the location of possible damaged areas on compressor blades. The results could be used for showing maximum stress concentration areas in the blades as visual slides as reference for carrying out non destructive inspections. In this manner the number of blades inspected by per unit time may substantially be increased to save inspection cost, repair time and result in focused fault isolation of cracks and damage in blades.

A numerical technique for fluid-structure interaction, which is based on the finite element method (FEM) and computational fluid dynamics (CFD), was developed for application to an industrial chimney equipped with a pendulum tuned mass damper (TMD). In order to solve the structural problem, a one-dimensional beam model (Navier-Bernoulli) was considered and, for the dynamical problem, the standard second-order Newmark method was used. Navier-Stokes equations for incompressible flow are solved in several horizontal planes to determine the pressure in the boundary of the corresponding cross-section of the chimney. Forces per unit length were obtained by integrating the pressure and are introduced in the structure using standard FEM interpolation techniques. For the fluid problem, a fractional step scheme based on a second order pressure splitting has been used. In each fluid plane, the displacements have been taken into account considering an Arbitrary Lagrangian Eulerian approach. The stabilization of convection and diffusion terms is achieved by means of quasi-static orthogonal subscales. For each period of time, the fluid problem was solved and the geometry of the mesh of each fluid plane is updated according to the structure displacements. Using this technique, along-wind and across-wind effects have been properly explained. The method was applied to an industrial chimney in three scenarios (with or without TMD and for different damping values) and for two wind speeds, showing different responses.

A possible new development concept for Floating LNG may include a single flowline along the sea floor that splits into dual or more flexible risers. Since the gas co-produces condensate and water, design rules are needed for the splitting of the phases at the riser base manifold. Multiphase flow splitting is much more complex than single-phase flow splitting. The latter is fully determined by the back pressure on each riser, but for multiphase flow the phase split (Liquid-Gas Ratio) into each of the risers may also depend on other factors, such as the flow regime in the riser/flowline, the precise geometric details of the splitting configuration and other parameters (e.g. the momentum flux ratio in the flowline). Ideally the phase volume ratio should be fully equal over the two risers and remain the same as in the flow line. To find the proper design rules for multiphase flow splitting, which ensures equal phase volume split, we have set up a research programme that includes lab experiments and simulations using Computational Fluid Dynamics. The hypothesis is that phase maldistribution can occur if the gas flow rate in the risers is so low that it gives churn flow or hydrodynamic slug flow in the risers, whereas an equal phase volume split is expected if the gas flow rate is sufficiently high to produce annular flow in both risers. The flow facility at the Shell Technology Centre in Amsterdam transports air and water through a 2", 100 m long flowline, splitting into dual, about 15 m high, risers, having a diameter of 2". The pressure is atmospheric at the riser top. For the splitting configuration, we used a symmetric lay-out, which is a so-called Impacting Tee. We created the splitting curve by systematically changing the opening of the chokes at the top of the risers. At low gas flows a non-symmetric flow split was found, with flip-flopping and hysteresis in the risers. For example, a stagnant liquid flow could develop in one riser, and churn flow in the other riser, with a sudden swap of flow behaviour between the two risers. This maldistribution gradually disappeared as the gas flow rate was increased. CFD simulations were carried out with the Fluent package using a Volume of Fluid approach for the multiphase flow through the symmetric splitter. As in the experiments, the CFD simulations also give the preference of all flow to be produced through a single riser, with a stagnant liquid column in the other riser. In the experiments this maldistribution disappeared for a sufficiently high gas throughput. For the first flow rate where an equal split is found in the experiments, however, the CFD model still predicts that all of the flow exits through only one of the two risers.