Purdue's Kessler Patterns in porous media
FLUID FLOW:
Model for Media Predicting fluid flow patterns in por ous media is much more an art than a science. Purdue University's Dr. David P. Kessler is trying to reverse the art/science ratio by constructing a mathematical model of media. Thus far, the associate professor of chem ical engineering has a statistical model of permeability, which is being sim plified, and is working on a model for dispersion calculations from which fluid flow predictions can be made. The purpose of the models is to tell how the media work, not how to build better media, which is a much more complex problem. Dr. Kessler is cooperating on this research with Dr. Robert A. Oreenkorn, chemical engineering depart ment head, and Dr. James Guin, a visiting assistant professor, under a grant from the Federal Water Pollu tion Control Administration. He and his coworkers see potential applica tions for their models in chemical re search, industrial chemical processes, movement of agricultural chemicals in soils, recovery of oil from wells, pre vention of salt water contamination of fresh water wells, and underground disposal of radioactive and other wastes. The models may also help give scientists an insight into fluid mechanics in the human body, in cluding the flow of blood, lymph, and other liquids as well as the exchange of gases in the lungs. There is at present no satisfactory way to determine the characteristics of fluid flow in porous media and to 18 C&EN JAN. 26, 1970
predict flow. Predicting fluid flow can become important in the economic recovery of oil, for example. If the oil flow under the ground could be predicted, wells could be more accu rately drilled, at only the optimum points in the field for oil recovery. Even with such aids to oil recovery as heating up well bores, pumping in water, and injecting steam, one third to one half of the oil in a typical field may remain untapped—a waste of valuable natural resources, Dr. Kessler points out. Another example of where the mod els could be put to quick use is in chemical processing, he adds. In many processes, reactors are packed with catalyst pellets which form a porous medium. The reaction rate depends upon the concentration at the catalyst surface, which depends upon mixing, which is influenced by dis persion, which is a function of per meability. Predicting flow in isotropic media— where resistance to flow is the same in all directions—has been possible for some time. However, for anisotropic media, usually found in nature, pre dictions are not now possible. The problem is complex because permea bility is a second-order tensor—nine components are required to describe it. Dispersion is a fourth-order ten sor, with 81 components if the medium is not symmetrical. To use Dr. Kessler's statistical model to determine permeability, only the average pore size of a medium and the measurement of flow (direc tions and pressures) in a small sample need be ascertained. With these few numbers the average behavior of the solid phase can be calculated. Porous media can be thought of as a bundle of capillary tubes. The statistical model essentially represents a series of capillary tubes of different lengths, radii, and direction orienta tions. The computer describes the movement of fluid successively through the various capillary tubes.
ENVIRONMENT:
A Job of Managing In the midst of a furious barrage of pre-State of the Union pronounce ments by politicians and activists on how to solve the nation's environmen tal problems, the National Academy of Sciences and National Academy of Engineering issued a background pa per on a national program for manag ing the environment. The paper, "In stitutions for Effective Management of the Environment," was pre pared last August at Stanford University by an environmental study group of the NAS-ΝΑΕ Environmen
tal Studies Board, but was released last week just a few days before the President's message. According to Environmental Stud ies Board chairman Harold Gershinowitz, the report's proposal will "pro vide a basis on which the board will make recommendations for effective approaches and institutional mecha nisms for dealing with environmental problems." One of the study group's pro posals—a call for a Board of Environ mental Affairs within the office of the President—has largely been included in the National Environmental Policy Act of 1969, signed into law before the release of the report, and in the provisions of Sen. Edmund S. Muskie's (D.-Me.) Water Quality Improve ment Act of 1969. Another of the study group's pro posals—not yet law but certain to be introduced in this session of Con gress—calls for a joint committee on the environment. The joint commit tee, the report says, would "provide a much needed focal point for the in formed discussion of environmental affairs." Environmental quality indices for evaluating the state of the environ ment are recommended in the report. Indices, such as transparency of air, purity of water, and noise level, would be combined into an overall environ mental quality index—which might be useful for developing priorities among programs affecting the environ ment. The paper points out that the Fed eral Government does not have a lab oratory carrying out systematic re search on the total environment and calls for establishing a National Lab oratory for the Environmental Sci ences. Decision making in environmental matters at all levels of government has been hampered by a lack of adequate analysis of what is now taking place and options, the paper says. To end this situation, the study group calls for setting up a privately funded Institute for Environmental Studies whose functions would include long-range planning, and analysis of factors that influence environmental decisions and management of the environment. To train manpower for coping with environmental problems the study group calls for creation of multidisciplinary programs of environmental af fairs within existing universities, and for establishment of an experimental problem-oriented graduate school. To stimulate public education and public action on the environment, the study group calls for the creation of a private National Environmental Coa lition—a sort of Urban Coalition on the environment.
