Correlations for the Choked Mass and Momentum Flux Density Considering Real-Gas Thermodynamics

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Matthias Banholzer ◽  
Michael Pfitzner
Keyword(s):  
Flux Density ◽  
Mass Flux ◽  
Momentum Flux ◽  
Second Phase ◽  
Cfd Simulations ◽  
Choked Flow ◽  
Saturation Properties ◽  
Isentropic Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Reduced Pressures

The choked mass flux density and the choked momentum flux density for the nonideal fluids methane and nitrogen have been calculated using the Soave–Redlich–Kwong equation of state (EoS). For the computation a steady, one-dimensional (1D), isenthalpic and isentropic flow is assumed. The developed algorithm for the calculation of the choked flow properties includes a bounded multidimensional Newton method. A possible second phase emerging in the critical nozzle area is excluded using the saturation properties of the considered fluids. The critical ratios of pressure, density, temperature, and speed of sound are discussed and compared to other publications. Formulations of the choked mass flux density and the choked momentum flux density explicit in Tr, pr, and Zr are given valid for different reduced pressures and temperatures depending on the fluid. Additional computational fluid dynamics (CFD) simulations are carried out in order to validate the findings of the algorithm and the proposed correlations.

scholarly journals Using CFD to Evaluate Natural Ventilation through a 3D Parametric Modeling Approach

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2197
Author(s):  
Nayara Rodrigues Marques Sakiyama ◽  
Jurgen Frick ◽  
Timea Bejat ◽  
Harald Garrecht
Keyword(s):  
Natural Ventilation ◽  
Parametric Modeling ◽  
Cfd Simulations ◽  
3D Design ◽  
Post Process ◽  
Test House ◽  
Model Set ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Passive Strategy

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

scholarly journals Dependence of the Flue Gas Flow on the Setting of the Separation Baffle in the Flue Gas Tract

2021 ◽  
Vol 11 (7) ◽  
pp. 2961
Author(s):  
Nikola Čajová Kantová ◽  
Alexander Čaja ◽  
Marek Patsch ◽  
Michal Holubčík ◽  
Peter Ďurčanský
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Negative Impact ◽  
Combustion Process ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Combustion Of Solid Fuels

With the combustion of solid fuels, emissions such as particulate matter are also formed, which have a negative impact on human health. Reducing their amount in the air can be achieved by optimizing the combustion process as well as the flue gas flow. This article aims to optimize the flue gas tract using separation baffles. This design can make it possible to capture particulate matter by using three baffles and prevent it from escaping into the air in the flue gas. The geometric parameters of the first baffle were changed twice more. The dependence of the flue gas flow on the baffles was first observed by computational fluid dynamics (CFD) simulations and subsequently verified by the particle imaging velocimetry (PIV) method. Based on the CFD results, the most effective is setting 1 with the same boundary conditions as those during experimental PIV measurements. Setting 2 can capture 1.8% less particles and setting 3 can capture 0.6% less particles than setting 1. Based on the stoichiometric calculations, it would be possible to capture up to 62.3% of the particles in setting 1. The velocities comparison obtained from CFD and PIV confirmed the supposed character of the turbulent flow with vortexes appearing in the flue gas tract, despite some inaccuracies.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

scholarly journals Rapid pivot feeding in pipefish: flow effects on prey and evaluation of simple dynamic modelling via computational fluid dynamics

2008 ◽  
Vol 5 (28) ◽  
pp. 1291-1301 ◽  
Author(s):  
Sam Van Wassenbergh ◽  
Peter Aerts
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Analytical Model ◽  
Dynamic Modelling ◽  
Head Rotation ◽  
Theoretical Models ◽  
Cfd Simulations ◽  
Deceleration Phase ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Effects

Most theoretical models of unsteady aquatic movement in organisms assume that including steady-state drag force and added mass approximates the hydrodynamic force exerted on an organism's body. However, animals often perform explosively quick movements where high accelerations are realized in a few milliseconds and are followed closely by rapid decelerations. For such highly unsteady movements, the accuracy of this modelling approach may be limited. This type of movement can be found during pivot feeding in pipefish that abruptly rotate their head and snout towards prey. We used computational fluid dynamics (CFD) to validate a simple analytical model of cranial rotation in pipefish. CFD simulations also allowed us to assess prey displacement by head rotation. CFD showed that the analytical model accurately calculates the forces exerted on the pipefish. Although the initial phase of acceleration changes the flow patterns during the subsequent deceleration phase, the accuracy of the analytical model was not reduced during this deceleration phase. Our analysis also showed that prey are left approximately stationary despite the quickly approaching pipefish snout. This suggests that pivot-feeding fish need little or no suction to compensate for the effects of the flow induced by cranial rotation.

Time-Dependent Computational Fluid Dynamics (CFD) Simulations of a Closing Blowout Preventer

2018 ◽  
Author(s):  
Daniel Barreca ◽  
Matthew Franchek ◽  
Mayank Tyagi
Keyword(s):  
Fluid Velocity ◽  
Maximum Pressure ◽  
Cfd Simulations ◽  
Environment Analysis ◽  
Erosion Rates ◽  
Velocity Magnitude ◽  
Blowout Preventer ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamic Meshing ◽  
Water Hammer Effect

Reliability of blowout preventers (BOP) is central for the safety of both rig workers and the surrounding environment. Analysis of dynamic fluid conditions within the wellbore and BOP can provide quantitative data related to this reliability. In cases of a hard shut in, it is suspected that the sudden closure of rams can cause a water hammer effect, creating pressure vibrations within the wellbore. Additionally, as the blowout preventer reaches a fully closed state, fluid velocity can drastically increase. This results in increased erosion rates within the blowout preventer. To investigate fluid movement and pressure vibrations during a well shut-in, CFD simulations will be conducted. Dynamic meshing techniques within ANSYS® FLUENT can be utilized to simulate closing blowout preventer configurations for both 2-D and 3-D geometries. These simulations would deliver information that could lead to a better understanding of certain performance issues during well shut-ins. Such information includes flow velocity magnitude within the BOP and maximum pressure pulse values within the wellbore.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

scholarly journals Probabilistic Performance Analysis of Eroded Compressor Blades

2005 ◽  
Author(s):  
A. Kumar ◽  
P. B. Nair ◽  
A. J. Keane ◽  
S. Shahpar
Keyword(s):  
Probabilistic Analysis ◽  
Surrogate Model ◽  
Uncertainty Propagation ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Compressor Blades ◽  
Geometry Modeling ◽  
Blade Section ◽  
Computational Fluid Dynamics Cfd ◽  
Fan Blade

This paper presents a probabilistic analysis of the effect of erosion on the performance of compressor fan blades. A realistic parametric CAD model is developed to represent eroded blades. Design of Experiments (DOE) techniques are employed to generate a set of candidate points, which are combined with a parametric geometry modeling and grid generation routine to produce a hybrid mesh. A multigrid Reynolds-Averaged Navier Stokes (RANS) solver HYDRA with Spalart Allmaras turbulence model is used for Computational Fluid Dynamics (CFD) simulations. The data generated is used to create a surrogate model for efficient uncertainty propagation. This method is applied to a typical Rolls Royce compressor fan blade section. Monte Carlo Simulation, using the surrogate model, is executed for the probabilistic analysis of the compressor fan blade. Results show upto 5% increase in pressure loss for the eroded compressor fan blades.

scholarly journals Catheter placement selection for convection-enhanced delivery of therapeutic agents to brain tumors

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 1415
Author(s):  
Lisa H. Antoine ◽  
Roy P. Koomullil ◽  
Timothy M. Wick ◽  
Louis B. Nabors ◽  
Ahmed K. Abdel Aal ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Tumor Volume ◽  
Therapeutic Agents ◽  
Catheter Placement ◽  
Volume Distribution ◽  
Convection Enhanced Delivery ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Magnetic Resonance Imaging Mri ◽  
Selection Of

Background: Convection-enhanced delivery (CED) of therapeutic agents to brain tumors allows clinicians to bypass the blood-brain barrier (BBB) to infuse virus therapy, biological, or chemotherapy directly into a brain tumor through convection. However, the effectiveness of infusions via CED may depend on catheter placement. Methods: This study used diffusion maps from magnetic resonance imaging (MRI) of human brain tumors and computational fluid dynamics (CFD) simulations to assess therapy volume distribution percentages based on catheter placement locations. Results: The primary outcome showed differences in volume distribution based on the catheter placement location. Total tumor volume filled ranged from 144.40 mm3 to 317.98 mm3. Percent filled of tumor volume ranged from 2.87% to 6.32%. Conclusions: The selection of the location for catheter placement using the region with the highest volume filled may provide optimal therapeutic effect.  The researchers conclude that CFD may provide guidance for catheter placement in CED of therapeutic agents.

scholarly journals Numerical simulation of the gas-liquid flow inside a horizontal static mixer

2020 ◽  
Vol 5 (2) ◽  
pp. 1-7
Author(s):  
Ryan Anugrah Putra ◽  
Akhlisa Nadiantya Aji Nugroho
Keyword(s):  
Liquid Flow ◽  
Liquid Velocity ◽  
Superficial Velocity ◽  
Static Mixer ◽  
Cfd Simulations ◽  
Mixing Behavior ◽  
Computational Fluid Dynamics Cfd ◽  
Gas Liquid Flow ◽  
Gas Layer ◽  
Superficial Liquid Velocity

The gas-liquid flow inside a horizontal static mixer was numerically investigated by using Euler-Euler Computational Fluid Dynamics (CFD) simulations. The results confirm that the liquid superficial velocity plays a significant role on the mixing behavior of the gas and liquid. The mixing behavior in this present study at a liquid superficial velocity of 0.2 m/s was the worst both axially and radially. Increasing the liquid superficial velocity significantly improve the mixing between gas and liquid. However, the unwanted gas layer still can be found at the superficial liquid velocity less than 0.8 m/s. A good mixing behavior in this study was achieved at a relatively high velocity (i.e. larger than 0.8 m/s).

scholarly journals The Aerodynamics of a Diabolo

2021 ◽  
Author(s):  
Darren Jia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Angular Momentum ◽  
Flow Pattern ◽  
High Spin ◽  
Angular Speed ◽  
Geometric Shape ◽  
Cfd Simulations ◽  
Resistive Torque ◽  
Computational Fluid Dynamics Cfd

Diabolo is a popular game in which the object can be spun at up to speeds of 5000 rpm. This high spin velocity gives the diabolo the necessary angular momentum to remain stable. The shape of the diabolo generates an interesting air flow pattern. The viscous air applies a resistive torque on the fast spinning diabolo. Through computational fluid dynamics (CFD) simulations it's shown that the resistive torque has an interesting dependence on the angular speed of the diabolo. Further, the geometric shape of the diabolo affects the dependence of torque on angular speed.

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