A5079799821- Fluid Dynamics and Turbulent Flows
- Wind and Air Flow Studies
- Particle Dynamics in Fluid Flows
- Meteorological Phenomena and Simulations
- Heat Transfer Mechanisms
- Plant Water Relations and Carbon Dynamics
- Fluid Dynamics and Vibration Analysis
- Hydrology and Sediment Transport Processes
- Aerodynamics and Acoustics in Jet Flows
- Aeolian processes and effects
- Soil Moisture and Remote Sensing
- Atmospheric aerosols and clouds
- Computational Fluid Dynamics and Aerodynamics
- Climate variability and models
- Climate change and permafrost
- Precipitation Measurement and Analysis
- Combustion and flame dynamics
- Tropical and Extratropical Cyclones Research
- Oceanographic and Atmospheric Processes
- Soil and Unsaturated Flow
- Hydraulic flow and structures
- Fluid Dynamics and Thin Films
- Geophysics and Gravity Measurements
- Heat Transfer and Optimization
- Cryospheric studies and observations
The University of Melbourne
2016-2025
American Military Academy
2020
United States Military Academy
2020
University of Cambridge
2018
California Institute of Technology
2009-2017
TU Wien
2012-2017
University of Connecticut
2017
Jet Propulsion Laboratory
2011-2013
University of California, Los Angeles
1973-1976
Global trends in a new multi‐satellite surface soil moisture dataset were analyzed for the period 1988–2010. 27% of area covered by showed significant (p = 0.05). Of these, 73% negative and positive. Subtle drying found Southern US, central South America, Eurasia, northern Africa Middle East, Mongolia northeast China, Siberia, Western Australia. The strongest wetting southern subarctic region. Intra‐annual analysis revealed that most are not uniform among seasons. prominent trend patterns...
Reliable full-scale prediction of drag due to rough wall-bounded turbulent fluid flow remains a challenge. Currently, the uncertainty is at least 10%, with consequences, for example, on energy and transport applications exceeding billions dollars per year. The crux difficulty large number relevant roughness topographies high cost testing each topography, but computational experimental advances in last decade or so have been lowering these barriers. In light advances, here we review...
Direct numerical simulations (DNS) are conducted for turbulent flow through pipes with three-dimensional sinusoidal roughnesses explicitly represented by body-conforming grids. The same viscous-scaled roughness geometry is first simulated at a range of different Reynolds numbers to investigate the effects low and $R_{0}/h$ , where $R_{0}$ pipe radius $h$ height. Results present class surfaces show that Hama function ${\rm\Delta}U^{+}$ only marginally affected (or ), observations outer-layer...
Abstract In this study we examine the impact of strength large-scale motions on amplitude and frequency small scales in high-Reynolds-number turbulent boundary layers. Time series hot-wire data are decomposed into large- small-scale components, large scale is considered. The modulation effect examined by conditionally averaging intensity ( ${ u}_{S}^{2} $ ) for various values fluctuation ${u}_{L} ). It shown that increases with increasing value near-wall region, whereas, farther away from...
We investigate statistics of large-scale structures from large-eddy simulation (LES) turbulent channel flow at friction Reynolds numbers Re τ = 2K and 200K (where K denotes 1000). In order to capture the behaviour properly, length is chosen be 96 times half-height. agreement with experiments, these are found give rise an apparent amplitude modulation underlying small-scale fluctuations. This effect explained in terms phase relationship between large- activity. The shape dominant structure...
We report large-eddy simulation (LES) of turbulent channel flow. This LES neither resolves nor partially the near-wall region. Instead, we develop a special subgrid-scale (SGS) model based on wall-parallel filtering and wall-normal averaging streamwise momentum equation, with an assumption local inner scaling used to reduce unsteady term. gives ordinary differential equation (ODE) for wall shear stress at every location that is coupled LES. An extended form stretched-vortex SGS model, which...
Abstract A single-column model (SCM) is developed for representing moist convective boundary layers. The key component of the SCM parameterization subgrid-scale vertical mixing, which based on a stochastic eddy-diffusivity/mass-flux (EDMF) approach. In EDMF framework, turbulent fluxes are calculated as sum kinetic energy–based eddy-diffusivity and mass-flux component. mass flux modeled fixed number steady-state plumes. main challenge to properly represent cumulus clouds, solutions have...
Abstract Using direct numerical simulation, we investigate stationary and homogeneous shear-driven turbulence in various stratifications, ranging from neutral to very stable. To attain maintain a flow, throttle the mean shear so that net production stays constant for all times. This results flow is characterized solely by its buoyancy gradient, independent of initial conditions. The method throttling validated comparison with experimental spectra case stratification. With increasing...
Abstract Results from direct numerical simulations of vertical natural convection at Rayleigh numbers $1.0\times 10^{5}$ – 10^{9}$ and Prandtl number $0.709$ support a generalised applicability the Grossmann–Lohse (GL) theory, which was originally developed for horizontal (Rayleigh–Bénard) convection. In accordance with GL it is shown that boundary-layer thicknesses velocity temperature fields in obey laminar-like Prandtl–Blasius–Pohlhausen scaling. Specifically, normalised mean scale $-1/2$...
Editors note: For easy download the posted pdf of State Climate for 2013 is a very low-resolution file. A high-resolution copy report available by clicking here. Please be patient as it may take few minutes file to download.
We describe a fast direct numerical simulation (DNS) method that promises to directly characterise the hydraulic roughness of any given rough surface, from hydraulically smooth fully regime. The circumvents unfavourable computational cost associated with simulating high-Reynolds-number flows by employing minimal-span channels (Jimenez & Moin 1991). Proof-of-concept simulations demonstrate in are sufficient for capturing downward velocity shift, is, Hama function, predicted full-span...
Abstract Simulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased oscillatory motion in the surface, with amount of reduction predicted to decline increasing number. Here, we report direct measurements substantial achieved using spanwise oscillations high friction ( $${{{\mathrm{Re}}}_{\tau }}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi>Re</mml:mi>...
Abstract The buoyancy-adjusted stretched-vortex subgrid-scale (SGS) model is assessed for a number of large-eddy simulations (LESs) corresponding to diverse atmospheric boundary layer conditions. cases considered are free convection, moderately stable [first Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS)] case, shallow cumulus [Barbados Oceanographic Meteorological Experiment (BOMEX)], precipitating [Rain in Cumulus over the Ocean (RICO)] nocturnal...
The present study considers the impact of various choices pertaining to numerical solution governing equations on large-eddy simulation (LES) prediction and association these with flow physics. These include effect dissipative versus nondissipative advection discretizations, different implementations constant-coefficient Smagorinsky subgrid-scale model, grid resolution. Simulations corresponding trade wind precipitating shallow cumulus composite case Rain in Cumulus over Ocean (RICO) field...
Technical Briefs Heat Transfer Across a Turbulent Falling Film With Cocurrent Vapor Flow G. L. Hubbard, Hubbard University of California, Los Angeles, Calif. Search for other works by this author on: This Site PubMed Google Scholar A. F. Mills, Mills D. K. Chung Atomics International, Canoga Park, Author and Article Information J. Transfer. May 1976, 98(2): 319-320 (2 pages) https://doi.org/10.1115/1.3450543 Published Online: 1, 1976 history Received: January 21, 1975 August 11, 2010
Wall-bounded turbulence, where it occurs in engineering or nature, is commonly subjected to spatial variations wall shear stress. A prime example spatially varying roughness. Here, we investigate the configuration stress varies only lateral direction. The investigation idealised order focus on one aspect, namely, similarity and structure of turbulent inertial motion over an imposed scale variation. To this end, analyse data from direct numerical simulation (DNS) pressure-driven flow through...
Roughness predominantly alters the near-wall region of turbulent flow while outer layer remains similar with respect to wall shear stress. This makes it a prime candidate for minimal-span channel, which only captures by restricting spanwise channel width be order few hundred viscous units. Recently, Chung et al. ( J. Fluid Mech. , vol. 773, 2015, pp. 418–431) showed that can accurately characterise hydraulic behaviour roughness. Following this, we aim investigate fundamental dynamics...
The occurrence of secondary flows is investigated for three-dimensional sinusoidal roughness where the wavelength and height elements are systematically altered. flow spanned from transitionally rough regime up to fully solidity ranged a wavy, sparse dense roughness. Analysing time-averaged velocity, observed in all cases, reflected coherent stress profile which dominant vicinity elements. sublayer, defined as region non-zero, scales with when geometrically scaled (proportional increase both...
Abstract
Abstract
Direct numerical simulations (DNS) are used to systematically investigate the applicability of minimal-channel approach (Chung et al. , J. Fluid Mech. vol. 773, 2015, pp. 418–431) for characterization roughness-induced drag on irregular rough surfaces. Roughness is generated mathematically using a random algorithm, in which power spectrum (PS) and probability density function (p.d.f.) surface height can be prescribed. Twelve different combinations PS p.d.f. examined, both transitionally...
This paper introduces a viscous vortex model for predicting the optimal drag reduction of riblet surfaces, eliminating need expensive direct numerical simulations (DNSs) or experiments. The footprint typical quasi-streamwise vortex, in terms spanwise and wall-normal velocities, is extracted from smooth-wall DNS flow fields close proximity to surface. velocities are then averaged used as boundary conditions Stokes-flow problem, wherein riblets with various cross-sectional shapes embedded....