Andrew Bragg
Civil and Environmental Engineering
Associate Professor of Civil and Environmental Engineering
Research Themes
Environmental Health Engineering, Hydrology & Fluid Dynamics, Risk & Resilient Systems
Research Interests
Physics and modeling of turbulence and turbulent transport; theoretical and computational fluid dynamics; applied mathematics.
Bio
My intellectual interests and passions revolve around the desire to understand and predict the beautifully complex, enigmatic motion of turbulent flows, and their role in natural and engineered systems. The environment provides one of the richest settings motivating research on this topic, with far reaching implications for understanding atmospheric clouds, oceans, global warming, among many others. To address the profound complexity of turbulence I utilize methods from applied mathematics, statistical and theoretical physics, and high-performance computing. I also work closely with experimentalists, being convinced that a multifaceted, collaborative approach is required for significant progress on this very challenging subject.
Turbulent flows are inherently multiscale, and in environmental contexts they involve motion on spatial scales ranging from kilometers down to micrometers. Large-scale numerical simulations of environmental flows cannot resolve all of the scales, and so the unresolved scales must be parametrized. However, the nonlinear physics of the unresolved processes are often poorly understood, leading to great uncertainty in their parameterizations. This challenge is a key motivation for my own research, namely to understand the nonlinear physics of these small-scale processes and then to develop models that capture them for use in large-scale numerical models.
Before joining the Duke University faculty, Dr. Bragg was a postdoctoral associate in the Applied Mathematics and Plasma Physics Group at the Los Alamos National Laboratory. Prior to that, he was a postdoctoral associate in the Sibley School of Mechanical and Aerospace Engineering at Cornell University. Dr. Bragg obtained his PhD in Theoretical Fluid Dynamics from Newcastle University in England.
Education
- Ph.D. Newcastle University (United Kingdom), 2012
Positions
- Associate Professor of Civil and Environmental Engineering
Awards, Honors, and Distinctions
- National Science Foundation CAREER award. CBET Fluid Dynamics. 2021
- EUROMECH Young Scientist Award, given at the 16th European Turbulence Conference at KTH in Stockholm. European Mechanics Society. 2017
Courses Taught
- ME 634: Turbulence 1
- CEE 701: Graduate Colloquium
- CEE 690: Advanced Topics in Civil and Environmental Engineering
- CEE 688: Turbulence 1
- CEE 301L: Fluid Mechanics
Publications
- Katul G, Bragg A, Mammarella I, Liu H, Li Q, Bou-Zeid E. Gas Transfer Across Air-Water Interfaces in Inland Waters: From Micro-Eddies to Super-Statistics. Water Resources Research. 2024 Nov 1;60(11).
- Bragg AD, De Bruyn Kops SM. Understanding the effect of Prandtl number on momentum and scalar mixing rates in neutral and stably stratified flows using gradient field dynamics. Journal of Fluid Mechanics. 2024 Aug 27;992.
- Simon JS, Bragg AD, Chaney NW. Heterogeneous Land-Surface Effects on TKE and Cloud Formation: Statistical Insights From LES Cases. Journal of Geophysical Research: Atmospheres. 2024 Jun 28;129(12).
- Bhattacharjee S, Tom J, Carbone M, Bragg AD. Investigating the parametric dependence of the impact of two-way coupling on inertial particle settling in turbulence. Journal of Fluid Mechanics. 2024 May 16;987.
- Waterman T, Bragg AD, Hay-Chapman F, Dirmeyer PA, Fowler MD, Simon J, et al. A Two-Column Model Parameterization for Subgrid Surface Heterogeneity Driven Circulations. Journal of Advances in Modeling Earth Systems. 2024 May 1;16(5).
- Song C, Liu Q, Wang J, Bragg AD, Wang S, Gao X, et al. Estimation of Particle Dispersion Characteristics in a Fluidized Bed with the Binary Mixture of Geldart A and B Types Using the Optical Fiber Probe Method. Industrial and Engineering Chemistry Research. 2024 May 1;63(17):7807–20.
- Grace AP, Richter DH, Bragg AD. A Reinterpretation of Phenomenological Modeling Approaches for Lagrangian Particles Settling in a Turbulent Boundary Layer. Boundary-Layer Meteorology. 2024 Apr 1;190(4).
- Johnson DR, Hammond AL, Bragg AD, Meng H. Detailed characterization of extreme clustering at near-contact scales in isotropic turbulence. Journal of Fluid Mechanics. 2024 Mar 7;982.
- Li S, Bragg AD, Katul G. Reduced Sediment Settling in Turbulent Flows Due To Basset History and Virtual Mass Effects. Geophysical Research Letters. 2023 Nov 28;50(22).
- Ma T, Hessenkemper H, Lucas D, Bragg AD. Fate of bubble clusters rising in a quiescent liquid. Journal of Fluid Mechanics. 2023 Oct 16;973.
- Ma T, Liao Y, Hessenkemper H, Lucas D, Bragg AD. A Note on Modeling the Effects of Surfactants on Bubble-Induced Turbulence. Chemical Engineering and Technology. 2023 Sep 1;46(9):1817–22.
- Ma T, Hessenkemper H, Lucas D, Bragg AD. Effects of surfactants on bubble-induced turbulence. Journal of Fluid Mechanics. 2023 Aug 30;970.
- Huang KY, Fu MK, Byers CP, Bragg AD, Katul GG. Logarithmic scaling of higher-order temperature moments in the atmospheric surface layer. International Journal of Heat and Fluid Flow. 2023 Aug 1;102.
- Zhang X, Carbone M, Bragg AD. Lagrangian model for passive scalar gradients in turbulence. Journal of Fluid Mechanics. 2023 Jun 5;964.
- Denzel CJ, Bragg AD, Richter DH. Stochastic model for the residence time of solid particles in turbulent Rayleigh-Bénard flow. Physical Review Fluids. 2023 Feb 1;8(2).
- Zhang Y, Bragg AD, Wang G. Asymptotic closure model for inertial particle transport in turbulent boundary layers. Physical Review Fluids. 2023 Jan 1;8(1).
- He XQ, Xiong YL, Bragg AD, Fischer P, Kellay H. The effect of tilt on turbulent thermal convection for a heated soap bubble. Physics of Fluids. 2022 Oct 1;34(10).
- Tom J, Carbone M, Bragg AD. How does two-way coupling modify particle settling and the role of multiscale preferential sweeping? Journal of Fluid Mechanics. 2022 Sep 25;947.
- Zhang X, Dhariwal R, Portwood G, De Bruyn Kops SM, Bragg AD. Analysis of scale-dependent kinetic and potential energy in sheared, stably stratified turbulence. Journal of Fluid Mechanics. 2022 Sep 10;946.
- Waterman T, Bragg AD, Katul G, Chaney N. Examining Parameterizations of Potential Temperature Variance Across Varied Landscapes for Use in Earth System Models. Journal of Geophysical Research: Atmospheres. 2022 Apr 27;127(8).
- Ma T, Hessenkemper H, Lucas D, Bragg AD. An experimental study on the multiscale properties of turbulence in bubble-laden flows. Journal of Fluid Mechanics. 2022 Apr 10;936.
- Li S, Bragg AD, Katul G. A Co-Spectral Budget Model Links Turbulent Eddies to Suspended Sediment Concentration in Channel Flows. Water Resources Research. 2022 Mar 1;58(3).
- Bragg AD, Hammond AL, Dhariwal R, Meng H. Hydrodynamic interactions and extreme particle clustering in turbulence. Journal of Fluid Mechanics. 2022 Feb 25;933.
- Momenifar M, Diao E, Tarokh V, Bragg AD. A Physics-Informed Vector Quantized Autoencoder for Data Compression of Turbulent Flow. In: Data Compression Conference Proceedings. 2022. p. 312–21.
- Momenifar M, Diao E, Tarokh V, Bragg AD. Dimension reduced turbulent flow data from deep vector quantisers. Journal of Turbulence. 2022 Jan 1;23(4–5):232–64.
- Bragg AD, Richter DH, Wang G. Settling strongly modifies particle concentrations in wall-bounded turbulent flows even when the settling parameter is asymptotically small. Physical Review Fluids. 2021 Dec 1;6(12).
- Ma T, Ott B, Fröhlich J, Bragg AD. Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows. Journal of Fluid Mechanics. 2021 Nov 25;927.
- Simon JS, Bragg AD, Dirmeyer PA, Chaney NW. Semi-Coupling of a Field-Scale Resolving Land-Surface Model and WRF-LES to Investigate the Influence of Land-Surface Heterogeneity on Cloud Development. Journal of Advances in Modeling Earth Systems. 2021 Oct 1;13(10).
- Bragg AD, Liao Y, Fröhlich J, Ma T. Assessment of the validity of a log-law for wall-bounded turbulent bubbly flows. International Journal of Heat and Fluid Flow. 2021 Oct 1;91.
- Bragg AD, Richter DH, Wang G. Mechanisms governing the settling velocities and spatial distributions of inertial particles in wall-bounded turbulence. Physical Review Fluids. 2021 Jun 1;6(6).
- He XQ, Bragg AD, Xiong YL, Fischer P. Turbulence and heat transfer on a rotating, heated half soap bubble. Journal of Fluid Mechanics. 2021 Jan 1;924.
- Tom J, Carbone M, Bragg AD. Exploring the turbulent velocity gradients at different scales from the perspective of the strain-rate eigenframe. Journal of Fluid Mechanics. 2021 Jan 1;910.
- Carbone M, Bragg A, Tom J, Wilczek M, Iovieno M. The Conservative Pressure Hessian and the Free Fluid Particle Model. In: Springer Proceedings in Physics. 2021. p. 215–21.
- Porporato A, Hooshyar M, Bragg AD, Katul G. Fluctuation theorem and extended thermodynamics of turbulence. Proceedings Mathematical, physical, and engineering sciences. 2020 Nov;476(2243):20200468.
- Ayet A, Katul GG, Bragg AD, Redelsperger JL. Scalewise Return to Isotropy in Stratified Boundary Layer Flows. Journal of Geophysical Research: Atmospheres. 2020 Aug 27;125(16).
- Ma T, Lucas D, Bragg AD. Explicit algebraic relation for calculating Reynolds normal stresses in flows dominated by bubble-induced turbulence. Physical Review Fluids. 2020 Aug 1;5(8).
- Momenifar M, Bragg AD. Local analysis of the clustering, velocities, and accelerations of particles settling in turbulence. Physical Review Fluids. 2020 Mar 1;5(3).
- Carbone M, Bragg AD. Is vortex stretching the main cause of the turbulent energy cascade? Journal of Fluid Mechanics. 2020 Jan 1;883.
- Carbone M, Iovieno M, Bragg AD. Symmetry transformation and dimensionality reduction of the anisotropic pressure Hessian. Journal of Fluid Mechanics. 2020 Jan 1;900.
- Momenifar M, Bragg AD. The influence of reynolds and froude number on the local distribution of settling, inertial particles in turbulence. In: AIAA Scitech 2020 Forum. 2020.
- Carbone M, Bragg AD, Iovieno M. Multiscale fluid-particle thermal interaction in isotropic turbulence. Journal of Fluid Mechanics. 2019 Dec 25;881:679–721.
- Tom J, Bragg AD. Corrigendum: Multiscale preferential sweeping of particles settling in turbulence (Journal of Fluid Mechanics (2019) 871 (244-270) DOI: 10.1017/jfm.2019.337). Journal of Fluid Mechanics. 2019 Aug 10;872:995.
- Tom J, Bragg AD. Multiscale preferential sweeping of particles settling in turbulence. Journal of Fluid Mechanics. 2019 Jul 25;871:244–70.
- Momenifar M, Dhariwal R, Bragg AD. Influence of Reynolds number on the motion of settling, bidisperse inertial particles in turbulence. Physical Review Fluids. 2019 May 1;4(5).
- Dhariwal R, Bragg AD. Enhanced and suppressed multiscale dispersion of bidisperse inertial particles due to gravity. Physical Review Fluids. 2019 Mar 1;4(3).
- Carbone M, Bragg AD, Iovieno M. Modulation of fluid temperature fluctuations by inertial particles in turbulence. In: Springer Proceedings in Physics. 2019. p. 247–52.
- Zorzetto E, Bragg AD, Katul G. Extremes, intermittency, and time directionality of atmospheric turbulence at the crossover from production to inertial scales. Physical Review Fluids. 2018 Sep 1;3(9).
- Dhariwal R, Bragg AD. Small-scale dynamics of settling, bidisperse particles in turbulence. Journal of Fluid Mechanics. 2018 Mar 25;839:594–620.
- Dou Z, Bragg AD, Hammond AL, Liang Z, Collins LR, Meng H. Effects of Reynolds number and Stokes number on particle-pair relative velocity in isotropic turbulence: A systematic experimental study. Journal of Fluid Mechanics. 2018 Mar 25;839:271–92.
- Bonetti S, Bragg AD, Porporato A. On the theory of drainage area for regular and non-regular points. Proceedings Mathematical, physical, and engineering sciences. 2018 Mar;474(2211):20170693.
- Dhariwal R, Bragg AD. Fluid particles only separate exponentially in the dissipation range of turbulence after extremely long times. Physical Review Fluids. 2018 Mar 1;3(3).
- Bragg AD, De Lillo F, Boffetta G. Irreversibility inversions in two-dimensional turbulence. Physical Review Fluids. 2018 Feb 1;3(2).
- Dou Z, Ireland PJ, Bragg AD, Liang Z, Collins LR, Meng H. Particle-pair relative velocity measurement in high-Reynolds-number homogeneous and isotropic turbulence using 4-frame particle tracking velocimetry. Experiments in Fluids. 2018 Feb 1;59(2).
- Reeks M, Swailes DC, Bragg AD. Is the kinetic equation for turbulent gas-particle flows ill posed? Physical review E. 2018 Feb;97(2–1):023104.
- Bragg AD. Analysis of the forward and backward in time pair-separation probability density functions for inertial particles in isotropic turbulence. Journal of Fluid Mechanics. 2017 Nov 10;830:63–92.
- Bragg AD. Developments and difficulties in predicting the relative velocities of inertial particles at the small-scales of turbulence. Physics of Fluids. 2017 Apr 1;29(4).
- Bragg AD, Kurien S, Clark TT. Model of non-stationary, inhomogeneous turbulence. Theoretical and Computational Fluid Dynamics. 2017 Feb 1;31(1):51–66.
- Ireland PJ, Bragg AD, Collins LR. The effect of Reynolds number on inertial particle dynamics in isotropic turbulence. Part 2. Simulations with gravitational effects. Journal of Fluid Mechanics. 2016 Jun 10;796:659–711.
- Ireland PJ, Bragg AD, Collins LR. The effect of Reynolds number on inertial particle dynamics in isotropic turbulence. Part 1. Simulations without gravitational effects. Journal of Fluid Mechanics. 2016 Jan 1;796:617–58.
- Bragg AD, Ireland PJ, Collins LR. Forward and backward in time dispersion of fluid and inertial particles in isotropic turbulence. Physics of Fluids. 2016 Jan 1;28(1).
- Bragg AD, Ireland PJ, Collins LR. On the relationship between the non-local clustering mechanism and preferential concentration. Journal of Fluid Mechanics. 2015 Sep 3;780:327–43.
- Bragg AD, Ireland PJ, Collins LR. Mechanisms for the clustering of inertial particles in the inertial range of isotropic turbulence. Physical Review E - Statistical, Nonlinear, and Soft Matter Physics. 2015 Aug 27;92(2).
- Bragg AD, Collins LR. New insights from comparing statistical theories for inertial particles in turbulence: II. Relative velocities. New Journal of Physics. 2014 Jan 1;16.
- Bragg AD, Collins LR. New insights from comparing statistical theories for inertial particles in turbulence: I. Spatial distribution of particles. New Journal of Physics. 2014 Jan 1;16.
- Bragg A, Swailes DC, Skartlien R. Drift-free kinetic equations for turbulent dispersion. Physical review E, Statistical, nonlinear, and soft matter physics. 2012 Nov;86(5 Pt 2):056306.
- Bragg A, Swailes DC, Skartlien R. Particle transport in a turbulent boundary layer: Non-local closures for particle dispersion tensors accounting for particle-wall interactions. Physics of Fluids. 2012 Oct 3;24(10).