Experimental Study and Computational Fluid Dynamics Modeling of Pulp Suspensions Flow in a Pipe

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Carla Cotas ◽  
Bruno Branco ◽  
Dariusz Asendrych ◽  
Fernando Garcia ◽  
Pedro Faia ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Flow Regime ◽  
Turbulent Regime ◽  
Cfd Model ◽  
Dynamics Modeling ◽  
Transition Flow ◽  
Pulp Suspensions ◽  
Transition Flow Regime

Eucalyptus and Pine suspensions flow in a pipe was studied experimentally and numerically. Pressure drop was measured for different mean inlet flow velocities. Electrical impedance tomography (EIT), was used to evaluate the prevailing flow regime. Fibers concentration distribution in the pipe cross section and plug evolution were inferred from EIT tomographic images. A modified low-Reynolds-number k–ε turbulence model was applied to simulate the flow of pulp suspensions. The accuracy of the computational fluid dynamics (CFD) predictions was significantly reduced when data in plug regime was simulated. The CFD model applied was initially developed to simulate the flow of Eucalyptus and Pine suspensions in fully turbulent flow regime. Using this model to simulate data in the plug regime leads to an excessive attenuation of turbulence which leads to lower values of pressure drop than the experimental ones. For transition flow regime, the CFD model could be applied successfully to simulate the flow data, similar to what happens for the turbulent regime.

Manufacturing and Computational Fluid Dynamics Modeling of a Patient-Specific Fistula Model

2017 ◽  
Author(s):  
Yang Liu ◽  
Yihao Zheng ◽  
John Pitre ◽  
William Weitzel ◽  
Joseph Bull ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Patient Specific ◽  
Cfd Model ◽  
Dynamics Modeling ◽  
Computational Fluid Dynamics Modeling ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Venous Wall ◽  
Good Agreement

Arteriovenous fistula is the joining of an artery to a vein to create vascular access for dialysis. The failure or maturation of fistula is affected by the vessel wall shear stress (WSS), which is difficult to measure in clinic. A computational fluid dynamics (CFD) model was built to estimate WSS of a patient-specific fistula model. To validate this model, a silicone phantom was manufactured and used to carry out a particle imaging velocimetry (PIV) experiment. The flow field from the PIV experiment shows a good agreement with the CFD model. From the CFD model, the highest WSS (40 Pa) happens near the anastomosis. WSS in the vein is larger than that in the artery. WSS on the outer venous wall is larger than that on the inner wall. The combined technique of additive manufacturing, silicone molding, and CFD is an effective tool to understand the maturation mechanism of a fistula.

Fibrous Filter Efficiency and Pressure Drop in the Viscous-Inertial Transition Flow Regime

2012 ◽  
Vol 46 (2) ◽  
pp. 138-147 ◽  
Author(s):  
J. A. Hubbard ◽  
J. E. Brockmann ◽  
J. Dellinger ◽  
D. A. Lucero ◽  
A. L. Sanchez ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Transition Flow ◽  
Fibrous Filter ◽  
Filter Efficiency ◽  
Transition Flow Regime

scholarly journals A Computational Fluid Dynamics Modeling and Experimental Study of the Mixing Process for the Dispersion of the Synthetic Fibers in Wet-Lay Forming

2008 ◽  
Vol 3 (1) ◽  
pp. 155892500800300 ◽  
Author(s):  
Melur K. Ramasubramanian ◽  
Donald A. Shiffler ◽  
Amit Jayachandran
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wire Mesh ◽  
Spherical Particles ◽  
Design Parameters ◽  
Mixing Process ◽  
Cfd Model ◽  
Discrete Phase Model ◽  
Dynamics Modeling ◽  
Synthetic Fibers

In this paper, we present results from a computational fluid dynamics (CFD) model for the mixing process used to disperse synthetic fibers in wet-lay process. We used CFD software, FLUENT, together with the MIXSIM user interface to accurately model the impeller geometry. A multiple reference frame (MRF) model and standard k-e turbulence model were used to model the problem. After obtaining a converged solution for the mixing tank with water, a discrete phase model was constructed by injecting spherical particles into the flow. A mixing tank with baffles and a centrally located impeller was used in experiments. PET fibers (1.5 denier, 6.35, 12.7, and 38.7 mm) at a concentration of 0.01% were mixed in water for the study. In regions behind the baffles, where the model predicted higher concentration of particles, experimental results showed a 34% higher concentration relative to the region in the high turbulence zone near the center. Instantaneous sheets were formed by rapidly dipping and removing a flat wire mesh strainer into the tank at two different locations to assess the state of dispersion in the tank. The sheets were transferred onto a blotting paper and examined under a microscope to count defects. Results show that the number of rope defects was 43% higher in sheets drawn from the region behind the baffles than in the sheets drawn from regions near the center of the tank. Changing baffles from a rectangular to a triangular cross section decreased the number of rope defects, but increased the number of log defects in the sample sheets at the same location. The CFD model can be used to optimize mixing tank design for wet lay fiber dispersion. The model provides further insight into the mixing process by predicting the effect of changes in design parameters on dispersion quality.

scholarly journals Computational Fluid Dynamics Model of Air Velocity through a Poultry Transport Trailer in a Holding Shed

2020 ◽  
Vol 36 (6) ◽  
pp. 963-973
Author(s):  
Christian L. Heymsfield ◽  
Yi Liang ◽  
Thomas A. Costello
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cooling System ◽  
Model Simulation ◽  
List Type ◽  
Cfd Model ◽  
Dynamics Modeling ◽  
Air Velocity ◽  
Space Module ◽  
Alternative Design

HighlightsComputational fluid dynamics modeling was an effective tool to simulate conditions on transport trailers in holding broilers for slaughter, to understand the performance of existing and alternative system configurations;Model simulation and measurements indicated that less than 32% of airflow generated by the cooling fans in the existing fan configuration in this study actually penetrated through the bird-occupied spaces;Simulations suggest that higher air velocity in the bird occupied zone within the modules can be achieved by alternative fan configurations at the holding shed, such as employing one fan per module, or with the addition of a transition enclosures from each fan outlet to the face of the receiving module. Abstract. The configuration of cooling systems in commercial holding sheds, where live broilers wait in cage modules for slaughter, varies between processing plants, with cooling system efficacies largely unknown. A computational fluid dynamics (CFD) model was developed to simulate airflow through cage modules in a poultry trailer in a typical holding shed configuration. Three alternative design configurations were simulated in order to better understand the air velocity profiles and to explore potential improvements for better cooling performance. Experimental data were collected within modules in a poultry trailer, parked in an existing commercial holding shed during warm summer conditions. Results from the CFD model had reasonable agreement with measured field data. Simulated air velocities were mostly within one standard deviation of measured values. Simulation of airflow through modules in the base configuration showed that less than 32% of airflow from the fans actually penetrated through the bird-occupied space. Module tiers experienced different airflow penetration due to the ad hoc positioning/alignment of the fans relative to the modules. In the base industry configuration, fans were in fixed positions and the number of fans and their centerline discharge axes did not align with the modules on the trailer. Regions not aligned with the faces of the fans, such as the uppermost and bottommost tiers, and horizontal locations offset from the fans, received the least airflow through the modules. Sections of modules experienced lower air velocity with increasing distance from the fans. Simulation of Design Alternative 2 (which added additional fans so that a fan was centered on each row) predicted an improved fan airflow of 3.08 and 3.05 kg s-1 through the cages in two adjacent rows, compared to 1.52 and 2.15 kg s-1 predicted for the original configuration. The increased air velocity using the alternative design illustrates the potential improvement and need to further optimize the design of these holding sheds. This research showed that a CFD model is an effective tool to simulate airflow conditions on poultry trailers in holding sheds to explore various holding shed cooling configurations and strategies. Keywords: Air velocity, CFD, Poultry Transportation, Poultry welfare.

Static Performance of Smooth Liquid Annular Seals in the Transition and Turbulent Regimes

2021 ◽  
Author(s):  
Dara W. Childs ◽  
Joshua Bullock
Keyword(s):  
Reynolds Number ◽  
Flow Regime ◽  
Operating Conditions ◽  
Radial Clearance ◽  
Turbulent Regime ◽  
Swirl Ratio ◽  
Transition Flow ◽  
Transition Flow Regime ◽  
San Andres ◽  
Annular Seals

Abstract Static test results are presented for smooth annular seals with a length-to-diameter ratio of 0.50, radius R = 51.00 mm, at the nominal radial clearance Cr = 0.2032 mm. Tests were conducted for angular shaft speeds; ω = 2, 4, 6, 8 krpm, axial pressure drops; ΔP = 2.1, 4.13, 6.21, 8.27 bars, and eccentricity ratios ϵ0 = e0/Cr = 0.00, 0.27, 0.53, 0.8 where e0 is the static eccentricity. Three pre-swirl inserts were used to target zero, medium, and high (0., 0.4, and 0.8) pre-swirl ratios for a set of pre-determined operating conditions with ISO VG 2 oil at 46.1°C. Pitot tubes measured the circumferential velocity at separate upstream and downstream seal locations and were used to calculate pre-swirl ratio, PSR = vinlet/Rω, and outlet-swirl ratio, OSR = voutlet/Rω. For all tested pre-swirl inserts, PSR tended to converge to 0.4∼0.5 as ω increased. PSR and OSR were poorly correlated. Volumetric leakage rate Q ˙ versus pressure differential ΔP was measured. The measured vector Reynolds number Re, combining the axial and circumferential Reynolds numbers ranged from ∼1000 to ∼3500. Based on Zirkelback and San Andrés 1996 publication, almost all of the flow regime is predicted to lie in the transition regime, with fewer points in the turbulent regime. Generally, the seals’ static centering properties were obtained by applying a static load Fs and measuring the resulting displacement vector e0. At many low-speed, low-ΔP test conditions, the seal would not remain in the desired centered or near-centered position and had to be forced into place with a centering force Fs. The authors believe that the observed de-centering effects resulted from test operations in the transition flow regime where the friction factor λ does not drop with increasing ΔP and increasing Re. A positive centering Lomakin effect requires that λ drop with increasing axial Reynolds number. The seals had positive centering effects over a large portion of the predicted transition flow regime, supporting the view that the shift from transition-to-turbulent flow regularly occurred at lower Re values than the Re = 3000 boundary used by Zirkleback and San Andrés.

CFD Analysis of Reversed Installation on Flow Measurements by a Plate Orifice

2019 ◽  
Author(s):  
Dezhi Zheng ◽  
Haibo Ma ◽  
Armin K. Silaen ◽  
Chenn Q. Zhou
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Drop ◽  
Orifice Plate ◽  
Cfd Analysis ◽  
Cfd Model ◽  
Flow Measurements ◽  
Significant Difference ◽  
Long Time ◽  
Computational Fluid Dynamics Cfd

Abstract The accidental reversal installation of an orifice plate could occur during maintenance operations and a long time may have elapsed before being noticed. The reversal installation can result in a significant mismeasurement of flow in a pipe. In the paper, a computational fluid dynamics (CFD) model has been developed to simulate the pressure and velocity distribution in a pipe with the correct and the reversed installation of an orifice plate. The results shown that there is a significant difference between the correct and reversed installation in terms of pressure. Using the CFD pressure drop results for flows in both installations, an estimate correlation between those installations was found. This result provides the method to solve the issue about the accidental reversal of an orifice plate using a correction factor.

scholarly journals 3D computational fluid dynamics modeling of temperature and humidity in a humidified greenhouse

2021 ◽  
Vol 13 (1) ◽  
pp. 17-31
Author(s):  
Cuauhtémoc Pérez-Vega ◽  
◽  
José Armando Ramírez-Arias ◽  
Irineo L. López-Cruz ◽  
Ramón Arteaga-Ramírez ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Ventilation ◽  
Temporal Distribution ◽  
Cfd Modeling ◽  
Cfd Model ◽  
Dynamics Modeling ◽  
Temperature And Humidity ◽  
Humidity Measurements ◽  
Computational Fluid Dynamics Cfd

Introduction: Medium and low technology greenhouses use natural ventilation as a method of temperature and humidity control. However, at certain times of the year, this is insufficient to extract excess heat inside the greenhouse, so devices such as hydrophanes (humidifiers) have been implemented to reduce the temperature. It is necessary to know the behavior of temperature and humidity, since both factors influence the development of crops and, therefore, their yield. Objective: To develop a computational fluid dynamics (CFD) model of a naturally ventilated zenithal greenhouse equipped with hydrophanes to understand the spatial and temporal distribution of temperature and humidity inside the greenhouse. Methodology: The experiment was carried out in a greenhouse equipped with hydrophanes and grown with bell pepper. Temperature and humidity measurements were performed from March 7 to 25, 2014. The ANSYS Workbench program was used for the 3D CFD modeling. Results: The CFD model satisfactorily described the temperature and humidity distribution of the greenhouse, with an error of 0.11 to 3.43 °C for temperature, and 0.44 to 10.80 % for humidity. Limitations of the study: Numerical modeling using CFD is inadequate to model the temporality of the variables. Originality: There are few studies that model humidity behavior with CFD and the use of hydrophanes in Mexico. Conclusions: The CFD model allowed visualizing the distribution of temperature and air humidity inside the greenhouse.

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