Chengyu Li

Case Western Reserve University | CWRU · Department of Mechanical and Aerospace Engineering

The ability to track odor plumes to their source (food, mate, etc.) is key to the survival of many insects. During this odor-guided navigation, flapping wings could actively draw odorants to the antennae to enhance olfactory sensitivity, but it is unclear if improving olfactory function comes at a cost to aerodynamic performance. Here, we computati...

The human nose serves vital physiological functions, including warming, filtration, humidification, and olfaction. These functions are based on transport phenomena that depend on nasal airflow patterns and turbulence. Accurate prediction of these airflow properties requires careful selection of computational fluid dynamics models and rigorous valid...

This study integrates high-speed photogrammetry, three-dimensional surface reconstruction, and computational fluid dynamics to explore a dragonfly (Erythemis Simplicicollis) in free flight. Asymmetric wing kinematics and the associated aerodynamic characteristics of a turning dragonfly are analyzed in detail. Quantitative measurements of wing kinem...

The wake topology and propulsive performance of low-aspect-ratio plates undergoing a pitching-rolling motion in a uniform stream were numerically investigated by an in-house immersed-boundary-method-based incompressible Navier-Stokes equation solver. A detailed analysis of the vortical structures indicated that the pitching-rolling plate produced d...

Nasal airflow that effectively transports ambient odors to the olfactory receptors is important for human olfaction. Yet, the impact of nasal anatomical variations on airflow pattern and olfactory function are not fully understood. In this study, 22 healthy volunteers were recruited and underwent CT scans for computational simulations of nasal airf...

In this paper, we examine the coupling between odor dynamics and vortex dynamics around undulating bodies, with a focus on bio-inspired propulsion mechanisms. Utilizing computational fluid dynamics simulations with an in-house immersed boundary method solver, we investigate how different waveform patterns, specifically carangiform and anguilliform,...

Flying insects exhibit remarkable capabilities in coordinating their olfactory sensory system and flapping wings during odour plume-tracking flights. While observations have indicated that their flapping wing motion can ‘sniff’ up the incoming plumes for better odour sampling range, how flapping motion impacts the odour concentration field around t...

Ctenophores employ flexible rows of appendages called ctenes that form the metachronal beating pattern. A complete cycle of such paddling consists of a power stroke that strokes backward to produce propulsion and a recovery stroke that allows the appendage to recover its initial position. Effective locomotion in these creatures relies on maximizing...

As insects fly, their wings generate complex wake structures that play a crucial role in their aerodynamic force production. This study focuses on utilizing reduced order modeling techniques to gain valuable insights into the fluid dynamic principles underlying insect flight. Specifically, we used an immersed-boundary-method-based computational flu...

In this paper, we examine the coupling between odor dynamics and vortex dynamics around undulating bodies, with a focus on bio-inspired propulsion mechanisms. Utilizing computational fluid dynamics (CFD) simulations with an in-house Immersed-Boundary Method (IBM) solver, we investigate how different waveform patterns, specifically carangiform and a...

By performing numerical simulations of the governing fluids and odorant transport equations, this study identified a relationship between the hydrodynamic interactions and olfactory chemoreception in a fish-like school. Simulations were performed using an in-house developed immersed-boundary method based incompressible Navier-Stokes flow solver cou...

Metachronous rowing is a swimming mechanism widely adopted by small marine invertebrate like comb jellies, in which rows of appendages perform propulsive strokes sequentially in a coordinated manner with a fixed phase difference. To simulate metachronous rowing at intermediate Reynolds number, in this paper, a row of flexible cilia models was place...

Odor-guided navigation is fundamental to the survival and reproductive success of many flying insects. Despite its biological importance, the mechanics of how insects sense and interpret odor plumes in the presence of complex flow fields remain poorly understood. This study employs numerical simulations to investigate the influence of turbulence, w...

Odor-guided navigation is an indispensable aspect of flying insects' behavior, facilitating crucial activities such as foraging and mating. The interaction between aerodynamics and olfaction plays a pivotal role in the odor-guided flight behaviors of insects, yet the interplay of these two functions remains incompletely understood. In this study, w...

Metachronal rowing is a biological propulsion mechanism employed by many swimming invertebrates (e.g. copepods, ctenophores, krill and shrimp). Animals that swim using this mechanism feature rows of appendages that oscillate in a coordinated wave. In this study, we used observations of a swimming ctenophore (comb jelly) to examine the hydrodynamic...

Insects rely on their olfactory system to forage, prey, and mate. They can sense odorant plumes emitted from sources of their interests with their bilateral odorant antennae, and track down odor sources using their highly efficient flapping-wing mechanism. The odor-tracking process typically consists of two distinct behaviors: surging upwind at hig...

Through direction numerical simulation (DNS) of a model manta ray body, pectoral fin scaled pitching effect on hydrodynamic performance and wake is investigated. The manta ray model is derived from high-speed video of manta ray swimming with motion of the model prescribed to match the actual manta ray. Rotation angles of the model skeletal joints i...

Metachronal motion is a unique swimming strategy widely adopted by many small animals on the scale of microns up to several centimeters (e.g., ctenophores, copepods, krill, and shrimp). During propulsion, each evenly spaced appendage performs a propulsive stroke sequentially with a constant phaselag from its neighbor, forming a metachronal wave. To...

The hawkmoth is able to sustain a steady hover or level flight at lower speeds. However, previous wind tunnel experiments have suggested that long sequences of steady forward flight are less common at higher flying speeds (>4.0m/s) despite changes to the flight posture. This flying speed is about one-half of the theoretical prediction based on its...

This study presents an effort on comparing the wake flow structures of hovering insects between experimental visualization and computational simulation. The wake flow on a freely hovering hawkmoth was visualized and captured, utilizing a high-speed schlieren photography system with isopropyl alcohol brushed on the wing surfaces. Meanwhile, an Immer...

Insects rely on their olfactory system to forage, prey, and mate. They can sense odorant plumes emitted from sources of their interests with their bilateral odorant antennae, and track down odor sources using their highly efficient flapping-wing mechanism. The odor-tracking process typically consists of two distinct behaviors: surging upwind and zi...

View Video Presentation: https://doi.org/10.2514/6.2021-2817.vid Insects rely on their olfactory system to forage, prey, and mate. They can sense odor emitted from sources of their interest, use their highly efficient flapping-wing mechanism to follow odor trails, and track down odor sources. During such an odor-guided navigation, flapping wings no...

This chapter is the first of two chapters demonstrating the wide variety of CFD studies in clinical applications presented from leading researchers in their respective fields. This chapter covers the latest research techniques and outcomes in airflow and conditioning in the nasal cavity; fluid and particle dynamics from sniffing; nasal obstruction...

Insect wings can passively maintain a high angle of attack during each flapping stroke without the aid of the active pitching motion due to the torsional flexibility of the wing basal region. However, there is no clear understanding of how torsional wing flexibility should be designed for achieving optimal aerodynamic performance. In this work, a c...

Insects can detect and locate distant odor sources (food, mate, etc.) by tracking odor plumes, which is key to their survival. During an odor-guided navigation, flapping wings have been speculated to actively draw odorants to the antennae and enhance olfactory sensitivity. Utilizing an in-house computational fluid dynamics solver, we have quantifie...

Flapping wings of insects serve for both generating aerodynamic forces and enhancing olfactory sensitivities when navigating on the odor-rich planet. Despite the extensive investigations of the aerodynamic function of flapping wings, we have limited understanding of how the flapping wings potentially affect the physiological sensitivities during fl...

The wake structures generated by rotating wings are studied numerically to investigate the complex vortex formation and evolution in both near-wake and far-wake regions. Flat rectangular wings with finite aspect ratios (AR = 1–8) that rotate from rest at an angle of attack ranging from 15° to 90° in a low Reynolds number regime (200–1600) are consi...

Background: Empty nose syndrome (ENS) remains a controversial disease primarily associated with inferior turbinate tissue loss. Cotton placement into the inferior meatus often alleviates ENS symptoms within minutes, but the physiologic explanation for this phenomenon is unknown. Computational fluid dynamics (CFD) was employed to evaluate the mecha...

Objectives/hypothesis: Patients are frequently advised to sneeze with an open mouth and avoid nose-blowing following an endoscopic endonasal approache (EEA) to the skull base, despite a lack of quantitative evidence. This study applies computational fluid dynamics (CFD) to quantify sinus pressures along the skull base during sneezing. Study desig...

Flapping wings of insects can passively maintain a high angle of attack due to the torsional flexibility of wing basal region without the aid of the active pitching motion. However, the lift force generated by such passive pitching motion has not been well explored in the literature. Consequently, there is no clear understanding of how torsional wi...

Background A nasal septal perforation (NSP) can lead to frustrating symptoms for some patients while remaining completely asymptomatic for others, without a clear mechanism differentiating them. Methods We applied individual computed tomography (CT)‐based computational fluid dynamics (CFD) to examine the nasal aerodynamics differences between 5 as...

Lift enhancement mechanism due to wing-body interaction (WBI) was previously proved to be significant in the forward flight of insect flyers with wide-shape bodies, such as cicada. In order to further explore WBI and its lift enhancement effect in a flapping flight platform with different wing and body shapes, numerical investigations of WBI was pe...

Background Empty nose syndrome (ENS) remains highly controversial, with aggressive inferior turbinate reduction (ITR) or mucociliary dysfunction frequently implicated. However, the appropriate degree of ITR is highly debatable. Methods We applied individual computed tomography (CT)‐based computational fluid dynamics (CFD) to 5 patients receiving r...

An adjoint-based optimization is applied to study the thrust performance of a pitching–rolling ellipsoidal plate in a uniform stream at Reynolds number 100. To achieve the highest thrust, the optimal kinematics of pitching–rolling motion is sought in a control space including the pitching amplitude, the rolling amplitude, and the phase delay betwee...

Background: The impact of middle turbinate resection (MTR) on olfaction remains a point of debate in the current literature. Few studies have objectively evaluated olfactory cleft airflow following MTR; thus, the mechanism by which MTR may impact olfaction is poorly understood. It is not known whether the postsurgical changes in airway volume, flo...

Background Empty nose syndrome (ENS) is a rare and debilitating disease with a controversial definition, etiology, and treatment. One puzzling fact is that patients who undergo an endoscopic endonasal approach (EEA) often have resection of multiple anatomic structures, yet seldom develop ENS. In this pilot study, we analyzed and compared the comput...

An adjoint-based optimization is applied to study the thrust performance of a pitching-rolling ellipsoidal plate in a uniform stream at Reynolds number 100. To achieve the highest thrust, the optimal kinematics of pitching-rolling motion is sought in a large control space including the pitching amplitude, the rolling amplitude, and the phase delay...

Objectives/Hypothesis Current techniques for airway characterization include endoscopic or radiographic measurements that produce static, two‐dimensional descriptions. As pathology can be multilevel, irregularly shaped, and dynamic, minimal luminal area (MLA) may not provide the most comprehensive description or diagnostic metric. Our aim was to ex...

Objectives Congenital nasal pyriform aperture stenosis (CNPAS) is a rare cause of airway obstruction in the neonate. Computational airway modeling has not been done in neonates and young infants to understand the impact of stenosis on functional nasal airflow. In this study, we 1) applied computational fluid dynamics (CFD) model to the airway of a...

Importance Inferior turbinate reduction (ITR) is a commonly performed procedure for the treatment of nasal obstruction. Which portion of the inferior turbinates should be surgically addressed to improve nasal airflow has yet to be determined. Objective To use computational fluid dynamics (CFD) analysis to evaluate the airflow changes after reducti...

Background: Abnormal nasal aerodynamics or trigeminal functions have been frequently implicated in the symptomology of empty nose syndrome (ENS), yet with limited evidence. Methods: Individual computed tomography (CT)-based computational fluid dynamics (CFD) was applied to 27 ENS patients to simulate their nasal aerodynamics and compared with 42...

OBJECTIVES/SPECIFIC AIMS: Tissue engineered tracheal grafts (TETG) could provide a life-saving cure for children with long segment airway defects. Computational fluid dynamics (CFD) is a novel and promising technique used to evaluate TETG performance. This pilot study examines the correlation of objective CFD simulations with subjective respiratory...

Background: Numerous surgical techniques exist to treat nasal septal perforation (NSP). The surgical closure of large NSPs (>2 cm) is still challenging. Posterior septectomy has been reported as a simple alternative to treat large NSP, yet its mechanisms for symptom relief are not clear, and if failed, its consequence cannot be easily reversed. M...

Objective: The precise pathogenesis of empty nose syndrome (ENS) remains unclear. Various factors such as nasal aerodynamics and sensorineural dysfunction have been suspected, although evidence is limited. This study reported the first examination of both nasal aerodynamics and trigeminal sensory factors in actual ENS patients. Study design: Pro...

The effects of wing–body interaction (WBI) on aerodynamic performance and vortex dynamics have been numerically investigated in the forward flight of cicadas. Flapping wing kinematics was reconstructed based on the output of a high-speed camera system. Following the reconstruction of cicada flight, three models, wing–body (WB), body-only (BD) and w...

It is important to understand the impact of wing-morphing on aerodynamic performance in the study of flapping-wing flight of birds and insects. We use a flapping plate hinged with a trailing-edge flap as a simplified model for flexible/morphing wings in hovering. The trailing-edge flapping motion is optimized by an adjoint-based approach. The optim...

In current work, effects of a controllable trailing-edge flap (TEF) on hovering flapping plates at low Reynolds number is computationally investigated. The leading-edge portion of flapping plate is driven by a prescribed kinematics in a horizontal stroke plane. The deflection of TEF follows a sinusoidal function with respect to the leading-edge and...

Understanding of vortex formation and aerodynamic loading is important for studying rotor wake and rotary-winged micro air vehicles. In this work, direct numerical simulation (DNS) is used to study three-dimensional flow structure and aerodynamic performance of low aspect ratio revolving plates in low Reynolds number flows. These plates are modeled...

Damselflies show abrupt, darting flight, which is the envy of aero-engineers. This amazing ability is used both to capture prey and, by males, to establish territories that can attract females. In this work, high-resolution, high-speed videos of a damselfly (Hetaerina Americana) in darting flight were obtained using a photogrammetry system. Using a...

In this work, high-resolution, high-speed videos of a Monarch butterfly (Danaus plexippus) in take-off flight were obtained using a photogrammetry system. Using a 3D subdivision surface reconstruction methodology, the butterfly's body/wing deformation and kinematics were modeled and reconstructed from those videos. High fidelity simulations were th...

A low aspect-ratio plate under translational or rotational motion in a wide range of angles of attack is studied using Direct Numerical Simulation (DNS). Vortex formation and aerodynamic performance generated in the two motions are discussed. The aerodynamic forces obtained from two methods are calculated and compared. One method is the typical sur...

It's widely thought insects are able to accomplish fast maneuver via adjustment of wing kinematics. However, it's still unclear how wing flexibility plays roles in this process. In this work, an integrated study combining high-speed photogrammetry and direct numerical simulation (DNS), for a freely flying dragonfly (Erythemis Simplicicollis) in 110...

In this video, effect of chordwise damage on a damselfly (American Rubyspot)'s wings is investigated. High speed photogrammetry was used to collect the data of damselflies' flight with intact and damaged wings along the wing chord. Different level of deterioration of flight performance can be observed. Further investigation will be on the dynamic a...