scholarly journals Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

2005 ◽  
Vol 219 (1) ◽  
pp. 53-67 ◽  
Author(s):  
D. A. Egarr ◽  
M. G. Faram ◽  
T O'Doherty ◽  
D. A. Phipps ◽  
N Syred
Keyword(s):  
Residence Time ◽  
Air Conditioning ◽  
Fluid Dynamic ◽  
Base Flow ◽  
Hydraulic Systems ◽  
Dynamic Prediction ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Separator ◽  
The Mean ◽  
Computational Fluid Dynamic Prediction

A hydrodynamic vortex separator (HDVS) has been modelled using computational fluid dynamics (CFD) in order to accurately determine the residence time of the fluid at the two outlets of the HDVS using a technique that was developed for use in heating, ventilation, and air conditioning (HVAC). The results have been compared with experimental data [1]. It is shown that, in using CFD, it is possible to study the response to a variety of inputs, and also to determine the mean residence time of the fluid within the separator. Although the technique used for determining the residence time was developed for use in HVAC, it is shown here to be applicable for the analysis of hydraulic systems, specifically, wastewater treatment systems.

Computational fluid dynamic prediction of the residence time of a vortex separator applied to disinfection

2005 ◽  
Vol 52 (3) ◽  
pp. 29-36 ◽  
Author(s):  
D. Egarr ◽  
M.G. Faram ◽  
T. O'Doherty ◽  
D. Phipps ◽  
N. Syred
Keyword(s):  
Fluid Dynamics ◽  
Residence Time ◽  
Air Conditioning ◽  
Fluid Dynamic ◽  
Dynamic Prediction ◽  
Disinfection Process ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Separator ◽  
The Mean ◽  
Computational Fluid Dynamic Prediction

A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

Residence time study of a hydrodynamic vortex separator applied to predicting disinfection performance

2009 ◽  
Vol 223 (3) ◽  
pp. 113-122 ◽  
Author(s):  
T O'Doherty ◽  
D A Egarr ◽  
M G Faram ◽  
I Guymer ◽  
N Syred
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Residence Time ◽  
Treated Wastewater ◽  
Time Study ◽  
Cfd Modelling ◽  
Computational Fluid Dynamics Cfd ◽  
Vortex Separator ◽  
Theoretical Performance

The fluid residence time characterization of a 3.4 m diameter hydrodynamic vortex separator (HDVS) has been carried out under laboratory conditions. Computational fluid dynamics (CFD) modelling has then been undertaken for the same conditions at which the experimental data were collected and validated against the experimental results, for which reasonable correspondence has been found. Using the results from the CFD modelling and batch inactivation results from the disinfection of secondary treated wastewater, it is shown that the theoretical performance of an HDVS as a contact vessel for disinfection can be determined and the practical applicability of an HDVS for disinfection is confirmed.

scholarly journals Turbulence Enhancement and Mixing Analysis for Multi-Inlet Vortex Photoreactor for CO2 Reduction

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2237
Author(s):  
Jesús Valdés ◽  
Jorge Luis Domínguez-Juárez ◽  
Rufino Nava ◽  
Ángeles Cuán ◽  
Carlos M. Cortés-Romero
Keyword(s):  
Residence Time ◽  
Turbulence Intensity ◽  
Mass Fraction ◽  
Fluid Dynamic ◽  
Co2 Reduction ◽  
Point Of View ◽  
Molar Ratio ◽  
Cylindrical Shape ◽  
Turbulent Regime ◽  
Computational Fluid Dynamics Cfd

In this article, we describe a prototype photoreactor of which the geometrical configuration was obtained by Genetic Algorithms to maximize the residence time of the reactant gases. A gas reaction mixture of CO2:H2O (1:2 molar ratio) was studied from the fluid dynamic point of view. The two main features of this prototype reactor are the conical shape, which enhances the residence time as compared to a cylindrical shape reference reactor, and the inlet heights and position around the main chamber that enables turbulence and mass transfer control. Turbulence intensity, mixing capability, and residence time attributes for the optimized prototype reactor were calculated with Computational Fluid Dynamics (CFD) software and compared with those from a reference reactor. Turbulence intensity near the envisioned catalytic bed was one percentage point higher in the reference than in the optimized prototype reactor. Finally, the homogeneity of the mixture was guaranteed since both types of reactors had a turbulent regime, but for the prototype the CO2 mass fraction was found to be better distributed.

Analysis of Volumetric Residence Time of Blood Elements in Stenosed Arteries

2003 ◽  
Author(s):  
M. C. Kim ◽  
C. S. Lee ◽  
C. J. Kim
Keyword(s):  
Residence Time ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Viscous Drag ◽  
Shear Stresses ◽  
Drag Forces ◽  
Area Reduction ◽  
Dynamic Factors ◽  
Recirculation Zones ◽  
Computational Fluid Dynamics Cfd

Blood flow in arteries is known to be closely related to atherosclerosis. Presence of recirculation zones, and low, high, and oscillatory wall shear stresses have been suggested to be important fluid dynamic factors causing development and progress of atherosclerosis. Our study was motivated to develop fluid mechanical indices between residence time of blood particles in arteries and atherosclerosis. In rigid models of stenosed arteries with 75% area reduction, trajectories of blood particles were numerically computed and used to determine local volumetric residence time (VRT) of platelets. The motion of particles in the model artery was computed by considering viscous drag forces between blood particles and presolved transient flow field from computational fluid dynamics (CFD). Many cardiac cycles were considered in the computation to reflect temporally accumulative characteristics of VRT in the recirculation zones. Our results showed that VRT in the recirculation zone was relatively low in the first cardiac cycle. However it increased in the subsequent cycles as more particles were trapped in the same zone. The results suggested that VRT contour calculated in the present study would be an effective indicator of the presence of atherosclerosis.

Performance of lamella clarifiers for juice and syrup clarification

2017 ◽  
pp. 144-150
Author(s):  
Peter W. Rein ◽  
M. Getaz ◽  
A. Raghunandan ◽  
N. du Pleissis ◽  
H. Saleh ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Characteristics ◽  
Preliminary Test ◽  
Practical Experience ◽  
Operating Costs ◽  
Capital Costs ◽  
Computational Fluid Dynamics Cfd ◽  
Improved Performance ◽  
Work Done ◽  
Good Flow

A new design for syrup and juice clarifiers is presented. The design takes advantage of the considerably improved performance of clarifiers incorporating lamella plates, and the reasons for the improvement are outlined. Computational fluid dynamics (CFD) work done to simulate the performance is summarised. This design enables the residence time to be dramatically reduced and the simplified design leads to cheaper and better clarifiers. Practical experience with factory scale units is described, confirming the good flow characteristics. The results of preliminary test work on a factory syrup clarifier are presented, which is also shown to operate efficiently as a phosphatation clarifier. In addition the performance of a full-scale juice clarifier has been evaluated and compared with the performance of a Rapidorr clarifier. This work confirms the considerable advantages which this type of design provides, in realising substantial reductions in residence time, capital costs and operating costs.

Precipitation and filtration of zinc, magnesium, copper and aluminium hydroxides

1982 ◽  
Vol 47 (12) ◽  
pp. 3362-3370
Author(s):  
Otakar Söhnel ◽  
Eva Matějčková
Keyword(s):  
Residence Time ◽  
Mean Residence Time ◽  
Filtration Resistance ◽  
Filtration Pressure ◽  
Bed Porosity ◽  
The Mean ◽  
Filtration Properties

Filtration properties of batchwise precipitated suspensions of Zn(OH)2, Mg(OH)2 and Cu(OH)2 and continuously precipitated Al(OH)3 were studied. For batchwise precipitated suspensions was verified the theoretically predicted dependence of specific filtration resistance on initial supersaturation and for the continuously precipitated Al(OH)3 the relation between the specific filtration resistance and the mean residence time of suspension in the reactor. Dependences were also recorded between the bed porosity and concentration of precipitated solutions, specific filtration resistance and used filtration pressure and the effect of aging of the batchwise precipitated suspension of Mg(OH)2on its filtration properties. The used CST method for determination of filtration characteristics of Zn(OH)2 suspension was also studied.

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

Nitrogen use efficiency: does a trade-off exist between the N productivity and the mean residence time within species?

2008 ◽  
Vol 56 (3) ◽  
pp. 272 ◽  
Author(s):  
Zhi Y. Yuan ◽  
Han Y. H. Chen ◽  
Ling H. Li
Keyword(s):  
Residence Time ◽  
Nitrogen Use Efficiency ◽  
Mean Residence Time ◽  
Negative Relationship ◽  
Controlled Experiments ◽  
Nitrogen Use ◽  
Trade Off ◽  
N Supply ◽  
Use Efficiency ◽  
The Mean

Nitrogen use efficiency (NUE) can be divided into two components, i.e. N productivity (A) and the mean residence time (MRT). Controlled experiments indicate that there is not a trade-off between A and MRT within species, but this theory has not been well tested in field conditions. Here, we studied the A, MRT and NUE of Stipa krylovii Roshev. in a grassland over 4 years of N fertilisation experimentation. The three parameters (A, MRT and NUE) were significantly related to soil N supply and there was a negative relationship between A and MRT within this species (r = –0.775, P < 0.05), i.e. plants with higher A had lower MRT. Our results showed a trade-off between A and MRT within this Stipa species and this observed trade-off was attributed to different responses of A and MRT to soil fertility.

scholarly journals Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Makoto Gozawa ◽  
Yoshihiro Takamura ◽  
Tomoe Aoki ◽  
Kentaro Iwasaki ◽  
Masaru Inatani
Keyword(s):  
Cfd Simulation ◽  
Simulation Analysis ◽  
Fluid Dynamic ◽  
Fluid Analysis ◽  
Intraocular Gas ◽  
Pars Plana ◽  
Computational Fluid Dynamics Cfd ◽  
Multiple Breaks ◽  
Gas Volume ◽  
Wall Wettability

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

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