Identification of Pulsation Mechanism in a Transonic Three-Stream Airblast Injector

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Wayne Strasser ◽  
Francine Battaglia
Keyword(s):  
Boundary Conditions ◽  
Industrial Applications ◽  
Driving Mechanism ◽  
Flow Conditions ◽  
Primary Droplet ◽  
Droplet Sizes ◽  
Computational Fluid Dynamics Cfd ◽  
Proportional Relationship ◽  
Nozzle Geometries ◽  
A Minor

Acoustics and ligament formation within a self-generating and self-sustaining pulsating three-stream injector are analyzed and discussed due to the importance of breakup and atomization of jets for agricultural, chemical, and energy-production industries. An extensive parametric study was carried out to evaluate the effects of simulation numerics and boundary conditions using various comparative metrics. Numerical considerations and boundary conditions made quite significant differences in some parameters, which stress the importance of using documented and consistent numerical discretization recipes when comparing various flow conditions and geometries. Validation exercises confirmed that correct droplet sizes could be produced computationally, the Sauter mean diameter (SMD) of droplets/ligaments could be quantified, and the trajectory of a droplet intersecting a shock wave could be accurately tracked. Swirl had a minor impact by slightly moving the ligaments away from the nozzle outlet and changing the spray to a hollow cone shape. Often, metrics were synchronized for a given simulation, indicating that a common driving mechanism was responsible for all the global instabilities, namely, liquid bridging and fountain production with shockletlike structures. Interestingly, both computational fluid dynamics (CFD) and the experimental non-Newtonian primary droplet size results, when normalized by distance from the injector, showed an inversely proportional relationship with injector distance. Another important outcome was the ability to apply the models developed to other nozzle geometries, liquid properties, and flow conditions or to other industrial applications.

Modelling solid transport in building drainage systems

1996 ◽  
Vol 33 (9) ◽  
pp. 9-16 ◽  
Author(s):  
John A. Swaffield ◽  
John A. McDougall
Keyword(s):  
Decision Making ◽  
Boundary Conditions ◽  
Numerical Solution ◽  
Water Conservation ◽  
Transient Flow ◽  
Drainage System ◽  
System Model ◽  
Flow Depth ◽  
Flow Conditions ◽  
Solid Transport

The transient flow conditions within a building drainage system may be simulated by the numerical solution of the defining equations of momentum and continuity, coupled to a knowledge of the boundary conditions representing either appliances discharging to the network or particular network terminations. While the fundamental mathematics has long been available, it is the availability of fast, affordable and accessible computing that has allowed the development of the simulations presented in this paper. A drainage system model for unsteady partially filled pipeflow will be presented in this paper. The model is capable of predicting flow depth and rate, and solid velocity, throughout a complex network. The ability of such models to assist in the decision making and design processes will be shown, particularly in such areas as appliance design and water conservation.

Isatin: A Scaffold with Innumerable Biodiversity

2020 ◽  
Vol 20 ◽  
Author(s):  
Priyobrata Nath ◽  
Agnish Mukherjee ◽  
Sougata Mukherjee ◽  
Sabyasachi Banerjee ◽  
Samarpita Das ◽  
...  
Keyword(s):  
Biological Effects ◽  
Scientific Information ◽  
Research Work ◽  
Chemical Properties ◽  
Industrial Applications ◽  
Biologically Relevant ◽  
Extensive Information ◽  
Relevant Compound ◽  
A Minor ◽  
Clinical Conditions

: Isatin is an endogenous and a significant category of fused heterocyclic component, widely been a part of several potential biologically useful synthetics. Since its discovery, tons of research work has been conducted with respect to the synthesis, chemical properties, and biological and industrial applications. It contains indole nucleus having both lactam and keto moiety which while being a part of a molecular framework exerted several biological effects, viz.; antimicrobial, antitubercular, anticonvulsant, anticancer etc. Isatin derivatives are synthetically significant substrates, which can be utilized for the synthesis of huge diversified chemical entities of which few members emerged to be a drug. The reason for this review is to provide extensive information pertaining to the chemistry and its significance in altering several pathological states of isatin and its derivatives. A Structure Activity Relationships study thus developed through a gamut of scientific information indicates the importance of mostly electron withdrawing groups, halogens, nitro, alkoxy and to a minor extent groups with positive inductive effects, such as methyl at position 1, 5, 6 and 7 of isatin in alleviating several clinical conditions. It is also observed from the survey that the presence of two oxo groups at position 2 and 3 sometimes become insignificant as fusion with a heterocycle at those position resulted in a biologically relevant compound.

Characterisation of supersonic gas jets for different nozzle geometries for laser-plasma acceleration experiments at SPARC_LAB

2022 ◽  
Vol 17 (01) ◽  
pp. C01049
Author(s):  
G. Costa ◽  
M.P. Anania ◽  
A. Biagioni ◽  
F.G. Bisesto ◽  
M. Del Franco ◽  
...  
Keyword(s):  
High Power ◽  
Plasma Channel ◽  
Laser Pulses ◽  
Industrial Applications ◽  
Point Of View ◽  
Theoretical Point ◽  
High Power Laser ◽  
Power Laser ◽  
Neutral Gas ◽  
Nozzle Geometries

Abstract Plasma-based technology promises a tremendous reduction in size of accelerators used for research, medical, and industrial applications, making it possible to develop tabletop machines accessible for a broader scientific community. The use of high-power laser pulses on gaseous targets is a promising method for the generation of accelerated electron beams at energies on the GeV scale, in extremely small sizes, typically millimetres. The gaseous target in question can be a collimated supersonic gasjet from a nozzle. In this work, a technique for optimising the so generated plasma channel is presented. In detail, a study on the influence of the nozzle throat shape in relation to the uniformity and density of the generated plasma profile is reported. These considerations are discussed first of all from a theoretical point of view, by means of a stationary one-dimensional mathematical model of the neutral gas, thus exploiting the possibility of comparing the properties of the output flow for different nozzle geometries. This is combined with an experimental approach using interferometric longitudinal density measurements of the plasma channel. The latter is generated by a high-power laser pulse focused on a helium gasjet, in the SPARC_LAB laboratories.

A Computational Fluid Dynamics (CFD) Guided Engineering Solution for Performance Improvement of a Multistage Pump

2021 ◽  
Author(s):  
Teymour Javaherchi ◽  
Susheel Brahmeshwarkar ◽  
Raja Faruq ◽  
Chinmay Deshpande
Keyword(s):  
Performance Improvement ◽  
Test Data ◽  
Industrial Applications ◽  
Pump Efficiency ◽  
Pump Impeller ◽  
Methodology Development ◽  
Engineering Team ◽  
Initial Hypothesis ◽  
Computational Fluid Dynamics Cfd ◽  
Multistage Pump

Abstract This work will demonstrate how the Energy Recovery Inc. (ERI) engineering team improved the efficiency of a multistage pump by about 10% at the first stage, which translated into a 3% increase in the overall multistage pump efficiency; according to a set of engineering calculations and review of the archived in-house test data for the legacy multistage pumps, it was hypothesized that the performance pain-point of the pump was inefficient performance of the first stage, due to the formation of a strong pre-swirl right before its inlet. The validity of this hypothesis then was confirmed via RANS CFD simulations of the flow field inside the inlet suction housing and pump impeller. Same CFD methodology was used to evaluate multiple engineering solutions to reduce the strength of the inflow pre-swirl by modifying the inlet suction housing geometry. The obtained RANS CFD solutions guided the engineering team towards the most promising hardware modification proposal. The proposed geometrical modification of the inlet suction housing was implemented and tested on different multistage pumps. All of the test results validated the obtained RANS CFD numerical solution. The state of the art in this successful performance improvement process was first the on-point hypothesis development based on fundamentals of engineering and archived test data. Second, the proper RANS CFD methodology development to model/confirm the initial hypothesis and vet all possible engineering solutions to maximize the multistage pump efficiently and accurately. This can be a great example for various relevant turbomachinery industrial applications.

scholarly journals An investigation of the interaction between a travelling shock wave and a solid rocket motor nozzle

2021 ◽  
Author(s):  
Harmanjit Singh Chopra
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Reflected Shock Wave ◽  
Convergence Region ◽  
Rocket Motors ◽  
Additional Information ◽  
Reflected Shock ◽  
Solid Propellant Rocket ◽  
Computational Fluid Dynamics Cfd ◽  
Nozzle Geometries

A gasdynamic mechanism has been identified as a potential source of combustion instability in solid-propellant rocket motors (SRMs). This mechanism involves the reinforcement of a reflected shock wave in the nozzle convergence region of an SRM's exhaust nozzle. A shock tube apparatus was developed for the experimental component of this study. Various factors, such as the effect of different nozzle geometries and driven channel pressures, were examined. Also, a model of the shock tube was developed for computational fluid dynamics (CFD) simulations. These simulations were generated for comparison with the experimental results and to provide additional information regarding the nature of the flow behaviour. A gasdynamic mechanism has been identified as a potential source of combustion instability in solid-propellant rocket motors (SRMs). This mechanism involves the reinforcement of a reflected shock wave in the nozzle convergence region of an SRM's exhaust nozzle.A shock tube apparatus was developed for the experimental component of this study. Various factors, such as the effect of different nozzle geometries and driven channel pressures, were examined. Also, a model of the shock tube was developed for computational fluid dynamics (CFD) simulations. These simulations were generated for comparison with the experimental results and to provide additional information regarding the nature of the flow behaviour.Experimental and numerical pressure-time profiles confirm the appearance of transient radial wave activity following the initial incidence of the normal shock wave on the convergence region of the nozzle. The results establish that the strength of this activity is markedly dependent upon the nozzle convergence wall angle and the location within the shock tube

scholarly journals Computational Analysis of the Pulmonary Arteries in Congenital Heart Disease: A Review of the Methods and Results

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
M. Conijn ◽  
G. J. Krings
Keyword(s):  
Congenital Heart Disease ◽  
Heart Disease ◽  
Boundary Conditions ◽  
Congenital Heart ◽  
Treatment Options ◽  
Pulmonary Arteries ◽  
Original Research ◽  
Numerical Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Definition Of

With the help of computational fluid dynamics (CFD), hemodynamics of the pulmonary arteries (PA’s) can be studied in detail and varying physiological circumstances and treatment options can be simulated. This offers the opportunity to improve the diagnostics and treatment of PA stenosis in biventricular congenital heart disease (CHD). The aim of this review was to evaluate the methods of computational studies for PA’s in biventricular CHD and the level of validation of the numerical outcomes. A total of 34 original research papers were selected. The literature showed a great variety in the used methods for (re) construction of the geometry as well as definition of the boundary conditions and numerical setup. There were 10 different methods identified to define inlet boundary conditions and 17 for outlet boundary conditions. A total of nine papers verified their CFD outcomes by comparing results to clinical data or by an experimental mock loop. The diversity in used methods and the low level of validation of the outcomes result in uncertainties regarding the reliability of numerical studies. This limits the current clinical utility of CFD for the study of PA flow in CHD. Standardization and validation of the methods are therefore recommended.

scholarly journals Swirler geometry effects (dh/do ratio) on synthetic gas flames. Part 2: dynamic flame behaviour at external y altered acoustic conditions

Energetika ◽  
2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Harun Yilmaz ◽  
Omer Cam ◽  
Ilker Yilmaz
Keyword(s):  
Boundary Conditions ◽  
Pressure Sensors ◽  
Acoustic Energy ◽  
Acoustic Boundary Conditions ◽  
Acoustic Damping ◽  
Pressure Profiles ◽  
Flame Response ◽  
Scale Variable ◽  
A Minor ◽  
Flame Behaviour

In a combustion device, unsteady heat release causes acoustic energy to increase when acoustic damping (energy loss) is not that effective, and, as a result, thermo-acoustic flame instabilities occur. In this study, effects of the swirler dh/do ratio (at different swirl numbers) on dynamic flame behaviour of the premixed 20%CNG/30%H2/30%CO/20%CO2 mixture under externally altered acoustic boundary conditions and stability limits (flashback and blowout equivalence ratios) of such mixture were investigated in a laboratory-scale variable geometric swirl number combustor. Therefore, swirl generators with different dh/do ratios (0.3 and 0.5) and geometric swirl numbers (0.4, 0.6, 0.8, 1.0 1.2 and 1.4) were designed and manufactured. Acoustic boundary conditions in the combustion chamber were altered using loudspeakers, and flame response to these conditions was perceived using photodiodes and pressure sensors. Dynamic flame behaviour of respective mixture was evaluated using luminous intensity and pressure profiles. Results showed that the dh/do ratio has a minor impact on dynamic flame behaviour.

scholarly journals Impact of Boundary Condition and Kinetic Parameter Uncertainties on NOx Predictions in Methane-Air Stagnation Flame Experiments

2021 ◽  
Author(s):  
Antoine Durocher ◽  
Jiayi Wang ◽  
Gilles Bourque ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Boundary Conditions ◽  
High Pressures ◽  
Laminar Flame ◽  
Combustion Process ◽  
Industrial Applications ◽  
Parameter Uncertainties ◽  
Nox Formation ◽  
Important Species ◽  
Spectral Expansions ◽  
Combustion Properties

Abstract A comprehensive understanding of uncertainty sources in experimental measurements is required to develop robust thermochemical models for use in industrial applications. Due to the complexity of the combustion process in gas turbine engines, simpler flames are generally used to study fundamental combustion properties and measure concentrations of important species to validate and improve modelling. Stable, laminar flames have increasingly been used to study nitrogen oxide (NOx) formation in lean-to-rich compositions in low-to-high pressures to assess model predictions and improve accuracy to help develop future low-emissions systems. They allow for non-intrusive diagnostics to measure sub-ppm concentrations of pollutant molecules, as well as important precursors, and provide well-defined boundary conditions to directly compare experiments with simulations. The uncertainties of experimentally-measured boundary conditions and the inherent kinetic uncertainties in the nitrogen chemistry are propagated through one-dimensional stagnation flame simulations to quantify the relative importance of the two sources and estimate their impact on predictions. Measurements in lean, stoichiometric, and rich methane-air flames are used to investigate the production pathways active in those conditions. Various spectral expansions are used to develop surrogate models with different levels of accuracy to perform the uncertainty analysis for 15 important reactions in the nitrogen chemistry and the 6 boundary conditions (ϕ, Tin, uin, du/dzin, Tsurf, P) simultaneously. After estimating the individual parametric contributions, the uncertainty of the boundary conditions are shown to have a relatively small impact on the prediction of NOx compared to kinetic uncertainties in these laboratory experiments. These results show that properly calibrated laminar flame experiments can, not only provide validation targets for modelling, but also accurate indirect measurements that can later be used to infer individual kinetic rates to improve thermochemical models.

Moments of the Flow Variables, Part II : The Effective Conductivity

2003 ◽  
Author(s):  
Yoram Rubin
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Effective Conductivity ◽  
Effective Property ◽  
Flow Equation ◽  
Laplace’S Equation ◽  
Flow Conditions ◽  
Laplace's Equation ◽  
Head Gradient ◽  
The Difference

Many applications require primary information such as average fluxes as a prelude to more complex calculations. In water balance calculations one may be interested only in the average fluxes. For both cases the concept of effective conductivity is useful. The effective hydraulic conductivity is defined by where the angled brackets denote the expected value operator. The local flux fluctuation is defined by the difference qi(x) — (qi(x)). Its statistical properties as well as those of the velocity will be investigated in chapter 6. To qualify as an effective property in the strict physical sense, Kef must be a function of the aquifer’s material properties and not be influenced by flow conditions such as the head gradient and boundary conditions (Landauer, 1978). Our goal in this chapter is to explore the concept of the effective conductivity Kef and to relate it to the medium’s properties under as general conditions as possible. Additionally, we shall explore the conditions where this concept is irrelevant and applicable, the important issue being that Kef is defined in an ensemble sense, but for applications we need spatial averages. Several methods for deriving Kef will be described below. The general approach for defining Kef includes the following steps. First, H is defined as an SRF and is expressed with the aid of the flow equation in terms of the hydro-geological SRFs (conductivity, mostly) and the boundary conditions. The H SRF is then substituted in Darcy’s law and an expression in the form equivalent to (5.1) is sought. If and only if the coefficient in front of the mean head gradient is not a function of the flow conditions will it qualify as Kef. The derivation of the effective conductivity employs the flow equation. In steady-state incompressible flow, for example, Laplace’s equation is employed. Solutions derived under Laplace’s equation are applicable, under appropriate conditions, for other physical phenomena governed by the same mathematical model. For example, the electrical field in steady state is also described by Laplace’s equation.

scholarly journals Comparison of Blade Element Method and CFD Simulations of a 10 MW Wind Turbine

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 73 ◽  
Author(s):  
Galih Bangga
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Separation ◽  
Spatial Interpolation ◽  
Flow Conditions ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Correction Terms ◽  
Selection Of ◽  
Blade Element

The present studies deliver the computational investigations of a 10 MW turbine with a diameter of 205.8 m developed within the framework of the AVATAR (Advanced Aerodynamic Tools for Large Rotors) project. The simulations were carried out using two methods with different fidelity levels, namely the computational fluid dynamics (CFD) and blade element and momentum (BEM) approaches. For this purpose, a new BEM code namely B-GO was developed employing several correction terms and three different polar and spatial interpolation options. Several flow conditions were considered in the simulations, ranging from the design condition to the off-design condition where massive flow separation takes place, challenging the validity of the BEM approach. An excellent agreement is obtained between the BEM computations and the 3D CFD results for all blade regions, even when massive flow separation occurs on the blade inboard area. The results demonstrate that the selection of the polar data can influence the accuracy of the BEM results significantly, where the 3D polar datasets extracted from the CFD simulations are considered the best. The BEM prediction depends on the interpolation order and the blade segment discretization.

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