Thermal Fluid-structure Interaction Research Articles

Enhancing heat transfer in laminar channel flow by tuning the mass distribution of a flexible reed

Recent studies have leveraged wall-mounted flexible reeds to augment heat transfer efficiency in channel flows. In this study, we demonstrate that tuning the reed's mass distribution can substantially elevate this heat transfer enhancement. Numerical simulations incorporating the fluid–structure–thermal interaction are performed to investigate the impact of mass distribution on the reed dynamics and the associated heat transfer augmentation. The results indicate that the mass distribution of the reed significantly affects its motion mode, which, in turn, critically modulates the heat transfer characteristics. The maximum thermal efficiency factor is obtained when the reed's mass is concentrated at its distal end. Furthermore, the enhancement effect of tuning reed's mass distribution on heat transfer efficiency is closely related to the bending stiffness γ. Within the range of bending stiffness considered in this study (0.02–0.14), the effect of tuning the reed's mass distribution on the thermal efficiency factor exhibits a trend of increase–decrease–increase as the bending stiffness increases. At high bending stiffness, simply tuning the reed's mass distribution can increase the channel heat flux and reduce energy loss, thereby achieving the goal of enhancing the thermal efficiency factor. At γ = 0.14, allocating the reed's mass at its distal end resulted in a notable enhancement, with a thermal efficiency factor surge of 11.1%.

Impact of Cu Pillar Bump Diameter and Solder Material on Reflow Soldering: A Computational Study with Thermal Fluid–Structure Interaction

Impact of Cu Pillar Bump Diameter and Solder Material on Reflow Soldering: A Computational Study with Thermal Fluid–Structure Interaction

A numerical investigation of the effect of vaned diffuser water cooling on the internal flow field of a centrifugal compressor

Due to their high pressure rises, the gas temperature of high-speed centrifugal compressors can be very high to the detriment of compressor aerodynamic performance. A water-cooled vaned diffuser technique is proposed to alleviate this problem. Compressor housing integrated water-cooling passages are employed to introduce cooling water to the vanes through holes near the vane centre. The technique was applied to a 180 mm turbocharger compressor running at the tip speed of 452 m/s, and numerical studies with conjugate heat transfer and fluid-structure thermal interaction were carried out to find the effects of the cooling to compressor performance and the mechanical stress of diffuser vanes. The results show that compressor efficiency is improved by the cooling, and the improvement increases as compressor mass flow reduces. At modest pressure ratios around 3.3, the maximum improvement of 1.09 percentage points is achieved using 30°C inlet water temperature. The cooling is found to significantly reduce the air temperature near diffuser passage solid walls, thus lead to more uniform air temperatures at compressor exit. The reduction of 1.33°C and 2.21°C in the diffuser outlet temperature have been found at 1.68 kg/s air mass flow with 70°C and 30°C water inlet temperature respectively. Moreover, the thermal stress in diffuser vanes is shown to be lower with the cooling.

Immersed boundary method based fluid–structure–thermal interaction solver with conjugate heat transfer

Immersed boundary method based fluid–structure–thermal interaction solver with conjugate heat transfer

An implicit immersed boundary method for Robin boundary condition

In this work, a novel boundary condition-enforced immersed boundary method (IBM) for simulating complex thermal–fluid–structure interaction (TFSI) problems with Robin boundary conditions is proposed. In this work, two auxiliary layers of Lagrangian points are introduced and placed within the inner and outer parts of the immersed object to enable the simultaneous evaluation of the temperature and its gradient on the solid surface. The mutual thermal interactions between the immersed object and the surrounding flow are taken into account through the temperature corrections on the Lagrangian points by accurately enforcing the Robin boundary condition on the solid boundary. Hence, a system of linear equations can be formulated to compute the temperature corrections. Subsequently, the temperature corrections are biasedly distributed to the Eulerian points located in the inner auxiliary layer to eliminate the diffusion generated by the smooth delta function on the temperature field outside the solid object. The proposed IBM integrated with the reconstructed thermal lattice Boltzmann flux solver (RTLBFS) is extensively and critically assessed with classical benchmark cases ranging from two-dimensional stationary problems to three-dimensional problems involving moving boundaries to demonstrate the robustness and accuracy of the proposed method for Robin boundary conditions. Results from the present work are extensively corroborated with previous works that adopt different approaches for imposing the Robin boundary condition. It shows that the proposed method not only provides a much more accurate representation of the Robin boundary condition but also introduces a simple implementation for the complex Robin boundary condition within the diffuse interface IBM framework.

An explicit boundary condition-enforced immersed boundary-reconstructed thermal lattice Boltzmann flux solver for thermal–fluid–structure interaction problems with heat flux boundary conditions

For the thermal–fluid–structure interaction (TFSI) problems with moving boundaries, the original implicit boundary condition-enforced immersed boundary method (IBM) by Wang et al. [1] has to generate a large correlation matrix and compute its inversion at each iteration, implying that the virtual memory requirement and computational cost would grow exponentially with the number of Lagrangian points. In this work, we proposed an efficient explicit boundary condition-enforced immersed boundary method for Neumann boundary condition (NBC) to achieve high computational efficiency and maintain similar accuracy as the original implicit IBM [1], which circumvents the needs to assemble a large correlation matrix and inverse it in the original implicit IBM [1] through second-order approximation based on the error analysis using Taylor series expansion. Most importantly, the proposed explicit IBM can efficiently solve practical physics problems with a tremendous amount of Lagrangian points involving Neumann boundary condition. The comparisons of the virtual memory and computational cost between the explicit and implicit IBMs demonstrate that the explicit boundary condition-enforced IBM is not only computational efficient, but also has memory saving performance. The proposed explicit IBM integrated with the reconstructed thermal lattice Boltzmann flux solver (RTLBFS) is validated with some classical benchmarks, and the results show that the proposed explicit IBM can successfully resolve TFSI problems with Neumann boundary condition.

Coupling edge-based smoothed finite element method with incompressible smoothed particle hydrodynamics for thermal fluid structure interaction problems

Numerical simulation of thermal fluid structure interaction (TFSI) problems with incompressible flows is one of the most challenging topics in computational fluid dynamics. In this paper, the recently developed edge-based smoothed finite element method (ES-FEM) is coupled with incompressible smoothed particle hydrodynamics (ISPH) for modeling TFSI problems, where the fluid domain is simulated by ISPH and the structure domain is simulated by ES-FEM method. A ghost particle based algorithm to couple the ES-FEM elements and ISPH particles is applied to implement the modeling of TFSI problems. The numerical simulation of TFSI problems using the ES-FEM-ISPH coupling method under pure Lagrangian scheme is very attractive because it can naturally handle the moving interface and free surface. The effectiveness of the ES-FEM-ISPH coupling method developed in this paper is verified by a number of numerical simulation examples with TFSI problems. From the obtained numerical results, we can conclude that the ES-FEM-ISPH coupling method is effective to simulate TFSI problems.

Enhanced thermal and mechanical performance of 3D architected micro-channel heat exchangers

Many crystals in nature have simple interatomic microstructures, such as simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC) lattice symmetries, making these structures extremely stable. Inspired by these arrangements, a series of architected micro-channel heat exchangers with rationally designed 3D microstructures were established. A multi-physics mathematical model using thermal-fluid-structure interaction (TFSI) was employed to investigate the coupled heat transfer performance and mechanical properties of these architected heat exchangers. When compared with the corrugated straight plate (CSP) microchannel heat exchanger, the thermal-hydraulic performance factors (TPC) of FCC and BCC microchannel heat transfer were 2.20 and 1.70 times that of SC microchannel heat exchanger, respectively. The micro-channel heat exchanger with FCC architectures could enhance the convective heat transfer performance by 201.0%, while the micro-channel heat exchanger with SC architectures reduced the Von-Mises equivalent (VME) stress by 20.0% when compared with the conventional 2D CSP heat exchanger. The proposed architected micro-channel heat exchangers could find a wide range of potential applications ranging from power electronics in electric vehicles to concentrated solar power systems, where both good convective heat transfer performance and high mechanical strength are simultaneously pursued.

Morton effect prediction with validation using a CFD based CNN for pad inlet temperatures

The Morton Effect (ME) is a thermal-fluid–structure interaction instability occurring in rotating machinery supported by hydrodynamic journal bearings. The mechanism of ME consists of a bowed rotor or mass imbalance induced shaft synchronous whirl vibration in the bearing, which causes local, asymmetric heating of the journal, which causes shaft bending, potentially leading to increasing vibration. This study presents an original ME simulation approach that includes a CFD (Computational Fluid Dynamics) bearing groove model, embedded in a deep learning algorithm for computational efficiency and non-expert usage. The groove model provides a 2D oil temperature distribution at the leading edge of the bearing pads, yielding a more accurate journal axisymmetric temperature distribution which is the source of the ME. The paper provides validation of the approach by test result correlation, and illustrates the effects of parameter variation and configuration variation, by examining various oil injection types. The approach may be used for correcting ME occurring in existing machinery, or for designing machinery to avoid the ME.

Numerical Investigation of the Influence of Part Geometric Tolerances on Piston/Cylinder Interface Performance

Manufacturing errors are inevitable in hydraulic machines. The manufactured geometry of solid parts directly governs the performance of these machines. This paper reports an extensive simulation study for manufactured inaccuracies on the performance of the piston/cylinder interface of an axial piston machine using the state-of-the-art simulation tool. The performance of swashplate type axial piston machines is characterized mainly by the three lubricating interfaces including the cylinder block/valve plate, slipper/swashplate and piston/cylinder interface. Among the three lubricating interfaces, the piston/cylinder interface is more sensitive to manufacturing inaccuracies such as roundness and conicity of the solid parts as well as the precision and accuracy of the manufactured nominal diameters of the solid parts. This is because the manufactured geometry of the cylinder bore, and the piston directly affects the height and the shape of the lubricating gap of the piston/cylinder interface. Therefore, the manufacturing form deviations of the solid parts directly affects the viscous friction, leakage flow, wear process and lifetime of such lubricating interfaces. The fully coupled fluid structure thermal interaction model can predict the energy dissipation, viscous friction, leakage flow and the gap height considering the geometry of the solid parts.

An explicit immersed boundary-reconstructed thermal lattice Boltzmann flux solver for thermal–fluid-structure interaction problems

Thermal–fluid–structure interaction (TFSI) problems involving multi-physics coupled effects are ubiquitous in natural environment and manmade devices. A novel coupling approach of the explicit immersed boundary-reconstructed thermal lattice Boltzmann flux solver (EIB-RTLBFS) is developed specifically to tackle TFSI problems, where a fractional method is introduced to solve TFSI problems in two successive steps. Firstly, the EIB is utilized to efficiently compute the velocity and temperature corrections that satisfy the Dirichlet boundary conditions on the surface of the solid domain. Secondly, RTLBFS, a weakly compressible finite volume solver with a clear mechanism to possess good numerical stability for high Rayleigh number convection problems, is employed to model the thermal flow. The EIB-RTLBFS is shown to be second-order accurate in space. Three benchmark cases, such as unsteady flow and natural convection that involves moving boundary, are used to evaluate the capability and robustness of EIB-RTLBFS for TFSI problems. Subsequently, a fully coupled thermal–fluid–structure system is established with a membrane structure governing equation, and the results demonstrate that the EIB-RTLBFS can accurately predict the nonlinear characteristics of this multiphysics system.

Transient Flow and Heat Transfer in a Horizontal Rectangular Channel Considering Thermal–Fluid–Structure Interaction

Abstract For the supercritical n-decane horizontally flowing in a rectangular channel of an active regenerative cooling system, a transient thermal–fluid–structure coupling method is employed to investigate the unsteady thermal-hydraulic characteristics and the wall deformation at a starting stage. The temperature distributions of the fluid domain and solid domain along the flow direction are investigated at fixed times as well as at a certain cross section. Streamlines in cross sections are employed to explain the temperature distribution. The velocity and pressure at a fixed point versus time are also given. Besides, the solid deformation is presented according to the uneven pressure distribution and temperature distribution. It is found that the response time is less than 30 s when the heat flux is less than 3.0 MW/m2. A larger heat flux contributes to promoting the steady state. The high-temperature part of the solid domain is close to the heated wall, but the situation is reversed for the fluid domain. This is because a bunch of dead-zone vortices appears in the vicinity of the upper wall of the channel. The maximum deformation is 0.132 mm for the condition of heat flux 3.0 MW/m2 and it is exacerbated by the uneven temperature and pressure distributions on the solid domain.

Fluid–structure–thermal interaction of a self-fluttering membrane in turbulent channel flow

This study investigated the fluid–structure–thermal interaction of a fluttering membrane in turbulent channel flow at three different modes (straight mode, unsaturated flutter mode, and saturated flutter mode) and increasing Reynolds number. Using a high-speed camera at 2 kHz and a data-acquisition system at 51.2 kHz, the deformation shapes of a piezoelectric membrane and the temporal voltage variations were simultaneously recorded. Unlike the fluttering membrane in a parallel, unconfined flow, the flutter amplitude of the membrane in the channel exhibited an asymptotic behavior with the Reynolds number and eventually reached a saturated state. Different from the membrane characteristics at the unsaturated flutter mode, the membrane at the saturated flutter mode exhibited a dramatic fluttering behavior, with large flutter amplitude and front stationary points. Furthermore, the statistical flow quantities and the heat transfer performance were examined. The variations in the streamwise and vertical velocity components were closely related to the pressure loss and the heat transfer enhancement, respectively. In addition, the thermal enhancement factor was largest at the unsaturated flutter mode because of the high friction factor. Finally, through membrane shape identification, the spatiotemporal evolutions of flow–structure dynamics were captured. The relationships between the streamwise velocity and the pressure loss and between the vertical velocity and the heat transfer enhancement were further investigated phase by phase. According to the vorticity distributions, two small vortices occurred at the saturated flutter mode, which enhanced the heat transfer performance.

Influence of tandem fluttering membranes on flow dynamics and heat transfer in turbulent channel flow

The fluid–structure–thermal interaction of tandem fluttering membranes with gap distance ratios ranging from D*=1.0 to 4.0 in turbulent channel flow at Reynolds number ReL = 2.05×104 was investigated. Three distinct coupling modes (strong, medium, and weak, with D*=1.0, 1.5, and 2.0, respectively) of the tandem membranes were compared. The coupled fluttering motions and output voltages of the tandem membranes were recorded simultaneously. The two tandem membranes fluttered at the same frequency but different amplitudes. The flutter amplitude of the rear membrane, enhanced by the front membrane, exhibited the largest and smallest values in the strong and weak coupling modes, respectively. The phase difference Δϕ was linearly dependent on D*. Furthermore, the statistical flow quantities and heat transfer performance were examined. As D* increased from 1.0 to 2.0, only minor variations occurred in the streamwise and vertical velocities, leading to a decreased pressure loss and enhanced heat transfer. Moreover, the largest thermal enhancement factor was attained in the strong coupling mode owing to the large space-averaged Nusselt number. Finally, a membrane-shape-identification method was used to capture the spatiotemporal evolutions of the flow–structure dynamics. The decrease in the pressure loss and enhancement in the heat transfer of the tandem fluttering membranes were clarified by investigating the spatiotemporal evolutions of the unsteady flow behaviors. This study may offer an important reference for the designing of an efficient heat transfer device using multiple membranes.

A Novel Approach of Studying the Fluid–Structure–Thermal Interaction of the Piston–Cylinder Interface of Axial Piston Pumps

The friction in the swash plate type axial piston pumps is mainly influenced by the fluid film in the friction interface. The piston–cylinder interface is one of the key friction interfaces in the pumps. The film geometry is determined by the gap between the piston and the cylinder. The dimensions of the parts determine the gap geometry, and the deformation of the structure also influences the gap geometry. The fluid viscosity is strongly influenced by temperature. Thus, a novel approach of studying the fluid film, the structure, and temperature interaction is provided in this paper. A full and quick fluid–structure–thermal interaction simulation is realized. Then, a dynamic model of the piston–cylinder interface, which integrated the fluid–structure–thermal interacting effects, has been developed. Finally, an approach for calculating the extra friction force between the piston and the cylinder is provided. Compared with the measurement data, the simulation results of the axial friction force achieve a good fit. The present work allows a fast prediction and detailed support for designing the piston–cylinder interfaces.

A novel coupling approach of smoothed finite element method with SPH for thermal fluid structure interaction problems

Thermal-fluid-structure interaction (TFSI) problems are significant in science and engineering, and usually pose great challenges for numerical simulations due to the coupled effects of thermal convection, fluid flow and structure deformation. In this paper, a novel coupling approach of smoothed finite element method (ES-FEM) with an improved smoothed particle hydrodynamic (SPH) method is developed for TFSI problems. In the coupling approach, the edge based ES-FEM is used to model solid domain and the Lagrangian SPH is used to model fluid flow. In ES-FEM, the temperature and velocity gradient smoothing technique are applied over the edge-based smoothing domain for thermal structure coupling problems. In SPH, some state-of-art algorithms including kernel gradient correction (KGC) and particle shift technique (PST) are integrated to ensure computational accuracy for simulating thermal fluid flows. A ghost particle coupling algorithm is developed to handle fluid-structure interaction and fluid-structure conjugate heat transfer, and the kinematic condition, dynamics conditions and conservation of energy are satisfied. Four numerical examples are tested to demonstrate the effectiveness of the present coupling approach of ES-FEM-SPH for TFSI problems.

Design and thermal fluid structure interaction analysis of liquid nitrogen cryostat of cryogenic molecular sieve bed adsorber for hydrogen isotopes removal system

Efficient design of Tritium Extraction System (TES) for the fuel cycle of any fusion reactor is very important to maintain the tritium breeding ratio and hence sustain the fusion reaction. Hydrogen Isotopes Removal System (HIRS) for Indian Tritium Breeder Blanket removes Q2 (Q = H, D or T) and impurities using Cryogenic Molecular Sieve Bed (CMSB) adsorber at 77 K. The CMSB is maintained at liquid nitrogen temperature using a double walled cryostat made up of SS304. The paper describes the design and thermal Fluid Structure Interaction (FSI) analysis of cryostat assembly for CMSB of HIRS. The coupled analysis performed in this work involves solving for the fluid domain and transferring the results to ANSYS Thermal-Static structural set up to determine the stresses and displacement due to combined effects in the system. The mechanical design of the cryostat components is analytically performed using ASME codes. The velocity, pressure drop and time taken to cool the CMSB are determined by solving the fluid and energy equations in ANSYS Fluent analysis system. The solutions are imported into ANSYS Thermal-Static structural analysis system and the thermal-structural stresses and deformations are determined considering the temperature, pressure and acceleration loads. The space between inner and outer vessel is maintained at vacuum, which might lead to buckling. So, the critical buckling load multiplier factor is determined. These results are used in fabricating the complete cryostat system for CMSB of HIRS.

Effect of Ambient Temperature Changes on Blood Flow in Anterior Cerebral Artery of Patients with Skull Prosthesis

In many cases, an injury to the head leads to the replacement of a part of the skull with materials such as titanium and polyether ether ketone. Three-dimensional heads model of 15 healthy individuals and 13 patients were prepared. The models were simulated using thermal fluid structure interaction analysis to evaluate the effects of cold (5°C) and hot (55°C) temperatures of the skull on the conditions of blood flow in the anterior cerebral artery. The results showed negligible changes (<3%) in wall shear stress (WSS) vessel and von Mises stress between the healthy individuals and patients both at 25°C and 55°C. However, at 5°C, the values of these 2 parameters in the patients were 2.1 and 2.5 times those in healthy individuals, respectively. The value of WSS in healthy individuals and the patients in cold temperature was 1.2 and 2.9 times those at normal temperature. The corresponding values for von Mises stress were 1.1 and 2.2, respectively. Accordingly, the stress changes between cold and hot ambient temperatures were found to be negligible in all samples. The changes in stress were significant only for the patients when exposed to cold ambient temperature, and only in patients, exposure to a cold ambient temperature significantly increased the risks of vascular aneurysm and damage to the brain tissue surrounding the blood vessels. These risks were found to be negligible for both healthy individuals and patients when exposed to hot ambient temperature and also for healthy individuals exposed to cold ambient temperature.

Heat transfer and stress characteristics of additive manufactured FCCZ lattice channel using thermal fluid-structure interaction model

Lattice channels designed for hot stamping, metal injection, and die casting should have high heat transfer and structural performances. In this study, a thermal fluid-structure interaction (TFSI) one-way coupled model is developed to estimate the heat transfer and stress characteristics of a face-centered cubic with vertical struts (FCCZ) lattice channel. Based on the simulation model, the heat transfer and stress characteristics of the FCCZ lattice channel produced by metal additive manufacturing (AM) are analyzed in terms of the thermal fluid field, convective heat transfer coefficient, pressure drop, and stress distribution by varying the porosity and inlet velocity. Considering the thermal-structural performance factor (TSPF), the optimum porosity of the FCCZ lattice channel is determined as 0.8. In addition, the performances of the FCCZ lattice channels using 17-4 PH, H13, and maraging steel are compared. The performance of the H13 channel is superior to those of the 17-4 PH and maraging steel channels.

Validation of a thermo-fluid-structure coupling approach for RPV creep failure analysis against FOREVER-EC2 experiment

The failure of reactor pressure vessel (RPV) during a severe accident of light water reactors is a thermal fluid-structure interaction (FSI) problem which involves melt pool heat transfer and creep deformation of the RPV. The present study is intended to explore a reliable coupling approach of thermo-fluid-structure analyses which will not only be able to reflect the transient thermal FSI feature, but also apply the advanced models and computational platforms to melt pool convection and structural mechanics, so as to improve simulation fidelity. For this purpose, the multi-physics platform of ANSYS encompassing Fluent and Structural capabilities was employed to simulate the fluid dynamics and structural mechanics in a coupled manner. In particular, the FOREVER-EC2 experiment was chosen to validate the coupling approach. The natural convection in melt pool was modeled with the SST turbulence model with a well-resolved boundary layer, while the creep deformation for the vessel made of 16MND5 steel was analyzed with a new three-stage creep model (modified theta projection model). A utility tool was introduced to transfer the transient thermal loads from Fluent to Structural which minimizes the user effort in performing the coupled analysis. The validation work demonstrated the well-posed capability of the coupling approach for prediction of the key parameters of interest, including temperature profile, total displacement of vessel bottom point and the evolution of wall thickness profile in the experiment.