A Fundamental Approach to Modeling Transport to an Impinging Spray

2007 ◽  
Author(s):  
Andrea C. Ashwood ◽  
Curtis Lane ◽  
Benjamin M. Regner ◽  
Timothy A. Shedd
Keyword(s):  
Numerical Model ◽  
Liquid Film ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Integrated Approach ◽  
Mean Velocity ◽  
Modeling Transport ◽  
Volume Of Fluid Model ◽  
The Mean ◽  
Impinging Sprays

This work presents an integrated approach to the modeling of the liquid film resulting from spray impingement. First, fundamental, micro-scale behaviors within the liquid film are investigated with a CFD simulation using a volume-of-fluid model. The mean velocity profile in the liquid film created by a stream of impacting droplets in this simulation are extracted and non-dimensionalized, and then used in the integral conservation equations for mass and momentum in the liquid film to create a 1-D numerical model of the system. An experiment is designed to obtain mean shear stress due to impinging sprays/jets, and the results are compared with the numerical model. Excellent agreement is observed using just one fitting parameter in the numerical model, and this fitting parameter appears to take on physically relevant values.

Abstract 1122‐000014: Effects of Patient‐Specific Blood Properties and Inflow Conditions on Hemodynamics in Cerebral Aneurysms

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Yuya Uchiyama ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Takashi Suzuki ◽  
Yuma Yamanaka ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Parent Artery ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Visual Evaluation ◽  
The Mean ◽  
Inflow Conditions

Introduction : Computational Fluid Dynamics (CFD) simulation is an effective tool to investigate pathologies and clinical outcomes of cerebral aneurysms from the hemodynamic perspective. However, simulation conditions such as the blood properties and boundary conditions are usually referred to in the literature do not consider patient‐specific values. In this study, we measured blood properties and extracted the inflow conditions from four‐dimensional digital subtraction angiography (4D‐DSA) images for patients who underwent flow diverter (FD) deployment. Then, we conducted CFD simulations considering the deployed FD geometry to investigate the effect of patient‐specific conditions on aneurysmal hemodynamics. Methods : We took whole blood samples of five patients with intracranial aneurysms just before the surgery and measured the blood density and viscosity with a densitometer and a falling needle rheometer. The patients underwent 4D‐DSA imaging, from which we calculated the patient‐specific inflow velocity of each patient using an in‐house flow extraction program. We used in‐house virtual FD deployment software to reproduce the FD geometry for each patient. We then defined the computational domain including the FD geometry. Four CFD simulations were performed for each of the five patients: (1) a steady CFD simulation under a referred Newtonian blood model and previously published inflow conditions as a basic simulation pattern (2) a CFD simulation including the patient‐specific non‐Newtonian blood properties only, (3) a CFD simulation including the inflow conditions only, and (4) a CFD simulation including both the patient‐specific blood properties and inflow conditions. We calculated the mean velocity in the aneurysm normalized by the mean velocity in the parent artery and the wall shear stress (WSS) of the aneurysm. We compared the results of the four CFD simulations and calculated their differences based on the values for the basic simulation pattern. Results : Based on the visual evaluation, the flow structures of the four CFD simulation patterns differed only slightly from each other, but a quantitative comparison revealed that there were large differences in the hemodynamic parameters. For the velocity, there was an average 14.2% difference with the steady CFD simulation results when the patient‐specific blood properties are considered, and an average 35.8% difference when the patient‐specific inflow conditions are considered. There was an average 60.7% difference when both the patient‐specific blood properties and inflow conditions are taken into account. For the WSS, there was an average 8.75% difference when including the patient‐specific blood properties and an average 66.8% difference in including the patient‐specific inflow conditions. There was an average 69.3% difference in including both conditions are considered. It appeared that the effect of including patient‐specific inflow conditions was more substantial than that of including the patient‐specific blood properties, and most robust when both conditions were included. Conclusions : The hemodynamics obtained from CFD simulations with the deployed FD appears to strongly depend on both the blood properties and the inflow conditions. This result implies that CFD simulations with the referred conditions may not accurately reproduce the hemodynamics. It was confirmed that patient‐specific conditions should be included in CFD simulations.

Analysis of Numerical Simulation on Near Surface Beneath Clean and Contaminated Small-Scale Wind-Driven Water Waves

2007 ◽  
Author(s):  
Xiaoxia Hu ◽  
Ali Dolatabadi ◽  
Kamran Siddiqul
Keyword(s):  
Numerical Model ◽  
Water Waves ◽  
Numerical Study ◽  
Surface Region ◽  
Surface Flow ◽  
Small Scale ◽  
Mean Velocity ◽  
Near Surface ◽  
The Mean ◽  
Good Agreement

We report on a numerical study conducted to investigate the near-surface flow beneath clean and contaminated small-scale wind-driven water surfaces. The numerical model is validated in terms of the velocity and surface wave characteristics. A good agreement is observed between the experimental and numerical values. The results from the numerical model show that the mean velocity in the near-surface region is 25–50% higher beneath the contaminated surface as compared to the clear surface. The present trend is also in agreement with the previous experimental observations.

CFD Simulation Gas-Liquid Flow in a Copper Converter with Bottom Air Injection

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Jesus Gonzalez ◽  
Cesar Real ◽  
Manuel Palomar-Pardave ◽  
Luis Hoyos ◽  
Marco Gutierrez ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Horizontal Cylinder ◽  
Copper Matte ◽  
Inlet Velocity ◽  
Air Inlet ◽  
Volume Of Fluid Model ◽  
Gas Liquid Flow ◽  
Bottom Injection

Peirce-Smith converters (PSC) are chemical reactors where copper matte reacts with air. A conventional PSC is a long horizontal cylinder where air is injected laterally into the cooper bath through submerged tuyeres. In these PSC, air is injected at high velocities to obtain an adequate mixing of the copper bath and to avoid tuyere blockage. An alternative PSC configuration uses top blowing of air accompanied by gentle nitrogen bottom stirring. In this work, the direct bottom injection of air at low inlet velocity was studied by means of transient multiphase 3D CFD numerical simulations considering three blowing conditions. The ?-? turbulence model and the volume of fluid model (VOF) were used in order to model the turbulent nature of the flow and to deal with the multiphase flow. Special attention was paid to the air bubbles formation and its effect on the copper bath mixing. The dynamic behavior of turbulent kinetic energy and the average velocity of the copper matte were analyzed. The numerical simulations suggest that the relationship between air inlet velocity and bath mixing is non linear. However, using the air bottom injection at low velocities, the obtained copper bath nominal velocity is similar to that reported in a conventional PSC.

scholarly journals Nonlinear Fluid Models for Biofluid Flow in Constricted Blood Vessels under Body Accelerations: A Comparative Study

2012 ◽  
Vol 2012 ◽  
pp. 1-27
Author(s):  
D. S. Sankar ◽  
Atulya K. Nagar
Keyword(s):  
Flow Rate ◽  
Fluid Model ◽  
Plug Flow ◽  
Casson Fluid ◽  
Fluid Models ◽  
Mean Flow ◽  
Mean Velocity ◽  
Casson Fluid Model ◽  
The Mean ◽  
Nonlinear Fluid

Pulsatile flow of blood in constricted narrow arteries under periodic body acceleration is analyzed, modeling blood as non-Newtonian fluid models with yield stress such as (i) Herschel-Bulkley fluid model and (ii) Casson fluid model. The expressions for various flow quantities obtained by Sankar and Ismail (2010) for Herschel-Bulkley fluid model and Nagarani and Sarojamma (2008), in an improved form, for Casson fluid model are used to compute the data for comparing these fluid models. It is found that the plug core radius and wall shear stress are lower for H-B fluid model than those of the Casson fluid model. It is also noted that the plug flow velocity and flow rate are considerably higher for H-B fluid than those of the Casson fluid model. The estimates of the mean velocity and mean flow rate are considerably higher for H-B fluid model than those of the Casson fluid model.

scholarly journals Numerical Study of Particle Interaction in Gas-Particle and Liquid-Particle Flows: Part II Particle Response

2009 ◽  
Vol 1 (3) ◽  
pp. 245-262
Author(s):  
K. Mohanarangam ◽  
J. Y. Tu
Keyword(s):  
Numerical Model ◽  
Numerical Study ◽  
Particle Interaction ◽  
Stokes Number ◽  
Steady Increase ◽  
Liquid Particle ◽  
Mean Velocity ◽  
Subsequent Increase ◽  
The Mean ◽  
Inlet Conditions

In this paper the numerical model, which was presented in the first paper (Mohanarangam & Tu; 2009) of this series of study, is employed to study the different particle responses under the influence of two carrier phases namely the gas and the liquid. The numerical model takes into consideration the turbulent behaviour of both the carrier and the dispersed phases, with additional equations to take into account the combined fluid particle behaviour, thereby effecting a two-way coupling. The first paper in this series showed the distinct difference in particulate response both at the mean as well as at the turbulent level for two varied carrier phases. In this paper further investigation has been carried out over a broad range of particle Stokes number to further understand their behaviour in turbulent environments. In order to carry out this prognostic study, the backward facing step geometry of Fessler and Eaton (1999) has been adopted, while the inlet conditions for the carrier as well as the particle phases correspond to that of the experiments of Founti and Klipfel (1998). It is observed that at the mean velocity level the particulate velocities increased with a subsequent increase in the Stokes number for both the GP (Gas-Particle) as well as the LP (Liquid-Particle) flow. It was also observed that across the Stokes number there was a steady increase in the particulate turbulence for the GP flows with successive increase in Stokes number. However, for the LP flows, the magnitude of the increase in the particulate turbulence across the increasing of Stokes number is not as characteristic as the GP flow. Across the same sections for LP flows the majority of the trend shows a decrease after which they remain more or less a constant.

The flow of liquid in a stream from the standard turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Ivan Fořt ◽  
Hans-Otto Möckel ◽  
Jan Drbohlav ◽  
Miroslav Hrach
Keyword(s):  
Reynolds Number ◽  
Kinematic Viscosity ◽  
Momentum Flux ◽  
Relative Size ◽  
Mean Velocity ◽  
Axial Profile ◽  
The Mean ◽  
Hot Film ◽  
Turbine Impeller

Profiles of the mean velocity have been analyzed in the stream streaking from the region of rotating standard six-blade disc turbine impeller. The profiles were obtained experimentally using a hot film thermoanemometer probe. The results of the analysis is the determination of the effect of relative size of the impeller and vessel and the kinematic viscosity of the charge on three parameters of the axial profile of the mean velocity in the examined stream. No significant change of the parameter of width of the examined stream and the momentum flux in the stream has been found in the range of parameters d/D ##m <0.25; 0.50> and the Reynolds number for mixing ReM ##m <2.90 . 101; 1 . 105>. However, a significant influence has been found of ReM (at negligible effect of d/D) on the size of the hypothetical source of motion - the radius of the tangential cylindrical jet - a. The proposed phenomenological model of the turbulent stream in region of turbine impeller has been found adequate for values of ReM exceeding 1.0 . 103.

The dominant frequency analysis of interfacial wave in wet-gas pipeline transportation based on NIR absorption

2021 ◽  
pp. 1-10
Author(s):  
Zhiyue Zhao ◽  
Ning Zhao ◽  
Lide Fang ◽  
Xiaoting Li
Keyword(s):  
Liquid Film ◽  
Predictive Accuracy ◽  
Film Surface ◽  
Dominant Frequency ◽  
Wave Frequency ◽  
Interfacial Wave ◽  
Long Distance ◽  
Wet Gas ◽  
The Mean ◽  
Predictive Correlation

During the long-distance transportation of wet-gas, the dominant frequency is of great significance for the study of pipeline fatigue and damage, and the safety production. Therefore, the theoretical and experimental researches for dominant frequency are carried out increasingly. However, most of the current prediction correlation of dominant frequency are mainly applicable to atmospheric pressure conditions (0.1 MPa), and the prediction accuracy is not accurate enough. The paper obtains the time series signal of liquid film thickness by near-infrared (NIR) sensor, and then calculates the wave frequency by the power spectrum density (PSD). The performance of typical predictive correlation is evaluated and analyzed by utilizing the experimental data at different flow and pressure conditions (0.1–0.8) MPa. The structure of Strouhal number and Lockhart-Martinelli (L-M) parameter are optimized reasonably, the mean velocity of the liquid film surface, the density increment of gas core, the gas core mass flow and average liquid film velocity are considered in the L-M parameter, a modified interfacial wave frequency correlation is proposed. The results indicate that the mean absolute error of the predictive correlation is 9.06% (current data) and 25.64% (literature data). The new correlation has a better predictive accuracy.

scholarly journals The mean velocity of posterior cerebral artery and basilar artery in Parkinson's disease with sleep disorders

2021 ◽  
Vol 4 ◽  
pp. 100207
Author(s):  
Muhammad Iqbal Basri ◽  
Ida Farida ◽  
Yudy Goysal ◽  
Jumraini Tammasse ◽  
Muhammad Akbar
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Sleep Disorders ◽  
Cerebral Artery ◽  
Basilar Artery ◽  
Posterior Cerebral Artery ◽  
Mean Velocity ◽  
The Mean

scholarly journals Effect of Mean Velocity-to-Critical Velocity Ratios on Bed Topography and Incipient Motion in a Meandering Channel: Experimental Investigation

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 883
Author(s):  
Nargess Moghaddassi ◽  
Seyed Habib Musavi-Jahromi ◽  
Mohammad Vaghefi ◽  
Amir Khosrojerdi
Keyword(s):  
Experimental Investigation ◽  
Critical Velocity ◽  
Velocity Ratio ◽  
Scour Depth ◽  
Incipient Motion ◽  
Mean Velocity ◽  
Straight Path ◽  
Meandering Channel ◽  
Bed Topography ◽  
The Mean

As 180-degree meanders are observed in abundance in nature, a meandering channel with two consecutive 180-degree bends was designed and constructed to investigate bed topography variations. These two 180-degree mild bends are located between two upstream and downstream straight paths. In this study, different mean velocity-to-critical velocity ratios have been tested at the upstream straight path to determine the meander’s incipient motion. To this end, bed topography variations along the meander and the downstream straight path were addressed for different mean velocity-to-critical velocity ratios. In addition, the upstream bend’s effect on the downstream bend was investigated. Results indicated that the maximum scour depth at the downstream bend increased as a result of changing the mean velocity-to-critical velocity ratio from 0.8 to 0.84, 0.86, 0.89, 0.92, 0.95, and 0.98 by, respectively, 1.5, 2.5, 5, 10, 12, and 26 times. Moreover, increasing the ratio increased the maximum sedimentary height by 3, 10, 23, 48, 49, and 56 times. The upstream bend’s incipient motion was observed for the mean velocity-to-critical velocity ratio of 0.89, while the downstream bend’s incipient motion occurred for the ratio of 0.78.

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