Eva A. Kanso, Ph.D. - US grants

Our Faculty Early Career Development (CAREER) research program focuses on the development of theoretical and computational infrastructures for modeling complex solid-fluid interactions in fishlike locomotion. Fish and cetaceans move in water with great agility and efficiency through rhythmic shape changes which generate unsteady flow around the animal's body (typically vortical flow past the body). It is widely believed, but not fully understood, that fish exploit the unsteadiness in the flow to their advantage hence achieving impressive hydrodynamic efficiencies. This research program will study the dynamic coupling between the animal shape changes and the surrounding . Our approach is to combine the classical theory of fluid dynamics with ideas from geometric mechanics, dynamical systems, control theory and computation to build reduced models of the solid-fluid motion that make the underlying principles of locomotion more transparent. These reduced models will be used to analyze the stability of motion of both individual and schools of fish interacting with vorticity - thus explaining the role of vorticity in aquatic locomotion and fish schooling. These models will also be used to devise strategies for control and motion planning, more specifically, to investigate optimum shape deformations for a desired locomotion. In addition to our direct contribution to modeling and control of solid-fluid interactions in aquatic locomotion, our efforts will provide valuable insights into a number of important problems such as insect and birdlike locomotion and will enable novel engineering applications such as the design of biologically-inspired vehicles that propel themselves by undulating their shape. Our educational efforts will focus on creating an integrated education and research environment and on building a bridge between engineering and mathematics. Indeed, involvement of undergraduate and graduate students (including women and minorities) and dissemination of our research results in journals, conferences, as well as in the classroom will be an integral part of this research effort.

Abstract - Aquatic Propulsion Laboratory
PIs ? Jarek Rossignac, Georgia Institute of Technology / Eva Kanso, University of Southern California

The oceans are filled with creatures with a wondrous array of shapes and swimming styles, yet only a small number of these have been studied. The goal of the Aquatic Propulsion Laboratory is to create computer tools for reverse engineering and evaluating the aquatic locomotion strategies across species in order to advance our knowledge of the biology and mechanics of swimming. Moreover, some of these unexplored swimming styles may inspire the design of better artificial swimmers for use in aquatic exploration, engineering, and medicine. The created tools, data sets, animations, and digital models of swimming styles will be made available to other researchers, students, and educators.

Our research combines: 1) inventing geometric representations of deforming bodies for aquatic locomotion, and interactive tools for combining them, 2) employing analytic and numerical techniques for simulating the motion of these digital swimmers, and 3) developing control and optimization methods that allow us to find the most efficient motion strategies for a given body. For validation, we are comparing our synthetic motion to published results of tail-driven motion of thunniform and carangiform fish. This validation informs our study of other swimming styles, including the flapping of the wing-like pectoral fins of rays, the vertical tail motions of whales and dolphins, the traveling waves along the dorsal fins of electric eels and the mantles of cuttlefish, the paddle-driven motion of sea turtles, the tail kicks of lobsters and the rippling bells of jellyfish. For each swimming style, we are designing a geometric model and a set of parameterized behaviors that can be controlled to achieve coordinated motion and task-level goals. We are also conducting studies of the effectiveness of these swimming styles under different fluid conditions and goals.

Time integrators are crucial computational tools for studying nonlinear dynamical systems. Numerous time stepping methods have been developed over the years, many of which are now available in off-the-shelf solvers. However energy drifts and numerical dissipation problems present even in highly accurate algorithms still routinely plague engineering applications. Geometric time integrators have been recently proven greatly useful to elucidate and fix these issues in solid mechanics. Yet these contributions have not carried over to the Eulerian setting, where they could impact both the understanding and the reliability of time integrators for computational fluid dynamics. The goal of this research project is thus to develop novel, geometrically-based Eulerian time integrators for the class of problems whose dynamics is described by an action principle, possibly including dissipation and forcing---which encompasses the canonical Euler and Navier-Stokes equations, as well as many other models. Eulerian discretizations of the Hamilton-Pontryagin principle will be explored, and combined with mathematical and numerical tools such as Discrete Exterior Calculus, the semigroup of positive doubly-stochastic matrices, and implicit functions. Resulting integrators are expected, just like in the Lagrangian setting, to respect the structure of the physics, i.e., to introduce no artificial numerical loss of crucial physical quantities such as energy or circulation.

The proposed research activities aim at developing an infrastructure for predictive and high-order accurate simulations of fluid-mechanical systems that combine the power of modern applied geometry with modern computational mechanics. In particular, it promises the introduction of novel variational fluid simulation algorithms: this innovative computational approach relies on a multidisciplinary effort drawing upon techniques from geometric mechanics, discrete geometry, numerical analysis, and graphics, thus promising a broad theoretical and practical impact. The development of such variational integrators from a unified geometric standpoint represents a stepping stone for our long-term goal of solving complex physical phenomena such as a flowing dress, a swimming fish or splashing water, the simulation of which requires considerable improvement of the current state of the art to become commonplace. The research experience acquired during this project is to be disseminated to a wide range of audiences through publishing in mathematics, engineering and computer science journals, books, and conferences, as well as on our web sites, in summer schools, workshops, and other educational activities. Outreach efforts at our three institutions include the recruitment of students from underrepresented groups to help with this research project, leveraging existing efforts for enhancing the participation of women and minorities in scientific research.

Accurate prediction of the flight range and landing site of an object descending under the influence of gravitational and aerodynamic forces is relevant to many engineering and science applications. Examples range from forecasting the touchdown locations of re-entry space vehicles to understanding the settlement patterns of marine larvae and their influence on marine population dynamics. While the descent motion follows the laws of classical mechanics, the delicate interplay between the fluid medium and the geometric and material properties of the descending objects makes the exact landing site difficult to predict a priori and, thus, best treated as probabilistic. This award supports fundamental research that aims to develop an experimentally and mathematically tractable framework for studying the coupling between the mechanics of objects descending passively in a fluid medium and the probabilistic outcome of landing sites. This research will draw from techniques developed in several disciplines including solid-fluid interactions, dynamical systems, and probabilistic modeling. This multi-disciplinary research approach will be combined with outreach efforts in the greater Los Angeles area to help broaden the participation of underrepresented groups in research and positively impact engineering and science education.

The descent motion of objects falling in a fluid medium is generally complex, even for regularly shaped objects such as coins and cards. For such objects, four types of descent trajectories have been identified: steady, fluttering, chaotic, or tumbling, depending on the object and fluid properties. This research team will explore the dependence of the probability distribution of landing sites on the type of descent trajectories through carefully designed experiments as well as by developing mathematical and computational models of increasing levels of fidelity to the physical systems. Research efforts will also focus on establishing design principles that an object should fulfill in order to achieve a desired distribution of landing sites.

1512192(Kanso) & 1509071(Sotiropoulos)

The goal of the proposed research is to investigate, experimentally and numerically, the motion of irregularly shaped objects as they cross fluid-air interfaces and the phenomena that occur at the interface and the bulk of the fluid because of the presence of the object. Understanding the underlying phenomena could lead to controlling the process by controlling the object shape or controlling the type of fluid. Results from this research can have implications for the design of small robotic vehicles that move across fluid-air interfaces or the design of off-shore wind turbines or oil platforms.

This problem of object entry is generally complex, even for regularly shaped objects, such as spheres and discs, but is particularly interesting for objects with sharp leading geometries, such as cone- or pyramid-shaped objects, where the interplay between the body geometry and the complex vortical flows that develop at and near the fluid-air interface could help to dissipate the impact energy away from the body crossing the fluids' boundary. This proposal will analyze the fluid-structure interactions of objects moving in and across multi-phase incompressible fluids, and will particularly explore how the interplay between the object's geometry and material properties and the complex flow structures (waves and vortices) that develop at and near the fluid interfaces can be exploited to hinder or facilitate the motion of the solid object. During this project, carefully designed experiments as well as through mathematical and computational models will be used to investigate the following two problems: (i) Forward problem: for a given multi-phase fluid medium and shape/material properties of the object, what is the forward dynamics of the body and the surrounding fluids? (ii) Inverse problem: two types of problems: a. For a desired response such as aiding the motion of the solid object in a given fluid environment, what geometric/materials design principles should the object fulfill? b. For a desired response such as hindering the motion of the solid object, what properties should the fluid medium have? Activities are also proposed that involve undergraduate curriculum development at USC and at the University of Minnesota, as well as outreach efforts to K-12 students in the greater LA area through the USC VAST program and the Cabrillo Aquarium in San Pedro.

This is an INSPIRE award that was co-funded by the Biosciences Directorate, Division of Molecular and Cellular Biosciences (MCB), Systems and Synthetic Biology (SSB) program, and the Engineering Directorate, Division of Civil, Mechanical, and Manufacturing Innovation (CMMI), Dynamics, Control and System Diagnostics (DCSD) program.

Beneficial and pathogenic bacteria alike, commonly interact with host cells along mucosal epithelia. These surfaces are often lined with dense fields of motile cilia that serve both a biomechanical function for generating mucociliary flows, and a biochemical function to detect and present molecular signals. The goal of this project is to investigate a the dynamic association of healthy and diseased ciliated tissues. The project posits that cilia-generated flows influence bacteria-host interactions, thereby challenging the conventional view in biology that attributes bacterial recruitment mostly to active bacterial behavior and passive diffusion, ignoring the effect of cilia-generated flows on both motility and mass transport. The broader impacts of this study are that this project provides excellent educational and training opportunities at the intersection of disciplines, while also generating new insight in microbial host colonization that are likely to reveal avenues for impactful strategies to block pathogenic bacteria from colonizing the host, while enhancing the colonization potential of beneficial organisms.

The approach incorporates interdisciplinary methods, ranging from cutting-edge imaging and genetic tools to novel microfluidic technologies, all combined with powerful mathematical and computational framework, to investigate this fundamental problem in bacteria-host associations, namely, the role of cilia-generated flows in shaping these associations. The project will build a quantitative and predictive model that is informed by experimental assays in two complementary model systems:
1. In vivo invertebrate model: the squid-vibrio system, an intact animal host operating in its natural fluid environment, will be used to study how the host's ciliated epithelium initiates contact with its native, flow-borne bacterial community. Events in the squid-vibrio association share remarkable similarities with host responses to human-relevant pathogens, while still being accessible to imaging and experimental manipulation.
2. In silico microfluidics: properly designed microfluidic channels will be used as a tool to analyze the response of bacterial cells to carefully controlled microenvironment. This approach is aimed at complementing the squid-vibrio studies by providing a platform that isolates the chemical gradients and flow shear gradients observed in the in vivo model, thus allowing to unravel the mechanisms dictating bacterial behavior and possibly triggering the changes in bacterial gene expressions causing the transition from free-swimming to biofilm state.

PROJECT SUMMARY Mucociliary clearance (MCC) is a critical mechanical defense mechanism of the human respiratory system. Poor MCC is a fundamental feature of many inherited and acquired respiratory diseases including primary ciliary dyskinesia (PCD), asthma, chronic bronchitis, and cystic fibrosis (CF). Due to the complex organization of the lung, it is largely unknown how defects of the ciliary machinery change functional MCC and how regional variability of airway epithelial structure, including cell type proportions and ciliary beat parameters, affect local MCC pathophysiology. These knowledge gaps dramatically impair our ability to predict the degree of pulmonary dysfunction imparted by specific ciliary defects, and to understand the airway region-specific onset observed in many lung diseases. While impaired MCC is a pre-determined functional consequence of PCD and other chronic lung diseases, to date, there is no established in vitro model that is able to accurately predict the relationship between genotype, cilia motility, MCC, and respiratory phenotype and, therefore, many genotype-phenotype relationships remain unexplained. Our transdisciplinary research program is designed to address an unmet need to understand how a) region-specific airway organization and b) ciliopathy- causing genotypes, impact MCC. To achieve this we will complete specific aims designed to: 1) use ex vivo lung tissues, that retain their in vivo epithelial organization, as models of ciliated airway epithelia to comprehensively evaluate biomechanical structure-function relationships in large and small airways (Aim 1); 2) use established in vitro models of the human tracheo-bronchial (large) airways to determine a minimal set of structural and functional parameters that are conserved between in vitro and ex vivo ciliated tissues (Aim 2); 3) apply state-of-the-art physics-based computational approaches to develop an in silico model that will be able to predict structure-function relationships of ciliated tissues (Aim 3) and 4) use the minimal set of parameters that define functional MCC in both in vitro and ex vivo models as input into the in silico model to predict regional- specific changes in MCC due to ciliary defects in both large and small airways (All Aims). Our specific objectives build to our long-term goal of combining in vitro and in silico models as a preclinical, precision medicine tool for evaluating small molecule or gene-editing therapeutics toward more targeted and efficient treatment regimens of pulmonary diseases characterized by poor mucociliary clearance.

High efficiency is a fundamental design goal of vehicles moving through both air and water. Although most human designs of propulsors such as wings or propellers are rigid, natural propulsors are generally flexible. Propulsive efficiencies of natural flyers and swimmers are typically higher than human-designed vehicles of similar weight and dimensions. However, attempts to emulate flexible animal designs have met with limited success. Recent comparative animal studies have demonstrated startlingly consistent patterns of bending kinematics among a broad diversity of swimmers and flyers constructed from very different materials and of very different physical dimensions. These patterns encompass cilia to whale flukes and fluid regimes from water to air. This project will use computational fluid dynamics and particle image velocimetry to measure fluid velocities to investigate the mechanical and fluid dynamic details that enable high force production by flexible natural propulsors. K-12 outreach activities are planned at the universities and at the Cabrillo Aquarium in San Pedro, CA and undergraduate and graduate student involvement is core to the research project.

The goal of this project is to develop a set of design rules that govern force production by flexible propulsors. To achieve this goal, experiments and computations will be used to investigate: a) bending kinematics of propulsors as control surfaces of vorticity, pressure fields and thrust, b) the hydrodynamic basis of vortex-vortex interactions that generate pressure fields and thrust and c) the advantageous limits of bending kinematics. Each of these will be investigated using a combination of experiments (particle image velocimetry) with natural organisms and computational fluid dynamic models. The results of this project will define the necessary design criteria that enable performance enhancement by bending propulsors of different types and across a range of fluid regimes. While contributing to interpretation of the natural world, the results will also contribute to novel engineered designs ranging from biomedical applications (cilia) to vehicle design (swimming, flight).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.