Transactions of Nanjing University of Aeronautics & Astronautics
Issue 2,2025 Table of Contents
2025(2):137-161.
DOI: 10.16356/j.1005-1120.2025.02.001
Abstract:
The diffuse-interface immersed boundary method （IBM） possesses excellent capabilities for simulating flows around complex geometries and moving boundaries. In this method， the flow field is solved on a fixed Cartesian mesh， while the solid boundary is discretized into a series of Lagrangian points immersed in the flow field. The boundary condition is implemented by introducing a force term into the momentum equation， and the interaction between the immersed boundary and the fluid domain is achieved via an interpolation process. Over the past decades， the diffuse-interface IBM has gained popularity and spawned many variants， effectively handling a wide range of flow problems from isothermal to thermal flows， from laminar to turbulent flows， and from complex geometries to fluid-structure interaction scenarios. This paper first outlines the basic principles of the diffuse-interface IBM， then highlights recent advancements achieved by the authors’ research group， and finally shows the method’s excellent numerical performance and wide applicability through several case studies involving complex moving boundary problems.
The diffuse-interface immersed boundary method （IBM） possesses excellent capabilities for simulating flows around complex geometries and moving boundaries. In this method， the flow field is solved on a fixed Cartesian mesh， while the solid boundary is discretized into a series of Lagrangian points immersed in the flow field. The boundary condition is implemented by introducing a force term into the momentum equation， and the interaction between the immersed boundary and the fluid domain is achieved via an interpolation process. Over the past decades， the diffuse-interface IBM has gained popularity and spawned many variants， effectively handling a wide range of flow problems from isothermal to thermal flows， from laminar to turbulent flows， and from complex geometries to fluid-structure interaction scenarios. This paper first outlines the basic principles of the diffuse-interface IBM， then highlights recent advancements achieved by the authors’ research group， and finally shows the method’s excellent numerical performance and wide applicability through several case studies involving complex moving boundary problems.
2025(2):162-177.
DOI: 10.16356/j.1005-1120.2025.02.002
Abstract:
The electro-thermal anti/de-icing systems have high heating efficiency and relatively simple structures， marking them as a key development direction for future icing protection. Existing simulation algorithms for electro-thermal de-icing seldom delve into comprehensive ice accretion-melting-deicing models that account for ice shedding. Therefore， the detachment behavior of ice layers during the heating process requires in-depth research and discussion. This paper physically models the phenomenon of ice shedding， incorporates the detachment behavior of ice layers during heating， improves the existing mathematical model for electro-thermal de-icing calculations， establishes an ice accretion-melting-deicing model for electro-thermal de-icing systems， and conducts numerical simulation， verification and optimization analysis of electro-thermal de-icing considering ice shedding. Through multi-condition de-icing numerical simulations of a specific wing model， it is found that ambient temperature can serve as a factor for adapting the electro heating anti/de-icing strategy to the environment. An optimization of heating heat flux density and heating/cooling time is conducted for the wing de-icing control law under the calculated conditions. The improved electro-thermal de-icing model and algorithm developed in this paper provide solid technical support for the design of electro-thermal de-icing systems.
The electro-thermal anti/de-icing systems have high heating efficiency and relatively simple structures， marking them as a key development direction for future icing protection. Existing simulation algorithms for electro-thermal de-icing seldom delve into comprehensive ice accretion-melting-deicing models that account for ice shedding. Therefore， the detachment behavior of ice layers during the heating process requires in-depth research and discussion. This paper physically models the phenomenon of ice shedding， incorporates the detachment behavior of ice layers during heating， improves the existing mathematical model for electro-thermal de-icing calculations， establishes an ice accretion-melting-deicing model for electro-thermal de-icing systems， and conducts numerical simulation， verification and optimization analysis of electro-thermal de-icing considering ice shedding. Through multi-condition de-icing numerical simulations of a specific wing model， it is found that ambient temperature can serve as a factor for adapting the electro heating anti/de-icing strategy to the environment. An optimization of heating heat flux density and heating/cooling time is conducted for the wing de-icing control law under the calculated conditions. The improved electro-thermal de-icing model and algorithm developed in this paper provide solid technical support for the design of electro-thermal de-icing systems.
2025(2):178-190.
DOI: 10.16356/j.1005-1120.2025.02.003
Abstract:
The icing characteristics of supercooled large droplet （SLD） impacting carbon fiber-reinforced composites （CFRCs） remain poorly understood， hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft. The paper systematically investigates the effects of the supercooling degree， the surface temperature， and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces. To address the ice-prone nature of CFRCs， nanoparticle-modified anti-icing coatings are developed， and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed. Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation. Under conditions of droplet temperature （-15 ℃） and surface temperature （-18 ℃）， the icing time of hydrophobic-modified CFRCs was delayed by over 1 100 ms， representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.
The icing characteristics of supercooled large droplet （SLD） impacting carbon fiber-reinforced composites （CFRCs） remain poorly understood， hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft. The paper systematically investigates the effects of the supercooling degree， the surface temperature， and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces. To address the ice-prone nature of CFRCs， nanoparticle-modified anti-icing coatings are developed， and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed. Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation. Under conditions of droplet temperature （-15 ℃） and surface temperature （-18 ℃）， the icing time of hydrophobic-modified CFRCs was delayed by over 1 100 ms， representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.
2025(2):191-200.
DOI: 10.16356/j.1005-1120.2025.02.004
Abstract:
This numerical simulation investigates the two-phase flow under the condition of supercooled large droplets impinging on the aircraft surface. Based on Eulerian framework， a method for calculating supercooled water droplet impingement characteristics is established. Then， considering the deformation and breaking effects during the movement， this method is extended to calculate the impingement characteristics of supercooled large droplets， as well as the bouncing and splashing effects during impingement. The impingement characteristics of supercooled large droplets is then investigated by this method. The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper. In addition， the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects. The bouncing effect mainly affects the mass loss near the impingement limits， while the splashing effect influences the result around the stagnation point. This investigation is beneficial for the analysis of aircraft icing and the design of anti-icing system with supercooled large droplet conditions.
This numerical simulation investigates the two-phase flow under the condition of supercooled large droplets impinging on the aircraft surface. Based on Eulerian framework， a method for calculating supercooled water droplet impingement characteristics is established. Then， considering the deformation and breaking effects during the movement， this method is extended to calculate the impingement characteristics of supercooled large droplets， as well as the bouncing and splashing effects during impingement. The impingement characteristics of supercooled large droplets is then investigated by this method. The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper. In addition， the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects. The bouncing effect mainly affects the mass loss near the impingement limits， while the splashing effect influences the result around the stagnation point. This investigation is beneficial for the analysis of aircraft icing and the design of anti-icing system with supercooled large droplet conditions.
ZHANG Dexin
,
ZENG Tenghui
,
WANG Liu
,
SUN Bo
,
CHENG Zikang
,
FENG Jiaxin
,
XIE Junlong
,
CHEN Jianye
2025(2):201-211.
DOI: 10.16356/j.1005-1120.2025.02.005
Abstract:
Accurate simulation of ice accretion of supercooled large droplet （SLD） is pivotal for the international airworthiness certification of large aircraft. Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions. A numerical model of multi-particle SLD coupling breaking， bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size. The results show that the peak value of droplet collection efficiency β decreases due to splashing. The bounce phenomenon will make the impact limit Sm of the water drops decrease. With the increase of the SLD particle size， the water drop bounce point gradually moves toward the trailing edge of the wing. The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100 μm. When the SLD particle size increases， the height of the water droplet shelter zone on the upper edge of the wing gradually decreases， and the velocity in the Y direction decreases first and then increases in the opposite direction， increasing the probability of SLD hitting the wing again. Large particle droplets have a higher effect on the impact limit Sm than smaller droplets. Therefore， in the numerical simulation of the SLD operating conditions， it is very important to ensure the proportion of large particle size water droplets.
Accurate simulation of ice accretion of supercooled large droplet （SLD） is pivotal for the international airworthiness certification of large aircraft. Its complex dynamics behavior and broad particle size distributions pose significant challenges to reliable CFD predictions. A numerical model of multi-particle SLD coupling breaking， bouncing and splashing behaviors is established to explore the relationship between dynamics behavior and particle size. The results show that the peak value of droplet collection efficiency β decreases due to splashing. The bounce phenomenon will make the impact limit Sm of the water drops decrease. With the increase of the SLD particle size， the water drop bounce point gradually moves toward the trailing edge of the wing. The critical breaking diameter of SLD at an airflow velocity of 50 m/s is approximately 100 μm. When the SLD particle size increases， the height of the water droplet shelter zone on the upper edge of the wing gradually decreases， and the velocity in the Y direction decreases first and then increases in the opposite direction， increasing the probability of SLD hitting the wing again. Large particle droplets have a higher effect on the impact limit Sm than smaller droplets. Therefore， in the numerical simulation of the SLD operating conditions， it is very important to ensure the proportion of large particle size water droplets.
2025(2):212-225.
DOI: 10.16356/j.1005-1120.2025.02.006
Abstract:
Existing icing detection technologies face challenges when applied to small and medium-sized aircraft， especially electric vertical take-off and landing （eVTOL） aircraft that meet the needs of low-altitude economic development. This study proposes a data-driven icing detection method based on rotor performance evolution. Through dry-air baseline tests and dynamic icing comparative experiments （wind speed 0—30 m/s， rotational speed 0—3 000 r/min， collective pitch 0°—8°） of a 0.6 m rotor in the FL-61 icing wind tunnel， a multi-source heterogeneous dataset containing motion parameters， aerodynamic parameters， and icing state identifiers is constructed. An innovative signal processing architecture combining adaptive Kalman filtering and moving average cascading is adopted. And a comparative study is conducted on the performance of support vector machine （SVM）， multilayer perceptron （MLP）， and random forest （RF） algorithms， achieving real-time identification of icing states in rotating components. Experimental results demonstrate that the method exhibits a minimum detection latency of 6.9 s and 96% overall accuracy in reserved test cases， featuring low-latency and low false-alarm， providing a sensor-free lightweight solution for light/vertical takeoff and landing aircraft.
Existing icing detection technologies face challenges when applied to small and medium-sized aircraft， especially electric vertical take-off and landing （eVTOL） aircraft that meet the needs of low-altitude economic development. This study proposes a data-driven icing detection method based on rotor performance evolution. Through dry-air baseline tests and dynamic icing comparative experiments （wind speed 0—30 m/s， rotational speed 0—3 000 r/min， collective pitch 0°—8°） of a 0.6 m rotor in the FL-61 icing wind tunnel， a multi-source heterogeneous dataset containing motion parameters， aerodynamic parameters， and icing state identifiers is constructed. An innovative signal processing architecture combining adaptive Kalman filtering and moving average cascading is adopted. And a comparative study is conducted on the performance of support vector machine （SVM）， multilayer perceptron （MLP）， and random forest （RF） algorithms， achieving real-time identification of icing states in rotating components. Experimental results demonstrate that the method exhibits a minimum detection latency of 6.9 s and 96% overall accuracy in reserved test cases， featuring low-latency and low false-alarm， providing a sensor-free lightweight solution for light/vertical takeoff and landing aircraft.
2025(2):226-237.
DOI: 10.16356/j.1005-1120.2025.02.007
Abstract:
This study addresses the issue of spray icing on the air intake grilles of ship power systems in cold maritime environments. Through numerical simulation methods， the influence of environmental parameters on icing characteristics is revealed， and an energy-efficient zoned electric heating anti-icing strategy is proposed. A three-dimensional grille model is constructed to systematically analyze the effects of environmental temperature （from -20 ℃ to -4 ℃）， droplet diameter （from 50 μm to 500 μm）， and liquid water content （from 0.5 g/m3 to 8 g/m3） on icing rates and blockage of the flow channel. The results indicate that low temperature and high liquid water content significantly exacerbate icing. Under the condition of an environmental temperature of -20 ℃， droplet diameter of 500 μm， and liquid water content of 8 g/m3， the flow channel blockage ratio reaches 30.95% within 10 min. Additionally， as droplet diameter increases， the droplet impingement and icing regions become more concentrated toward the leading edge of blades. To mitigate grille icing in cold environments， an electric heating film configuration is employed for thermal protection. Optimization of the heating strategy reveals that the zoned heating approach， compared to the initial uniform heating scheme， effectively homogenizes surface temperature distribution while reducing total power consumption by 37.47%. This study validates the engineering applicability of the zoned electric heating anti/de-icing strategy， providing theoretical and technical support for the design of anti-icing systems in ship power systems operating in cold maritime regions.
This study addresses the issue of spray icing on the air intake grilles of ship power systems in cold maritime environments. Through numerical simulation methods， the influence of environmental parameters on icing characteristics is revealed， and an energy-efficient zoned electric heating anti-icing strategy is proposed. A three-dimensional grille model is constructed to systematically analyze the effects of environmental temperature （from -20 ℃ to -4 ℃）， droplet diameter （from 50 μm to 500 μm）， and liquid water content （from 0.5 g/m3 to 8 g/m3） on icing rates and blockage of the flow channel. The results indicate that low temperature and high liquid water content significantly exacerbate icing. Under the condition of an environmental temperature of -20 ℃， droplet diameter of 500 μm， and liquid water content of 8 g/m3， the flow channel blockage ratio reaches 30.95% within 10 min. Additionally， as droplet diameter increases， the droplet impingement and icing regions become more concentrated toward the leading edge of blades. To mitigate grille icing in cold environments， an electric heating film configuration is employed for thermal protection. Optimization of the heating strategy reveals that the zoned heating approach， compared to the initial uniform heating scheme， effectively homogenizes surface temperature distribution while reducing total power consumption by 37.47%. This study validates the engineering applicability of the zoned electric heating anti/de-icing strategy， providing theoretical and technical support for the design of anti-icing systems in ship power systems operating in cold maritime regions.
2025(2):238-249.
DOI: 10.16356/j.1005-1120.2025.02.008
Abstract:
To reduce the complexity of mixing systems and improve mixing efficiency， this paper proposes a valveless piezoelectric pump integrated with airfoil baffles， which embodies both active and passive mixing attributes. The airfoil baffles are designed using the asymmetric NACA63-412 profile. The impact of the airfoil angle of attack on the flow field within the tube and the output and mixing performance of the piezoelectric pump is investigated. Computational simulations of the tube with airfoil baffle indicated that as the angle of attack increases， the position of vortex generation at the leading and trailing edge regions of the airfoil baffle progressively moves forward in the direction of fluid flow. Then the vortex volume enlarges， and the vortex intensity within the flow field rises. Subsequently， the prototypes of valveless piezoelectric pumps at four different angles of attack are fabricated and their output performances are experimentally evaluated. The results demonstrate that the maximum output flow rate of the pump decreases with an increasing angle of attack. At an angle of attack of 0°， the maximum output flow rate of the pump reaches 225.3 ml/min. Mixing performance experiments are conducted using the piezoelectric pump for the synthesis of Fe3O4 particles. The findings indicate that as the angle of attack increases， the number of Fe3O4 particles formed in the mixture significantly rises， with a narrower particle size distribution and more regular morphology. At an angle of attack of 15°， the synthesized Fe3O4 particles have an approximate diameter of 10 μm. The outcomes of this paper offer valuable insights for the design of microfluidic systems， catering to the demands of material synthesis， chemistry， and biomedical applications.
To reduce the complexity of mixing systems and improve mixing efficiency， this paper proposes a valveless piezoelectric pump integrated with airfoil baffles， which embodies both active and passive mixing attributes. The airfoil baffles are designed using the asymmetric NACA63-412 profile. The impact of the airfoil angle of attack on the flow field within the tube and the output and mixing performance of the piezoelectric pump is investigated. Computational simulations of the tube with airfoil baffle indicated that as the angle of attack increases， the position of vortex generation at the leading and trailing edge regions of the airfoil baffle progressively moves forward in the direction of fluid flow. Then the vortex volume enlarges， and the vortex intensity within the flow field rises. Subsequently， the prototypes of valveless piezoelectric pumps at four different angles of attack are fabricated and their output performances are experimentally evaluated. The results demonstrate that the maximum output flow rate of the pump decreases with an increasing angle of attack. At an angle of attack of 0°， the maximum output flow rate of the pump reaches 225.3 ml/min. Mixing performance experiments are conducted using the piezoelectric pump for the synthesis of Fe3O4 particles. The findings indicate that as the angle of attack increases， the number of Fe3O4 particles formed in the mixture significantly rises， with a narrower particle size distribution and more regular morphology. At an angle of attack of 15°， the synthesized Fe3O4 particles have an approximate diameter of 10 μm. The outcomes of this paper offer valuable insights for the design of microfluidic systems， catering to the demands of material synthesis， chemistry， and biomedical applications.
2025(2):250-260.
DOI: 10.16356/j.1005-1120.2025.02.009
Abstract:
The structural dynamic response reconstruction technology can extract unmeasured information from limited measured data， significantly impacting vibration control， load identification， parameter identification， fault diagnosis， and related fields. This paper proposes a dynamic response reconstruction method based on the Kalman filter， which simultaneously identifies external excitation and reconstructs dynamic responses at unmeasured positions. The weighted least squares method determines the load weighting matrix for excitation identification， while the minimum variance unbiased estimation determines the Kalman filter gain. The excitation prediction Kalman filter is constructed through time， excitation， and measurement updates. Subsequently， the response at the target point is reconstructed using the state vector， observation matrix， and excitation influence matrix obtained through the excitation prediction Kalman filter algorithm. An algorithm for reconstructing responses in continuous system using the excitation prediction Kalman filtering algorithm in modal space is derived. The proposed structural dynamic response reconstruction method evaluates the response reconstruction and the load identification performance under various load types and errors through simulation examples. Results demonstrate the accurate excitation identification under different load conditions and simultaneous reconstruction of target point responses， verifying the feasibility and reliability of the proposed method.
The structural dynamic response reconstruction technology can extract unmeasured information from limited measured data， significantly impacting vibration control， load identification， parameter identification， fault diagnosis， and related fields. This paper proposes a dynamic response reconstruction method based on the Kalman filter， which simultaneously identifies external excitation and reconstructs dynamic responses at unmeasured positions. The weighted least squares method determines the load weighting matrix for excitation identification， while the minimum variance unbiased estimation determines the Kalman filter gain. The excitation prediction Kalman filter is constructed through time， excitation， and measurement updates. Subsequently， the response at the target point is reconstructed using the state vector， observation matrix， and excitation influence matrix obtained through the excitation prediction Kalman filter algorithm. An algorithm for reconstructing responses in continuous system using the excitation prediction Kalman filtering algorithm in modal space is derived. The proposed structural dynamic response reconstruction method evaluates the response reconstruction and the load identification performance under various load types and errors through simulation examples. Results demonstrate the accurate excitation identification under different load conditions and simultaneous reconstruction of target point responses， verifying the feasibility and reliability of the proposed method.
2025(2):261-274.
DOI: 10.16356/j.1005-1120.2025.02.010
Abstract:
Minimum quantity lubrication （MQL） is a technique that achieves effective lubrication and cooling of the cutting zone by using a minimal amount of cutting fluid. This results in a decrease in the cutting temperature， extending the cutting tool life and improving the surface quality of the workpiece. Optimizing the nozzle settings can enhance the cooling and lubrication performance of MQL， leading to increased processing efficiency and product quality. Nozzles with different shapes are fabricated， and different outlet diameters and wall thicknesses are set. The cutting process takes into account the impact of spindle speed and feed rate. An experimental study is conducted to investigate the atomization cone angle and particle size distribution of different nozzles. The circular nozzle is more conducive to the concentrated injection of an atomized liquid beam. The atomization cone angle is the largest when the nozzle outlet diameter is 1.2 mm. Enlarging the nozzle outlet diameter will increase the diameter of the atomized droplets. The atomization cone angle increases while the droplet diameter decreases with the increase of outlet wall thickness. Properly increasing the outlet wall thickness is beneficial to improving the atomization quality. The droplet diameter increases firstly and then decreases with the increase of spindle speed and feed rate. Increasing the MQL gas supply pressure and reducing the lubricating oil flow rate will improve the atomization quality of the nozzle. Studies on the influence of the MQL nozzle processing technology on the atomization effect can help to enhance the cooling and lubrication performance of the MQL technology， leading to improved processing efficiency and quality.
Minimum quantity lubrication （MQL） is a technique that achieves effective lubrication and cooling of the cutting zone by using a minimal amount of cutting fluid. This results in a decrease in the cutting temperature， extending the cutting tool life and improving the surface quality of the workpiece. Optimizing the nozzle settings can enhance the cooling and lubrication performance of MQL， leading to increased processing efficiency and product quality. Nozzles with different shapes are fabricated， and different outlet diameters and wall thicknesses are set. The cutting process takes into account the impact of spindle speed and feed rate. An experimental study is conducted to investigate the atomization cone angle and particle size distribution of different nozzles. The circular nozzle is more conducive to the concentrated injection of an atomized liquid beam. The atomization cone angle is the largest when the nozzle outlet diameter is 1.2 mm. Enlarging the nozzle outlet diameter will increase the diameter of the atomized droplets. The atomization cone angle increases while the droplet diameter decreases with the increase of outlet wall thickness. Properly increasing the outlet wall thickness is beneficial to improving the atomization quality. The droplet diameter increases firstly and then decreases with the increase of spindle speed and feed rate. Increasing the MQL gas supply pressure and reducing the lubricating oil flow rate will improve the atomization quality of the nozzle. Studies on the influence of the MQL nozzle processing technology on the atomization effect can help to enhance the cooling and lubrication performance of the MQL technology， leading to improved processing efficiency and quality.
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