Browsing by Author "Simons, D. B., advisor"

Now showing 1 - 3 of 3

Open Access
Hydraulics of rigid boundary basins
(Colorado State University. Libraries, 1968) Watts, Frederick Jay, author; Simons, D. B., advisor; Shen, M. L., committee member; Albertson, M. L., committee member; Frisinger, H. H., committee member
The object of the study was to develop design criteria for three classes (A, B and C) of rigid boundary energy dissipating structures. The Class A basin has a smooth floor and flaring vertical walls; the Class B basin is a rectangular basin with smooth floor and vertical walls; the Class C basin is a rectangular basin with smooth vertical walls and an artificially roughened floor. Design aids developed during this study include: dimensionless coefficients for the energy and momentum equations which correct for nonhydrostatic pressure distribution and nonuniform velocity distribution at the outfall sections of circular and rectangular conduits; dimensionless water surface contours and velocity vectors for freely expanding jets supported on the bottom, downstream of circular and rectangular abrupt expansions; drag coefficients for roughness elements of known size and spacing; and other minor criteria. Numerous existing criteria, including Blaisdell's criterion for wall flare, Ippen's relationships for predicting the angle of oblique standing waves and Albertson, et al.'s relationships for determining the properties of the flow field downstream of culvert outlets operating under high tailwater conditions were verified. Design procedures based on continuity of flow and the balance of impulse and momentum from station to station are presented for the three classes of basins. Alternate refined procedures utilizing backwater computations are outlined for Class A and B basins. Numerous example problems are solved in detail in Chapter VII. It is suggested that the energy basin be constructed within the roadway prism as an integral portion of the culvert barrel. Discussions concerning the necessity of tailwater control and of other important factors which should be considered accompany the design computations.
Open Access
Statistical properties of dune profiles
(Colorado State University. Libraries, 1968) Nordin, Carl F., Jr., author; Simons, D. B., advisor; Siddiqui, M. M., committee member; Plate, E. J., committee member; Creely, Scott, committee member; Richardson, E. V., committee member
Properties of sand waves formed by subcritical unidirectional water currents are investigated by statistical analyses of records of streambed profiles. Records of bed elevation y as a function of distance x along the channel, y = y(x), and time records at a fixed point of the channel, y = y (t), were collected in three laboratory flumes that were 8 inches, 2 ft and 8 ft wide and in a straight alluvial channel that was 55 ft wide. For all cases, the bed material was fine sand. The continuous analogue records were converted to discrete data points and were analyzed by digital computer. The analyses show that both types of records, y(x) and y (t), can be approximately represented as stationary Gaussian processes. When the data are standardized and the length or distance are expressed as ratios of the mean duration between zero-crossings of y, the statistical properties of all the flume data are similar, with no distinguishing characteristics that can be attributed to size of flume or to whether the bed forms were ripples or dunes. The field data, however, reflect the influence of large alternate bars that were not present in the flumes. I The Gaussian assumption, together with the spectral properties of the records as expressed by a dimensionless parameter, 6, permit predicting the distributions of maximum and minimum values of y between successive zeros of y. These distributions represent the probability distributions of the depth of local scour and fill due to the formation and migration of sand waves, and the parameters that specify the distributions relate approximately to flow velocity and depth. Observed values of the number of zero and h-level crossings, the mean duration between zero crossings, and the mean duration of upward excursions of the process y(t) above the fixed level h compared reasonably well with theoretical values for the Gaussian model. The distribution of the duration of upward excursions is the conditional probability distribution of the rest period of a particle, given that it is deposited on the downstream face of a ripple or dune at the level h. Observed distributions of these durations can be approximated by a gamma distribution with parameters that relate to h, where h is measured in units of standard deviation from the mean bed level. These distributions and other probability distributions that enter into stochastic models of sediment transport can be determined either from the theoretical model or empirically from the observed data. The results of the study show that even though the bed elevation deviates somewhat from the postulated normal distribution, reasonable estimates of many properties of the bed profiles can be derived from fairly simple statistical models.
Open Access
Terminal fall velocity of particles of irregular shapes as affected by surface area
(Colorado State University. Libraries, 1964) Alger, George R., author; Simons, D. B., advisor; Albertson, Maurice L., committee member; Karaki, Susumu, committee member; Fead, John W. N., committee member; Johnson, Roberta F., committee member
The objective of this research is to study the effect of surface area on terminal fall velocity of particles and objects of irregular shapes. An auxiliary study was also made in a qualitative manner on the effect of various concentrations of neutrally buoyant fine material on the fall velocity of spheres. The results of this auxiliary study are given in Appendix (B). It is expected that these investigations will lead to further research in areas related to these topics. Various shapes of gravel-sized particles were studied. The terminal fall velocities were obtained by repeatedly dropping the same particles in fluids with different viscosities. A photographic technique was used to determine these terminal velocities. A new shape parameter was developed and the variation of drag coefficient with Reynolds number using this new parameter is given. This Cd versus Re relation leads to the possibility of a model law for the irregular shapes with the new shape parameter as the third variable. A limited verification is given for several selected machined shapes and for ordinary concrete test cylinders. The model verification was accomplished by dropping larger scale particles in water and measuring terminal fall velocity using a specially constructed large scale speedometer. Plastic (Vestyron) particles were used to form a neutrally buoyant suspension in salt water. A small plastic sphere was dropped through various concentrations of this suspension and the fall velocity was determined with a stop watch. The results indicate the nee d to study the electrochemical properties of the suspended fine material as they appear to affect the fall velocity of the larger particle. The writer believes from the results obtained that the consideration of the Zeta potential of the fine material would ultimately lead to a better description of the apparent viscosity effects when used in conjunction with existing theories.