About

David Henann is an Associate Professor of Engineering at Brown University. His research interests include theoretical and computational mechanics, granular materials, and soft materials. He is involved in undergraduate research and serves as a concentration advisor within the Mechanical Engineering department. Henann is also recognized for sharing a $1.7 million ONR grant as part of the larger PANTHER program, highlighting his active engagement in significant research initiatives.

Research topics

• Materials science
• Mechanics
• Composite material
• Classical mechanics
• Physics

Selected publications

• An Equilibrium Constrained Genetic Algorithm (ECGA) calibration framework for isotropic hyperelastic constitutive models with application to an elastomeric foam material

  Computer Methods in Applied Mechanics and Engineering · 2026-04-16

  articleOpen accessSenior authorCorresponding

  This work introduces a calibration framework for material parameter identification in isotropic hyperelastic constitutive models. The framework defines an objective function based on equilibrium constraints, which is then minimized using a Genetic Algorithm (GA) to facilitate automated calibration. The formulation of the objective function uses experimental displacement fields measured from Digital Image Correlation (DIC) synchronized with load cell data and can accommodate data from experiments involving homogeneous or inhomogeneous deformation fields. The framework places no restrictions on the target isotropic hyperelastic constitutive model, accommodating models with coupled dependencies on deformation invariants and specialized functional forms with a number of material parameters, and assesses material stability, eliminating sets of material parameters that potentially lead to non-physical behavior for the target hyperelastic constitutive model. To minimize the objective function, a GA is deployed as the optimization tool due to its ability to navigate the intricate landscape of material parameter space. The Equilibrium Constrained Genetic Algorithm (ECGA) framework is evaluated by applying it to a hyperelastic constitutive model for compressible elastomeric foams. The evaluation process entails a number of tests that employ both homogeneous and inhomogeneous displacement fields collected from DIC experiments on open-cell foam specimens. The results demonstrate the framework’s robust and efficient capability to handle material parameter identification for a complex hyperelastic constitutive model.

  PublisherDOI

• Determination of high strain-rate, viscoelastic material properties of soft solids using inertial microcavitation in a thin layer

  Extreme Mechanics Letters · 2025-07-25 · 1 citations

  articleOpen accessSenior authorCorresponding

  Determining the high strain-rate mechanical properties of soft hydrogels and biological tissues is important for a number of biological and engineering applications but remains challenging due to the high compliance of these materials. Inertial microcavitation rheometry (IMR) is a recently developed experimental technique aimed at addressing this need and requires the optical resolution of cavitation bubble kinematics via high-speed videography. While this approach works well for optically transparent samples of dimensions much larger than the typical micron to sub-millimeter bubble sizes, IMR is challenged in highly light scattering media, such as nearly opaque tissues. One remedy to decrease the light scattering within a tissue is to prepare a thinner sample, which facilitates successful recording of the cavitation bubble dynamics. However, the thickness of the required thin samples can approach the size of the microbubbles, and the resulting confinement of the soft material layer between two boundaries changes the fundamental character of the assumed nearly infinite domain of the IMR theoretical framework, leading to erroneous material property estimates. To address this issue and to facilitate successful application of IMR to thin layers of soft materials under confinement, we developed a modified, thin-layer IMR approach for the accurate determination of high strain-rate viscoelastic material properties of soft solids that utilizes axisymmetric finite-element simulations of bubble dynamics in a thin layer. The approach is applied to two transparent, benchmark gels: 6% and 14% gelatin, and the material parameters estimated using the thin-layer IMR approach are validated against experimental data for isolated, spherical bubbles and oversized bubbles in a thin layer. The thin-layer IMR approach provides a robust methodology for applying IMR to nearly opaque, soft materials, such as tissues.

  PublisherDOI

• Anti-plane segregation and diffusion in dense, bidisperse granular shear flow

  Physical Review Fluids · 2024-09-05 · 4 citations

  articleSenior author

  Dense granular mixtures consisting of particles of different sizes tend to segregate based on size during shear flow, yet predicting the evolution of the composition of a granular mixture in general geometries remains a challenge. This paper systematically studies a key aspect of the three-dimensional nature of segregation and diffusion in dense, bidisperse granular mixtures: segregation and diffusion acting along the direction perpendicular to the plane of shearing, referred to as the anti-plane mode. We utilize discrete-element method simulations to inform, calibrate, and test constitutive equations for the segregation and diffusion fluxes in their anti-plane modes.

  PublisherDOI

• Continuum modelling of size segregation and flow in dense, bidisperse granular media: accounting for segregation driven by both pressure gradients and shear-strain-rate gradients

  Journal of Fluid Mechanics · 2024-06-10 · 11 citations

  articleOpen accessSenior authorCorresponding

  Dense mixtures of particles of varying size tend to segregate based on size during flow. Granular size segregation impacts many industrial and geophysical processes, but the development of coupled, continuum models capable of predicting the evolution of segregation dynamics and flow fields in dense granular media across different geometries remains a challenge. One reason is because size segregation stems from two driving forces: pressure gradients and shear-strain-rate gradients. Another reason is the challenge of integrating segregation models with rheological constitutive equations for dense granular flow. In this paper we develop a continuum model that accounts for pressure-gradient-driven and shear-strain-rate-gradient-driven segregation, coupled to rheological modelling of a dense granular medium across the quasi-static and dense inertial flow regimes. To calibrate and test the continuum model, we perform discrete element method (DEM) simulations of dense flow of bidisperse granular systems in two flow geometries in which both segregation driving forces are present: inclined plane flow and planar shear flow with gravity. Steady-state DEM data from inclined plane flow is used to determine the dimensionless material parameters in the pressure-gradient-driven segregation model for both spheres and disks. Then, predictions of the continuum model are tested against DEM data across different cases of inclined plane flow and planar shear flow with gravity, while varying parameters such as the size of the flow geometry, the flow speed and the initial conditions. We find that it is crucial to account for both driving forces to capture segregation dynamics across both flow geometries with a single set of parameters.

  PublisherDOI

• Anti-plane segregation and diffusion in dense, bidisperse granular shear flow

  arXiv (Cornell University) · 2024-05-26

  preprintOpen accessSenior author

  Many dense granular systems are non-monodisperse, consisting of particles of different sizes, and will segregate based on size during flow. This phenomenon is an important aspect of many industrial and geophysical processes, necessitating predictive continuum models. This paper systematically studies a key aspect of the three-dimensional nature of segregation and diffusion in flowing, dense, bidisperse granular mixtures -- namely, segregation and diffusion acting along the direction perpendicular to the plane of shearing, which we refer to as the anti-plane modes of segregation and diffusion. To this end, we consider discrete-element method (DEM) simulations of flows of dense, bidisperse mixtures of frictional spheres in an idealized configuration that isolates anti-plane segregation and diffusion. We find that previously-developed constitutive equations, calibrated to DEM simulation results from flows in which both the segregation and diffusion processes occur within the plane of shearing, do not capture aspects of the anti-plane segregation dynamics. Accordingly, we utilize DEM simulation results to inform and calibrate constitutive equations for the segregation and diffusion fluxes in their anti-plane modes. Predictions of the resulting continuum model for the anti-plane segregation dynamics are tested against additional DEM simulation results across different cases, while parameters such as the shear strain rate and mixture composition are varied, and we find that the calibrated model predictions match well with the DEM simulation results. Finally, we suggest a strategy for generalizing the constitutive forms for the segregation and diffusion fluxes to obtain three-dimensional constitutive equations that account for both the in-plane and anti-plane modes of the segregation and diffusion processes.

  PublisherOA PDFDOI

• Modeling high strain-rate microcavitation in soft materials: the role of material behavior in bubble dynamics

  Soft Matter · 2023-01-01 · 11 citations

  articleSenior authorCorresponding

  ). Then, a theoretical modeling framework for inertial microcavitation, incorporating all the dominant physics, is used to extract information regarding the mechanical behavior of the soft material by fitting model predictions to the experimentally measured bubble dynamics. To model the cavitation dynamics, approaches based on extensions of the Rayleigh-Plesset equation are commonly used; however, these approaches cannot consider bubble dynamics that involves appreciable compressible behavior and place a limit on the nonlinear viscoelastic constitutive models that may be employed to describe the soft material. To circumvent these limitations, in this work, we develop a finite-element-based numerical simulation capability for inertial microcavitation of spherical bubbles that enables appreciable compressibility to be accounted for and more complex viscoelastic constitutive laws to be incorporated. We first apply the numerical simulation capability to understanding the role of material compressibility during violent spherical bubble collapse, and based on finite-element simulations, we propose a Mach-number-based threshold of 0.08, beyond which bubble collapse is violent, and the bubble dynamics involves compressibility not accounted for in Rayleigh-Plesset-based approaches. Second, we consider more complex viscoelastic constitutive models for the surrounding material, including nonlinear elastic and power-law viscous behavior, and apply IMR by fitting computational results to experimental data from inertial microcavitation of polyacrylamide (PA) gels in order to determine material parameters for PA gels at high strain rates.

  PublisherDOI

• Coupled continuum modelling of size segregation driven by shear-strain-rate gradients and flow in dense, bidisperse granular media

  Journal of Fluid Mechanics · 2023-11-28 · 10 citations

  articleOpen accessSenior authorCorresponding

  Dense granular systems that consist of particles of disparate sizes segregate based on size during flow, resulting in complex, coupled segregation and flow patterns. The ability to predict how granular mixtures segregate is important in the design of industrial processes and the understanding of geophysical phenomena. The two primary drivers of size segregation are pressure gradients and shear-strain-rate gradients. In this work, we isolate size segregation driven by shear-strain-rate gradients by studying two dense granular flow geometries with constant pressure fields: gravity-driven flow down a long vertical chute with rough parallel walls and annular shear flow with rough inner and outer walls. We perform discrete element method (DEM) simulations of dense flow of bidisperse granular systems in both flow geometries, while varying system parameters, such as the flow rate, flow configuration size, fraction of large/small grains and grain-size ratio, and use DEM data to inform continuum constitutive equations for the relative flux of large and small particles. When the resulting continuum model for the dynamics of size segregation is coupled with the non-local granular fluidity model – a non-local continuum model for dense granular flow rheology – we show that both flow fields and segregation dynamics may be simultaneously captured using this coupled, continuum system of equations.

  PublisherOA PDFDOI

• Continuum modeling of size-segregation and flow in dense, bidisperse granular media: Accounting for segregation driven by both pressure gradients and shear-strain-rate gradients

  arXiv (Cornell University) · 2023-07-18

  preprintOpen accessSenior authorCorresponding

  Dense mixtures of particles of varying size tend to segregate based on size during flow. Granular size-segregation plays an important role in many industrial and geophysical processes, but the development of coupled, continuum models capable of predicting the evolution of segregation dynamics and flow fields in dense granular media across different geometries has remained a longstanding challenge. One reason is because size-segregation stems from two driving forces: (1) pressure gradients and (2) shear-strain-rate gradients. Another reason is due to the challenge of integrating segregation models with rheological constitutive equations for dense granular flow. In this paper, we build upon our prior work, which combined a model for shear-strain-rate-gradient-driven segregation with a nonlocal continuum model for dense granular flow rheology, and append a model for pressure-gradient-driven segregation. We perform discrete element method (DEM) simulations of dense flow of bidisperse granular systems in two flow geometries, in which both segregation driving forces are present: namely, inclined plane flow and planar shear flow with gravity. Steady-state DEM data from inclined plane flow is used to determine the dimensionless material parameters in the pressure-gradient-driven segregation model for both spheres and disks. Then, predictions of the coupled, continuum model accounting for both driving forces are tested against DEM simulation results across different cases of both inclined plane flow and planar shear flow with gravity, while varying parameters such as the size of the flow geometry, the driving conditions of flow, and the initial conditions. Overall, we find that it is crucial to account for both driving forces to capture segregation dynamics in dense, bidisperse granular media across both flow geometries with a single set of parameters.

  PublisherOA PDFDOI

• Pressure sensitivity in non-local flow behaviour of dense hydrogel particle suspensions

  arXiv (Cornell University) · 2023-07-31 · 2 citations

  preprintOpen access

  Slowly sheared particulate media like sand and suspensions flow heterogeneously as they yield via narrow shear bands where most of the strain is accumulated. Understanding shear band localization from microscopics is still a major challenge. One class of so-called non-local theories identified that the width of the shearing zone should depend on the stress field. We explicitly test this picture by using a uniquely stress-sensitive suspension while probing its flow behavior in a classic geometry in which shear bands can be well-tuned: the Split-Bottom Shear Cell (SBSC). The stress-sensitive suspension is composed of mildly polydisperse soft, slippery hydrogel spheres submersed in water. We measure their flow profiles and rheology while controlling the confinement stress via hydrostatic effects and compression. We determine the average angular velocity profiles in the quasi-static flow regime using Magnetic Resonance Imaging based particle image velocimetry (MRI-PIV) and discrete element method (DEM) simulations. We explicitly match a pressure-sensitive non-local granular fluidity (NGF) model to observed flow behavior. We find that shear bands for this type of suspension become extremely broad under the low confining stresses from the almost density-matched fluid particle mixture, while collapsing to a narrow shear zone under finite, externally imposed compression levels. The DEM and NGF results match the observations quantitatively, confirming the conjectured pressure sensitivity for suspensions and its role in NGF. Our results indicate that pressure sensitivity should be part of non-local flow rules to describe slow flows of granular media.

  PublisherOA PDFDOI

• Mechanosensitive traction force generation is regulated by the neutrophil activation state

  Scientific Reports · 2023-07-09 · 8 citations

  articleOpen access

  Abstract The generation of traction forces by neutrophils regulates many crucial effector functions responsible for host defense, such as attachment, spreading, migration, phagocytosis, and NETosis. The activation state of the cell is a strong determinant of the functional efficacy of the neutrophil; however, the effect of activation on traction force production has not yet been determined experimentally. Previously, the mapping of cellular-generated forces produced by human neutrophils via a Traction Force Microscopy (TFM) method has required a three-dimensional imaging modality to capture out-of-plane forces, such as confocal or multiphoton techniques. A method newly developed in our laboratories can capture out-of-plane forces using only a two-dimensional imaging modality. This novel technique—combined with a topology-based single particle tracking algorithm and finite element method calculations—can construct high spatial frequency three-dimensional traction fields, allowing for traction forces in-plane and out-of-plane to the substrate to now be differentially visualized and quantified with a standard epifluorescence microscope. Here we apply this technology to determine the effect of neutrophil activation on force generation. Sepsis is a systemic inflammatory response that causes dysregulated neutrophil activation in vivo. We found that neutrophils from septic patients produced greater total forces than neutrophils from healthy donors and that the majority of this dysregulation occurred in-plane to the substrate. Ex vivo activation of neutrophils from healthy donors showed differential consequences depending on activation stimuli with mechanosensitive force decreases observed in some cases. These findings demonstrate the feasibility of epifluorescence-based microscopy in mapping traction forces to ask biologically significant questions regarding neutrophil function.

  PublisherOA PDFDOI

Recent grants

• CAREER: A continuum model for simultaneous prediction of granular flow and size-segregation in general geometries

  NSF · $508k · 2016–2022

Frequent coauthors

• Christian Franck

  University of Wisconsin–Madison

  41 shared

• Daren Liu

  Brown University

  33 shared

• Alexander K. Landauer

  National Institute of Standards and Technology

  20 shared

• Ken Kamrin

  20 shared

• Hadley Witt

  Brown University

  14 shared

• Michael Jandron

  13 shared

• Zicheng Yan

  12 shared

• Xiuqi Li

  Chongqing University of Science and Technology

  12 shared

Awards & honors

• $1.7M ONR grant as part of larger PANTHER program