Development of Venturi-Tube With Spiral-Shaped Fin for Water Treatment

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Dong Ho Shin ◽  
Yeonghyeon Gim ◽  
Dong Kee Sohn ◽  
Han Seo Ko
Keyword(s):  
Water Treatment ◽  
Numerical Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Volume Fraction ◽  
Volume Flow Rate ◽  
Numerical Data ◽  
The Body ◽  
Venturi Tube ◽  
Type Water

Detailed numerical data were presented for the development of a venturi-type water purifier which had a cavitation nozzle to enhance turbulent kinetic energy and vapor volume fraction. Numerical analysis for cavitation was conducted in multiphase flow using the software, cfx. The numerical method used in this study was verified by the experimental data of pressure distribution in tube and the observation of cavitation from previous studies. From the result of the numerical analysis, a logarithmic relation between the vapor volume fraction and volume flow rate of water according to the area ratio between the throat and the entrance of a venturi-tube was derived. In addition, spiral-shaped fins were developed to enhance the turbulent kinetic energy in the body of a venturi-tube. Thus, it was confirmed that the volume fraction and turbulent kinetic energy of the developed water purifier were enhanced compared with the normal venturi-tube without the spiral-shaped fin. Finally, the improved water treatment performance of the advanced design of the venturi-tube was confirmed by the removal test of the representative solutions.

Numerical Analysis of Aluminium Oxide Nano Particles with Biodiesel in a Diesel Engine Fitted with Hemispherical Groove in the Piston

2021 ◽  
pp. 3691-3700
Keyword(s):  
Diesel Engine ◽  
Numerical Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Nano Particles ◽  
Fuel Injector ◽  
Biodiesel Blends ◽  
Closed Position ◽  
Combustion Features ◽  
Engine Valves

For proper combustion, bowl in the piston geometry plays a crutial role when the engine valves are in closed position. In the present work, the combustion geometry is of hemi-spherical groove in the upper region of the piston.simulations weres conducted for different blends( b20+al40, b20+al80) to analyze the combustion features in a four stroke diesel engine using ansys r18.1 software considering above geometry of the piston. . Pertaining to greater amount of density, viscosity of biodiesel blends, variations for b20+al80 render more performance than the biodiesel. Turbulent kinetic energy of both the fuels follow similar trend due to proper mixing of air with the fuel from fuel injector.

The Application of Eddy-Viscosity Stress Limiters for Modeling Cross-Flow Separation

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
P. A. Gregory ◽  
P. N. Joubert ◽  
M. S. Chong ◽  
A. Ooi
Keyword(s):  
Kinetic Energy ◽  
Skin Friction ◽  
Turbulent Kinetic Energy ◽  
Flow Separation ◽  
Eddy Viscosity ◽  
Cross Flow ◽  
The Body ◽  
Mean Flow ◽  
Viscosity Models ◽  
Experimental Apparatus

The ability of eddy-viscosity models to simulate the turbulent wake produced by cross-flow separation over a curved body of revolution is assessed. The results obtained using the standard k−ω model show excessive levels of turbulent kinetic energy k in the vicinity of the stagnation point at the nose of the body. Additionally, high levels of k are observed throughout the wake. Enforcing laminar flow upstream of the nose (which replicates the experimental apparatus more accurately) gives more accurate estimates of k throughout the flowfield. A stress limiter in the form of Durbin’s T-limit modification for eddy-viscosity models is implemented for the k−ω model, and its effect on the computed surface pressures, skin friction, and surface flow features is assessed. Additionally, the effect of the T-limit modification on both the mean flow and the turbulent flow quantities within the wake is also examined. The use of the T-limit modification gives significant improvements in predicted levels of turbulent kinetic energy and Reynolds stresses within the wake. However, predicted values of skin friction in regions of attached flow become up to 50% greater than the experimental values when the T-limit is used. This is due to higher values of near-wall turbulence being created with the T-limit.

Numerical Analysis of Nanofluids in Heat Pipe

2011 ◽  
Author(s):  
Pawan K. Singh ◽  
Nouman Zahoor Ahmed ◽  
Mohamed Ibrahim Ali ◽  
Youssef Shatilla
Keyword(s):  
Numerical Analysis ◽  
Heat Pipe ◽  
Mass Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
The Other ◽  
Software Modeling ◽  
Homogeneous Fluid

The numerical analysis of nanofluids in heat pipe is investigated using CFD, computational fluid dynamics, software modeling, FLUENT. The modeling was completed for base fluids and validated against earlier study. The alumina-water nanofluids are used for the investigation due to availability of huge literature. The thermal conductivity and viscosity are evaluated on the basis of literature and used in the study. For the other thermo-physical properties such as density and specific heat, mass based mixture model approach has been used. To see the concentration effect of nanofluids, mixtures with volume fraction of 1, 2, 3 and 5% are considered. The nanofluids mixture assumed to be homogeneous fluid flow in this simulation. The inlet velocity boundary condition, BC, is given by two approaches, mass flow arte and volume flow rate. The results showed that the nanofluids performance is similar to the base fluids while inlet BC is constant volume flow rate. On the other hand, nanofluids enhanced the performance over the base fluid while constant mass flow rate BC is used.

Pseudo-turbulent gas-phase velocity fluctuations in homogeneous gas–solid flow: fixed particle assemblies and freely evolving suspensions

2015 ◽  
Vol 770 ◽  
pp. 210-246 ◽  
Author(s):  
M. Mehrabadi ◽  
S. Tenneti ◽  
R. Garg ◽  
S. Subramaniam
Keyword(s):  
Kinetic Energy ◽  
Phase Velocity ◽  
Turbulent Kinetic Energy ◽  
Gas Phase ◽  
Reynolds Stress ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Particle Assemblies

Gas-phase velocity fluctuations due to mean slip velocity between the gas and solid phases are quantified using particle-resolved direct numerical simulation. These fluctuations are termed pseudo-turbulent because they arise from the interaction of particles with the mean slip even in ‘laminar’ gas–solid flows. The contribution of turbulent and pseudo-turbulent fluctuations to the level of gas-phase velocity fluctuations is quantified in initially ‘laminar’ and turbulent flow past fixed random particle assemblies of monodisperse spheres. The pseudo-turbulent kinetic energy $k^{(f)}$ in steady flow is then characterized as a function of solid volume fraction ${\it\phi}$ and the Reynolds number based on the mean slip velocity $\mathit{Re}_{m}$. Anisotropy in the Reynolds stress is quantified by decomposing it into isotropic and deviatoric parts, and its dependence on ${\it\phi}$ and $Re_{m}$ is explained. An algebraic stress model is proposed that captures the dependence of the Reynolds stress on ${\it\phi}$ and $Re_{m}$. Gas-phase velocity fluctuations in freely evolving suspensions undergoing elastic and inelastic particle collisions are also quantified. The flow corresponds to homogeneous gas–solid systems, with high solid-to-gas density ratio and particle diameter greater than dissipative length scales. It is found that for the parameter values considered here, the level of pseudo-turbulence differs by only 15 % from the values for equivalent fixed beds. The principle of conservation of interphase turbulent kinetic energy transfer is validated by quantifying the interphase transfer terms in the evolution equations of kinetic energy for the gas-phase and solid-phase fluctuating velocity. It is found that the collisional dissipation is negligible compared with the viscous dissipation for the cases considered in this study where the freely evolving suspensions attain a steady state starting from an initial condition where the particles are at rest.

Experimental Analysis of Venturi-Tube Behavior in Wet Gas Conditions

2020 ◽  
Author(s):  
Olav Mehlum ◽  
Øyvind Hundseid ◽  
Lars E. Bakken
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Fraction ◽  
Volume Flow Rate ◽  
Venturi Tube ◽  
Low Flow ◽  
Detailed Knowledge ◽  
Operation Conditions ◽  
Wet Gas ◽  
Compressor Inlet

Abstract Subsea wet gas compressors have been successfully in operation for approximately 5 years. Their use has proven to increase the recovery by approximately 10% and achieve a reliability up to 98%. Further developed and operation of subsea wet gas compression require detailed knowledge of compressor operability and how shift in operational conditions affect the compressor system. The compressors ability to handle wet gas is documented in detail for a gas volume fraction limited down to 0.90. The 4–5 last year of operation proves the wet gas concepts capability. As years pass by, well pressure and production rate declines which causes the compressor operation point to shift towards the high head and low flow (surge) area of the characteristics. In addition, compressor inlet transients increase due to pipe surge (slugs), requiring a robust control system to prevent instabilities, e.g. compressor surge. It is therefore vital to understand how the compressor inlet flow device behaves at different wet operation conditions. The article documents how a standard dry gas venturi tube behave at different wet gas operation conditions. The venturi is designed according to ISO5167-4 for dry gas conditions and is tested at the low-pressure air water compressor test rig at NTNU. The primary objective of the work has been to visualize the wet flow regime through the transparent venturi tube and to document the wet gas flow rate measurements by means of single-phase meters. The venturi tube is tested in a GMF range from 1 to 0.83 at an air volume flow rate of 1.3m3/s.

Effects of surface roughness on self-excited cavitating water jet intensity in the organ-pipe nozzle: Numerical simulations and experimental results

2019 ◽  
Vol 33 (27) ◽  
pp. 1950324
Author(s):  
Xiangdong Han ◽  
Yong Kang ◽  
Deng Li ◽  
Weiguo Zhao
Keyword(s):  
Numerical Simulation ◽  
Surface Roughness ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Energy Intensity ◽  
Volume Fraction ◽  
Water Jet ◽  
The Self ◽  
Simulation Results ◽  
Organ Pipe

This study was conducted to investigate effects of surface roughness on self-excited cavitating water jet intensity in an organ-pipe nozzle. Roughness average (Ra) values are 0.8, 1.6, 3.2, 6.3, 12.5, and 25 [Formula: see text]m, respectively. Numerical simulation results indicate that at inlet pressure of 10 MPa, the maximum, minimum, and real-time pressures in the self-excited oscillation chamber reach their respective peak values. The turbulent kinetic energy intensity in the external flow region is also most intense at this point, the vapor volume fraction in orifice is the highest, the vortex distribution scope in the orifice is the largest under [Formula: see text], and the self-excited cavitating water jet intensity is the strongest. The opposite variations emerge at [Formula: see text] compared to those of [Formula: see text], where the intensity is weakest. Pressure varies only slightly as Ra varies from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. Turbulent kinetic energy intensity behaves similarly as Ra increases from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m. At [Formula: see text], it was weaker than at Ra = 0.8–3.2 [Formula: see text]m. Similarly, there are only slight differences in vapor volume fraction and vortex distribution scope with Ra from 0.8 [Formula: see text]m to 6.3 [Formula: see text]m. The intensities at Ra = 0.8–3.2 [Formula: see text]m are similar, and weaker at Ra = 6.3 [Formula: see text]m. Pressure values are maximal at inlet pressure of 20 MPa, turbulent kinetic energy intensity is most intense, vapor volume fraction is highest, vortex distribution scope is largest under [Formula: see text] [Formula: see text]m, and intensity is strongest. Distinctions among pressure, turbulent kinetic energy intensity, vapor volume fraction, and vortex distribution scope values with Ra from 0.8 [Formula: see text]m to 3.2 [Formula: see text]m are slight. Differences in the corresponding intensities are also slight; all decrease with Ra from 12.5 [Formula: see text]m to 25 [Formula: see text]m as the intensity gradually weakens. Numerical simulation results were validated by comparison against corresponding experimental phenomena.

Direct numerical simulation of turbulence modulation by particles in compressible isotropic turbulence

2017 ◽  
Vol 832 ◽  
pp. 438-482 ◽  
Author(s):  
Qi Dai ◽  
Kun Luo ◽  
Tai Jin ◽  
Jianren Fan
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Rotational Motion ◽  
Isotropic Turbulence ◽  
Volume Fraction ◽  
Stokes Number ◽  
Systematic Investigation ◽  
Turbulence Modulation ◽  
Physical Mechanisms ◽  
Preferential Concentration

In this paper, a systematic investigation of turbulence modulation by particles and its underlying physical mechanisms in decaying compressible isotropic turbulence is performed by using direct numerical simulations with the Eulerian–Lagrangian point-source approach. Particles interact with turbulence through two-way coupling and the initial turbulent Mach number is 1.2. Five simulations with different particle diameters (or initial Stokes numbers, $St_{0}$) are conducted while fixing both their volume fraction and particle densities. The underlying physical mechanisms responsible for turbulence modulation are analysed through investigating the particle motion in the different cases and the transport equations of turbulent kinetic energy, vorticity and dilatation, especially the two-way coupling terms. Our results show that microparticles ($St_{0}\leqslant 0.5$) augment turbulent kinetic energy and the rotational motion of fluid, critical particles ($St_{0}\approx 1.0$) enhance the rotational motion of fluid, and large particles ($St_{0}\geqslant 5.0$) attenuate turbulent kinetic energy and the rotational motion of fluid. The compressibility of the turbulence field is suppressed for all the cases, and the suppression is more significant if the Stokes number of particles is close to 1. The modifications of turbulent kinetic energy, the rotational motion and the compressibility are all related with the particle inertia and distributions, and the suppression of the compressibility is attributed to the preferential concentration and the inertia of particles.

Investigating Multiphase Turbulence Statistics of Large-Scale Two-Way Coupled Gravity-Driven Flows

2014 ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins ◽  
Rodney O. Fox
Keyword(s):  
Kinetic Energy ◽  
Kinetic Theory ◽  
Turbulent Kinetic Energy ◽  
Particle Velocity ◽  
Volume Fraction ◽  
Constitutive Relations ◽  
Granular Temperature ◽  
Particle Phase ◽  
Simulation Results ◽  
Filtering Approach

Starting from the kinetic theory (KT) model for monodisperse granular flow, the exact Reynolds-average (RA) equations were recently derived for the particle phase in a collisional gas-particle flow by Fox [1]. The turbulence model solves for the RA particle volume fraction, the phase-average (PA) particle velocity, the PA granular temperature, and the PA particle turbulent kinetic energy (TKE). A clear distinction is made between the PA granular temperature, which appears in the kinetic theory constitutive relations, and the particle-phase turbulent kinetic energy, which appears in the turbulent transport coefficients. Mesoscale direct numerical simulation (DNS) can be used to assess the validity of the closures proposed for the unclosed terms that arise due to nonlinearities in the hydrodynamic model. In order to extract meaningful statistics from simulation results, a separation of length scales must be established to distinguish between the PA particle TKE and the PA granular temperature. In this work, we introduce an adaptive spatial filter with an averaging volume that varies with the local particle-phase volume fraction. This filtering approach ensures sufficient particle sample sizes in order to obtain meaningful statistics while remaining small enough to avoid capturing variations in the mesoscopic particle field. Two-point spatial correlations are computed to assess the validity of the filter in extracting meaningful statistics. The filtering approach is applied to fully-developed cluster-induced turbulence (CIT), where the production of fluid-phase kinetic energy results entirely from momentum coupling with finite-size inertial particles. Simulation results show a strong correlation between the local volume fraction and granular temperature, with maximum values located just upstream of clusters (i.e., where maximum compressibility of the particle velocity field exists), and negligible particle agitation is observed within clusters.

The Abrasive Flow Machining Simulation of Common Rail Tube Holes Based on FLUENT

2014 ◽  
Vol 687-691 ◽  
pp. 4376-4381 ◽  
Author(s):  
Li Feng Zhu ◽  
Kai Wang ◽  
Huan Wu ◽  
Dong Xiu ◽  
Li Zhong Sun
Keyword(s):  
Numerical Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Common Rail ◽  
Machining Process ◽  
Two Phase ◽  
Abrasive Flow Machining ◽  
Solid Liquid

Based on the solid - liquid two-coupling theory, Use abrasive medium viscosity-temperature characteristics related to the mathematical model, using solid - liquid two-phase solution method Mixture models and standards, turbulence model combining with common rail pipe hole as the research object, choose different initial temperatures and processing procedures, numerical analysis was carried out on the flow channel wall temperature and turbulent kinetic energy. Using numerical analysis software FLUENT Abrasive Flow Machining rail tube orifice structure was three-dimensional numerical analysis; obtain a steady-state pressure, dynamic pressure, velocity, turbulent kinetic energy image, to study Abrasive Flow Machining process provides a theoretical basis and technical support.

Investigation of self-excited oscillation chamber cavitation effect with special emphasis on wall shape

2020 ◽  
Vol 44 (2) ◽  
pp. 244-255 ◽  
Author(s):  
Zhaohui Wang ◽  
Yanan Hu ◽  
Si Chen ◽  
Lin Zhou ◽  
Wenxia Xu ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Volume Fraction ◽  
Growth Cycle ◽  
The Self ◽  
Energy Concentration ◽  
Wall Structure ◽  
Cavitation Effect ◽  
Excited Oscillation ◽  
Oscillating Jet

Analysis of the self-excited oscillating jet nozzle makes it possible to investigate the influence of structural and geometric shapes on the effect of self-excited oscillation cavitation and energy efficiency. In this paper, a new self-excited oscillation chamber structure was obtained using a Bézier curve to reconstruct the wall transition surface, and the cavitation airbag energy concentration was maximized to efficiently utilize the pulse energy. Numerical analysis and simulation were used to study the turbulent kinetic energy, steam volume fraction, and vortex growth cycle of the outlet. The results showed that the novel chamber wall structure weakens the interior secondary vortex in the self-excited oscillation chamber and forms a large cavitation airbag area and reduces energy dissipation. In addition, using the new chamber with redesigned wall structure, the peak turbulent kinetic energy, the velocity at the jet exit, and the vapor volume fraction inside the chamber increased approximately 10.3%, 14.6%, and 9.1%, respectively.

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