scholarly journals Analysis of Vortex Pool-and-Chute Fishway

2016 ◽  
Vol 13 (4) ◽  
Author(s):  
Mathew Nyberg ◽  
Brian Draeger ◽  
Brian Weekly ◽  
Eileen Cashman ◽  
Michael Love
Keyword(s):  
Dimensional Analysis ◽  
Calculation Method ◽  
Fish Passage ◽  
Scale Model ◽  
Flow Conditions ◽  
Flow Rates ◽  
Flow Calculation ◽  
Flow Method ◽  
Streaming Flow ◽  
Plunging Flow

Fishways are constructed in riverine habitats where structures such as culverts, dams, and flood channels have negatively impacted flow conditions suitable for the movement of native and migratory fish species. These auxiliary channels are engineered to resist gravitational force with frictional force, resulting in sustained depth and reduced velocity over a range of design flow rates. The Chézy hydraulic resistance coefficient accounts for such forces and provides a metric useful for determining the effectiveness of a fishway to alter flow conditions prohibitive to the passage of fish. The objective of this analysis was to use a scale model of an innovative vortex pool-and-chute fishway, that operates with both plunging and streaming flow simultaneously, designed by Michael Love and Associates, to determine the Chézy resistance coefficients over a range of flow rates under controlled hydraulic conditions. Using dimensional analysis to ensure proper scaling allowed laboratory measurements of the model to be translated into a real-world prototype design. The conceptual prototype fishway is a 144-foot-long by 30-foot-wide channel with an 8% slope. A 1:15 scale model was constructed to evaluate the design at prototype equivalent flow rates between 58 and 283 cubic feet per second (cfs). Chézy coefficients were estimated by two different calculation methods; the streaming flow method and the streaming and plunging flow method. Coefficients ranging between 22.3 and 39.2 ft1/2/s were determined by the streaming flow calculation method, whereas the streaming and plunging flow calculation method yielded estimates from 18.9 to 25.0 ft1/2/s at corresponding flow rates. For flows that were exclusively plunging, values of 32.2 to 41.9 ft1/2/s were found. In general, Chézy coefficient estimates were observed to decrease with increasing discharge and values were found to be comparable to those calculated for fishways implemented at similar slopes. The preliminary model fishway results indicated that implementation of a prototype fishway could effectively alter flows for adequate fish passage under the given conditions. KEYWORDS: Hydraulics; Fish Passage; Fishway; Chézy Coefficient; Geometric Scaling; Froude Scaling; Streaming Flow; Plunging Flow; Dimensional Analysis; Similitude

A Power Flow Method for VSC-Multi-Terminal Hybrid System Based on Asynchronous Iteration Algorithm

2014 ◽  
Vol 672-674 ◽  
pp. 863-869
Author(s):  
Kun Zhao ◽  
Qiang Li ◽  
Xiao Yang ◽  
Li Li ◽  
Yu Zou ◽  
...  
Keyword(s):  
Hybrid System ◽  
Calculation Method ◽  
Power Flow ◽  
Current Model ◽  
Mixed System ◽  
Iteration Algorithm ◽  
Flow Calculation ◽  
Flow Method ◽  
Asynchronous Iteration ◽  
Power Flow Method

With the continuous development of HVDC technology, the increase in the number of ports in the MTDC system and the increasing complexity of network topology, the deficiency of traditional flow calculation method is becoming clear. In this paper, a power flow calculation method that contains distribution of VSC-MTDC mixed system which based on asynchronous iterative method is put forward. On the basis of the current model converter, by dividing the hybrid system and coordinating calculation of boundary variables, this method achieves the global convergence of the whole system. The shortcomings that numerous converter stations in VSC-MTDC power flow method, slow operations and poor convergence in communication network with large number of nodes, are overcome in this method. Moreover, more control modes in the operation of the converter station are considered. Finally, through the example, the correctness and effectiveness of this method are verified.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

Rapid energy flow calculation method for integrated electrical and thermal systems

2020 ◽  
Vol 123 ◽  
pp. 106317 ◽  
Author(s):  
Guoqiang Sun ◽  
Wenxue Wang ◽  
Xiao Lu ◽  
Yi Wu ◽  
Wei Hu ◽  
...  
Keyword(s):  
Calculation Method ◽  
Energy Flow ◽  
Thermal Systems ◽  
Flow Calculation

The Research on Flow Calculation Method of the Ball Solenoid Valve

2014 ◽  
Vol 721 ◽  
pp. 370-373
Author(s):  
Yi Yang ◽  
Liang Chu ◽  
Di Fan ◽  
Yu Ting Huang
Keyword(s):  
Calculation Method ◽  
Solenoid Valve ◽  
Matlab Simulink ◽  
Flow Calculation ◽  
Simulink Model ◽  
Flow Demand

This paper proposes a flow calculation method of the ball solenoid valve, by measuring diameter of the input valve spool, we can estimate the rated flow of the solenoid valve. Aiming at the calculation method, we have built a MATLAB/Simulink model to calculate the valve flow, and we also validated the model by the flow demand of one type of RBS system.

scholarly journals Temperature log simulations in high-enthalpy boreholes

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Jia Wang ◽  
Fabian Nitschke ◽  
Maziar Gholami Korzani ◽  
Thomas Kohl
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Flow Rate ◽  
Fluid Loss ◽  
Flow Conditions ◽  
Flow Rates ◽  
High Enthalpy ◽  
Fluid Losses ◽  
Lateral Heat

Abstract Temperature logs have important applications in the geothermal industry such as the estimation of the static formation temperature (SFT) and the characterization of fluid loss from a borehole. However, the temperature distribution of the wellbore relies on various factors such as wellbore flow conditions, fluid losses, well layout, heat transfer mechanics within the fluid as well as between the wellbore and the surrounding rock formation, etc. In this context, the numerical approach presented in this paper is applied to investigate the influencing parameters/uncertainties in the interpretation of borehole logging data. To this end, synthetic temperature logs representing different well operation conditions were numerically generated using our newly developed wellbore simulator. Our models account for several complex operation scenarios resulting from the requirements of high-enthalpy wells where different flow conditions, such as mud injection with- and without fluid loss and shut-in, occur in the drill string and the annulus. The simulation results reveal that free convective heat transfer plays an important role in the earlier evolution of the shut-in-time temperature; high accuracy SFT estimation is only possible when long-term shut-in measurements are used. Two other simulation scenarios for a well under injection conditions show that applying simple temperature correction methods on the non-shut-in temperature data could lead to large errors for SFT estimation even at very low injection flow rates. Furthermore, the magnitude of the temperature gradient increase depends on the flow rate, the percentage of fluid loss and the lateral heat transfer between the fluid and the rock formation. As indicated by this study, under low fluid losses (< 30%) or relatively higher flow rates (> 20 L/s), the impact of flow rate and the lateral heat transfer on the temperature gradient increase can be ignored. These results provide insights on the key factors influencing the well temperature distribution, which are important for the choice of the drilling data to estimate SFT and the design of the inverse modeling scheme in future studies to determine an accurate SFT profile for the high-enthalpy geothermal environment.

scholarly journals Carotid Bifurcation Hemodynamics in Older Adults: Effect of Measured Versus Assumed Flow Waveform

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Yiemeng Hoi ◽  
Bruce A. Wasserman ◽  
Edward G. Lakatta ◽  
David A. Steinman
Keyword(s):  
Magnetic Resonance ◽  
Older Adult ◽  
Blood Flow Rate ◽  
Carotid Bifurcation ◽  
Flow Waveform ◽  
Flow Conditions ◽  
Flow Rates ◽  
Relative Residence Time ◽  
Contrast Magnetic Resonance ◽  
Dynamics Models

Recent work has illuminated differences in carotid artery blood flow rate dynamics of older versus young adults. To what degree flow waveform shape, and indeed the use of measured versus assumed flow rates, affects the simulated hemodynamics of older adult carotid bifurcations has not been elucidated. Image-based computational fluid dynamics models of N=9 normal, older adult carotid bifurcations were reconstructed from magnetic resonance angiography. Subject-specific hemodynamics were computed by imposing each individual’s inlet and outlet flow rates measured by cine phase-contrast magnetic resonance imaging or by imposing characteristic young and older adult flow waveform shapes adjusted to cycle-averaged flow rates measured or allometrically scaled to the inlet and outlet areas. Despite appreciable differences in the measured versus assumed flow conditions, the locations and extents of low wall shear stress and elevated relative residence time were broadly consistent; however, the extent of elevated oscillatory shear index was substantially underestimated, more by the use of assumed cycle-averaged flow rates than the assumed flow waveform shape. For studies of individual vessels, use of a characteristic flow waveform shape is likely sufficient, with some benefit offered by scaling to measured cycle-averaged flow rates. For larger-scale studies of many vessels, ranking of cases according to presumed hemodynamic or geometric risk is robust to the assumed flow conditions.

Decoupled AC/DC Power Flow Strategy for Multiterminal HVDC Systems

2018 ◽  
Vol 19 (1) ◽  
Author(s):  
Yixiang Gao ◽  
Shuhui Li ◽  
Weizhen Dong ◽  
Bing Lu
Keyword(s):  
Power Flow ◽  
Control Mode ◽  
Power Flow Calculation ◽  
Flow Calculation ◽  
Power System Control ◽  
Flow Method ◽  
Hvdc System ◽  
Dc Power ◽  
Bus System ◽  
Power Flow Method

AbstractThis paper proposes a decoupled AC/DC power flow approach for multi-terminal HVDC systems. The proposed method simplifies the power flow computation of multi-terminal HVDC systems while accurately reflecting the operation and control characteristics of VSC (voltage source converter) stations in a HVDC network. In the DC network, the power flow calculation is conducted based on a slack DC bus VSC station and power commends issued to other VSC stations from the power system control center. Then, in the AC power flow calculation, VSC stations are treated as special AC generators that can generate and absorb power from the AC grid in active and reactive power or active power and bus voltage control mode. For validation purpose, the conventional unified power flow method for multi-terminal HVDC systems is built. The paper compares the proposed method with the unified power flow method for an 8-bus multi-terminal HVDC system based on MATPOWER. Then, more case studies for different VSC control modes are conducted and evaluated for the 8-bus system. Afterwards, the proposed method is applied to the power flow study of a more practical and complicated multi-terminal HVDC system based on the IEEE 118-bus system.

Application of the optimal network flow method to the problem of locomotive selection for freight trains on the Eastern Polygon

2019 ◽  
pp. 94-106
Author(s):  
Александр Борисович Шабунин ◽  
Андрей Куркенович Такмазьян
Keyword(s):  
Network Flow ◽  
Optimal Solution ◽  
Global Optimum ◽  
Full Scale ◽  
Scale Model ◽  
Test Cases ◽  
Processor Time ◽  
Flow Method ◽  
Optimal Network ◽  
Locomotive Assignment

Моделируется подбор тяговых ресурсов (локомотивов - в данном случае) для провоза грузовых поездов. В качестве входных данных рассматриваются маршрут поезда, время готовности поезда к отправлению, средняя скорость и вес поезда. Имеется множество локомотивов, обладающих грузоподъемностью и областью разрешенного действия. Цель - оптимально подобрать ресурс для каждого участка маршрута поезда. Решение ищется методом потока ресурсов минимальной суммарной стоимости через специально сконструированную сеть. Сеть построена на основе взвешенного орграфа из ребер графика поездов на линейных участках и ребер альтернативы, в процессе прохода по которым осуществляется “смена деятельности” локомотива (например, отцепление от одного поезда и подцепка к другому). Полученное решение обладает свойством глобальной оптимальности по времени. The selection of traction resources (locomotives) for the transport of freight trains is modelled. The input data are the train route, the readiness time of the train for departure, the average speed and weight of the train. In addition, there are many locomotives with a carrying capacity and an area of permitted action. The research objective is to optimally select a resource for each segment of the train route. The solution is sought by the resource flow method of the minimum total cost through a specially designed network. The network includes edges created from train schedule segments whose filling means locomotive assignment to train at the segment, and special alternative edges, passing through which a locomotive alternates its assignment. The algorithm for finding the optimal solution is the method of pushing through the pre-flow proposed by A. Goldberg and R. Tarjan. This is one of the fastest algorithms converging to a global optimum. Two test cases were investigated: a trivial one, out of six trains and three locomotives, and a more complicated one, which is a model example the size of 10% of the full scale model and consists of 150 trains. Full scale calculations provide planning of the freight transportation on the Eastern Operational domain of the Russian Railways. The model includes 1800 locomotives and about 3000 trains on the time horizon of 48 hours. Solution is found in less than 5 minutes of processor time for a PC powered by Intel(R) Pentium(R) G2010 2.80 GHz processor.

Sign in / Sign up

Export Citation Format

Share Document