Article
Mechanics
Dmitri Maklakov, Anna Lexina
Summary: In this paper, the free streamline problem of two-dimensional re-entrant jet cavity flow past an obstacle is investigated. It is shown numerically and analytically that the direction of the jet should be chosen almost opposite to the incident flow, and in the limiting configurations, the re-entrant jet vanishes and a free-surface flow with a symmetric bubble and two stagnation points is formed.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Anubhav Bhatt, Harish Ganesh, Steven L. Ceccio
Summary: Partial cavity flows on a NACA0015 hydrofoil were visualized and studied using high-speed cinematography and time-resolved X-ray densitometry. Both near-surface liquid re-entrant flow and bubbly shock waves were identified as mechanisms causing cavity pinch-off and cloud shedding. The frequency of cavity shedding was examined and found to be related to the underlying flow dynamics. The probability of re-entrant flow or bubbly shock-induced shedding processes was quantified, and it was shown that the dominant mechanism for large-scale cavity shedding and cloud cavitation is shock waves when the Mach number exceeds unity.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Mahamadou Adama Maiga, Olivier Coutier-Delgosha
Summary: The combination of ventilated cavitation and natural cavitation is studied using a numerical model. The transition between the two regimes is primarily related to a critical shift of the vortices generated behind the body, due to air injection. The critical value at the transition depends strongly on the shape of the body. The influence of the baseline flow without air injection on the transition is also analyzed.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2022)
Article
Engineering, Marine
Chandra Shekhar Pant, Steven H. Frankel
Summary: Numerical simulations were conducted to investigate the impact of active flow control on unsteady cavitation on a modified scaled-down Francis turbine, showing that the efficacy of wall jet injection in mitigating cavitation is limited by large pressure fluctuations induced by the interaction between the re-entrant jet and the wall jet under the studied operating conditions.
Article
Engineering, Electrical & Electronic
Piyush Sinha, Ch. V. N. Rao, K. J. Vinoy, Rajeev Jyoti
Summary: This paper presents the design and experimental validation of an inertial grade microwave reentrant cavity-based accelerometer with RF readout, which achieves a high scale factor with a simple method of locking the oscillator to the cavity for low phase noise output.
IEEE SENSORS JOURNAL
(2021)
Article
Engineering, Marine
Jiakun Zhang, Liang Hao, Qin Wu, Biao Huang
Summary: The paper investigates the cloud shedding processes around the NACA66 hydrofoil, focusing on the formation of re-entrant flows and the transformation of shedding modes. The LES method with the Schnerr-Sauer cavitation model in OpenFOAM is used to capture detailed flow structures. The cloud shedding process is divided into main re-entrant flow mode, transition mode, and side re-entrant flow mode based on experimental observation. The velocity in the side re-entrant flow mode fluctuates more significantly compared to the main re-entrant flow mode. The transition between the two modes is characterized by the normalized cavity length (lmax/c) and the cavity shedding frequency (St number).
Article
Mechanics
Yunqing Gu, Zhuofan Yin, Songwei Yu, Chendong He, Wenting Wang, Junjun Zhang, Denghao Wu, Jiegang Mou, Yun Ren
Summary: In order to suppress the cavitation phenomenon of fluid machinery under high-velocity flow conditions, a shark gill slit jet structure was designed based on the principle of bionics. The selected hydrofoil was an expanding symmetric structure with a chord length of 100 mm and a span length of 80 mm. A bionic jet with a velocity of 4.836 m/s was placed on the suction surface of the hydrofoil. Numerical simulations were performed for the jet hydrofoil with different chordwise jet positions, and the results showed that the optimal position was at 0.6c.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2023)
Article
Engineering, Multidisciplinary
Ziyang Wang, Huaiyu Cheng, Bin Ji
Summary: This study investigates the unsteady cavity shedding mechanism around a NACA66 hydrofoil using a self-defined compressible cavitation solver and dynamic subgrid-scale model. The results show satisfactory agreement with experimental data and provide deeper insight into pressure wave characteristics during cavity contraction. The study compares the influences of re-entrant jet and condensation shock on local flow patterns in terms of duration, velocity, cavity behavior, formation mechanism, and pressure intensity.
APPLIED MATHEMATICAL MODELLING
(2021)
Article
Engineering, Marine
Runyu Zhu, Haitao Zhu, Xiaohui Zhang
Summary: This paper numerically investigates the unsteady behavior of a free submerged cavitating jet. The results show that cavitation cloud forms around the jet core, and its shedding involves complex factors such as shear layer instability, complex pressure gradients, and re-entrant motion, which may also be related to the potential core and jet core instability. Additionally, the development of the cavitation cloud is closely related to the jet core and exhibits synchronous behavior. After the collapse of the cavitation cloud, a local high pressure is observed and cavity rebound is generated, where the collapse can be either mild or intensive.
Article
Mechanics
Aibo Wei, Limin Qiu, Xiaobin Zhang
Summary: In this paper, the unsteady cavitating flows of liquid nitrogen through a three-dimensional venturi tube in different thermal cavitation modes are modeled and simulated using the mixture multiphase model with the LES method and Sauer-Schnerr cavitation model. The study investigates the effects of thermal effects on cavitation dynamics and reveals the process of condensation shock wave propagation and the interactions between cavitation and vortex. The numerical results show good agreement with previous experiments and provide valuable insights into cryogenic cavitation dynamics.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2024)
Article
Engineering, Multidisciplinary
Ali Musa Mohammed, Yi Wang, Talal Skaik, Sheng Li, Moataz Attallah
Summary: This paper proposes a technique for measuring the effective conductivity of conductor materials using a 3D printed re-entrant cavity resonator. An analytical formula for extracting the effective conductivity has been derived based on the energy stored in the volume of the cavity. The method utilizes microwave losses to characterize the material through resonant cavity measurements, offering a simplified analytical approach and supporting the measurement of samples with arbitrary thickness. Measurements on samples produced from different manufacturing processes demonstrate the effectiveness of the method, with the copper coated polymer sample showing similar conductivity to CNC copper, indicating the good quality of the copper coating used in 3D printed polymer devices.
MEASUREMENT SCIENCE AND TECHNOLOGY
(2022)
Article
Mechanics
Rui-Nan Cui, Rui Han, Shao-Cong Pei, Shi-Ping Wang
Summary: In this study, a three-dimensional model is established to investigate the dynamics of underwater explosion bubbles. The model is based on a weakly compressible theory implemented in the boundary integral method. The accuracy and reliability of the model are validated by comparing its results with theoretical solutions, an axisymmetric model, and experimental data. The study systematically explores the jet characteristics of underwater explosion bubbles in the free field and reveals the power laws for the height, width, and velocity of the liquid jet with respect to the buoyancy parameter. The findings show that the strength parameter also plays a significant role in determining the height of the jet, especially when the buoyancy parameter is less than 0.3. The impact of an inclined wall on jet features is further investigated, and an analytical expression for the jet angle near a vertical wall is provided using the Kelvin impulse theory.
Article
Engineering, Electrical & Electronic
Ali M. Mohammed, Abarasi Hart, Joe Wood, Yi Wang, Michael J. Lancaster
Summary: This paper introduced a dielectric metrology technique using a microwave resonator-based approach and a unified analytical model to extract complex permittivity of low-loss liquid materials. The modified cavity design aimed to enhance the interaction with the material while maintaining a high quality factor. Fabrication was facilitated by SLA 3D printing, with resonator characteristics well-matched to literature values, enabling successful measurements of crude oil samples.
SENSORS AND ACTUATORS A-PHYSICAL
(2021)
Article
Multidisciplinary Sciences
Jubin Nathawat, Ishiaka Mansaray, Kohei Sakanashi, Naoto Wada, Michael D. Randle, Shenchu Yin, Keke He, Nargess Arabchigavkani, Ripudaman Dixit, Bilal Barut, Miao Zhao, Harihara Ramamoorthy, Ratchanok Somphonsane, Gil-Ho Kim, Kenji Watanabe, Takashi Taniguchi, Nobuyuki Aoki, Jong E. Han, Jonathan P. Bird
Summary: Stacking graphene with h-BN can change its bands, creating narrow minigaps and wider minibands. Hot carrier dynamics in these bands are crucial for functional (opto)electronic devices. In this study, we use rapid electrical pulsing to drive carriers into the strong electron-phonon coupling limit. By adjusting the chemical potential, we observe a cyclical evolution between metallic and semiconducting states. Our results show the importance of considering the dynamics of hot carriers and hot phonons in functional graphene superlattices.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Jian Gan, Kang Zhang, Deming Wang
Summary: This study experimentally investigated the dynamic cavitation characteristics of normal-temperature water flowing through a transparent jet pump under different cavitation conditions by adjusting the pressure ratio. The results showed that the cavitation cloud is generated by periodic oscillations of the jet traveling pressure wave and the bubble traveling pressure wave. The oscillation of these waves is caused by the collapse of the bubbles, which is the main mechanism of the bubble cloud shedding. It was also found that the pressure ratio affects the length and frequency of oscillation of the jet cloud and bubble cloud, and the strong impact between the jet traveling pressure wave and the bubble traveling pressure wave is the main cause of noise.
Article
Computer Science, Interdisciplinary Applications
Van-Tu Nguyen, Thanh-Hoang Phan, Trong-Nguyen Duy, Dong-Hyun Kim, Warn-Gyu Park
Summary: We propose a fully compressible multiphase model for simulating compressible interfacial flows. The model is based on the typical conservation laws for mixtures and is solved using a high-resolution shock-capturing finite-volume method. It can maintain sharp interfaces and achieve high accuracy, conservation properties, and thermodynamic consistency.
COMPUTERS & FLUIDS
(2022)
Article
Thermodynamics
Thanh-Hoang Phan, Van-Tu Nguyen, Trong-Nguyen Duy, Dong-Hyun Kim, Warn-Gyu Park
Summary: This study explores the effects of phase-change on the dynamics of cavitation bubbles over multiple cycles. A two-phase homogeneous mixture model combined with an interface-capturing method was used to simulate the bubble dynamics, taking into account compressibility, heat transfer, condensation, and evaporation.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Van-Tu Nguyen, Thanh-Hoang Phan, Trong-Nguyen Duy, Dong-Hyun Kim, Warn-Gyu Park
Summary: This study investigated the dynamic behavior of bubble collapses near walls and a free surface using numerical simulation, validating the results with experiments and providing important references for exploring phenomena related to bubble collapse.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2022)
Article
Engineering, Marine
Van-Tu Nguyen, Warn-Gyu Park
Summary: In this study, the thermodynamic behavior and supercavitating flow around high-subsonic to supersonic speed projectiles were analyzed using numerical methods. The mathematical model, based on conservation laws, was solved on a body-fitted grid. The results showed that increasing the stream velocity significantly raised the temperature around the stagnation point, potentially damaging the projectile's steel encasing.
Article
Mathematics, Applied
Trong-Nguyen Duy, Van-Tu Nguyen, Thanh-Hoang Phan, Dong-Hyun Kim, Warn-Gyu Park
Summary: This paper presents a free surface flow solver based on an improved coupling method for practical, highly nonlinear, and complex free surface flows. The solver is validated with practical engineering applications, demonstrating its capability and potential for further applications.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2022)
Article
Mechanics
Trong-Nguyen Duy, Van-Tu Nguyen, Warn-Gyu Park
Summary: In this study, numerical simulations were used to investigate the formation of bubbles by gas injection through an orifice in a stagnant liquid column and the flow field surrounding the bubbles after detachment under various flow conditions. The results indicated that the orifice radius and gas volume flow rate could predict the detachment time of bubbles and had a notable influence on the detached volume of bubbles. Additionally, the gas injection flow rate significantly affected the pressure field surrounding the bubbles after detachment, providing useful insights for studying bubbling flows and optimizing small-scale systems.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2022)
Article
Thermodynamics
Trong-Nguyen Duy, Van-Tu Nguyen, Thanh-Hoang Phan, Hyun-Sung Hwang, Warn-Gyu Park
Summary: In this study, the dynamics of ventilated hot gas in underwater vehicles were investigated through numerical simulations. The effects of ventilated temperatures on the cavitating flow were examined, providing valuable insights for the design and optimization of the ventilation system in underwater vehicles.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Engineering, Marine
Van-Tu Nguyen, Thanh-Hoang Phan, Trong-Nguyen Duy, Warn-Gyu Park
Summary: This study investigates the flow behavior of cavitation around projectiles moving beneath a free surface using a numerical method. The findings are significant for the design and control of submerged vehicles and projectiles operating in such flow fields.
Article
Mechanics
Quang-Thai Nguyen, Van-Tu Nguyen, Thanh-Hoang Phan, Trong-Nguyen Duy, Seong-Ho Park, Warn-Gyu Park
Summary: This paper numerically studies the dynamics of initially spherical bubble collapse near an oscillating rigid wall. Numerical simulations were conducted using a compressible two-phase flow model and the volume of fluid (VOF) interphase-sharpening technique on a general curvilinear moving grid. The effects of the oscillating wall on bubble collapse were investigated, and the interface deformation, jetting behavior, bubble collapse time, and bubble migration were determined.
Review
Physics, Fluids & Plasmas
Van-Tu Nguyen, Warn-Gyu Park
Summary: This review paper summarizes recent advancements in time-marching schemes for solving Navier-Stokes equations in multiphase flow simulations, focusing on dual-time stepping, local preconditioning, and artificial compressibility methods. These methods have been proven effective in achieving high time accuracy and converting incompressible NS equations into a hyperbolic form for solution convergence acceleration and simulation of compressible flows at all Mach numbers. The continuing growth of literature on these methods provides deeper understanding of underlying physical processes and supports technological advancements. The paper also emphasizes the imposition of dual-time stepping on both incompressible and compressible NS equations. It provides an updated overview for the CFD community to develop methods and select the most suitable two-phase flow solver for their respective applications.
Article
Engineering, Marine
Trong-Nguyen Duy, Thanh-Hoang Phan, Quang-Thai Nguyen, Seong-Ho Park, Warn-Gyu Park
Summary: This study investigates bubble dynamics with highly nonlinear interactions between an oscillating bubble and gas-liquid interface in the vicinity of a rigid wall with a gas-entrapping hole through numerical simulations. The simulations show that the gas entrapped inside the hole significantly affects the formation and redirection of the liquid jet, as well as the dynamics of the cavitation bubble.
Article
Mechanics
Van-Tu Nguyen, Thanh-Hoang Phan, Warn-Gyu Park
Summary: This study validates the applicability of the fully conservative compressible multiphase flow model in simulating the collapse of cavitation bubbles. The numerical method effectively captures the strong shocks induced by the collapse, and the simulation results show a high level of agreement with experimental data. The study provides valuable insight into the complex behavior of cavitation bubbles in a free field.
Article
Construction & Building Technology
Van My Nguyen, Hoang Nam Phan, Thanh Hoang Phan
Summary: This paper develops an efficient surrogate model based on the Gaussian process to rapidly predict the nonlinear hydrodynamic pressure coefficients on submerged bodies near the water surface. By establishing surrogate models using outcome from CFD simulations, the mean and oscillation amplitudes of pressure coefficients can be rapidly predicted without re-simulation, allowing for the assessment of hydrodynamic forces and their instability of civil structures.
Article
Thermodynamics
Mahsa Taghavi, Swapnil Sharma, Vemuri Balakotaiah
Summary: This study investigates the natural convection effects in the insulation layers of spherical storage tanks and their impact on the tanks' performance. The permeability and Rayleigh number of the insulation material are considered as key factors. The results show that as the Rayleigh number increases, new convective cells emerge and cause the cold boundary to approach the external hot boundary. In the case of large temperature differences, multiple solutions may coexist.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinyang Xu, Fangjun Hong, Chaoyang Zhang
Summary: This study introduces a self-induced jet impingement device for enhancing pool boiling performance in high power electronic cooling. Through visualization and parametric investigations, the effects of this device on pool boiling performance are studied, revealing the promotion of additional liquid supply and vapor exhausting. The flow rate of the liquid jet is found to positively impact boiling performance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Wenchao Ke, Yuan Liu, Fissha Biruke Teshome, Zhi Zeng
Summary: Underwater wet laser welding (UWLW) is a promising and labor-saving repair technique. A thermal multi-phase flow model was developed to study the heat transfer, fluid dynamics, and phase transitions during UWLW. The results show that UWLW creates a water keyhole, making the welding environment similar to in air laser welding.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Xingrong Lian, Lin Tian, Zengyao Li, Xinpeng Zhao
Summary: This study investigates the heat transfer mechanisms in natural fiber-derived porous structures and finds that thermal radiation has a significant impact on the thermal conductivity in low-density regions, while natural convection rarely occurs. Insulation materials derived from micron-sized natural fibers can achieve minimum thermal conductivity at specific densities. Strategies to lower the thermal conductivity include increasing porosity and incorporating nanoscale pores using nanosize fibers.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Yasir A. Malik, Kilian Koebschall, Stephan Bansmer, Cameron Tropea, Jeanette Hussong, Philippe Villedieu
Summary: Ice crystal icing is a significant hazard in aviation, and accurate modeling of sticking efficiency is essential. In this study, icing wind tunnel experiments were conducted to quantify the volumetric liquid water fraction, sticking efficiency, and maximum thickness of ice layers. Two measurement techniques, calorimetry and capacitive measurements, were used to measure the liquid water content and distribution in the ice layers. The experiments showed that increasing wet bulb temperatures and substrate heat flux significantly increased sticking efficiency and maximum ice layer thickness.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinqi Hu, Tongtong Geng, Kun Wang, Yuanhong Fan, Chunhua Min, Hsien Chin Su
Summary: This study experimentally examined the heat dissipation of vibrating fans and demonstrated its inherent mechanism through numerical simulation. The results showed that the flow fields induced by the vibrating blades exhibited pulsating features and formed large-scale and small-scale vortical structures, significantly improving heat dissipation. The study also identified the impacts of different blade structures and developed a trapezoidal-folding blade, which effectively reduced the maximum temperature of the heat source and alleviated high-temperature failure crisis.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Dan-Dan Su, Xiao-Bin Li, Hong-Na Zhang, Feng-Chen Li
Summary: The boiling heat transfer of low-boiling-point working fluid is a common heat dissipation technology in electronic equipment cooling. This study analyzed the interfacial boiling behavior of R134a under different conditions and found that factors such as the initial thickness of the liquid film, solid-liquid interaction force, and initial temperature significantly affect the boiling mode and thermal resistance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinyi Wu, Dongke Sun, Wei Chen, Zhenhua Chai
Summary: A unified lattice Boltzmann-phase field scheme is proposed to simulate dendrite growth of binary alloys in the presence of melt convection. The effects of various factors on the growth are investigated numerically, and the model is validated through comparisons and examinations.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Shaokun Ge, Ya Ni, Fubao Zhou, Wangzhaonan Shen, Jia Li, Fengqi Guo, Bobo Shi
Summary: This study investigated the temperature distribution of main cables in a suspension bridge during fire scenarios and proposed a prediction model for the maximum temperature of cables in different lane fires. The results showed that vehicle fires in the emergency lane posed a greater thermal threat to the cables.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Shuang-Ying Wu, Shi-Yao Zhou, Lan Xiao, Jia Luo
Summary: This paper investigates the two-phase flow and heat transfer characteristics of low-velocity jet impacting on a cylindrical surface. The study reveals that the heat transfer regimes are non-phase transition and nucleate boiling with the increase of heat transfer rate. The effects of jet impact height and outlet velocity on local surface temperatures are pronounced at the non-phase transition stage. The growth rates of heat transfer rate and liquid loss rate increase significantly from the non-phase transition to nucleate boiling stage.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Emad Hasani Malekshah, Wlodzimierz Wlodzimierz, Miros law Majkut
Summary: Cavitation has significant practical importance and can be controlled by air injection. This study investigates the natural to ventilated cavitation process around a hydrofoil through numerical and experimental methods. The results show that the location and rate of air injection have a meaningful impact on the characteristics of cavitation.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Feriel Yahiat, Pascale Bouvier, Antoine Beauvillier, Serge Russeil, Christophe Andre, Daniel Bougeard
Summary: This study explores the enhancement of mixing performance in laminar flow equipment by investigating the generation of chaotic advection using wall deformations in annular geometries. The findings demonstrate that the combined geometry can achieve perfect mixing at various Reynolds numbers.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Hui He, Ning Lyu, Caihua Liang, Feng Wang, Xiaosong Zhang
Summary: This study investigates the condensation, frosting, and defrosting processes on superhydrophobic surfaces with millimeter-scale structures. The results reveal that the structures can influence the growth and removal of frost crystals, with the bottom grooves creating a frost-free zone and conical edges promoting higher frost crystal heights. Two effective methods for defrosting are observed: hand-lifting the groove and airfoil retraction contraction on protruding structures. This research provides valuable insights into frost formation and defrosting on millimeter-structured superhydrophobic surfaces, with potential applications in anti-frost engineering.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Thiwanka Arepolage, Christophe Verdy, Thibaut Sylvestre, Aymeric Leray, Sebastien Euphrasie
Summary: This study developed two thermal concentrators, one with a 2D design of uniform thickness and another with a 3D design, using the coordinate transformation technique and metamaterials. By structuring the thermal conductor, the desired local density-heat capacity product and anisotropic thermal conductivities were achieved. The homogenized thermal conductivities were obtained from finite element simulations and cylindrical symmetry consideration. A 3D concentrator was fabricated using 3D metal printing and characterized using a thermal camera. Compared to devices that solely consider anisotropic conductivities, the time evolution characteristics of the metadevice designed with coordinate transformation were closer to those of an ideal concentrator.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Liangyuan Cheng, Qingyang Wang, Jinliang Xu
Summary: In this study, we investigated the supercritical heat transfer of CO2 in a horizontal tube with a diameter of 10.0 mm, covering a wide range of pressures, mass fluxes, and heat fluxes. The study revealed a non-monotonic increase in wall temperatures along the flow direction and observed both positive and negative wall temperature differences between the bottom and top tube. The findings were explained by the thermal conduction in the solid wall interacting with the stratified-wavy flow in the tube.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
