Geology topics

R.A. Baltzer

Publications and source records attributed to R.A. Baltzer.

5 recordsLinked to original sources

USGS2002

Conservation-form equations of unsteady open-channel flow

The unsteady open-channel flow equations are typically expressed in a variety of forms due to the imposition of differing assumptions, use of varied dependent variables, and inclusion of different source/sink terms. Questions often arise as to whether a particular equation set is expressed in a form consistent with the conservation-law definition. The concept of conservation form is developed to clarify the meaning mathematically. Six sets of unsteady-flow equations typically used in engineering practice are presented and their conservation properties are identified and discussed. Results of the theoretical development and analysis of the equations are substantiated in a set of numerical experiments conducted using alternate equation forms. Findings of these analytical and numerical efforts demonstrate that the choice of dependent variable is the fundamental factor determining the nature of the conservation properties of any particular equation form.

Journal of Hydraulic Research↗

USGS1997

Observations of tidal flux between a submersed aquatic plant stand and the adjacent channel in the Potomac River near Washington, D.C.

Dye injection studies and direct velocity and water-level measurements were made in macrophyte stands and adjacent channels in order to observe the effects of the macrophyte stand on flow and mass exchange in the tidal Potomac River. During the summer, dense stands of submersed aquatic plants cover most shoals <2 m deep. Continuous summertime water-level records within a submersed aquatic plant stand and in the adjacent channel revealed time-varying gradients in water-surface elevation between the two areas. Water-level gradients are created by differing rates of tidal water-level change in vegetated and unvegetated areas. Results were consistent with the idea that on a rising tide the water was slower to enter a macrophyte stand, and on a falling tide it was slower to leave it. Differences in water elevation between the stand and the open channel generated components of velocity in the stand that were at right angles to the line of flow in the channel. Seasonal differences in flow speed and direction over the shoals indicate substantial differences in resistance to flow as a result of the vegetation.

Limnology and Oceanography↗

USGS1996

Time-dependent Data System (TDDS); an interactive program to assemble, manage, and appraise input data and numerical output of flow/transport simulation models

A system of functional utilities and computer routines, collectively identified as the Time-Dependent Data System CI DDS), has been developed and documented by the U.S. Geological Survey. The TDDS is designed for processing time sequences of discrete, fixed-interval, time-varying geophysical data--in particular, hydrologic data. Such data include various, dependent variables and related parameters typically needed as input for execution of one-, two-, and three-dimensional hydrodynamic/transport and associated water-quality simulation models. Such data can also include time sequences of results generated by numerical simulation models. Specifically, TDDS provides the functional capabilities to process, store, retrieve, and compile data in a Time-Dependent Data Base (TDDB) in response to interactive user commands or pre-programmed directives. Thus, the TDDS, in conjunction with a companion TDDB, provides a ready means for processing, preparation, and assembly of time sequences of data for input to models; collection, categorization, and storage of simulation results from models; and intercomparison of field data and simulation results. The TDDS can be used to edit and verify prototype, time-dependent data to affirm that selected sequences of data are accurate, contiguous, and appropriate for numerical simulation modeling. It can be used to prepare time-varying data in a variety of formats, such as tabular lists, sequential files, arrays, graphical displays, as well as line-printer plots of single or multiparameter data sets. The TDDB is organized and maintained as a direct-access data base by the TDDS, thus providing simple, yet efficient, data management and access. A single, easily used, program interface that provides all access to and from a particular TDDB is available for use directly within models, other user-provided programs, and other data systems. This interface, together with each major functional utility of the TDDS, is described and documented in this report.

Water-Resources Investigations Report↗

USGS1989

Convergance experiments with a hydrodynamic model of Port Royal Sound, South Carolina

A two-demensional, depth-averaged, finite-difference, flow/transport model, SIM2D, is being used to simulate tidal circulation and transport in the Port Royal Sound, South Carolina, estuarine system. Models of a subregion of the Port Royal Sound system have been derived from an earlier-developed model of the entire system having a grid size of 600 ft. The submodels were implemented with grid sizes of 600, 300, and 150 ft in order to determine the effects of changes in grid size on computed flows in the subregion, which is characterized by narrow channels and extensive tidal flats that flood and dewater with each rise and fall of the tide. Tidal amplitudes changes less than 5 percent as the grid size was decreased. Simulations were performed with the 300-foot submodel for time steps of 60, 30, and 15 s. Study results are discussed.

South Carolina↗

USGS1981

A model for simulation of flow in singular and interconnected channels

A one-dimensional numerical model is presented for simulating the unsteady flow in singular riverine or estuarine reaches and in networks of reaches composed of interconnected channels. The model is both general and flexible in that it can be used to simulate a wide range of flow conditions for various channel configurations. The channel geometry of the network to be modeled should be sufficiently simple so as to lend itself to characterization in one spatial dimension. The flow must be substantially homogenous in density, and hydrostatic pressure must prevail everywhere in the network channels. The slope of each channel bottom ought to be mild and reasonably constant over its length so that the flow remains subcritical. The model accommodates tributary inflows and diversions and includes the effects of wind shear on the water surface as a forcing function in the flow equations. Water-surface elevations and flow discharges are computed at channel junctions, as well as at specified intermediate locations within the network channels. The one-dimensional branch-network flow model uses a four-point, implicit, finite-difference approximation of the unsteady-flow equations. The flow equations are linearized over a time step, and branch transformations are formulated that describe the relationship between the unknowns at the end points of the channels. The resultant matrix of branch-transformation equations and required boundary-condition equations is solved by Gaussian elimination using maximum pivot strategy. Five example applications of the flow model are illustrated. The applications cover such diverse conditions as a singular upland river reach in which unsteady flow results from hydropower regulations, coastal rivers composed of sequentially connected reaches subject to unsteady tide-driven flow, and a multiply connected network of channels whose flow is principally governed by wind tides and seiches in adjoining lakes. The report includes a listing of the FORTRAN IV computer program and a description of the input data requirements. Model supporting programs for the processing and input of initial and boundary-value data are identified, various model output formats are illustrated, and instructions are given to permit the production of graphical output using the line printer, electromechanical pen plotters, cathode-ray-tube display units, or microfilm recorders.

Techniques of Water-Resources Investigations↗