Harry Edmar Schulz

Qualidade microbiológica da água em rios de áreas urbanas e periurbanas no baixo Amazonas : o caso do Amapá

This study presents the spatial and temporal variability of water quality parameters in rivers of Macapa and Santana region, State of Amapa, Brazil, especially faecal coliforms (FC), being used as indicators. Laboratory and field experiments were conducted in four estuarine rivers. The experiment included five sampling locations and the research was conducted from September 1999 to September 2002. Samples were collected once a monthly. The results of analysis provided us useful information for sanitary and public health planning. In addiction, a socio-economic study of several critical areas in the watershed was carried out. The results showed high faecal coliform concentrations. The complexity of space-temporal variability of the water quality was affected by various factors, such as climatic conditions, tidal variation and human activities. This information can be used in forecasting environmental and public health risks.

Stepped and smooth spillways: resistance effects on stilling basin lengths

The Darcy–Weisbach equation was used in the analysis of flow over spillways, furnishing theoretical tools to design stilling basins. Predictions for the length of hydraulic jump stilling basins downstream of stepped and smooth spillways are presented, together with ranges of values for the Darcy–Weisbach friction factor of both spillways. The experimental data were compared with results of the theoretical solution of the gradually varied flow equation. All comparisons were made in non-dimensional form. The values of the Darcy–Weisbach friction factor were roughly five times smaller for smooth spillways than for stepped spillways. The theoretical predictions and the experimental data allow to present approximate equations for a preliminary evaluation of the length and the bed level of hydraulic jump stilling basins. In the same way, approximate equations were presented for the evaluation of the friction factor in smooth and stepped spillways, as a function of the Froude number at the downstream cross-section.

Medidas da concentração de oxigênio dissolvido na superfície da água

Gas transfer across the air-water interface is an important process for large-scale climate cycles as well as smaller environmental systems such as rivers, lakes, streams, and wastewater treatment basins. To improve the understanding of the basic principles involved in this phenomenon it is necessary to use suitable apparatus and experimental techniques. In this study, a microprobe has been used for measurements of oxygen concentration in an oscillating-grid tank. The microprobe has tip dimensions of the order of a few microns. The results demonstrate that it is feasible to measure, under controlled turbulence conditions that are representative for environmental situations, the fluctuating oxygen concentrations that take place in a boundary layer below the air-water interface.

Kinetic energy in grid turbulence: comparison between data and theory

The properties of turbulence induced in a viscous fluid by oscillating a grid within it are investigated. Vertical and horizontal components of fluctuating velocities are measured using the Digital Particle Image Velocimetry technique (DPIV). Vertical profiles of turbulent kinetic energy k, obtained from the fluctuating velocities, are presented and compared with theoretical predictions obtained using the k-e turbulence model.

Transition length between water and air-water flows on stepped chutes

This study presents the steps followed to obtain mathematical models for the length of the transition region between the “full-water” and “full-mixed” flows in stepped spillways. This transition length is defined here as the distance along the flow, parallel to the pseudo-bottom, starting at the end of the “full-water” region and ending at the beginning of the “full-mixed” region. The definition is proposed based on experimental profiles of the surface obtained with an acoustic sensor in a stepped chute, which allows one to locate adequately the minima and maxima of the profile. A set of profiles obtained for different flow conditions is shown, and a comparison between predicted and calculated transition lengths is made. Experimental data and theoretical predictions superpose adequately for the present set of data.

Lower nappe aeration in smooth channels: experimental data and numerical simulation

Bed aerators designed to increase air void ratio are used to prevent cavitation and related damages in spillways. Air entrained in spillway discharges also increases the dissolved oxygen concentration of the water, which can be important for the downstream fishery. This study considers results from a systematic series of measurements along the jet formed by a bed aerator, involving concentration profiles, pressure profiles, velocity fields and corresponding air discharges. The experimental results are, then, compared, with results of computational fluid dynamics (CFD) simulations with the aim of predicting the air discharge numerically. Comparisons with jet lengths and the air entrainment coefficients from the literature are also made. It is shown that numerical predictive tools furnish air discharges comparable to measured values. However, if more detailed predictions are desired, verification experiments are still necessary.

Stepped Spillways: Theoretical, Experimental and Numerical Studies

Flows on stepped spillways have been widely studied in various research institutions motivated by the attractive low costs related to the dam construction using roller-compacted concrete and the high energy dissipations that are produced by such structures. This is a very rich field of study for researchers of Fluid Mechanics and Hydraulics, because of the complex flow characteristics, including turbulence, gas exchange derived from the twophase flow (air/water), cavitation, among other aspects. The most common type of flow in spillways is known as skimming flow and consists of: (1) main flow (with preferential direction imposed by the slope of the channel), (2) secondary flows of large eddies formed between steps and (3) biphasic flow, due to the mixture of air and water. The details of the three mentioned standards may vary depending on the size of the steps, the geometric conditions of entry into the canal, the channel length in the steps region and the flow rates. The second type of flow that was highlighted in the literature is called nappe flow. It occurs for specific conditions such as lower flows (relative to skimming flow) and long steps in relation to their height. In the region between these two “extreme” flows, a “transition flow” between nappe and skimming flows is also defined. Depending on the details that are relevant for each study, each of the three abovementioned types of flow may be still subdivided in more sub-types, which are mentioned but not detailed in the present chapter. Figure 1 is a sketch of the general appearance of the three mentioned flow regimes.

One Dimensional Turbulent Transfer Using Random Square Waves – Scalar/Velocity and Velocity/Velocity Interactions

The mathematical treatment of phenomena that oscillate randomly in space and time, generating the so called “statistical governing equations”, is still a difficult task for scientists and engineers. Turbulence in fluids is an example of such phenomena, which has great influence on the transport of physical proprieties by the fluids, but which statistical quantification is still strongly based on ad hoc models. In turbulent flows, parameters like velocity, temperature and mass concentration oscillate continuously in turbulent fluids, but their detailed behavior, considering all the possible time and space scales, has been considered difficult to be reproduced mathematically since the very beginning of the studies on turbulence. So, statistical equations were proposed and refined by several authors, aiming to describe the evolution of the “mean values” of the different parameters (see a description, for example, in Monin & Yaglom, 1979, 1981). The governing equations of fluid motion are nonlinear. This characteristic imposes that the classical statistical description of turbulence, in which the oscillating parameters are separated into mean functions and fluctuations, produces new unknown parameters when applied on the original equations. The generation of new variables is known as the “closure problem of statistical turbulence” and, in fact, appears in any phenomena of physical nature that oscillates randomly and whose representation is expressed by nonlinear conservation equations. The closure problem is described in many texts, like Hinze (1959), Monin & Yaglom (1979, 1981), and Pope (2000), and a general form to overcome this difficulty is matter of many studies. As reported by Schulz et al. (2011a), considering scalar transport in turbulent fluids, an early attempt to theoretically predict RMS profiles of the concentration fluctuations using “ideal random signals” was proposed by Schulz (1985) and Schulz & Schulz (1991). The authors used random square waves to represent concentration oscillations during mass transfer across the air-water interface, and showed that the RMS profile of the concentration fluctuations may be expressed as a function of the mean concentration profile. In other words, the mean concentration profile helps to know the RMS profile. In these studies, the authors did not consider the effect of diffusion, but argued that their

Analysis of Two Phase Flows on Stepped Spillways

Self-areation is a very relevant phenomenon that occurs in flows on stepped chutes, and is one of the reasons of building such structures. In this sense, the main purposes of stepped chute structures is to increase the energy dissipation of the flows by internal friction and to protect the bed of spillways through the presence of the air absorbed from the atmosphere. It is a “lucky coincidence” that, while the steps significantly increase the energy dissipation rate, they also increase the air uptake, reducing the risks of cavitation along the bed of the channel (Peterka, 1953; Frizell & Melford, 1991). An additional consequence of the use of stepped chutes is the reduction of the size of the energy dissipation basins at the toe of the spillways, implying in reduction of the total costs of the spillway structures. Physically, it is observed that the superficial air uptake begins at the cross section where the turbulent boundary layer attains the water surface, as described for example by Chanson (1997), and predictions of the location where water depth and boundary layer thickness coincide, and of the amount of air absorbed by the water, are important for the design of spillways. As a consequence of the abovementioned characteristics, stepped chutes are extensively used in hydraulics and environmental engineering. The air-water two-phase flow along the stepped channels is generally classified accordingly to its regime, as Skimming flow, Nappe flow and Transition flow, and the change from one regime to the other is still matter of discussion in the literature. In this chapter, a procedure is followed, aiming to adjust numerical tools in order to adequately represent the air-water interface along stepped chutes. In this case, it implies in finding conditions that allow the “breaking” of the surface, so that air can be incorporated by the water. Such a tool is interesting for the prediction of gas transfer in stepped spillways, and it is expected to be used by designers that need to quantify the so called selfaerated flows. As mentioned, the air is incorporated into the water through the surface, and knowing the distribution of the entrained air and the flow conditions, the gas transfer along the different positions in the cross section of the flow can be estimated, until it attains the bottom of the chute. In addition, having a good numerical code, it may be possible to obtain the pressure distribution along the structure and to localize the potential cavitation regions, allowing to “test numerically” possible solutions to enhance the air content and to reduce

Hydrosedimentological dynamic on Água Fria Watershed

This study aimed surveying the amount of sediment yielded from the Agua Fria watershed (Palmas, Tocantins, Brazil), from February-1998 to January-1999, and investigating the relations between the sediment yield and some environmental and/or antropic factors. The Colbys method was the technique employed for this investigation. The specific sediment yield and sediment delivery ratio were also determined for this period. It was estimated that 138,619 tons of sediment were yielded and the specific sediment yield for the study area was 827 t km-2 y-1, while the sediment delivery ratio was 6.2%. The suspended load was the most dominating fraction in almost all the studied period.