Environmental Fluid Mechanics: Naturally Occurring Flow Systems

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Environmental Fluid MechanicsNaturally
Occurring Flow Systems

• Lian-Ping Wang
• Department of Mechanical Engineering
• University of Delaware
• lwang_at_udel.edu
• Seminar at Third Annual Business, Technology
  Careers Conference
• Clayton Hall Conference Center

Acknowledgments Dr. Target, Dr. Prasad,
Kobayashi, Dr. Kirby, Dr. Puleo, Dr. Di Toro, Dr.
Veron NSF, USDA, NSFC NCAR
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Outline

• Introduction to Environmental Fluid Mechanics
• Examples of naturally occurring flow systems
• Related research activities at UD

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Outline

• Introduction to Environmental Fluid Mechanics
• Examples of naturally occurring flow systems
• Related research activities at UD

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Environmental Fluid Mechanics
The study of naturally occurring fluid flows of
air and water on our planet Earth, especially of
those that affect the environmental quality of
those fluids (Cushman-Roisin, 2006). Overlap
with Meteorology, Climatology, Hydrology,
Hydraulics, Limnology, and Oceanography.
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Length, velocity, and time scales (from
Cushman-Roisin, 2006)
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Environmental Fluid Mechanics
Stratification vertical variation of fluid
density (warm air next to cold air fresh water
next to saline seawater) Turbulence complex
motion due to instabilities in fluid flows
Ubiquitous but hard to describe (Exception
subsurface flow in porous soils)
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Environmental Fluid Mechanics

• Scientific methods
• Field observation
• Laboratory experimentation
• Theory (conservation laws)
• Computer simulation

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Adapted from Cushman-Roisin (2006)
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Warm Rain Process and Cloud Microphysics (with
Dr. Grabowski at NCAR)
Analog to air-conditioning Cooling with
dehumidification
Growth of cloud droplets
How does air turbulence affect the collision
rates and collision efficiency of cloud
droplets? What is the impact on warm rain
initiation?
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Why studying clouds and precipitation?
Affect the temperature on the Earth surface (1)
Clouds create cooling effect during the day by
reflecting the sun light (short-wave radiation
energy) back to space (2) Clouds create warming
effect at night by trapping long-wave radiation
energy from the surface

Other indirect effects Removing aerosols
Removing water vapor
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Why studying clouds and precipitation?
A big part of weather All forms of
precipitations start with clouds

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Why studying clouds and precipitation?
Contribute to the water cycle on the Earth
Precipitation versus evaporation

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Global Warming

Intergovernmental Panel on Climate Change 2007
Report Warming of the climate system is
unequivocal, as is now evident from observations
of increases in global average air and ocean
temperatures, widespread melting of snow and ice,
and rising global average sea level. very
high confidence that the global averaged net
effect of human activities since 1750 has been
one of warming, with a radiative forcing of 0.6
to 2.4 W/m2. Most of the observed warming
is very likely due to the observed increase in
anthropogenic greenhouse gas concentrations Clou
ds represent a source of significant uncertainty
in numerical weather prediction and climate
models.


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The Price Tags for fixing global warming
Debated by scientists, politicians, economists
and policy makers Alternative energy Nuclear or
Renewable
Monday, October 30, 2006, 1113 PM Global
Warming Price Tag - 7 Trillion BBC reports A
report by economist Sir Nicholas Stern suggests
that global warming could shrink the global
economy by 20. But taking action now would cost
just 1 of global gross domestic product, the
700-page study says.
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Direct Numerical Simulations of droplets in
turbulent flow
Microhydrodynamics Relative grazing trajectories
What are the important physical
mechanisms? How to quantify them
theoretically? How fast rain drops form from
small cloud droplets? How to better understand
droplet-droplet and droplet-turbulence
interactions?
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The hybrid DNS approach
Background turbulent flow
Droplet-droplet hydrodynamic interactions
Features Background turbulent flow can affect
the disturbance flows No-slip
condition on the surface of each droplet is
satisfied on average Both
near-field and far-field interactions are
considered.
Wang, Ayala, and Grabowski, J. Atmos. Sci. 62(4)
1255-1266 (2005). Ayala, Wang, and Grabowski, J.
Comp. Phys., In press (2007).
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Xue, Wang, and Grabowski, 2007, J. Atmos. Sci.,
submitted.
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Multi-scale simulation of turbulent
collision-coalescence (With Dr. G. He at Chinese
Academy of Sciences)
LES
DNS
Microhydrodynamics
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Lab measurements of turbulent collision-coalescenc
e (With Prof. Alberto Aliseda, U. Washington)
Two-phase PIV with high temporal and spatial
resolution
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Gas-liquid flow in porous soils with Prof. Y. Jin
in Plant and Soil Sciences
Issues Interfacial effects electro-chemical
forces on colloids
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Ajay Prasad Mechanical Eng.A laboratory
analogue for cumulus cloud formation

• Developed laboratory analogues in combination
  with modern experimental diagnostic tools to
  study cumulus cloud entrainment without resorting
  to expensive field measurements.
• Applied laser induced fluorescence and particle
  image velocimetry to measure the entrainment
  within the heated jet.

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Center for Applied Coastal Research (CACR)Nobu
Kobayashi (Director), Jim Kirby, Jack PuleoCivil
Environmental Eng

• Nearshore waves and currents
• Sediment transport
• Wetlands and water quality
• Coastal disaster prediction and mitigation.

Directional wave basin (20 m x 20 m x 1.1 m)
generates three-dimensional wind waves.
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J. Kirby Civil Environmental Eng.

• Modeling tsunamis
• Tsunamis are long waves in a relatively shallow
  ocean
• Studying mechanism for tsunamis
• Computational modeling

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Jack Puleo Civil Environmental Eng. Field
studies of sediment transport
Optical backscatter sediment concentration data
Large cross-shore spatial gradients Strong
vertical gradients in sediment concentration in
backwash
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P. T. Imhoff Civil Environmental Eng.

• Modeling preferential flow of water and solutes
  in the vadose zone
• Using gas tracers to infer water movement in
  soils
• Sponsor National Science Foundation

Simulations of gas tracer transport in 2D domain
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D.M. Di Toro Civil Environmental Eng.

• Developing benthic suspension feeder model for
  Chesapeake Bay
• - Interaction with dissolved oxygen

Di Toro, D. M. (2001) Sediment Flux Modeling J.
Wiley and Sons.
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College of Marine and Earth Studies

• Oceanography Program
• Physical Ocean Science and Engineering Program
• Marine Bioscience program
• Marine Policy Program
• Department of Geological Sciences

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Researchers in Marine and Earth Studies have
conducted work in every ocean and on nearly
every continent. The bullets on the map below
indicate where our scientists are currently
doing research.
CMES Conducts
Research Worldwide
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146-foot coastal research vessel
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Fabrice Veron College of Marine and Earth
Studies - Air-Sea Interaction Laboratory
Air-Sea Interactions
Airflow separation over the waves Momentum flux
and Hurricane modeling
Wave effects on air-sea heat fluxes Global
climate modeling
Air-Sea Transfers of momentum by rainfall
Mixing and gas flux
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HF Radar Radial and Total Velocities
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Department of Geography, University of Delaware

• Center for Climatic Research (David Legates)
• Delaware Environmental Observing System
  (deos.udel.edu)
• Ph.D. in Climatology
• B.S. in Environmental Science

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Take-Home Messages

• Environmental Fluid Mechanics
• many exciting applications
• interdisciplinary
• complexities
• Learn to talk others language and to cross the
• boundary of mechanical engineering
• The activities at UD are expanding in this area
• Sea / space / land grant college
• Joining UCAR this year