scholarly journals Investigation on the Effect of Structural Parameters on Cavitation Characteristics for the Venturi Tube Using the CFD Method

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2194 ◽  
Author(s):  
Pan Tang ◽  
Juan Manzano Juárez ◽  
Hong Li
Keyword(s):  
Cavity Length ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Differential Pressure ◽  
Venturi Tube ◽  
Research Issues ◽  
Contraction Ratio ◽  
Cfd Method ◽  
Throat Section ◽  
Contraction Angle

The venturi tube is a special kind of pipe which has been widely applied in many fields. Cavitation is one of the most important research issues for the Venturi tube. Hence, three key structural parameters (contraction angle, diffusion angle and contraction ratio) were selected to investigate the influence of different factors on cavitation characteristics, using the computational fluid dynamics (CFD) method. A series of experiments for measuring the relationship between differential pressure and flow rate were carried out to verify the accuracy of the simulation method. Results showed that the simulation results had a high accuracy and the numerical method was feasible. The average vapor volume fraction of cross-section from the throat in the axial direction increased with increasing contraction angle. The cavity length increased with increasing contraction angle. The average volume fraction in the diffusion section rapidly decreased with increasing diffusion angle. The diffusion angle had no significant effect on the cavitation characteristics in the throat section and had a significant influence in the diffusion section. The average vapor volume fraction increased with decreasing contraction ratio. The contraction ratio had no significant effect on the cavity length under the same differential pressure. The average vapor volume fraction increased with decreasing contraction ratio. However, the variation in the throat section was less than the diffusion section. Under the same inlet and outlet pressure, the cavity lengths for different contraction ratios were basically the same, which indicated that the contraction ratio had no significant effect on the cavity length.

The effect of NCG on the characteristics of hydraulic cavitation

2020 ◽  
Vol 21 (5) ◽  
pp. 504
Author(s):  
Qiang Li ◽  
Wei Li ◽  
Jian Zhang ◽  
Dezhi Ming ◽  
Weiwei Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Cavity Length ◽  
Volume Fraction ◽  
Venturi Tube ◽  
Hydrodynamic Cavitation ◽  
Cavitation Model ◽  
Noncondensable Gas ◽  
Hydrodynamic Phenomenon ◽  
Increasing Temperature

Hydraulic cavitation, as an important and complex hydrodynamic phenomenon, has long drawn attention. In this paper, the ZGB (Zwart-Gerber-Belamri) cavitation model is improved and the effect of NCG (noncondensable gas) on cavitation in water is studied by numerical simulation. The influence of NCG on the cavity length, the temperature of the cavities and the mixed viscosity of the cavities is investigated through the improved ZGB cavitation model. In addition, experiments on hydrodynamic cavitation produced by a Venturi tube are used to validate the improved ZGB cavitation model. The results show that NCG not only shortens the length of the cavity but also reduces the volume fraction of the vapor. The existence of NCG decreases the viscosity in the cavity of the Venturi tube but increases the viscosity at the sidewall of the tube. In addition, the temperature in the cavities increases with increasing NCG. Regardless of whether air is injected, the volume fraction of the vapor in the cavities increases first and then decreases with increasing temperature. However, the transition temperature decreases somewhat after injecting air. Therefore, the influence of NCG on hydraulic cavitation is significant, and the role of NCG should be considered in industry.

The Numerical Simulation of Aerated Cavity Length and Negative Pressure on Stepped Spillway Combined with Y-Shape Asymmetrical Flaring Gate Pier

2013 ◽  
Vol 864-867 ◽  
pp. 2185-2192
Author(s):  
Xiao Xia Hou ◽  
Ju Rui Yang ◽  
Jian Shu Zhen
Keyword(s):  
Negative Pressure ◽  
Cavity Length ◽  
Lateral Side ◽  
Stepped Spillway ◽  
Body Type ◽  
Two Phase ◽  
Vof Model ◽  
Contraction Ratio ◽  
Simulation Results ◽  
Contraction Angle

In order to study the aerated cavity length and negative pressure on stepped spillway which combined with Y-shape asymmetric flaring gate pier body type, this paper applied RNG turbulence model,VOF model of water vapor two-phase, iterative solution of geometry reconstruction format of unsteady flow to generate free surface. Numerically simulated the length of aerated cavity and negative pressure of stepped spillway which combined with asymmetrical Y-shape flaring gate pier that with the contraction ratio respectively of 598, 0.497 and 0.445, the range from the upstream reservoir to downstream stilling basin. And compared the simulation results with experimental results, found that the aerated cavity length on steps basically consistent with the measured cavity length, the maximum error is 9.7%. The simulation results shows that the aeration cavity length on steps increases with asymmetric flaring gate pier contraction ratio decreases, and the aerated cavity length of lateral side with smaller contraction angle is larger 4 to 5 times than lateral side with larger contraction angle.

Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

Soft Matter ◽  
2021 ◽  
Author(s):  
D. Zeb Rocklin ◽  
Lilian C Hsiao ◽  
Megan E Szakasits ◽  
Michael J Solomon ◽  
Xiaoming Mao
Keyword(s):  
Coordination Number ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Structural Heterogeneity ◽  
Colloidal Gels ◽  
Shear Moduli ◽  
Rheological Measurements

Rheological measurements of model colloidal gels reveal that large variations in the shear moduli as colloidal volume-fraction changes are not reflected by simple structural parameters such as the coordination number,...

CFD Based Analysis of Laminar Forced Convection of Nanofluid Separated Flow Under the Presence of Magnetic Field

2016 ◽  
Vol 32 (6) ◽  
pp. 777-785
Author(s):  
M. Besanjideh ◽  
M. Hajabdollahi ◽  
S. A. Gandjalikhan Nassab
Keyword(s):  
Magnetic Field ◽  
Fluid Flow ◽  
Volume Fraction ◽  
Separated Flow ◽  
Fluid Temperature ◽  
Flow And Heat Transfer ◽  
Contraction Ratio ◽  
Nanoparticles Volume Fraction ◽  
Energy Equations ◽  
Laminar Forced Convection

AbstractThis paper deals with studying fluid flow and heat transfer of nanofluid through a forward facing step channel which is affected by a uniform magnetic field transverse to fluid flow. All the channel walls are assumed to be in constant temperature and the fluid temperature at the channel inlet is less than that of the walls. Also, the nanofluid is considered as a single-phase Newtonian fluid and the proper correlations were utilized to determine the thermophysical properties of nanofluid. Therefore, a code has been developed and two-dimensional continuity, momentum and energy equations were solved, using CFD technique. The computations were conducted for different values of the Reynolds and Hartmann numbers, and contraction ratio and an extensive range of nanoparticles volume fraction. The results indicated that flow separation and reattachment phenomena, in vicinity of the step edge, could be influenced strongly by magnetic field and the average Nusselt number is increased significantly by increasing nanoparticles volume fraction and Hartmann number.

scholarly journals Effects of Reservoir Parameters on Separation Behaviors of the Spiral Separator for Purifying Natural Gas Hydrate

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5346
Author(s):  
Shunzuo Qiu ◽  
Guorong Wang
Keyword(s):  
Particle Size ◽  
Natural Gas ◽  
Removal Efficiency ◽  
Flow Rate ◽  
Gas Hydrate ◽  
Volume Fraction ◽  
Differential Pressure ◽  
Separation Performance ◽  
Recovery Efficiency ◽  
Natural Gas Hydrate

The spiral separator is an important tool for desanding in natural gas hydrate production, and the change of hydrate reservoir parameters has a great impact on spiral separator behavior. Mastering the influence law is helpful to improve the separation performance. Until now, there was still no detailed analysis of the effect mechanism between reservoir parameters and spiral separator behavior. In this paper, a downhole spiral separator was designed. Then, the effects of reservoir parameters (particle size, hydrate, volume fraction, and sand volume fraction) on separation performance (discrete phase distribution, separation efficiency, and differential pressure) with different flow rates were investigated by numerical simulation method Fluent 18.0. The results show that effects degree of reservoir parameters is in order from large to small: sand phase volume fraction, particle size, hydrate volume fraction. As the particle size increases, the separation performance is improved. When the sand volume fraction increases, the natural gas hydrate (NGH) recovery efficiency and differential pressure both increase, but the sand removal efficiency decreases. When the hydrate fraction increases, the separation performance change law is opposite to that when the sand volume fraction increases. In addition, with increasing the flow rate, the efficiency and differential pressure increase. Therefore, reservoir saturation and porosity can balance NGH recovery efficiency and sand removal efficiency. Furthermore, the spiral separator has good performance under the change of reservoir parameters. The performance of the NGH spiral separator can be also maintained by increasing the flow rate.

Visual Criteria for Measuring Two-phase Flow Rate in Venturi with Flow Homogenizer

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Sangho Sohn ◽  
Jaebum Park ◽  
Dong-Wook Oh
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
Differential Pressure ◽  
Phase Flow ◽  
Two Phase ◽  
3 Dimensional ◽  
Lower Amplitude ◽  
Gas Volume

A simple use of Venturi might be used to measure two-phase flow rate within relatively low GVF(gas volume fraction). Upstream flow entering Venturi can be improved with installed flow homogenizer which is easily fabricated by 3-dimensional printer with multiple holes. Simultaneous measurement between high-speed flow visualization and dynamic differential pressure measurement was made to find visual criteria for two-phase flow rate measurement with different GVF ranged from 0% to 30%. It was observed that the two-phase flow rate can be reliably measured up to 15% of GVF using flow homogenizer. FFT(Fast-Fourier Transform) results proved that the long flow homogenizers (type 2 and 4) showed a lower amplitude of differential pressure (Δp) than the short flow homogenizers (type 1 and 3) respectively. So the optimized flow homogenizer can be useful to measure two-phase flow rate at low GVF.

Small Angle Scattering from Nanocrystalline Pd

1988 ◽  
Vol 132 ◽  
Author(s):  
G. Wallner ◽  
E. Jorra ◽  
H. Franz ◽  
J. Peisl ◽  
R. Birringer ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Size Distribution ◽  
Small Angle ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Spatial Arrangement ◽  
Small Angle Scattering ◽  
X Rays ◽  
Angle Scattering ◽  
Log Normal

ABSTRACTThe microstructure of nanocrystalline Pd was investigated by small angle scattering of neutrons and X-rays. The samples were prepared by compacting small crystallites produced by evaporation and condensation in an inert gas atmosphere. The strong scattering signal is interpreted to arise from crystallites embedded in a matrix of incoherent interfaces. Size distributions were deduced from the scattering curves. They consist of two parts: the crystallite size distribution dictated by the production process, and a structureless contribution due to the correlation in the spatial arrangement of the crystallites. The crystallite size distribution may be described by a log-normal distribution centred at R=2nm. The characteristic form of the correlation contribution arises from the dense packing of non-spherical crystallites. From the scattering cross-section in absolute units the volume fraction vc of crystallites was obtained as vc≈0.3, and the mean atomic density ρi in the interfaces as ρi≈0.52. The change of structural parameters during thermal annealing of the samples was studied. Up to high temperatures an appreciable volume fraction of crystallites with nearly unchanged size remains along with large particles.

High Temperature Low Cycle Fatigue of Superalloys Inconel 713LC and Inconel 792-5A

2007 ◽  
Vol 348-349 ◽  
pp. 101-104 ◽  
Author(s):  
Martin Petrenec ◽  
Karel Obrtlík ◽  
Jaroslav Polák
Keyword(s):  
Fatigue Life ◽  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Structural Parameters ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Plastic Strain Amplitude ◽  
Nickel Base Superalloy ◽  
Polycrystalline Nickel ◽  
Stress Strain

Cylindrical specimens of cast polycrystalline nickel base superalloy Inconel 713 LC and Inconel 792-5A were cyclically strained under total strain control at 23 and 700 °C. Morphology and volume fraction of γ´ precipitates are different in both materials. Cyclic hardening/softening curves, cyclic stress-strain curves, and fatigue life curves were obtained at both temperatures. The cyclic hardening/softening curves depend both on temperature and plastic strain amplitude. The cyclic stressstrain curves can be fitted by power law. Experimental data of fatigue life curves can be approximated by the Manson-Coffin and Basquin laws. Dislocation structure was studied in transmission electron microscope. Planar dislocation arrangements in the form of bands parallel to {111} planes were identified in both superalloys at both temperatures. Stress-strain response and fatigue life characteristics are compared at both temperatures and discussed in relation to dislocation arrangement and structural parameters of the materials studied.

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