231 research outputs found
Data for: Hummingbirds use wing inertial effects to improve maneuverability
No full textThis dataset is associated with an article with the same title published on the Journal of Royal Society Interface
sj-docx-1-car-10.1177_19476035231207778 – Supplemental material for Novel-miR-81 Promotes the Chondrocytes Differentiation of Bone Marrow Mesenchymal Stem Cells Through Inhibiting Rac2 Expression
No full textSupplemental material, sj-docx-1-car-10.1177_19476035231207778 for Novel-miR-81 Promotes the Chondrocytes Differentiation of Bone Marrow Mesenchymal Stem Cells Through Inhibiting Rac2 Expression by Ziwei Luo, Jinqi Xie, Haoxiang Ye, Jie Zhang, Yangping Liu, Chunmei Ma, Jiahui Cao, Hao Pan, Xiaosheng Liu, Xianxi Zhou, Jiechen Kong, Dongfeng Chen and Aijun Liu in CARTILAGE</p
sj-tif-2-car-10.1177_19476035231207778 – Supplemental material for Novel-miR-81 Promotes the Chondrocytes Differentiation of Bone Marrow Mesenchymal Stem Cells Through Inhibiting Rac2 Expression
No full textSupplemental material, sj-tif-2-car-10.1177_19476035231207778 for Novel-miR-81 Promotes the Chondrocytes Differentiation of Bone Marrow Mesenchymal Stem Cells Through Inhibiting Rac2 Expression by Ziwei Luo, Jinqi Xie, Haoxiang Ye, Jie Zhang, Yangping Liu, Chunmei Ma, Jiahui Cao, Hao Pan, Xiaosheng Liu, Xianxi Zhou, Jiechen Kong, Dongfeng Chen and Aijun Liu in CARTILAGE</p
Computational Modeling of the Hummingbird Escape Maneuver
No full textHummingbirds are perhaps the most agile flyers in nature. Studying the underlying physics of hummingbird flight may provide inspiration for developing highly maneuverable micro aerial vehicles (MAVs). In this work, we have developed a high-fidelity computational fluid dynamics (CFD) model to analyze the aerodynamics and flight mechanics of the hummingbird escape maneuver, in which hovering hummingbirds were startled and perform a rapid (less than 0.2 seconds) maneuver to back away from a perceived looming threat on the front side. Several novel mechanisms were discovered in this study. First, we found evidence across several species that hummingbirds use the inertial forces of their wings to increase their body rotational acceleration. For example, at pronation when the wings switch from upstroke to downstroke, the wing inertial forces create a torque that helps pitch up the bird’s body to move the head away from the threat. Such inertial steering effects are accompanied by aerodynamic steering of the wings to generate a fast rotational speed to improve maneuverability. Second, we studied the actuation of the wings during the escape maneuver by considering the muscle input at the shoulder joint in addition to the wings’ aerodynamic and inertial outputs. Contrary to previous thoughts that wing pitch rotation is primarily passive due to the wings’ own inertia, our results show that significant power input was required to pitch up the wings during downstroke to enhance aerodynamic force production. As a result, an active mechanism is required to pitch the wings for maximal force output. Third, we found that pitch, roll, and yaw rotations of the bird body may overlap with one another, which may create a nonlinear, inertial coupling effect that hummingbirds utilize as a passive mechanism for flight control, e.g., to stabilize body pitching during the maneuver. These novel findings have significantly improved our understanding of hummingbirds’ great maneuverability and may be useful for the future development of bioinspired MAVs
Subject-specific computational fluid-structure interaction modeling of type-1 thyroplasty
No full textUnilateral vocal fold paralysis (UVFP) is a condition in which one side of the vocal fold loses its adduction function and thus the vocal fold cannot vibrate normally, leading to difficulties in voice production. In type-1 thyroplasty, an implant is introduced through the thyroid cartilage to medialize the paralyzed vocal fold and restore voice. To improve implant design, our primary focus is to develop a high-fidelity fluid-structure interaction (FSI) model of the vocal fold undergoing the surgery, and to validate the model using integrated experimental studies of rabbit larynges.
First, we performed 3D FSI simulations of healthy phonation, where the two sides of the vocal fold were medialized symmetrically. By incorporating the subject-specific anatomical features reconstructed from magnetic resonance scans, as well as individualized tissue properties estimated using a simple flow model, the high-fidelity model was able to capture the subject-specific vibratory characteristics that matched the in vivo phonation test.
Next, we conducted an integrated experimental and computational study of an ex vivo rabbit larynx at both the UVFP and type-1 thyroplasty conditions. The model was built upon the pre-operative scan and the simulation consisted of two steps: 1) a finite-element method simulation of the vocal fold adduction to model the medialization of the implant; 2) an FSI simulation with the implant incorporated to model the vibration of the vocal fold. The results from both steps agree with experiment data, i.e., post-operative scan and high-speed imaging, thus showing successful model validation.
Finally, we employed the computational model to optimize implant position and depth. The degree of static displacement due to implant medialization and the vibration amplitude were used for implant assessment. The results show that the optimal implant position for vibration differed from that for maximal displacement, which highlights the need for FSI modeling to predict the implant's comprehensive effects. The model prediction is generally aligned with previous experimental studies but also shows that optimal implant depends on subject-specific features. Thus, a computational modeling-based tool would be useful for pre-surgical planning
Computational Modeling of the Hummingbird Escape Maneuver
No full textHummingbirds are perhaps the most agile flyers in nature. Studying the underlying physics of hummingbird flight may provide inspiration for developing highly maneuverable micro aerial vehicles (MAVs). In this work, we have developed a high-fidelity computational fluid dynamics (CFD) model to analyze the aerodynamics and flight mechanics of the hummingbird escape maneuver, in which hovering hummingbirds were startled and perform a rapid (less than 0.2 seconds) maneuver to back away from a perceived looming threat on the front side. Several novel mechanisms were discovered in this study. First, we found evidence across several species that hummingbirds use the inertial forces of their wings to increase their body rotational acceleration. For example, at pronation when the wings switch from upstroke to downstroke, the wing inertial forces create a torque that helps pitch up the bird’s body to move the head away from the threat. Such inertial steering effects are accompanied by aerodynamic steering of the wings to generate a fast rotational speed to improve maneuverability. Second, we studied the actuation of the wings during the escape maneuver by considering the muscle input at the shoulder joint in addition to the wings’ aerodynamic and inertial outputs. Contrary to previous thoughts that wing pitch rotation is primarily passive due to the wings’ own inertia, our results show that significant power input was required to pitch up the wings during downstroke to enhance aerodynamic force production. As a result, an active mechanism is required to pitch the wings for maximal force output. Third, we found that pitch, roll, and yaw rotations of the bird body may overlap with one another, which may create a nonlinear, inertial coupling effect that hummingbirds utilize as a passive mechanism for flight control, e.g., to stabilize body pitching during the maneuver. These novel findings have significantly improved our understanding of hummingbirds’ great maneuverability and may be useful for the future development of bioinspired MAVs
Effects of Particle Hydrodynamic Behaviors on the Electrochemical Performance of Slurry Electrodes
No full textIn flowable slurry electrodes, charge is transferred from stationary electrodes to particle clusters through hydrodynamic interactions; however, so far little is known about the particle dynamic behavior under continuous flow. This dissertation aims to uncover new understandings about these behaviors and their effects on the electrochemical performance of flowable electrodes through numerical and experimental methods.
Using Stokesian dynamics, we explore the effects of conductive additive on the charging of a slurry electrode and present a unified expression for the dynamically varying electrical network of particles. The results suggest that at lower concentrations of activated carbon particles, the conductive additive enhances charge transfer by filling interstitial spaces and establishing contacts between carbon particles; however, at higher concentrations, the benefits are not as clear since direct contacts between particles dominate the charge transfer process.
Next, a novel microfluidic electrochemical flow capacitor (µ-EFC) platform was constructed using transparent materials to directly visualize particle hydrodynamics and measure electrochemical charging and discharging performance. It is found that as the flowrate varies, particle distribution along the channel height is significantly affected as particles tend to migrate away from the stationary electrodes where the shear is high; however, higher rates of shear also increase the number of interactions between particle clusters. These competing effects lead to a non-monotonic trend in the normalized charging and discharging current versus flowrate plot.
Finally, the µ-EFC design was iterated to include three-dimensional (3D) gold electrodes of varying lengths to directly visualize particle behavior in the boundary layer around stationary electrodes and the resulting electrochemical performance. These experiments revealed distinct particle flow behaviors at each 3D electrode length, and the electrochemical data is clearly affected by the inclusion of 3D electrodes. Specifically, the average resting charging current was increased by a factor of 4.8 and the discharging current was increased by a factor of 2.8.
These novel findings have significantly enhanced our understandings of the hydrodynamic effects on the electrochemical performance of flowable electrodes and pave the road for optimal operation of EFCs with slurry electrodes
Computational Modeling of the Hummingbird Escape Maneuver
No full textHummingbirds are perhaps the most agile flyers in nature. Studying the underlying physics of hummingbird flight may provide inspiration for developing highly maneuverable micro aerial vehicles (MAVs). In this work, we have developed a high-fidelity computational fluid dynamics (CFD) model to analyze the aerodynamics and flight mechanics of the hummingbird escape maneuver, in which hovering hummingbirds were startled and perform a rapid (less than 0.2 seconds) maneuver to back away from a perceived looming threat on the front side. Several novel mechanisms were discovered in this study. First, we found evidence across several species that hummingbirds use the inertial forces of their wings to increase their body rotational acceleration. For example, at pronation when the wings switch from upstroke to downstroke, the wing inertial forces create a torque that helps pitch up the bird’s body to move the head away from the threat. Such inertial steering effects are accompanied by aerodynamic steering of the wings to generate a fast rotational speed to improve maneuverability. Second, we studied the actuation of the wings during the escape maneuver by considering the muscle input at the shoulder joint in addition to the wings’ aerodynamic and inertial outputs. Contrary to previous thoughts that wing pitch rotation is primarily passive due to the wings’ own inertia, our results show that significant power input was required to pitch up the wings during downstroke to enhance aerodynamic force production. As a result, an active mechanism is required to pitch the wings for maximal force output. Third, we found that pitch, roll, and yaw rotations of the bird body may overlap with one another, which may create a nonlinear, inertial coupling effect that hummingbirds utilize as a passive mechanism for flight control, e.g., to stabilize body pitching during the maneuver. These novel findings have significantly improved our understanding of hummingbirds’ great maneuverability and may be useful for the future development of bioinspired MAVs
Subject-specific computational fluid-structure interaction modeling of type-1 thyroplasty
No full textUnilateral vocal fold paralysis (UVFP) is a condition in which one side of the vocal fold loses its adduction function and thus the vocal fold cannot vibrate normally, leading to difficulties in voice production. In type-1 thyroplasty, an implant is introduced through the thyroid cartilage to medialize the paralyzed vocal fold and restore voice. To improve implant design, our primary focus is to develop a high-fidelity fluid-structure interaction (FSI) model of the vocal fold undergoing the surgery, and to validate the model using integrated experimental studies of rabbit larynges.
First, we performed 3D FSI simulations of healthy phonation, where the two sides of the vocal fold were medialized symmetrically. By incorporating the subject-specific anatomical features reconstructed from magnetic resonance scans, as well as individualized tissue properties estimated using a simple flow model, the high-fidelity model was able to capture the subject-specific vibratory characteristics that matched the in vivo phonation test.
Next, we conducted an integrated experimental and computational study of an ex vivo rabbit larynx at both the UVFP and type-1 thyroplasty conditions. The model was built upon the pre-operative scan and the simulation consisted of two steps: 1) a finite-element method simulation of the vocal fold adduction to model the medialization of the implant; 2) an FSI simulation with the implant incorporated to model the vibration of the vocal fold. The results from both steps agree with experiment data, i.e., post-operative scan and high-speed imaging, thus showing successful model validation.
Finally, we employed the computational model to optimize implant position and depth. The degree of static displacement due to implant medialization and the vibration amplitude were used for implant assessment. The results show that the optimal implant position for vibration differed from that for maximal displacement, which highlights the need for FSI modeling to predict the implant's comprehensive effects. The model prediction is generally aligned with previous experimental studies but also shows that optimal implant depends on subject-specific features. Thus, a computational modeling-based tool would be useful for pre-surgical planning
COMPUTATIONAL FLUID-STRUCTURE INTERACTION OF SOFT TISSUES USING AN IMMERSED-BOUNDARY METHOD
No full textFluid—structure interaction (FSI) of a soft tissue exists in many places in human body (e.g., heart and venous valves, vocal fold, blood vessels, kidney, aneurysm, sleep apnea). Computational modeling of these FSI problems has potential applications in diagnostics, disease management, surgical planning, and device design, and so on. We use an immersed-boundary method coupled with the finite-element method to solve the three-dimensional (3D) FSI problems involving complex anatomy and tissue deformations. A 3D domain decomposition strategy is incorporated in parallel computing to greatly accelerate the flow simulation. We consider specifically the FSI of aortic valve and vocal fold using the same computational framework, where blood and air are governed by the viscous incompressible Navier—Stokes equation.
In the case of aortic valve, we focused on effect of the leaflets’ bending rigidity on blood flow, valve deformation, and the hemodynamic force on the valve. The thickness of the leaflets is varied to span a wide range of non-dimensional bending rigidity that is normalized by the transvalvular pressure gradient. The results suggest that there is an optimal range of bending rigidity for the valve. In addition to 3D simulations, we have also developed a novel one-dimensional (1D) unsteady flow model, which takes into consideration of valve movement and pressure loss. We use this 1D flow model in place of 3D flow in the FSI simulation. The results show that the hybrid simulation is able to capture reasonably well deformation of the leaflets, the valve opening area, and the flow rate.
In the case of vocal fold, we aim to develop patient-specific modeling tools to simulate vibration of vocal fold during phonation. We have developed an efficient 1D flow model that can be used in estimation of unknown tissue stiffness or optimization of the implant in medialization laryngoplasty. Both idealized and realistic laryngeal models are set up to test the performance of the reduced-order FSI simulation. Results show that our model produces results that match well either with the 3D FSI simulation or with the in vivo phonation experiment
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