Navigation Links
Where does the fluid go?
Date:2/24/2010

MADISON, WI, FEBRUARY 22, 2010 Combined mechanisms of transport have important applicationstransport of nutrients across cell membranes in plants and animals, the aeration of agricultural soils, performance of chemical reactors, the design of membranes for desalting brackish water, and the design of clay membranes for retaining dangerous chemicals. Because mass transport of fluid constituents has important roles in biology, physics, and chemistry, one would assume that such transport would be well understood by the scientific community. However, transport of fluid constituents continues to be a source of confusion, particularly regarding models for combining transport by molecular diffusion and advection.

In a recent article in Vadose Zone Journal, A.T. Corey, W.D. Kemper (both of Colorado State Univ., Fort Collins), and J.H. Dane (Auburn Univ., Auburn, AL) show that the developers of popular models of diffusion have made invalid assumptions. Currently popular models define diffusion of a particular constituent as a flux relative to mass average flux so that diffusive flux of all constituents in a fluid mixture must sum to zero, and self-diffusion of a single-specie fluid cannot exist, contradicting experimental evidence previously reported in the literature. Research conducted and referenced by the authors shows that these assumptions and their models do not provide a satisfactory description of the flux taking place in media with small pores. The authors provide an improved analysis, based on the principle that driving forces (for both advection and diffusion) are each equal in magnitude (and opposite in direction) to the associated rate of change of momentum. Mass average flux resulting from combined advection and diffusion is shown to be evaluated as the vector sum of advective and diffusive fluxes, rather than diffusive flux being evaluated as a flux relative to a mass average flux. This procedure is necessary because "mean flux" cannot be determined independent of an evaluation of diffusive flux.

Corey et al. describe two experiments with transport of gas constituents through porous media (providing data consistent with their revised model) that contradict widely accepted models. One of the experiments presents previously published data and the other describes new data obtained by the authors. Three additional experiments are presented (one representing new data) showing that self-diffusion of pure liquid water occurs in response to a temperature gradient, contradicting theory that diffusion of a single-specie fluid cannot occur, and showing that the sum of diffusion fluxes do not sum to zero in the general case. The measured diffusion of water was proportional to the gradient of the vapor pressure, which is a well-documented measure of the kinetic energy of water.


'/>"/>

Contact: Sara Uttech
suttech@sciencesocieties.org
608-268-4948
American Society of Agronomy
Source:Eurekalert

Related medicine news :

1. The Doctor Is in...But Where Is the Tax Advisor?
2. Using gold nanoparticles to hit cancer where it hurts
3. For Valentine's Day, Lifestyle Correspondent and Her Two Sets of Twins Show a Little Love Where Its Needed the Most
4. Dog Flu Risk Highest Where Canines Mingle
5. How does an outfielder know where to run for a fly ball?
6. It's January...Do You Know Where Your Thyroid Is? Thyroid Awareness Month Focuses on Millions of Undiagnosed Americans with Thyroid Problems
7. New Study Says Doctors' Offices -- Not the DMV -- Should Be Where Americans Decide to Become Organ Donors
8. Duda, whered my spines go?
9. Children & Health Reform: Where We Stand
10. The importance of attractiveness depends on where you live
11. Blue Cross and Blue Shield of Minnesota and Fairview Health Services Launch Online Care Anywhere(TM)
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/13/2016)... ... ... With FCPX Overlay Embers from Pixel Film Studios users can now apply ... user can select from up to 40 effect overlays. With FCPX Overlay Embers users ... value, contrast, glow, and more all within a click of a mouse. , ...
(Date:2/13/2016)... ... , ... When an Au Pair comes all the way around the world to ... and they are often worried things won’t go well. More often than not, however, they ... Pair of the Year winner’s all commented how their Au Pairs have become a part ...
(Date:2/12/2016)... ... February 12, 2016 , ... Mystic Buddha Publishing House presents Valentine’s ... Buddha, the biography of Rama - Dr. Frederick Lenz. , According to ... of a Buddhist teacher for teaching and helping others. Valentine’s Day celebrates love ...
(Date:2/12/2016)... ... ... , Back to the Future , Feb. 25, 2016 — 11:00 a.m. – 12:30 p.m. ... learn from history are doomed to repeat it.” , An analysis of CDRH’s enforcement actions ... takes time. , Take a close look at the warning letters the agency sent ...
(Date:2/12/2016)... ... ... Coco Libre, the maker of coconut water beverages with a purpose, is ... Coco Libre will offer musicians and celebrities the company’s signature Organic Coconut Water, a ... suite, held this year at the W Hollywood Hotel, has become a pre-show “must” ...
Breaking Medicine News(10 mins):
(Date:2/12/2016)... -- Memorial Hermann Health System has teamed up with Houston ... a one-of-a-kind experience to pediatric patients at Children,s ... 360-degree video and Google Cardboard, Howard was able to ... the patients and their families an unexpected, and energetically ... video . Memorial Hermann IRONMAN Sports ...
(Date:2/12/2016)... 12, 2016  Aralez Pharmaceuticals Inc. (Nasdaq: ARLZ ... Company will ring the Nasdaq Closing Bell at the ... at 4:00 p.m. ET on Tuesday, February ... Adrian Adams , will perform the honorary ... 4:00 p.m. ET.  A live webcast will be available ...
(Date:2/12/2016)... 12, 2016 --> ... Chronic Inflammation Global Clinical Trials Review, H2, 2015 ... global clinical trials landscape along with top level ... Country (G7 & E7), Trial Status, Trial Phase, ... top companies involved and enlists all trials (Trial ...
Breaking Medicine Technology: