Physically Similar Systems - A History of the Concept

PreprintThe concept of similar systems arose in physics, and appears to have originated with Newton in the seventeenth century. This chapter provides a critical history of the concept of physically similar systems, the twentieth century concept into which it developed. The concept was used in the nineteenth century in various fields of engineering (Froude, Bertrand, Reech), theoretical physics (van der Waals, Onnes, Lorentz, Maxwell, Boltzmann) and theoretical and experimental hydrodynamics (Stokes, Helmholtz, Reynolds, Prandtl, Rayleigh). In 1914, it was articulated in terms of ideas developed in the eighteenth century and used in nineteenth century mathematics and mechanics: equations, functions and dimensional analysis. The terminology physically similar systems was proposed for this new characterization of similar systems by the physicist Edgar Buckingham. Related work by Vaschy, Bertrand, and Riabouchinsky had appeared by then. The concept is very powerful in studying physical phenomena both theoretically and experimentally. As it is not currently part of the core curricula of STEM disciplines or philosophy of science, it is not as well known as it ought to be

Geothermal power production: accidental fluid releases, waste disposal, and water use

Environmental problems related to the use and disposal of fluids can accompany the operation of geothermal power plants using hot water resources (temperature > 150/sup 0/C). More than 100 kg of fluids must be extracted, processed, and disposed for each kW.h of electricity generated from a facility relying on a geothermal reservoir with fluids of 150/sup 0/C. The low thermal efficiencies of geothermal power plants result in large requirements for cooling water - over 7.4 x 10/sup 4/ m/sup 3//MW.y compared with 1.7 x 10/sup 4/ m/sup 3//MW.y for coal-fired plants. Geothermal fluids can contain as much as 250,000 mg/1 total dissolved solids. Toxic substances like boron and NH/sub 3/ are often present in fluids. This paper focuses on impacts associated with accidental releases of geothermal fluids as well as the disposal of liquid and solid wastes. The consequences of consuming alternative sources of cooling water are also addressed. Inadvertent discharges of fluids are of concern because they could contaminate soils and surface waters, adversely affecting crops and aquatic organisms. The pretreatment of fluids before subsurface injection could lead to solid waste problems - especially when toxic substances are produced. The consumption of alternative cooling waters can pose problems involving the disposal of blowdown from cooling towers. In addition, the toxicity of drift emitted from cooling towers depends on the kind of cooling water used

Health and environmental effects document on geothermal energy: 1981

Several of the important health and environmental risks associated with a reference geothermal industry that produces 21,000 MW/sub e/ for 30 y (equivalent to 20 x 10/sup 18/ J) are assessed. The analyses of health effects focus on the risks associated with exposure to hydrogen sulfide, particulate sulfate, benzene, mercury, and radon in air and arsenic in water. Results indicate that emissions of hydrogen sulfide are likely to cause odor-related problems in geothermal resources areas, assuming that no pollution controls are employed. For individuals living within an 80 km radius of the geothermal resources, chronic exposure to particulate sulfate could result in between 0 to 95 premature deaths per 10/sup 18/ J of electricity generated. The mean population risk of leukemia from the inhalation of benzene was calculated to be 3 x 10/sup -2/ cases per 10/sup 18/ J. Exposure to elemental mercury in the atmosphere could produce between 0 and 8.2 cases of tremors per 10/sup 18/ J of electricity. Inhalation of radon and its short-lived daughters poses a mean population risk of 4.2 x 10/sup -1/ lung cancers per 10/sup 18/ J. Analysis of skin cancer risk from the ingestion of surface water contaminated with geothermally derived arsenic suggests that a dose-response model is inconsistent with data showing that arsenic is an essential element and that excessive body burdens do not appear even when arsenic reaches 100 ..mu..g/liter in drinking water. Estimates of occupational health effects were based on rates of accidental deaths and occupational diseases in surrogate industries. According to calculations, there would be 14 accidental deaths per 10/sup 18/ J of electricity and 340 cases of occupational diseases per 10/sup 18/ J. The analysis of the effects of noncondensing gases on vegetation showed that ambient concentrations of hydrogen sulfide and carbon dioxide are more likely to enhance rather than inhibit the growth of plants

Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies

Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2 Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2 Both intravenous infusion of [Phe(2),Ile(3),Orn(8)]-vasopressin and infusion of N(G)-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8-17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r(2) = 0.87-0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2 Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1-0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10-50% of the change in pelvic urine/medullary Po2 Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury