Environmental Fluid Dynamics Education Laboratory

 

HIG 109

Honolulu, HI 96822

Geno Pawlak email: gpawlak X ore.hawaii.edu

 

The dynamics of moving fluids forms the physical basis of the natural environment through the ocean and atmosphere, in turn affecting biological, chemical and geological systems.  Fluid motion is also fundamental to engineering problems ranging from aerodynamics to biomedical research.  The concepts of fluid dynamics are not learned from textbooks and equations alone, however.  These ideas require hands-on experience and observation that complements classroom learning.  The goal of the Environmental Fluid Dynamics Education Laboratory (EFDEL) is to serve as a center for teaching of fluids phenomena for SOEST and the general UHM community.

The EFDEL offers support for laboratory demonstration of environmental and geophysical fluid dynamics phenomena.  We have carried out lab experiments as part of ORE 601 (Ocean and Resources Engineering Laboratory), ORE 664 (Nearshore Processes and Sediment Transport) and have conducted demonstrations for ORE 603 (Oceanography for Ocean Engineers), ORE 641 (Environmental Fluid Dynamics) and OCN 620 (Physical Oceanography) as well as for visiting high school students from the Sea Grant Ocean Learning Academy and for the SOEST Open House. A sample of the variety of fluids experiments are shown below.

Links to other fluids labs:

Geophysical Fluid Dynamics Laboratory, University of Washington (Peter Rhines, Eric Lindahl)

Environmental Fluid Mechanics Laboratory, Stanford University

 

Experiments

                                               

                                                                       

 

Stratified Flows

Intrusion generated by boundary mixing in a two layer fluid

 Rotating Flows

Equipotential surface in a rotating flow

 

Sediment Dynamics

Ripples under a standing wave

 

 

                                

Special Events:

 

    SOEST Open House

 

Stratified Flows

Boundary Mixing / Intrusions

Waves and tides generate significant motion along the bottom that can generate strong mixing and lead to lateral variations in the density field which, in turn, drive horizontal flows.  In the photo sequence below, turbulence is generated by an oscillating grid along a slope.  The tank filled with two  layers with differing salinities (and thus different density). A third layer of mixed fluid develops and propagates between the two initial layers. This is visualized by injecting fluorescing dye through the moving grid between the two layers and using 'black' light.
 

                                               

Salt fingers

Salt fingers are a double diffusive phenomena that are created as a result of the differing diffusive rates for salt and temperature.   They can be produced by carefully pouring warmer and saltier water (blue) above cooler and less salty water. Initially, a stable density gradient exists due to the variation in temperature. Since the temperature diffusion is faster than the diffusion of salt, dense cool and salty water is created at the interface between the two fluids which sinks in the form of narrow fingerlike plumes.

 

 

 

Rotating Flows

Because the earth is rotating, the Coriolis and centrifugal forces play important roles in many environmental fluid dynamics problems. A rotating table can be used to demonstrate phenomena like Ekman pumping, Taylor columns and conservation of vorticity.

Ekman layer visualization in spin-down

 

Sediment Dynamics

RIpple Dynamics under Standing Waves

This experiment examines the response of various sediment particles to oscillating flow under a standing wave.

Fine grained sediments

       

Medium grained sediments

       

Coarse grained sediments

Wave Driven Porewater Exchange

Wave induced motion does not end at the bed surface.  Waves also create pressure gradients within the sediment bed that can generate significant flows.  These porewater flows can drive exchanges between the sediment bed and water column that have important effects on benthic ecosystems.  Dye traces (below) outline the paths for fluid within the bed in response to ripples at the bed surface.

    

 

Particle Settling in Laminar and Turbulent Flow

Settling velocity is a key dynamic quantity of interest in sediment transport. The goal of this experiment is to explore the relationship between settling velocities and turbulence for a variety of sediment particles

                      

 

Credits: Special thanks to Fabian Schloesser for his assistance in carrying out many of the experiments and assembling this page.  Also thanks to Jerome Aucan for his work on the boundary mixing experiment and to Andy Hebert for his work on the porewater experiments.

 

 

      

 

 

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