Sustainable Hydraulics in the Era of Global Change
Because the hydraulic jump is a dissipative singularity, it is used to dissipate energy for examp... more Because the hydraulic jump is a dissipative singularity, it is used to dissipate energy for example in stilling basins downstream of spillways. On the other hand, concerns about stilling basins are the possibility of cavitation and uplift of baffle blocks, which are mainly related to pressure fluctuations, and the water depths along the hydraulic jump, relevant for the design of the walls of the stilling basins. Interestingly, pressure fluctuations and depth fluctuations are caused by the same turbulence in the roller. So, both phenomena may present similar behaviors for the statistical properties. This paper analyzes instantaneous water depth data, measured using ultrasonic sensors, for inflow Froude numbers from 2.8 to 5.3. Statistical parameters of the water depth data were obtained and compared to data of pressure fluctuations found in the literature. As ex-pected, it is shown that there are similarities between the behavior of both phenomena.
The Engineering Education is a strategic branch of the educational system of any organized State ... more The Engineering Education is a strategic branch of the educational system of any organized State that aims to maintain an adequate interaction between the development and application of new technologies, and the transmission of concepts used to build the physical environments of their societies. These educational activities involve the controlled observation of facts and their correct interpretation, usually conducted during in-person experimental classroom lectures. The blooming of viruses in the highly concentrated modern societies, which the recent experience showed that may conduce to pandemics, exposes the need of experimental lectures or activities in the context of online, or hybrid online/in-person Engineering classes. This study presents a successful application of an experimental learning activity, which required students to launch a theoretical investigation, collect experimental data, compare theoretical and experimental results, interacting effectively to present a report with their understanding of the experiment. The study was conducted joining two hybrid Statics classes (with online and in-person students), a fundamental discipline of Civil Engineering, using as challenging motivator an adaptation of the Zeeman's machine. A competition was organized for the students to present solutions of questions related to the machine. The equations and data obtained by the students are described in this study for further applications. Aspects of didactics, students' reception, feasibility of the activity are discussed, showing the adequacy of this initiative in experimental learning for remote and hybrid teaching models.
Self-areation is a predominant phenomenon of flow on stepped spillways. At the upstream end the f... more Self-areation is a predominant phenomenon of flow on stepped spillways. At the upstream end the flow is smooth and no air entrainment occurs. Therefore, the flow turns into the so called "white water" or two-phase flow only after a distance has been traversed, which may involve some steps. Strongly aerated flows also present high levels of turbulence. The air inception begins in the cross section where the turbulent boundary layer intersects the water surface. Of course, the air is incorporated into the water along a distance in which the flow is still not fully aerated. The flow is named fully areated when the air bubbles achieve the bottom of the channel. The air entrainment continues until the flow achieves an uniform air distribution along the channel, usually named as "fully developed flow" [1, 2]. In this study we consider skimmimg flows, which are mainly characterized by the transfer of momentum from the main stream to the recirculation zones between the s...
Knowing the details of the interaction between people and runoff flows caused by heavy rainfall o... more Knowing the details of the interaction between people and runoff flows caused by heavy rainfall or by floods due for example by the rupture of reservoirs or dams is essential to prevent accidents with humans. There are information in the literature on the equilibrium capacity of individuals partially immersed in flows occurring in flat-bottomed channels, but there are many gaps regarding the use of urban draining staircases during the occurrence of rainfalls that generate runoff over their steps, and their impact on people. This study considered the effect of the flow on the stability of five obstacles positioned on one of the steps of a reduced model of a draining staircase. The results were used to calculate dimensionless parameters which involve the mass and height of the obstacle, the water density, critical depth of the flow and step height. These parameters were justified by a fundamental toppling and drag formulation, and good correlations between the obtained dimensionless parameters were obtained following adequate power laws. Comparisons between the data obtained in the present reduced model of staircase and literature data of flat bottom channels showed similar behaviors. Finally, a scaling procedure to compare results of different scales and situations was also presented. Excellent correlations using different literature data and those of the present study were obtained.
Microelectrodes were built to measure the dissolved oxygen (DO) concentration in different positi... more Microelectrodes were built to measure the dissolved oxygen (DO) concentration in different positions in the interior of biofilm reactors at laboratorial scale. The use of only one kind of measurement equipment facilitates the data analyses and comparisons of records obtained at different points in the reactor. This study presents the manufacturing details of the microsensors, as well as the results for measurements at the air-water interface and in biofilms. The tests were conducted in two laboratory equipments, a tank with oscillating grids and a flow cell. The results show that the microsensors are adequate for both measurements: at the air-water interface and in biofilms.
International journal of environmental and science education, 2018
A case study is presented, showing results and discussion of a procedure followed to help the rea... more A case study is presented, showing results and discussion of a procedure followed to help the reading from chalkboards. A conceptual model of words hierarchy is presented for the usual reading. The difficulty of locating the relevant word in a board or page is considered in the context of this model. A device named shortly “Line Finder” is then proposed as a help to maintain the correct sequence of words in a line when reading from the chalkboard. The results are discussed considering 1) a positive effect of the device, and 2) the possibility of increasing attention of the child during the experiment, which may affect the conclusions. The first results are positive, but the two possibilities point to the convenience of more studies, in order to allow comparisons and statistical analyses. To obtain a proper exploratory prototype for the device, the joint work of professionals of different areas was necessary (in this case, pharmacy linked to education, and engineering). The methodolo...
Journal of Transportation Engineering, Part B: Pavements, 2021
AbstractThe quantification of water depths resulting from rain events on highways is presented us... more AbstractThe quantification of water depths resulting from rain events on highways is presented using concepts of flows along flat plates. The hydrodynamics of the water film was developed by taking...
International Journal of Computational Methods and Experimental Measurements, Oct 31, 2017
The quantification of overall mass transfers in gas-liquid systems depends on the spatial evoluti... more The quantification of overall mass transfers in gas-liquid systems depends on the spatial evolution of the relevant variables close to the interface of the two phases. When turbulence is present (in the present study the turbulence is considered in the liquid phase), the methods of treating the problem consider the differential form of the momentum and mass conservation equations. The continuous hypothesis that underlies these equations in principle allows verifying the limiting trends very close to the interface. Because the theoretical concepts of turbulence are defined using statistical tools, the mentioned verification depends on the intrinsic definitions used in the statistical approach. In this study the turbulent mass transfer parameters are calculated for the thin region close to the interface based on the tool of random square waves (RSW). Theoretical results are obtained and analyzed in the context of existing experimental data and conceptual discussions of the literature, using a constant 'reduction function', a parameter defined in this methodology. The results of the present analysis show that the RSW method allows obtaining functional trends, as well as indicate the adequacy of using a variable reduction function to better represent reality.
Computational and Experimental Methods in Multiphase and Complex Flow X, Jul 30, 2019
Mass exchange through gas-liquid interfaces, whose liquid side has a turbulent nature, are still ... more Mass exchange through gas-liquid interfaces, whose liquid side has a turbulent nature, are still difficult to quantify due to the unclosed set of turbulence equations, which are also nonlinear. This paper describes an efficient method to overcome this difficulty, by substituting the statistical variables of the original equations by statistical relationships furnished by the Random Square Waves (RSW) tool. Oscillatory records are simplified using random square waves (ideal and binary), which allow a theoretical statistical treatment of the signals. This tool was applied to the concentration boundary layer at the gas-liquid interface. Normalized mass fluxes and mean concentration profiles were obtained using Taylor-series-based solutions, which allow for consideration of transient situations through the successive calculation of the higher order coefficients (derivatives). Comparisons with experimental data available in open literature are presented as a first evaluation of the Taylor series, showing promising results. This method is a viable tool, and this study shows novel conclusions that reproduce general tendencies observed in one-dimensional mass transfer phenomena in boundary layers.
AbstractThe smoothed particle hydrodynamics (SPH) method was used to simulate the flow over smoot... more AbstractThe smoothed particle hydrodynamics (SPH) method was used to simulate the flow over smooth and stepped spillways in the nonaerated, skimming flow regime. Two-dimensional numerical simulatio...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2003
The properties of turbulence induced in a viscous fluid by oscillating a grid within it are inves... more 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-ε turbulence model.
Experimental results for water level oscillations in vertical tubes, together with a theoretical ... more Experimental results for water level oscillations in vertical tubes, together with a theoretical solution for the flow in such tubes considering local and distributed energy losses, are presented and compared. The experimental data were obtained in small scale experiments, allowing adequately controlling the oscillations. The governing equation for the oscillations was obtained by applying the conservation laws of mass, momentum and energy for fluids. It is a second order nonlinear differential equation which was reduced to a first order differential Bernoulli equation. The obtained solution is composed by two different equations, one for the upwards motion and the other for the downwards motion, which together reproduce the oscillatory damped behavior of such flows. Numerical solutions of the differential equation were also checked. The experimental data and the theoretical and numerical results showed a good agreement between measured and calculated values of velocity and surface level for the first periods of oscillation.
Geysers of air–water mixtures in urban drainage systems is receiving considerable attention due t... more Geysers of air–water mixtures in urban drainage systems is receiving considerable attention due to public safety concerns. However, the geyser formation process and its relation with air release from pressurized pipes are still relatively little known. A large-scale physical model, that consisted of a main tunnel with a diameter of 270 mm and a length of 25 m connecting two reservoirs and a vertical vent pipe, was established to investigate geyser evolution and pressure transients. Experimental results including dynamic pressure data and high speed videos were analysed in order to characterize geysering flow through the vent pipe. Pressure transients were observed during geysering events. Their amplitudes were found to be about three times the driving pressure head and their periods were close to the classic surge tank predictions. The influence of flow rate and vent pipe size were examined: geyser heights and pressure peaks decreased for small flow rate and large diameter vent pipe...
(Test of numerical simulation for reservoirs sedimentation: the case of the Represa Velha reservo... more (Test of numerical simulation for reservoirs sedimentation: the case of the Represa Velha reservoir-SP-Brazil). Neste estudo testou-se um código numérico para reproduzir o assoreamento observado em situação de campo, no reservatório Represa Velha, em Pirassununga, SP, visando avaliar seu desempenho. Usou-se o modelo MIKE 21C, que se baseia nas equações de Navier-Stokes 2D com integração na vertical para águas rasas e em equações empíricas, juntamente com a equação de advecção-difusão, para os sedimentos. O teste foi realizado utilizando parâmetros de ajuste obtidos em escala laboratorial em estudo precedente. Os resultados numéricos foram comparados com dados de campo, como vazão, concentração de sedimento e levantamentos batimétricos realizados em períodos secos e úmidos no reservatório. Os resultados mostram que os parâmetros responsáveis pela mistura no meio fluido necessitam a princípio de melhores avaliações. Palavras-chave: Simulação numérica. Transporte de sedimento. Assoream...
Computational Methods in Multiphase Flow VII, 2013
The one-dimensional turbulent mass transfer was quantified using the nonlinear unclosed statistic... more The one-dimensional turbulent mass transfer was quantified using the nonlinear unclosed statistical governing equations derived from the traditional statistical methods. Further, this study considers the a priori simplifications of the bimodal Random Square Waves (RSW) approximation. This model enables the formulation of parametric equations for the variables of the statistical governing equations, but intrinsic aspects of this method still need to be clarified. In this sense, this study considers details of a version of the RSW equation for turbulent mass transfer which uses a constant reduction function. The mentioned details are related to discontinuities of higher order derivatives of the nondimensional concentration profile in the vicinity of a singular point. Numerical integrations were conducted at the air-water interface in both directions: from the liquid to the gas phase, and from the gas to the liquid phase. The results suggest that the continuity and smoothness of the calculated concentration profile does not depend on the discontinuities of the higher order derivatives, but the behaviour of the higher order derivatives depends strongly on the values of the nondimensional parameters existing in the formulation. Adequate boundary conditions were defined in the liquid phase, involving a new condition for the second derivative of the concentration profile. A fourth order Runge-Kutta method was used. This paper presents the proposed methodology; the comparison between results of calculated and measured concentration profiles,
Sustainable Hydraulics in the Era of Global Change
Because the hydraulic jump is a dissipative singularity, it is used to dissipate energy for examp... more Because the hydraulic jump is a dissipative singularity, it is used to dissipate energy for example in stilling basins downstream of spillways. On the other hand, concerns about stilling basins are the possibility of cavitation and uplift of baffle blocks, which are mainly related to pressure fluctuations, and the water depths along the hydraulic jump, relevant for the design of the walls of the stilling basins. Interestingly, pressure fluctuations and depth fluctuations are caused by the same turbulence in the roller. So, both phenomena may present similar behaviors for the statistical properties. This paper analyzes instantaneous water depth data, measured using ultrasonic sensors, for inflow Froude numbers from 2.8 to 5.3. Statistical parameters of the water depth data were obtained and compared to data of pressure fluctuations found in the literature. As ex-pected, it is shown that there are similarities between the behavior of both phenomena.
The Engineering Education is a strategic branch of the educational system of any organized State ... more The Engineering Education is a strategic branch of the educational system of any organized State that aims to maintain an adequate interaction between the development and application of new technologies, and the transmission of concepts used to build the physical environments of their societies. These educational activities involve the controlled observation of facts and their correct interpretation, usually conducted during in-person experimental classroom lectures. The blooming of viruses in the highly concentrated modern societies, which the recent experience showed that may conduce to pandemics, exposes the need of experimental lectures or activities in the context of online, or hybrid online/in-person Engineering classes. This study presents a successful application of an experimental learning activity, which required students to launch a theoretical investigation, collect experimental data, compare theoretical and experimental results, interacting effectively to present a report with their understanding of the experiment. The study was conducted joining two hybrid Statics classes (with online and in-person students), a fundamental discipline of Civil Engineering, using as challenging motivator an adaptation of the Zeeman's machine. A competition was organized for the students to present solutions of questions related to the machine. The equations and data obtained by the students are described in this study for further applications. Aspects of didactics, students' reception, feasibility of the activity are discussed, showing the adequacy of this initiative in experimental learning for remote and hybrid teaching models.
Self-areation is a predominant phenomenon of flow on stepped spillways. At the upstream end the f... more Self-areation is a predominant phenomenon of flow on stepped spillways. At the upstream end the flow is smooth and no air entrainment occurs. Therefore, the flow turns into the so called "white water" or two-phase flow only after a distance has been traversed, which may involve some steps. Strongly aerated flows also present high levels of turbulence. The air inception begins in the cross section where the turbulent boundary layer intersects the water surface. Of course, the air is incorporated into the water along a distance in which the flow is still not fully aerated. The flow is named fully areated when the air bubbles achieve the bottom of the channel. The air entrainment continues until the flow achieves an uniform air distribution along the channel, usually named as "fully developed flow" [1, 2]. In this study we consider skimmimg flows, which are mainly characterized by the transfer of momentum from the main stream to the recirculation zones between the s...
Knowing the details of the interaction between people and runoff flows caused by heavy rainfall o... more Knowing the details of the interaction between people and runoff flows caused by heavy rainfall or by floods due for example by the rupture of reservoirs or dams is essential to prevent accidents with humans. There are information in the literature on the equilibrium capacity of individuals partially immersed in flows occurring in flat-bottomed channels, but there are many gaps regarding the use of urban draining staircases during the occurrence of rainfalls that generate runoff over their steps, and their impact on people. This study considered the effect of the flow on the stability of five obstacles positioned on one of the steps of a reduced model of a draining staircase. The results were used to calculate dimensionless parameters which involve the mass and height of the obstacle, the water density, critical depth of the flow and step height. These parameters were justified by a fundamental toppling and drag formulation, and good correlations between the obtained dimensionless parameters were obtained following adequate power laws. Comparisons between the data obtained in the present reduced model of staircase and literature data of flat bottom channels showed similar behaviors. Finally, a scaling procedure to compare results of different scales and situations was also presented. Excellent correlations using different literature data and those of the present study were obtained.
Microelectrodes were built to measure the dissolved oxygen (DO) concentration in different positi... more Microelectrodes were built to measure the dissolved oxygen (DO) concentration in different positions in the interior of biofilm reactors at laboratorial scale. The use of only one kind of measurement equipment facilitates the data analyses and comparisons of records obtained at different points in the reactor. This study presents the manufacturing details of the microsensors, as well as the results for measurements at the air-water interface and in biofilms. The tests were conducted in two laboratory equipments, a tank with oscillating grids and a flow cell. The results show that the microsensors are adequate for both measurements: at the air-water interface and in biofilms.
International journal of environmental and science education, 2018
A case study is presented, showing results and discussion of a procedure followed to help the rea... more A case study is presented, showing results and discussion of a procedure followed to help the reading from chalkboards. A conceptual model of words hierarchy is presented for the usual reading. The difficulty of locating the relevant word in a board or page is considered in the context of this model. A device named shortly “Line Finder” is then proposed as a help to maintain the correct sequence of words in a line when reading from the chalkboard. The results are discussed considering 1) a positive effect of the device, and 2) the possibility of increasing attention of the child during the experiment, which may affect the conclusions. The first results are positive, but the two possibilities point to the convenience of more studies, in order to allow comparisons and statistical analyses. To obtain a proper exploratory prototype for the device, the joint work of professionals of different areas was necessary (in this case, pharmacy linked to education, and engineering). The methodolo...
Journal of Transportation Engineering, Part B: Pavements, 2021
AbstractThe quantification of water depths resulting from rain events on highways is presented us... more AbstractThe quantification of water depths resulting from rain events on highways is presented using concepts of flows along flat plates. The hydrodynamics of the water film was developed by taking...
International Journal of Computational Methods and Experimental Measurements, Oct 31, 2017
The quantification of overall mass transfers in gas-liquid systems depends on the spatial evoluti... more The quantification of overall mass transfers in gas-liquid systems depends on the spatial evolution of the relevant variables close to the interface of the two phases. When turbulence is present (in the present study the turbulence is considered in the liquid phase), the methods of treating the problem consider the differential form of the momentum and mass conservation equations. The continuous hypothesis that underlies these equations in principle allows verifying the limiting trends very close to the interface. Because the theoretical concepts of turbulence are defined using statistical tools, the mentioned verification depends on the intrinsic definitions used in the statistical approach. In this study the turbulent mass transfer parameters are calculated for the thin region close to the interface based on the tool of random square waves (RSW). Theoretical results are obtained and analyzed in the context of existing experimental data and conceptual discussions of the literature, using a constant 'reduction function', a parameter defined in this methodology. The results of the present analysis show that the RSW method allows obtaining functional trends, as well as indicate the adequacy of using a variable reduction function to better represent reality.
Computational and Experimental Methods in Multiphase and Complex Flow X, Jul 30, 2019
Mass exchange through gas-liquid interfaces, whose liquid side has a turbulent nature, are still ... more Mass exchange through gas-liquid interfaces, whose liquid side has a turbulent nature, are still difficult to quantify due to the unclosed set of turbulence equations, which are also nonlinear. This paper describes an efficient method to overcome this difficulty, by substituting the statistical variables of the original equations by statistical relationships furnished by the Random Square Waves (RSW) tool. Oscillatory records are simplified using random square waves (ideal and binary), which allow a theoretical statistical treatment of the signals. This tool was applied to the concentration boundary layer at the gas-liquid interface. Normalized mass fluxes and mean concentration profiles were obtained using Taylor-series-based solutions, which allow for consideration of transient situations through the successive calculation of the higher order coefficients (derivatives). Comparisons with experimental data available in open literature are presented as a first evaluation of the Taylor series, showing promising results. This method is a viable tool, and this study shows novel conclusions that reproduce general tendencies observed in one-dimensional mass transfer phenomena in boundary layers.
AbstractThe smoothed particle hydrodynamics (SPH) method was used to simulate the flow over smoot... more AbstractThe smoothed particle hydrodynamics (SPH) method was used to simulate the flow over smooth and stepped spillways in the nonaerated, skimming flow regime. Two-dimensional numerical simulatio...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2003
The properties of turbulence induced in a viscous fluid by oscillating a grid within it are inves... more 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-ε turbulence model.
Experimental results for water level oscillations in vertical tubes, together with a theoretical ... more Experimental results for water level oscillations in vertical tubes, together with a theoretical solution for the flow in such tubes considering local and distributed energy losses, are presented and compared. The experimental data were obtained in small scale experiments, allowing adequately controlling the oscillations. The governing equation for the oscillations was obtained by applying the conservation laws of mass, momentum and energy for fluids. It is a second order nonlinear differential equation which was reduced to a first order differential Bernoulli equation. The obtained solution is composed by two different equations, one for the upwards motion and the other for the downwards motion, which together reproduce the oscillatory damped behavior of such flows. Numerical solutions of the differential equation were also checked. The experimental data and the theoretical and numerical results showed a good agreement between measured and calculated values of velocity and surface level for the first periods of oscillation.
Geysers of air–water mixtures in urban drainage systems is receiving considerable attention due t... more Geysers of air–water mixtures in urban drainage systems is receiving considerable attention due to public safety concerns. However, the geyser formation process and its relation with air release from pressurized pipes are still relatively little known. A large-scale physical model, that consisted of a main tunnel with a diameter of 270 mm and a length of 25 m connecting two reservoirs and a vertical vent pipe, was established to investigate geyser evolution and pressure transients. Experimental results including dynamic pressure data and high speed videos were analysed in order to characterize geysering flow through the vent pipe. Pressure transients were observed during geysering events. Their amplitudes were found to be about three times the driving pressure head and their periods were close to the classic surge tank predictions. The influence of flow rate and vent pipe size were examined: geyser heights and pressure peaks decreased for small flow rate and large diameter vent pipe...
(Test of numerical simulation for reservoirs sedimentation: the case of the Represa Velha reservo... more (Test of numerical simulation for reservoirs sedimentation: the case of the Represa Velha reservoir-SP-Brazil). Neste estudo testou-se um código numérico para reproduzir o assoreamento observado em situação de campo, no reservatório Represa Velha, em Pirassununga, SP, visando avaliar seu desempenho. Usou-se o modelo MIKE 21C, que se baseia nas equações de Navier-Stokes 2D com integração na vertical para águas rasas e em equações empíricas, juntamente com a equação de advecção-difusão, para os sedimentos. O teste foi realizado utilizando parâmetros de ajuste obtidos em escala laboratorial em estudo precedente. Os resultados numéricos foram comparados com dados de campo, como vazão, concentração de sedimento e levantamentos batimétricos realizados em períodos secos e úmidos no reservatório. Os resultados mostram que os parâmetros responsáveis pela mistura no meio fluido necessitam a princípio de melhores avaliações. Palavras-chave: Simulação numérica. Transporte de sedimento. Assoream...
Computational Methods in Multiphase Flow VII, 2013
The one-dimensional turbulent mass transfer was quantified using the nonlinear unclosed statistic... more The one-dimensional turbulent mass transfer was quantified using the nonlinear unclosed statistical governing equations derived from the traditional statistical methods. Further, this study considers the a priori simplifications of the bimodal Random Square Waves (RSW) approximation. This model enables the formulation of parametric equations for the variables of the statistical governing equations, but intrinsic aspects of this method still need to be clarified. In this sense, this study considers details of a version of the RSW equation for turbulent mass transfer which uses a constant reduction function. The mentioned details are related to discontinuities of higher order derivatives of the nondimensional concentration profile in the vicinity of a singular point. Numerical integrations were conducted at the air-water interface in both directions: from the liquid to the gas phase, and from the gas to the liquid phase. The results suggest that the continuity and smoothness of the calculated concentration profile does not depend on the discontinuities of the higher order derivatives, but the behaviour of the higher order derivatives depends strongly on the values of the nondimensional parameters existing in the formulation. Adequate boundary conditions were defined in the liquid phase, involving a new condition for the second derivative of the concentration profile. A fourth order Runge-Kutta method was used. This paper presents the proposed methodology; the comparison between results of calculated and measured concentration profiles,
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Papers by Harry Schulz