Syphon Diaphragms : A Method for Predicting Their Performance for Purposes of Instrument Design

Here, the purpose is to show that the characteristic performance of a syphon diaphragm can be predicted from a knowledge of its stiffness and of its dimensions. The proof is based on a mathematical analysis of this type of diaphragm, together with enough experimental data to prove the validity of the assumptions and the sufficiency of the analysis. Equations are developed for the performance of syphons under various conditions of loading, both for concentrated loads and for hydrostatic pressure

Investigation of damping liquids for aircraft instruments

This report covers the results of an investigation carried on at the Bureau of Standards under a research authorization from, and with the financial assistance of, the National Advisory Committee for Aeronautics. The choice of a damping liquid for aircraft instruments is difficult owing to the range of temperature at which aircraft operate. Temperature changes affect the viscosity tremendously. The investigation was undertaken with the object of finding liquids of various viscosities otherwise suitable which had a minimum change in viscosity with temperature. The new data relate largely to solutions. The effect of temperature on the kinematic viscosity of the following liquids and solutions was determined in the temperature interval -18 degrees to +30 degrees C. (1) solutions of animal and vegetable oils in xylene. These were poppy-seed oil, two samples of neat's-foot oils, castor oil, and linseed oil. (2) solutions of mineral oil in xylene. These were Squibb's petrolatum of naphthene base and transformer oil. (3) glycerine solutions in ethyl alcohol and in mixture of 50-50 ethyl alcohol and water. (4) mixtures of normal butyl alcohol with methyl alcohol. (5) individual liquids, kerosene, mineral spirits, xylene, recoil oil. The apparatus consisted of four capillary-tube viscometers, which were immersed in a liquid bath in order to secure temperature control. The method of calibration and the related experimental data are presented

Investigation of Damping Liquids for Aircraft Instruments : II

Data are presented on the kinematic viscosity, in the temperature range -50 degrees to +30 degrees C. of pure liquids and of solutions of animal oils, vegetable oils, mineral oils, glycerine, and ethylene glycol in various low freezing point solvents. It is shown that the thermal coefficient of kinematic viscosity as a function of the kinematic viscosity of the solutions of glycerine and ethylene glycol in alcohols is practically independent of the temperature and the chemical composition of the individual liquids. This is similarly true for the mineral oil group and, for a limited temperature interval, for the pure animal and vegetable oils. The efficiency of naphthol, hydroquinone, and diphenylamine to inhibit the change of viscosity of poppyseed and linseed oils was also investigated

Transporte de sedimentos en cauces de alta pendiente

[ES] En este trabajo se constata que ni el número de Reynolds del contorno ni el parámetro de Shields son variables adecuadas para predecir las condiciones críticas de iniciación del movimiento de partículas sueltas en el lecho de canales o ríos con contornos de gran rugosidad (profundidad menor que 10 veces la rugosidad) y alta pendiente (pendiente mayor que 0,005). Se analiza el criterio de la velocidad media del flujo en la definición de las condiciones de iniciación del movimiento y se considera el número de Froude crítico de la partícula como criterio alterno para estimar las condiciones hidráulicas de iniciación del movimiento. Se contrastan los resultados de la formulación teórica con datos experimentales de diversos autores. Se describen algunos de los procedimientos más empleados en la estimación del transporte del material sólido constitutivo del lecho de una corriente de alta pendiente. Las dos características comunes de tales métodos es que no fueron desarrollados con el propósito específico de estimar el transporte de sólidos en cauces de altas pendientes y segundo, que consideran como parámetro regulador del transporte la diferencia ente el esfuerzo cortante medio en el lecho y el esfuerzo cortante crítico correspondiente a las condiciones de iniciación del movimiento. Luego se presentan dos metodologías desarrolladas específicamente para estimar el transporte sólido en cauces de alta pendiente. La primera considera el exceso de caudal sobre el caudal crítico unitario como variable determinante de las condiciones de arrastre y la segunda incorpora la influencia del número de Froude densimétrico de las partículas en exceso a su valor crítico. Se comparan los resultados de las diferentes aproximaciones con mediciones de laboratorio y con bancos de datos de ríos, disponibles en la literatura. Se propone una nueva función de transporte, que se ajusta mejor que las relaciones funcionales analizadas, para estimar el transporte de sedimentos gruesos en ríos de alta pendiente y gran rugosidad.Aguirre-Pe, J.; Olivero, M.; Moncada, A. (2000). Transporte de sedimentos en cauces de alta pendiente. Ingeniería del Agua. 7(4):353-365. https://doi.org/10.4995/ia.2000.2851SWORD35336574Ackers, P. y W. R. White (1973). Sediment transport: New approach and analysis. Journal of the Hydraulic Division, ASCE, Vol. 99, HY11, pp. 2041-2060.Aguirre-Pe, J. (1975). Incipient erosion in high gradient open channel flow with artificial roughness elements. Proceedings of the XVI International Congress, IAHR, Vol. 2, pp. 173-180, Sao Paulo, Brasil.Aguirre-Pe, J. (1976). Arrastre de sedimentos en flujos torrenciales de alta pendiente. Informe del Laboratorio de Hidráulica de la Universidad de los Andes, Mérida, Venezuela.Aguirre-Pe, J. (1984). Fricción y condiciones críticas de gravas. Informe de Laboratorio de Hidráulica, Universidad de los Andes, Mérida, Venezuela.Aguirre-Pe, J. (1990). Resistencia y condiciones críticas en flujo de canal empinado. Informe del Laboratorio de Hidráulica de la Universidad de los Andes, Mérida, Venezuela.Aguirre-Pe, J. y R. Fuentes (1988). Un modelo para la fricción en canales con macrorugosidades uniformes y compuestas. Memorias del XIII Congreso Latinoamericano de Hidráulica, AIIH, Vol. 1, pp. 55-66, La Habana, Cuba.Aguirre-Pe, J. y R. Fuentes (1990). Resistance to flow in steep rough streams. Journal of the Hydraulic Division, ASCE, Vol. 116, No. 11, pp. 1374-1387.Aguirre-Pe, J. y R. Fuentes (1991). Movement of big particles in steep macro-rough streams. Proceedings of the XXIV International Congress, IAHR, Vol. A, pp. 149-158, Madrid, España.Aguirre-Pe, J., R. Fuentes y M. L. Olivero (1986). Una fórmula para la fricción en escurrimientos macrorugososa superficie libre. Memorias del XII Congreso Latinoamericano de Hidráulica, AIIH, Vol. 1, pp. 86-95, Sao Paulo, Brasil.Aguirre-Pe, J., R. Fuentes, G. Picón y A. Moncada (1992). Estudio experimental de transporte de sedimentos gruesos. Memorias del XV Congreso Latinoamericano de Hidráulica, AIIH, Vol. 3, pp. 129-139, Cartagena, Colombia.Ashida, K. y M. Bayazit (1973). Initiation of motion and roughnes of flows in steep channels. Proceedings of the XV International Congress, IAHR, Vol. 1, pp. 475-484, Estambul, Turquía.Bathurst, J. C., H. H. Cao y W. H. Graf (1984). The data from the EPFL study of hydraulics and sediment transport in a steep flume. Report CH-1015, Ecole Politechnique Féderale de Lausanne, Suiza.Bathurst, J. C., W. H. Graf y H. H. Cao (1983). Initiation of sediment transport in steep channels with coarse bed material. Mechanics of sediment transport, Editado por Sumer, B. M. Y Müller, A., Balkema, Rotterdam, Holanda, pp. 207-213.Bathurst, J. C., W. H. Graf y H. H. Cao (1987). Bed load discharge equations for steep mountain rivers. Cap. 15 de Sediment transport in gravel bed rivers, Editado por C.R. Thorne, J. C. Bathurst y R. D. Hey, John Wiley and Sons, New York, USA, pp. 453-491.Bettes, R. (1984). Initiation of sediment transport in gravel streams. Proceedings Institute of Civil Engineering, Vol. 77, No. 2, pp. 79-88.Brahms, A. (1753). Anfangsgründe de Deich-und Wasser-baukunst. Austria.Breusers, H. N. C. (1982). Lecture notes on sediment transport. International Course in Hydraulic Engineering, Delft, Holanda.Brownlie, W. R. (1981). Compilation of alluvial channel data: laboratory and field. Report No. KH-R-43B, California Institute of Technology, Pasadena, California, USA.Dubuat, L. G. (1779). Principes d'hydraulique et de pyrodynamique. Paris, Francia.Einstein, H. A. (1942). Formulas for the transpolation of bed load. Transactions ASCE, Vol. 107, Paper 2140, p.p 561-573.Fuentes, R. y S. Carrasquel (1978). Una ecuación empírica para zonas de transición. Publicación 10-78 del Laboratorio Nacional de Hidráulica, Caracas, Venezuela, pp. 10.Keulegan, G. H. (1938). Laws of turbulent flow in open channels. Journal Research at the National Bureau of Standards, 21, Research Paper RP 1151, pp. 707-741.Maza, J. A. y M. García (1978). Velocidades medias para el inicio del movimiento de partículas. Memorias del VIII Congreso Latinoamericano Hidráulica, AIIH, pp. 195-206, Quito, Ecuador.Maza, J. A. y M. García (1996). Transporte de sedimentos. Capítulo 10, Instituto de Ingeniería, UNAM, México, D.F., México, pp. 531,Meyer-Peter y R. Müller (1948). Formulations of the bed-load transport. II International Congress IAHR, pp. 39-64, Stockholm, Suecia.Mora, E. (1990). Estudio comparativo de fórmulas de gasto sólido para material grueso. Trabajo como credencial para el ascenso a la categoría de Profesor Agregado. Universidad de los Andes, Mérida, Venezuela.Mora, E.; J. Aguirre-Pe y R. Fuentes (1990). Fórmulas de gasto sólido para el flujo macrorugoso. Memorias del XIV Congreso Latinoamericano de Hidráulica, AIIH, Vol. 3, pp. 1537-1548, Montevideo, Uruguay.Neill, C. R. (1967). Mean velocity criterion for scour of coarse uniform bed-material. Proceedings of the XII International Congress, IAHR, Vol. 3, pp. 46-54, Fort Collins, Colorado.Olivero, M.L. (1984). Umbral de movimiento. Trabajo de Ascenso para Profesor Asociado, Universidad de los Andes, Mérida, Venezuela.Picón, G. A. (1991). Estudio experimental de transporte de sedimentos en ríos de montaña. Tesis para optar al grado de Magister Scientiae, CIDIAT, Universidad de los Andes, Mérida, Venezuela.Schlichting, H. (1968). Boundary-layer theory. 6ta ed., McGraw-Hill.Schoklitsch, A. (1962). Handbuch des Wasserbaues. 3ra ed, Springer-Verlag, Vienna, Austria.Shields, A. (1936). Anwendung der aehnlichkeitsmechanik der turbulenzforchung auf die geschiebebewwegung. Mitt. der Preuss. Versuchsanstalt für Wasserbau und Schiffbau, Berlin, AlemaniaSmart, G. M. (1984). Sediment transport formula for steep channels. Journal of Hydraulic Engineering, ASCE, Vol. 10, No. 3, pp. 39-64.Smart, G. M. y M. Jaeggi (1983). Sediment transport on steep slopes. V.A.W., Mitteil 64, Hidrologie und Glaziologie, ETH, Zurich, Suiza, pp. 191.Van Rijn, L. C. (1987). Mathematical modelling of morphological processes in the case of suspended sediment transport. Delft Hydraulics Communication No. 382, Delft, Holanda.Vanoni, V. A. y Brooks, N. H. (1957). Laboratory studies of the roughness and suspended load of alluvial streams. Sedimentation Laboratory, California Institute of Technology, Report E-68, Pasadena, California, USA

Jump at the onset of saltation

We reveal a discontinuous transition in the saturated flux for aeolian saltation by simulating explicitly particle motion in turbulent flow. The discontinuity is followed by a coexistence interval with two metastable solutions. The modification of the wind profile due to momentum exchange exhibits a second maximum at high shear strength. The saturated flux depends on the strength of the wind as $q_s=q_0+A(u_*-u_t)(u_*^2+u_t^2)$

Boussinesq/Boussinesq systems for internal waves with a free surface, and the KdV approximation

We study here some asymptotic models for the propagation of internal and surface waves in a two-fluid system. We focus on the so-called long wave regime for one dimensional waves, and consider the case of a flat bottom. Starting from the classical Boussinesq/Boussinesq system, we introduce a new family of equivalent symmetric hyperbolic systems. We study the well-posedness of such systems, and the asymptotic convergence of their solutions towards solutions of the full Euler system. Then, we provide a rigorous justification of the so-called KdV approximation, stating that any bounded solution of the full Euler system can be decomposed into four propagating waves, each of them being well approximated by the solutions of uncoupled Korteweg-de Vries equations. Our method also applies for models with the rigid lid assumption, and the precise behavior of the KdV approximations depending on the depth and density ratios is discussed for both rigid lid and free surface configurations. The fact that we obtain {\it simultaneously} the four KdV equations allows us to study extensively the influence of the rigid lid assumption on the evolution of the interface, and therefore its domain of validity. Finally, solutions of the Boussinesq/Boussinesq systems and the KdV approximation are rigorously compared and numerically computed.Comment: To appear in M2A

Visco-potential free-surface flows and long wave modelling

In a recent study [DutykhDias2007] we presented a novel visco-potential free surface flows formulation. The governing equations contain local and nonlocal dissipative terms. From physical point of view, local dissipation terms come from molecular viscosity but in practical computations, rather eddy viscosity should be used. On the other hand, nonlocal dissipative term represents a correction due to the presence of a bottom boundary layer. Using the standard procedure of Boussinesq equations derivation, we come to nonlocal long wave equations. In this article we analyse dispersion relation properties of proposed models. The effect of nonlocal term on solitary and linear progressive waves attenuation is investigated. Finally, we present some computations with viscous Boussinesq equations solved by a Fourier type spectral method.Comment: 29 pages, 13 figures. Some figures were updated. Revised version for European Journal of Mechanics B/Fluids. Other author's papers can be downloaded from http://www.lama.univ-savoie.fr/~dutyk

The apparent roughness of a sand surface blown by wind from an analytical model of saltation

We present an analytical model of aeolian sand transport. The model quantifies the momentum transfer from the wind to the transported sand by providing expressions for the thickness of the saltation layer and the apparent surface roughness. These expressions are derived from basic physical principles and a small number of assumptions. The model further predicts the sand transport rate (mass flux) and the impact threshold (the smallest value of the wind shear velocity at which saltation can be sustained). We show that, in contrast to previous studies, the present model's predictions are in very good agreement with a range of experiments, as well as with numerical simulations of aeolian saltation. Because of its physical basis, we anticipate that our model will find application in studies of aeolian sand transport on both Earth and Mars

Nonlinearity of Apparent Mass for Multielement Bodies

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140689/1/1.j054214.pd