Multi-physics Analysis Research Articles

Multiphysics analysis of a high-intensity ultrasound system applied to a three-layer animal tissue

High-intensity ultrasound systems for medical therapy must be carefully designed, implemented, and applied to avoid tissue damage or injury considering stimulation and relaxation time, frequency, and intensity of ultrasound. Based on these concerns and considering a test three-layer animal tissue consisting of skin, muscle, and bone, we determined the frequency and intensity at which ultrasound effectively stimulates the test animal tissues. In addition, from these ultrasound frequencies and intensities, and taking care the critical temperature recommended to preserve the integrity of the human tissue and avoid any tissue injury, we determine the stimulation and relaxation times. For this purpose, we performed a multiphysics simulation that describes the spatial and temporal dynamics of the thermoacoustic effect of ultrasound applied to test animal tissues. To practically demonstrate this ultrasound behavior, we perform an experimental setup based on an electronic HITU device designed and implemented to freely adjust the ultrasound intensity and frequency, as well as the stimulation time of the test animal tissues. Finally, we conclude that, depending on the test tissue, an ultrasound therapy system should allow the selection of the intensity and frequency of applied ultrasound, as well as the stimulation time to avoid tissue injury, which can be considered by health ministries around the world.

Multiphysics and multi-scale design and analysis of nuclear thermal propulsion pellet bed reactor based on spherical cermet fuel element

Due to the advantages of high thrust and high specific impulse, nuclear thermal propulsion (NTP) is a preferred near-term rocket engine technology for future Mars missions. This article introduces the reactor design based on spherical cermet fuel element, with the aim of studying the feasibility of applying this new fuel in NTP system. First, design requirements are determined based on the unique features of NTP. In terms of neutronics, the effect of rocket launch accidents and fuel loss caused by high-temperature hydrogen are considered. Thermal hydraulics refer to the requirements of NASA's Mars Design Reference Architecture 5.0 (DRA 5.0) for impulse, thrust, and thrust to weight ratio. Second, based on the requirements above, the optimal reactor configuration parameters are obtained with the goal of maximizing the thrust to weight ratio: reactor radius 51.1 cm, height 106 cm, aspect ratio 1.04, reflector 13 cm, and reactor mass 3940 kg. Finally, the performances of the optimal reactor design are analyzed. The neutron spectrum shows a characteristic of fast neutron spectrum, and fuel loss analysis shows that the core can withstand a fuel mass loss of about 4 wt%. In addition, the core axial and radial power distribution are calculated, with an overall power peak factor of 1.26. The thermal hydraulic calculation provides a range of core operating conditions that satisfy the design requirements of DRA 5.0 and temperature, with power of 620 ∼ 950 MW and flow rate of 16 ∼ 24 kg/s. Compared with the ANL200/2000 reactor using prismatic cermet, it has the advantage of higher specific impulse. The main disadvantage is the large pressure drop, which prevents it from being applied to the scenarios of high power and high thrust. Therefore, for NTP reactor using spherical cermet elements, it should be applied to low to medium power scenarios.

Multiphysics Analysis of PLOFC and DLOFC Accidents in the HTGR-TR

High-temperature, gas-cooled reactors (HTGRs) are promising advanced reactor designs. Leveraging passive safety features, higher core outlet temperatures, previous commercial operational experience, and potential coupling with nonelectrical systems, HTGRs present many advantages over traditional light water reactors and other advanced reactor designs. The High-Temperature, Gas-Cooled Test Reactor (HTGR-TR) is a point design developed by Idaho National Laboratory as a response to the need for the expansion of U.S. test reactor capabilities. The HTGR-TR was designed to serve as a test reactor for Generation-IV small modular prismatic block HTGRs and to provide irradiation data, two crucial contributions to the development of advanced reactors. As in any reactor design, it is necessary to understand the behavior of the reactor during accident scenarios to determine the overall safety of the design. Pressurized loss of forced cooling (PLOFC) and depressurized loss of forced cooling (DLOFC) are two accidents that can occur in HTGRs and that present challenges to decay heat removal. In order to understand the behavior of the fuel during these accidents, the resulting mechanical behavior and fission product migration in the fuel are evaluated. Using the HTGR-TR design, which utilizes tristructural isotropic (TRISO) fuel, a multiphysics analysis during the PLOFC and DLOFC transients was performed. This study utilizes neutronics, thermal hydraulics, and fuel performance modeling to analyze the behavior of TRISO particles during steady-state operation and the described transients. This analysis aims to characterize the hoop stress and strain during the transients, as well as predict fission product migration and radiological release. Due to the startup conditions of the HTGR-TR, the silicon carbide (SiC) layer for both of the transients and steady-state conditions are initially in compression for both the hoop stress and strain. The DLOFC transient at the beginning of cycle was the most challenging overall to the fuel, having the closest to tensile behavior and the closest to tensile strain. Because the integrity of the SiC layer was not challenged during any of the transients, the release of 90Sr and 137Cs was found to be negligible. The PLOFC transient at the end of cycle resulted in the largest 110mAg release and subsequent radioactivity increase. However, the increase in radioactivity was minor when compared to typical operating conditions due to the relatively large diffusivity of 110mAg though SiC at normal operating temperatures. Highlights include Neutronics and thermal-hydraulic modeling generating steady-state and transient conditions for use in fuel performance analysis.2. Detailed BISON analysis demonstrating the excellent performance of TRISO fuel during PLOFC and DLOFC transients.3. Fuel behavior showing negligible fission product release.

Multi-physical Field Analysis Method for Enclosed Isolated Phase Busbar of Hydropower Station

In this paper, geometrical modelling and finite element multi-physical field analysis method are carried out for the actual layout of the enclosed isolated phase busbar (EIPB) of a hydropower station, for the horizontal and vertical connection parts that can hardly be considered in the analytical calculation process. The finite element model is able to accurately represent the main structure of the EIPB by reasonably simplifying some of the components. Meanwhile, the finite element model incorporates the coupling of magnetic field and transient structural field, allowing for analysis of the magnetic field distribution, stress-strain distribution, modal analysis, and harmonic response of each component of the EIPB. It is capable of analyzing the vibration response of the complex horizontal-vertical structure EIPB under different excitations. This method can overcome the limitations of analytical calculation methods in calculating complex structure EIPBs. It can also provide valuable guidance for the structural optimization design of future EIPBs.

Multiphysics Simulation of In-Service Welding and Induction Preheating: Part 2

In-service welding simulations were carried out using a multiphysics finite element analysis (FEA). Calculated data as temperature and thermal cycles were validated by comparing them with experimental welding results carried out in a carbon steel pipe attached to a water loop. Two in-service welding cases were tested using the GMAW-P process with and without the assistance of induction preheating. The molten zone of weld macrographs and the simulated models were matched with excellent accuracy. The great agreement between the simulation and experimental molten zone generated a maximum error in the peak temperature of 1%, while in the cooling curve, the error was about 10% at lower temperatures. A higher hardness zone appeared in the weld’s toe within the CGHAZ, where the maximum induction preheating temperature achieved was 90°C with a power of 35 kW. Induction preheating reduced the maximum hardness from 390 HV to 339 HV.

A local–global optimization approach for maximizing the multiphysics frequency response of laminated functionally graded CNTs reinforced magneto-electro-elastic plates

Smart materials have garnered significant attention due to their distinct properties and potential applications in various engineering fields. In line with this, this study presents a local–global optimization approach aimed at maximizing the multiphysics frequency of laminated functionally graded carbon nanotube reinforced magneto-electro-elastic (FG-CNTMEE) plates. The laminated FG-CNTMEE plate is composed of layers of functionally graded carbon nanotubes embedded in an electro-elastic matrix, rendering it capable of exhibiting exceptional properties in response to magnetic and electric fields. To optimize its performance, a Balance Enhanced Symbiotic Organisms Search (BESOS) algorithm with new modifications of phases is proposed for global optimization, and integrated with a multiphysical isogeometric analysis using refined zigzag theory (MIARZ) for precise local–global analysis of laminated FG-CNTMEE plates within a Computer-Aided Design (CAD) environment. The effectiveness, robustness, and reliability of the proposed approach are demonstrated through numerical examples that highlight its applicability in achieving optimal designs for smart laminated FG-CNTMEE plates.

Multi-physics coupling simulation and design of magnetic field-driven soft microrobots in liquid environments

Magnetic field-driven soft microrobots have widespread applications in biomedical science, microfluidic chips, nanoengineering, and various other domains. However, the existing methods for designing such magnetic-driven flexible robots largely rely on experimental trial and error or steady-state numerical simulated results, which fall short of meeting the intricate requirements for magnetic field editing and magnetic domain distribution. Addressing this issue, a multi-physics coupling numerical analysis method encompassing Magnetic-Fluid-Solid mechanics was developed. A complete process for transient numerical simulation resolution has been achieved. Utilizing this analysis method, the motion patterns of two typical prototypes of magnetic-driven miniature soft bionic robots, a bionic midge larvae robot, and a bionic jellyfish robot, have been analyzed. The central role of the magnetic field in driving these robotic designs—causing deformation in microrobots by designing magnetic domains and spinning the microrobots by controlling the magnetic field—has been revealed. We developed a theoretical model of a bionic fish tail fin robot driven solely by a rotating magnetic field and conducted comparative studies on the swimming efficiency, flexibility, stability, and relative advantages of the three types of robots. The impact of different magnetic domain distribution rules and different magnetic field driving methods on a robot's performance is analyzed, validating that higher swimming efficiency can be achieved by designing a robot's magnetic domains so that they undergo magnetic displacement under magnetic torque resulting in deformation. This innovative analysis method holds potential to provide valuable references for designing motion patterns of magnetically driven microrobots within liquid environments, thereby deepening our understanding toward various complex gait mechanisms involved in biological swimming.

Research on multi-physical field analysis and assessment technique of virtual connection defects in cluster cable joints based on digital twin technology

As the “blood vessels” and “nerves” of the power grid, cables are important carriers for transmitting electric energy, and their failures will affect the safe and stable operation of the power grid. In this paper, a digital twin model of thermal characteristics is constructed for 10 kV YJV×400 cluster cable and its joint model. Based on the multi-physical field coupling analysis method, the fluid field, temperature field and current-carrying capacity of the cluster cable are analyzed. The temperature rise and airflow distribution characteristics of the joint and its external insulation when the defect of joint false connection occurs are analyzed. Based on the fuzzy analytic hierarchy process (FAHP), weights are assigned to the locations of multiple measurement points of the cable external insulation, and the temperature distribution of each measurement point is combined with the digital twin technology to calculate the hot spot temperature of the cable, so as to assess the defects of the joints of the cables. The digital twin platform is used for real-time monitoring of cable status and assessment of defects. The temperature rise experiments of cables under different carrying capacity and joint defects show that this method can accurately and efficiently calculate hot spot temperatures and assess defects of joints in cluster cables.

Temperature effects on noise radiated by concrete railway structures

In recent years, concerns have arisen regarding the periodic deformation of high-speed railway tracks owing to the temperature effects caused by the solar radiation. This phenomenon has prompted investigations into temperature-induced changes in the dynamic responses of vehicle–track–bridge systems. Previous studies have commonly taken the additional track irregularity caused by thermal deformation as the sole factor affecting dynamic responses while neglected changes in the structural frequency response characteristics. Structural radiation noise is also a prominent issue that affects the lives of people and the environment. However, studies on track–bridge-borne noise rarely consider the influence of temperature. To address the impact of temperature on structure-borne noise radiated by tracks and bridges, this study employed a sequentially coupled multi-physics analysis method. This approach allowed a comprehensive exploration of the temperature effects on track irregularities, structural frequency responses, and sound radiation efficiency. A full-scale temperature deformation field test of a CRTS III slab was also conducted to determine the necessary initial thermodynamic boundary conditions. The analysis results revealed that the thermally induced deterioration of track irregularity and changes in structural frequency response characteristics were the primary factors affecting structure-borne noise radiated by track–bridges under local climate conditions.

Multiphysics analysis of chip and resonator designs for increased damage threshold of external cavity high-power laser diodes.

We present a detailed analysis of multiphysics simulation results to evaluate the threshold for catastrophic optical damage (COD) of high-power laser diodes under misaligned external optical feedback. Three different chip designs are investigated: the non-injecting mirror concept, the non-absorbing mirror concept and the introduction of an additional energy barrier within the waveguide near the front facet. Furthermore, a modification of the external resonator that promises a lower sensitivity towards misalignments is considered. The dependence of the COD threshold on the additional design parameters (bandgap change, modification length, focal length) and the impact of the different approaches on electro-optical efficiency as well as beam quality are analyzed. Compared to the initial design, the different chip design concepts promise an increase of the achievable output power by 8%, 27% and 27% respectively, whereas the modified resonator fully prevents feedback-induced failure.

Multiphysics analysis of a metal hydride moderated megawatt heat pipe reactor with burnable poisons

With the development of nuclear energy, microreactors have received increasing interest among researchers in recent years. In this paper, a megawatt heat pipe reactor with metal hydride moderators and burnable poisons is proposed. The hydrogen stability of the reactor under accident conditions, including reactivity insertion accidents, loss of power conversion unit heat sink accidents, and heat pipe failure accidents are analyzed. In this work, Gd2O3 is introduced as a burnable poison in the form of mixing with the UO2 fuel. According to the results of the burnable poison design, the 0.1% mass fraction of Gd2O3 is selected as the burnable poison loaded in the core. Safety analysis indicates that the introduction of burnable poisons can be beneficial during the positive reactivity insertion accident as it can reduce the excessive reactivity at BOL, thus reducing power peak and preventing hydrogen dissociation in ZrH1.4 rods. However, during the loss of PCU heat sink accident, ZrH1.4 rods will dissociate regardless of the presence of burnable poisons, whereas YH1.7 rods show better hydrogen stability. Moreover, in the event of the heat pipe failure accident, ZrH1.4 rods are more susceptible to dissociation than YH1.7 rods. As a result, the YH1.7+BP core is a better choice compared with other designs proposed in this paper as it provides a relatively high temperature margin.

A review of research on turbines for supercritical carbon dioxide power systems

Supercritical carbon dioxide (S-CO2) Brayton cycle has been known as a potential power cycle technology because of its high efficiency, compact structure and suitability for different heat sources. As one of the key components in the cycle, the turbine has an important impact on the cycle efficiency. Compared with traditional steam and gas turbines, S-CO2 turbines have high working pressure and small size. The internal flow characteristics are significantly different. In this paper, the research progress of S-CO2 turbines in recent years is reviewed. The design and performance evaluation methods for S-CO2 turbines of different types and power levels are summarized, and research on loss correlations and optimization algorithms are introduced. The features of flow field in S-CO2 turbines are discussed. Current studies mainly evaluate the flow field and flow losses through Computational Fluid Dynamics (CFD), and some studies further analyze the influencing mechanism of turbine geometric parameters on flow characteristics. The applications of multi-physical field analysis on S-CO2 turbines are also reviewed. The construction and operation of S-CO2 test loops, and relevant turbine experimental study findings are introduced. Future research directions of S-CO2 turbines are proposed.

Multiphysics Simulation of In-Service Welding and Induction Preheating: Part 1

A finite element model was developed using a multiphysics finite element analysis (FEA) coupling heat transfer, fluid flow, and electromagnetic heating. Part 1 presents the software implementation and model equations beside the mesh setting and modeling approach to simulate circumferential welding of Type B sleeve repair. The simulation was divided into four steps running sequentially for each physic solved in the model. Induction preheating was simulated and validated by comparing simulated temperature with experimental measurements. The multiphysics model differs from the usual simulations present in the literature, expressing more reliability in the results and making way for more-complete modeling for in-service applications.

Design and Simulation of a System-in-Package Chip for Combined Navigation.

This paper proposes a system-in-package combination navigation chip. We used wire bonding, chip stacking, surface mount, and other processes to integrate satellite navigation chips, inertial navigation chips, microprocessor chips, and separation devices. Finally, we realized the hardware requirements for combined navigation in a 20 mm × 20 mm chip. Further, we performed a multi-physics simulation analysis of the package design. For antenna signals, the insertion loss was greater than -1 dB@1 GHz and the return loss was less than -10 dB@1 GHz. The amplitude of these noises of the signal between the MCU and the IMU was approximately 20%, and the maximum value of the coupling coefficient between signal lines on the top surface was 13.4174%. The ninth mode of the power plane yielded a maximum voltage of 55 mV, and all power delivery networks had a DC voltage drop of less than 2%. The highest temperature in the microsystem was approximately 42 °C. These results show that our design performed well in terms of signal, power, and thermal performance.

Multi-physical field simulation calculation and analysis of simulated high-level waste liquid spray calcination.

Aiming at the independent research and development of a simulated high-level waste liquid spray calcination transformation treatment test device, a three-dimensional multi-physical field model of spray calcination was established by means of finite element analysis method. In this paper, the simulated high-level waste liquid is a mixed solution of nitrate solution and sucrose. The main chemical components of nitrate dissolution are HNO3 and NaNO3. The process of evaporation and calcination of high-level waste liquid to form oxides is also called the pretreatment of high-level waste liquid or the conversion of high-level waste liquid. In this experiment, the atomized droplets sprayed at high speed are evaporated, dried and calcined in turn in the calciner to obtain the calcined product. The distribution law of temperature flow field and chemical reaction state and results inside the test device were revealed by simulation calculation. The results show that under the condition of multi-physical field coupling, the chemical reaction temperature has an effect on the yield of the product. The temperature is positively correlated with the product concentration, and the effect of temperature on the yield of NO2 is greater than that of Na2O. At the same time, in this chemical reaction, the concentration of reactants (NaNO3 and HNO3) had a positive correlation with the concentration of main products (NO2 and Na2O). However, the rate of increase in the concentration of the main products (NO2 and Na2O) decreased with the increase of the concentration of the reactants (NaNO3 and HNO3).

Specified Velocity Launching of Reluctance Coil Gun Based on Genetic Algorithm

In this study, a method is proposed to obtain the initial voltage of the capacitor and the initial relative position of the projectile of a reluctance coil gun using a genetic algorithm to make the projectile launch at a specified muzzle velocity with high efficiency. Firstly, the equivalent inductance change during the launching process is used as a link for multi-physics field analysis, and a set of electromagnetic dynamics equations is derived to correct the effect of magnetic saturation on the inductance according to the current value in the coil. Further the set of equations is constructed as a Simulink discretized numerical computational program and called by a genetic algorithm written in MATLAB to approximate the optimal solution by generation-by-generation optimization. When the specified projectile muzzle velocity is set to 10 m/s, the initial voltage of the capacitor calculated using the genetic algorithm is 156 V, and the initial position of the projectile is -14.3 mm. We input the parameters into the finite element analysis model and the launch experiment platform, and the obtained projectile muzzle velocity is 9.67 m/s and 9.8 m/s respectively, and the efficiency is close to the optimal value, also the comparison of voltage and current waveforms also shows that the method proposed in this study is effective.

Electromagnetic–thermal field coupling in tissue ablation: The EAES design and optimization

The coupling control of multi-physics fields has become a focal issue in the engineering domain, especially for achieving a more precise simulation and prediction of physical phenomena. This approach plays a crucial role in enhancing design efficiency and optimizing material selection. Focusing primarily on the controllability between microwave and temperature fields, the Emission Area Extension Structure (EAES) is a novel structure in response to the demand for high circularity in microwave ablation. Finite element analysis was employed to examine the distribution characteristics of electromagnetic and temperature fields in liver tissue under varying power and time conditions. Comparative analyses were conducted to evaluate the impact and performance of the EAES vs traditional structures in ablation. Incorporating the EAES into conventional ablation needles allows for a more concentrated distribution of the electromagnetic field without altering the needle diameter. In the simulation of tissue ablation, the circularity of ablation increased by 10%, while water-cooling efficiency increased by 11%. The introduction of EAES, while maintaining its minimally invasive characteristics, effectively enhanced the controllability of conformal ablation. Furthermore, a mathematical model was developed to serve as a theoretical basis for selecting optimal preoperative parameters, incorporating conditions such as ablation time, power, range, and circularity. Overall, by conducting a multi-physics field coupling analysis on microwave ablation needles and proposing the EAES solution, this study aims to enhance the predictability, controllability, and safety of conformal ablation.

Fast Calculation of Electromagnetic Vibration of Surface-Mounted PMSM Considering Teeth Saturation and Tangential Electromagnetic Force

In view of the shortcomings of the existing calculation methods of electromagnetic forces, this paper proposes an analytical method (AM) combining the magnetomotive force (MMF)-permeance method and the improved subdomain method. The amplitude of each force density component considering stator teeth saturation and current harmonics is calculated, and the specific order and frequency components in the radial and tangential electromagnetic force densities are analyzed and sorted out. In modal analysis, the stator core and the casing are regarded as cylindrical shells with axial ribs, the natural frequencies of the stator are obtained based on the energy method, and the accuracy is well verified by the modal test. Finally, the frequency response functions of low-order modes of the stator only related to the stator structure parameters are determined, and the vibration accelerations under different working conditions are obtained based on the linear superposition principle by only updating the electromagnetic forces. Compared with the multi-physical coupling finite element analysis, the total calculation time of the proposed AM is reduced by more than 92%, which facilitates the fast prediction and effective reduction of electromagnetic vibrations in the motor design stage.

Research on the suppression method of sensor impact vibration parasitic effects in surface reflection pressure measurement.

Ground reflection pressure plays a crucial role in evaluating the destructive power of ammunition explosions. Accurately measuring this pressure is essential for assessing ammunition's destructive capability and guiding ammunition design. In this study, a theoretical analysis of the parasitic effect of shock and vibration was conducted and COMSOL was employed for performing a multi-physics finite element numerical simulation analysis to elucidate the attenuation characteristics of stress waves in commonly used shock- and vibration-resistant materials. Furthermore, a device was designed using aluminum foam and polytetrafluoroethylene to mitigate the parasitic effects on the ground reflection pressure sensor. Experimental testing was conducted to validate the device's effectiveness. The results demonstrated that the device successfully reduced the intensity of stress waves reaching the ground reflection pressure sensor, with a relative attenuation rate of 29.6% in peak stress values. The sensor measurements obtained with the suppression device exhibited smoother curves and higher signal-to-noise ratios, significantly improving the reliability of the measurement results. Our study holds considerable engineering application value in enhancing the accuracy of shock wave pressure measurements in explosive fields.

Design and Comprehensive Multiphysics Analysis of Permanent Magnet Synchronous Motor for Podded Propulsion in Marine Applications

Design and Comprehensive Multiphysics Analysis of Permanent Magnet Synchronous Motor for Podded Propulsion in Marine Applications