scholarly journals Numerical Simulation of Imported Sediment in a Stilling Basin

2021 ◽  
Vol 9 ◽  
Author(s):  
Rui Wang ◽  
Peng Li ◽  
Zhanbin Li ◽  
Jianchun Han ◽  
Yubin Zhu
Keyword(s):  
Energy Dissipation ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Sediment Deposition ◽  
Dam Failure ◽  
Phase Flow ◽  
Two Phase ◽  
Stilling Basin ◽  
Unit Width

Sediment buildup at the bottom of a stilling basin can result in premature drainage of spillway structures and can even lead to dam failure in severe cases. Such failures pose ecological and human safety hazards to downstream areas. To evaluate the sudden discharge and potential dam failure associated with sediment buildup, we developed a two-dimensional two-phase flow simulation model built on a particle-based force balance equation. We compared the flow patterns and energy dissipation effects in the stilling basin at different inlet flows (2, 3, 4.5, and 6.75 m2/s), and the subsequent bottom deposition was compared across different sand discharge mass flow rates (0.1, 0.2, and 0.3 kg/s). The results show that the turbulent energy increased with the increasing inlet unit width flow rate. When more vortices were generated and the flow velocity was reduced significantly, the energy dissipation was more effective. The sediment deposition at the bottom of the stilling basin gradually increased with the decrease of inlet unit width flow and the decrease of the sediment mass flow rate. Meanwhile, at a fixed inlet shape, the change in inlet unit width flow had little effect on the maximum sedimentation height at the bottom of the basin. In addition, the average deposition rate at the bottom of the stilling basin was positively correlated with the inlet sedimentation concentration, and the correlation coefficient could be as high as 0.97. In this two-phase flow method, the error of the simulated value over the theoretical value was less than 10%. This simulation of sediment deposition at the bottom of the stilling basin provides a practical reference for dam managers.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

Experimental Research on Pulsating Two-Phase Flow Pressure Drop Characteristics in Horizontal Rectangular Channel

2014 ◽  
Author(s):  
Siqi Zhang ◽  
Puzhen Gao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Mean Values ◽  
Water Mass Flow Rate

In spite of most previous studies since 1970, the theory of pulsating pipe flows supported by experimental investigations has not yet completed in comparison with the well-defined theory of steady pipe flows. Therefore, it seems that there is much to be done about experimental research in this field. In order to determine the resistance characteristics of two-phase flow under pulsatile conditions, an experimental investigation on two-phase flow with periodically fluctuating flow rates in a narrow rectangular channel is carried out. A frequency inverter is used to obtain experimental conditions with different fluctuating frequencies, amplitudes and mean values of water mass flow rate. After obtaining experimental results, comparisons between experimental frictional pressure drop values and theoretical calculations have been done. Two-phase flow on pulsating conditions is far more complicated than that on steady conditions because pulsating flow is composed of two parts: a steady component and a superimposed periodical time varying component called oscillation. In this paper, the influence of different fluctuating frequencies, amplitudes and mean values of liquid and gas mass flow rate on two-phase flow pressure drop characteristics is also discussed. The results show that the total pressure drop and water mass flow rate change with the same fluctuating period except for a phase difference. The phase lag also changes with the fluctuating frequencies and amplitude. The accelerating pressure drop changes dramatically in a fluctuating period, especially at the end of acceleration. Also, the time when the acceleration pressure drop has its maximum value lags the time when the acceleration reaches its peak, mainly because of the inertial of the fluid.

Theoretical study and experimental measurement of the gas liquid two-phase flow through a vertical Venturi meter

2020 ◽  
pp. 095440622094711
Author(s):  
Ammar Zeghloul ◽  
Abdelkader Messilem ◽  
Nabil Ghendour ◽  
Abdelsalam Al-Sarkhi ◽  
Abdelwahid Azzi ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Void Fraction ◽  
Mass Flow ◽  
Flow Rate ◽  
Test Section ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Conductance Probe

An accurate two-phase flow rate measurement is essential in many applications and industries such as; oil/gas, chemical, pipeline transportation and nuclear industry. This paper presents the findings obtained from two-phase flow rate measurements using Venturi meters coupled with conductance probe sensors. The measurement system and presented methodology can be used to directly and continuously measure the mass flow rate of gas-liquid flows without any need for using a separator. Most of the available data in literature on mass flow rate using Venturis in gas-liquid two phase flows are limited/valid to a certain flow regime. However, the experimental data presented in this paper covered a wide range of flows (i.e. bubbly, slug and churn flows). Three Venturis with different diameter ratios, β = 0.40, β = 0.55 and β = 0.75 have been employed using an air-water vertical test section. The effect of the Venturi’s geometry on the flow behaviour was also evaluated. The average void fraction and void fraction time series have been measured along the test section by nine different conductance probe sensors covering the convergent, throat and divergent sections. In addition, the two-phase pressure drop across the Venturi was measured. Moreover, a new correlation for the gas-liquid slip ratio was proposed in this paper, which is necessary for calculating the two-phase mass flow rate. The proposed slip ratio correlation showed more accuracy than the ones available in literature. It was found that the correlation proposed by Chisholm to predict the two-phase mass flow rate in Venturis with a diameter ratio, β = 0.55, shows the best accuracy among others such as; Murdock, Lin, James and Zhang correlations.

Cryogenic Two-Phase Flow and Heat Transfer Under Terrestrial and Microgravity

2005 ◽  
Author(s):  
Kun Yuan ◽  
J. N. Chung ◽  
Yan Ji
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Normal Gravity ◽  
Two Phase Flow ◽  
Microgravity Condition ◽  
Phase Flow ◽  
Gravity Effect ◽  
Two Phase ◽  
Micro Gravity

This paper presents experimental investigations of cryogenic nitrogen two-phase flow in horizontal transparent tubes (diameters of 11.1mm) under terrestrial and micro-gravity (10−4g) conditions during the chilldown process, and the focus is on the film boiling region. Constant mass flow rate is achieved by a motor driven bellows, and three different mass fluxes from 9.2 to 27.6kg/m2 · s are tested in the experiments. A drop tower is applied to simulate the micro-gravity environment. During the chilldown process, we measure the time-dependent temperatures at three circumferential locations at different downstream locations. Video images are recorded for identifying the flow patterns. The experiments show that under normal gravity, the flow pattern change from dispersed flow to inverted annular flow and then to unsteady stratified flow according to different wall temperatures, the temperature differences between the lower and upper part of the test section increase with increasing flow rate. Under microgravity, when the temperature is high, the liquid chunks trend to be lifted up and confined mainly in the central core of the tube; when the temperature is low, the liquid chunks are more evenly dispersed inside the whole tube, and some touch the upper wall. It is also found that the measured wall temperatures drop more quickly under microgravity condition compared with that under normal gravity. Moreover, under microgravity condition, the measured temperatures drop more quickly with lower wall temperature. The gravity effect on the quenching curves is alleviated with increasing mass flow rate. Thus gravity effect is more important in low mass flow rate two-phase flow.

scholarly journals Numerical Simulation of Flow Behavior within a Venturi Scrubber

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
M. M. Toledo-Melchor ◽  
C. del C. Gutiérrez-Torres ◽  
J. A. Jiménez-Bernal ◽  
J. G. Barbosa-Saldaña ◽  
S. A. Martínez-Delgadillo ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Venturi Scrubber

The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water) in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in five geometries with different converging and diverging angles while the two-phase flow was only simulated for one geometry. The results obtained were validated with experimental data obtained by other researchers. The results show that the pressure drop depends significantly on the gas flow rate and that water flow rate does not have significant effects neither on the pressure drop nor on the fluid maximum velocity within the scrubber.

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