scholarly journals Synchronized Multiple Drop Impacts into a Deep Pool

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 141 ◽  
Author(s):  
Manfredo Guilizzoni ◽  
Maurizio Santini ◽  
Stephanie Fest-Santini
Keyword(s):  
Fluid Dynamics ◽  
High Speed ◽  
Laboratory Experiments ◽  
Distilled Water ◽  
Single Drop ◽  
Two Phase ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Drop Impacts ◽  
The Impact

Drop impacts (onto dry or wet surfaces or into deep pools) are important in a wide range of applications, and, consequently, many studies, both experimental and numerical, are available in the literature. However, such works are focused either on statistical analyses of drop populations or on single drops. The literature is heavily lacking in information about the mutual interactions between a few drops during the impact. This work describes a computational fluid dynamics (CFD) study on the impact of two, three, and four synchronized drops into a deep pool. The two-phase finite-volume solver interFoam of the open source CFD package OpenFOAM® was used. After validation with respect to high speed videos, to confirm the performance of the solver in this field, impact conditions and aspects that would have been difficult to obtain and to study in experiments were investigated: namely, the energy conversion during the crater evolution, the effect of varying drop interspace and surface tension, and multiple drop impacts. The results show the very significant effect of these aspects. This implies that an extension of the results of single-drop, distilled-water laboratory experiments to real applications may not be reliable.

CFD Modelling of Multiphase Flows: An Overview

2003 ◽  
Author(s):  
Rajnish K. Calay ◽  
Arne E. Holdo
Keyword(s):  
Fluid Dynamics ◽  
Mass Transfer ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Mathematical Models ◽  
Cfd Modelling ◽  
Two Phase ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Modeling Of Flows

The Computational Fluid Dynamics (CFD) is now increasingly being used for modeling industrial flows, i.e. flows which are multiphase and turbulent. Numerical modeling of flows where momentum, heat and mass transfer occurs at the interface presents various difficulties due to the wide range of mechanisms and flow scenarios present. This paper attempts to provide a summary of available mathematical models and techniques for two-phase flows. Some comments are also made on the models available in the commercially available codes.

CFD Analysis of the Behavior of Airborne Allergens in Carpeted and Uncarpeted Dwellings

2002 ◽  
Author(s):  
Bradley A. Cicciarelli ◽  
David L. Davidson ◽  
Edward H. Hart ◽  
P. Robert Peoples
Keyword(s):  
Fluid Dynamics ◽  
Quantitative Data ◽  
Transient Behavior ◽  
Particle Dynamics ◽  
Government Officials ◽  
Carpet Industry ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Airborne Allergens

There is considerable concern today over indoor air quality (IAQ). The factors that influence IAQ may be numerous, and there is considerable research aimed at quantifying these factors. This research is of particular interest to industries that manufacture products used in residential and commercial dwellings, such as the carpet industry. With respect to carpet, there are various opinions about its role in IAQ, but little quantitative data. Much of the quantitative data that does exist either ignores or makes crude assumptions about the influence of fluid dynamics on the experimental observations. In this paper we discuss our use of Computational Fluid Dynamics (CFD) to model the transient behavior of airborne particles in dwellings with and without carpeted floors to quantify the impact of floor covering on IAQ. In particular, we discuss the theoretical considerations that are required to construct an accurate and practical CFD model that captures the correct fluid and particle dynamics, and present and summarize CFD predictions that account for the effects of HVAC systems, room geometry and virtual objects, such as people moving about the dwelling. In addition to getting the fluid and particle dynamics correct, there are two additional aspects of this problem that will be discussed. First, in order to draw reasonable conclusions about IAQ, a large number of simulations are required to capture the wide range of realistic dwelling conditions of interest. In order to perform these simulations in a timely manner, the process of building and meshing the geometry, specifying all relevant room conditions, conducting the simulation and interrogating the results has been automated by constructing a Digital Expert for the problem, wherein the user can automatically complete these tasks with little CFD expertise and no intervention. Second, it is essential to communicate the results of these simulations to lay audiences — the wide range of people interested in IAQ, including school boards, politicians and other government officials. We have developed a means of generating “Hollywood grade” animations that are more realistic in appearance than conventional CFD animations, and consequently more appealing and more readily understandable, but that reflect the correct fluid and particle dynamics. We believe that the integration of CFD with realistic animation capability will see greater applicability as our society becomes increasingly dependent on technology and decreasingly technically literate.

The Effect of Turbulence and Real Gas Models on the Two Phase Spontaneously Condensing Flows in Nozzle

2013 ◽  
Author(s):  
Yogini Patel ◽  
Giteshkumar Patel ◽  
Teemu Turunen-Saaresti
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Two Phase ◽  
Real Gas ◽  
Spontaneous Condensation ◽  
Condensing Flows ◽  
Computational Fluid Dynamics Cfd

The aim of the paper is to analyse the effect of turbulence and real gas models on the process of spontaneous condensation in converging diverging (CD) nozzle by using commercial Computational Fluid Dynamics (CFD) code. The calculations were based on the 2-D compressible Navier-Stokes (NS) equations coupled with two-equation turbulence model, and the non-equilibrium spontaneous condensing steam flow was solved on the basis of the classical nucleation theory. The results were validated to the available experimental data.

scholarly journals Computational Fluid Dynamics (CFD) as a tool for the analysis of ventilation and indoor microclimate in agricultural buildings

1997 ◽  
Vol 45 (1) ◽  
pp. 81-96 ◽  
Author(s):  
A. Mistriotis ◽  
T. De Jong ◽  
M.J.M. Wagemans ◽  
G.P.A. Bot
Keyword(s):  
Fluid Dynamics ◽  
Laboratory Experiments ◽  
Numerical Technique ◽  
Design Tool ◽  
Indoor Climate ◽  
Pressure Coefficients ◽  
Computational Fluid Dynamics Cfd ◽  
Basic Concepts ◽  
Experimental Values ◽  
Broiler House

The basic concepts of CFD are presented in relation to applications in modelling the ventilation process and the resulting indoor climate of agricultural buildings. The validity and the advantages of this numerical technique are presented using 3 examples. Firstly the pressure coefficients along the roof of a 7-span Venlo-type greenhouse were calculated and compared with the corresponding experimental values. Next, the ventilation process in a single-span greenhouse was investigated and the results were compared to laboratory experiments. Finally, the use of CFD as a design tool for more efficient ventilation systems was demonstrated for the case of a broiler house.

scholarly journals The Protect Air Film of an Exterior Window

2021 ◽  
Author(s):  
Sanaz Dianat
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Glass Temperature ◽  
Experimental Procedure ◽  
Wind Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
Air Film ◽  
The Impact

The research paper investigates the impact of a window’s exterior air film on the assembly temperature. The exterior air film constitutes a vital portion of a window’s insulating values. The air film increases the temperature of the window exterior pane to a temperature above ambient temperature. The air film also rises the interior glass temperature and reduces the heat transfer from the interior surface. According to computational fluid dynamics (CFD), the air film is removed in windy conditions, decreasing the window temperature on the outside as well as on the inside. The idea behind the project is to carry out an experimental procedure on three different windows to validate the CFD results, which indicates the effect of various wind speeds. Keyword: Exterior air film, computational fluid dynamics, window assembly, wind speed

scholarly journals The Protect Air Film of an Exterior Window

2021 ◽  
Author(s):  
Sanaz Dianat
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Glass Temperature ◽  
Experimental Procedure ◽  
Wind Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
Air Film ◽  
The Impact

The research paper investigates the impact of a window’s exterior air film on the assembly temperature. The exterior air film constitutes a vital portion of a window’s insulating values. The air film increases the temperature of the window exterior pane to a temperature above ambient temperature. The air film also rises the interior glass temperature and reduces the heat transfer from the interior surface. According to computational fluid dynamics (CFD), the air film is removed in windy conditions, decreasing the window temperature on the outside as well as on the inside. The idea behind the project is to carry out an experimental procedure on three different windows to validate the CFD results, which indicates the effect of various wind speeds. Keyword: Exterior air film, computational fluid dynamics, window assembly, wind speed

scholarly journals Modeling the Separation of Microorganisms in Bioprocesses by Flotation

2018 ◽  
Author(s):  
Stefan Schmideder ◽  
Christoph Kirse ◽  
Julia Hofinger ◽  
Sascha Rollié ◽  
Heiko Briesen
Keyword(s):  
Fluid Dynamics ◽  
Separation Efficiency ◽  
Algebraic Model ◽  
Balance Model ◽  
Separation Processes ◽  
Dissolved Air Flotation ◽  
Computational Fluid Dynamics Cfd ◽  
Cell Size Distributions ◽  
Fermentation Broths ◽  
The Impact

Bioprocesses for the production of renewable energies and materials lack efficient separation processes for the utilized microorganisms such as algae and yeasts. Dissolved air flotation (DAF) and microflotation are promising approaches to overcome this problem. The efficiency of these processes depends on the ability of microorganisms to aggregate with microbubbles in the flotation tank. In this study, different new or adapted aggregation models for microbubbles and microorganisms are compared and investigated for their range of suitability to predict the separation efficiency of microorganisms from fermentation broths. The complexity of the heteroaggregation models range from an algebraic model to a 2D population balance model (PBM) including the formation of clusters containing several bubbles and microorganisms. The effect of bubble and cell size distributions on the flotation efficiency is considered by applying PBMs, as well. To determine the impact of the model assumptions, the modeling approaches are compared and classified for their range of applicability. Evaluating computational fluid dynamics (CFD) of a DAF system shows the heterogeneity of the fluid dynamics in the flotation tank. Since analysis of the streamlines of the tank show negligible backmixing, the proposed aggregation models are coupled to the CFD data by applying a Lagrangian approach.

Comparison of four types of membrane bioreactor systems in terms of shear stress over the membrane surface using computational fluid dynamics

2013 ◽  
Vol 68 (12) ◽  
pp. 2534-2544 ◽  
Author(s):  
N. Ratkovich ◽  
T. R. Bentzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Two Phase Flow ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Phase Flow ◽  
Two Phase ◽  
Computational Fluid Dynamics Cfd

Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement, which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be greatly improved with a two-phase flow (sludge–air) or higher liquid cross-flow velocities. However, the optimization process of these systems is complex and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop and optimize these systems.

Computational Fluid Dynamics (CFD) Study of the 4th Generation Prototype of a Continuous Flow Ventricular Assist Device (VAD)

2004 ◽  
Vol 126 (2) ◽  
pp. 180-187 ◽  
Author(s):  
Xinwei Song ◽  
Houston G. Wood ◽  
Don Olsen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Ventricular Assist Device ◽  
Continuous Flow ◽  
Surrounding Tissue ◽  
Assist Device ◽  
Ventricular Assist ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd

The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.

Flow conditions in the grooves of a Low-Consistency refiner

2012 ◽  
Vol 27 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Lisa Prahl Wittberg ◽  
Magnus Björkman ◽  
Gohar Khokhar ◽  
Ulla-Britt Mohlin ◽  
Anders Dahlkild
Keyword(s):  
Fluid Dynamics ◽  
Flow Pattern ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Conditions ◽  
Shear Forces ◽  
High Speed Imaging ◽  
Newtonian Flows ◽  
Computational Fluid Dynamics Cfd ◽  
Vortical Motion

Abstract The flow pattern in the grooves plays a major role for the homogeneity of refining as well as for the transfer and loading of fiber flocs in refining position on the bar edges. However, it is an area where very little information is available. In the present study, flow conditions in the grooves in a Low-Consistency (LC) - disc refiner were studied both experimentally and numerically. The experimental study involved high-speed imaging through a 3 cm peephole into a commercial refiner. The Computational Fluid Dynamics (CFD) simulation focused on the flow condition in a radial groove, considering both Newtonian and non-Newtonian flows. Flow conditions for stator and rotor grooves were modeled along the groove at different angular speeds and pressure differences over the refiner. Both the experimental and the modeling results show a dual flow pattern in the grooves; a rotational/spiral movement at the top of the groove and a flow in the direction of the groove at the bottom, which to the authors knowledge has not been reported in literature. The strong vortical motion at the top of the grooves observed both for the rotor and the stator are believed to be important for placing the fibers onto the bar edges and to induce shear forces in such a way that the fibers get treated. Moreover, a large sensitivity to suspension properties in terms of the development of flow pattern was detected.

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