Verification strategies for fluid-based plasma simulation models
NASA Astrophysics Data System (ADS)
Mahadevan, Shankar
2012-10-01
Verification is an essential aspect of computational code development for models based on partial differential equations. However, verification of plasma models is often conducted internally by authors of these programs and not openly discussed. Several professional research bodies including the IEEE, AIAA, ASME and others have formulated standards for verification and validation (V&V) of computational software. This work focuses on verification, defined succinctly as determining whether the mathematical model is solved correctly. As plasma fluid models share several aspects with the Navier-Stokes equations used in Computational Fluid Dynamics (CFD), the CFD verification process is used as a guide. Steps in the verification process: consistency checks, examination of iterative, spatial and temporal convergence, and comparison with exact solutions, are described with examples from plasma modeling. The Method of Manufactured Solutions (MMS), which has been used to verify complex systems of PDEs in solid and fluid mechanics, is introduced. An example of the application of MMS to a self-consistent plasma fluid model using the local mean energy approximation is presented. The strengths and weaknesses of the techniques presented in this work are discussed.
Modeling of Magma Dynamics Based on Two-Fluid Hydrodynamics
NASA Astrophysics Data System (ADS)
Perepechko, Y. V.; Sorokin, K.
2012-12-01
Multi-velocity multi-porous models are often used as a hydrodynamic basis to describe dynamics of fluid-magma systems. These models cover such problems as fast acoustic processes or large-scaled dynamics of magma systems having non-compressible magma. Nonlinear dynamics of magma as multiphase compressible medium has not been studied sufficiently. In this work we study nonlinear thermodynamically consistent two-liquid model of magma system dynamics, based on conservation law method. The model is restricted by short times of local heat balance between phases. Pressure balance between phases is absent. Two-fluid magma model have various rheological properties of the composing phases: viscous liquid and viscoelastic Maxwell medium. The dynamics of magna flows have been studied for two types of magma systems: magma channels and intraplate intermediate magma chambers. Numerical problem of the dynamics for such media is solved using the control volume method ensuring physical correctness of the solution. The solutions are successfully verified for benchmark one-velocity models. In this work we give the results of numerical modeling using CVM for a number of non-stationary problems of nonlinear liquid filtering through granulated medium in magma channels and problems two-liquid system convection in intraplate magma chambers for various parameters. In the last case the convection regimes vary depending on non-dimensional Rayleigh and Darcy numbers and the parameter field, where compressibility effects appear, is located. The given model can be used as a hydrodynamic basis to model the evolution of magma, fluid-magma systems to study thermo-acoustic influence on hydrodynamic flows in such systems. This work was financially supported by the Russian Foundation for Basic Research, Grant #12-05-00625.
Kelly, Sinead; O'Rourke, Malachy
2012-04-01
This article describes the use of fluid, solid and fluid-structure interaction simulations on three patient-based abdominal aortic aneurysm geometries. All simulations were carried out using OpenFOAM, which uses the finite volume method to solve both fluid and solid equations. Initially a fluid-only simulation was carried out on a single patient-based geometry and results from this simulation were compared with experimental results. There was good qualitative and quantitative agreement between the experimental and numerical results, suggesting that OpenFOAM is capable of predicting the main features of unsteady flow through a complex patient-based abdominal aortic aneurysm geometry. The intraluminal thrombus and arterial wall were then included, and solid stress and fluid-structure interaction simulations were performed on this, and two other patient-based abdominal aortic aneurysm geometries. It was found that the solid stress simulations resulted in an under-estimation of the maximum stress by up to 5.9% when compared with the fluid-structure interaction simulations. In the fluid-structure interaction simulations, flow induced pressure within the aneurysm was found to be up to 4.8% higher than the value of peak systolic pressure imposed in the solid stress simulations, which is likely to be the cause of the variation in the stress results. In comparing the results from the initial fluid-only simulation with results from the fluid-structure interaction simulation on the same patient, it was found that wall shear stress values varied by up to 35% between the two simulation methods. It was concluded that solid stress simulations are adequate to predict the maximum stress in an aneurysm wall, while fluid-structure interaction simulations should be performed if accurate prediction of the fluid wall shear stress is necessary. Therefore, the decision to perform fluid-structure interaction simulations should be based on the particular variables of interest in a given
NASA Astrophysics Data System (ADS)
Huang, Yu-Ning
In this work, we derive necessary and sufficient conditions for turbulent secondary flows of a Newtonian fluid and necessary and sufficient conditions for laminar steady secondary flows of a Non-Newtonian fluid in a straight tube. It is found that there is a striking similarity between them. This similarity motivates the assumption used in developing a generalized non-linear K- epsilon model. Based on an analogy that exists between the constitutive relations for turbulent mean flows of a Newtonian fluid and that for laminar flows of a Non -Newtonian fluid, and making use of the constitutive framework of extended thermodynamics, we develop a generalized non -linear K-epsilon model with the same relaxation time as that which appears in the turbulence model proposed by Yakhot, Orszag, Thangam, Gatski and Speziale in 1992. We show that the non-linear K-epsilon model developed by Speziale in 1987 is unable to predict the relaxation phenomena of the Reynolds stresses because of involving no K and dotepsilon , and a coefficient of which leads to a negative relaxation time for the Reynolds stresses. To correct this deficiency, we resort to making use of the relaxation time in the model of Yakhot et al.. The approximate form of our generalized non-linear K-epsilon model, which can predict the relaxation phenomena of the Reynolds stresses and is frame indifferent, is an extension of the standard K-epsilon model and the non-linear K-epsilon model of Speziale.
Whole body acid-base and fluid-electrolyte balance: a mathematical model.
Wolf, Matthew B
2013-10-15
A cellular compartment was added to our previous mathematical model of steady-state acid-base and fluid-electrolyte chemistry to gain further understanding and aid diagnosis of complex disorders involving cellular involvement in critically ill patients. An important hypothesis to be validated was that the thermodynamic, standard free-energy of cellular H(+) and Na(+) pumps remained constant under all conditions. In addition, a hydrostatic-osmotic pressure balance was assumed to describe fluid exchange between plasma and interstitial fluid, including incorporation of compliance curves of vascular and interstitial spaces. The description of the cellular compartment was validated by close comparison of measured and model-predicted cellular pH and electrolyte changes in vitro and in vivo. The new description of plasma-interstitial fluid exchange was validated using measured changes in fluid volumes after isoosmotic and hyperosmotic fluid infusions of NaCl and NaHCO3. The validated model was used to explain the role of cells in the mechanism of saline or dilutional acidosis and acid-base effects of acidic or basic fluid infusions and the acid-base disorder due to potassium depletion. A module was created that would allow users, who do not possess the software, to determine, for free, the results of fluid infusions and urinary losses of water and solutes to the whole body. PMID:23884137
Fluid identification in tight sandstone reservoirs based on a new rock physics model
NASA Astrophysics Data System (ADS)
Sun, Jianmeng; Wei, Xiaohan; Chen, Xuelian
2016-08-01
To identify pore fluids, we establish a new rock physics model named the tight sandstone dual-porosity model based on the Voigt–Reuss–Hill model, approximation for the Xu–White model and Gassmann’s equation to predict elastic wave velocities. The modeling test shows that predicted sonic velocities derived from this rock physics model match well with measured ones from logging data. In this context, elastic moduli can be derived from the model. By numerical study and characteristic analyzation of different elastic properties, a qualitative fluid identification method based on Poisson’s ratio and the S–L dual-factor method based on synthetic moduli is proposed. Case studies of these two new methods show the applicability in distinguishing among different fluids and different layers in tight sandstone reservoirs.
An Image-Based Model of Fluid Flow Through Lymph Nodes.
Cooper, Laura J; Heppell, James P; Clough, Geraldine F; Ganapathisubramani, Bharathram; Roose, Tiina
2016-01-01
The lymphatic system returns fluid to the bloodstream from the tissues to maintain tissue fluid homeostasis. Lymph nodes distributed throughout the system filter the lymphatic fluid. The afferent and efferent lymph flow conditions of lymph nodes can be measured in experiments; however, it is difficult to measure the flow within the nodes. In this paper, we present an image-based modelling approach to investigating how the internal structure of the node affects the fluid flow pathways within the node. Selective plane illumination microscopy images of murine lymph nodes are used to identify the geometry and structure of the tissue within the node and to determine the permeability of the lymph node interstitium to lymphatic fluid. Experimental data are used to determine boundary conditions and optimise the parameters for the model. The numerical simulations conducted within the model are implemented in COMSOL Multiphysics, a commercial finite element analysis software. The parameter fitting resulted in the estimate that the average permeability for lymph node tissue is of the order of magnitude of [Formula: see text]. Our modelling shows that the flow predominantly takes a direct path between the afferent and efferent lymphatics and that fluid is both filtered and absorbed across the blood vessel boundaries. The amount that is absorbed or extravasated in the model is dependent on the efferent lymphatic lumen fluid pressure. PMID:26690921
Yield shear stress model of magnetorheological fluids based on exponential distribution
NASA Astrophysics Data System (ADS)
Guo, Chu-wen; Chen, Fei; Meng, Qing-rui; Dong, Zi-xin
2014-06-01
The magnetic chain model that considers the interaction between particles and the external magnetic field in a magnetorheological fluid has been widely accepted. Based on the chain model, a yield shear stress model of magnetorheological fluids was proposed by introducing the exponential distribution to describe the distribution of angles between the direction of magnetic field and the chain formed by magnetic particles. The main influencing factors were considered in the model, such as magnetic flux density, intensity of magnetic field, particle size, volume fraction of particles, the angle of magnetic chain, and so on. The effect of magnetic flux density on the yield shear stress was discussed. The yield stress of aqueous Fe3O4 magnetreological fluids with volume fraction of 7.6% and 16.2% were measured by a device designed by ourselves. The results indicate that the proposed model can be used for calculation of yield shear stress with acceptable errors.
NASA Astrophysics Data System (ADS)
Leibs, C.; Chacon, L.; Knoll, D. A.
2013-10-01
Recently, fluid acceleration of a fully implicit kinetic particle-in-cell (PIC) simulation has been successfully demonstrated. Central to these algorithms is robust preconditioning of the fluid system. In the context of kinetic simulations, the fluid system features conservation equations for both ions and electrons, plus field evolution equations, and must allow for charge separation effects. In this work, we concern ourselves with electrostatic and electromagnetic two-fluid models in multiple dimensions. Electromagnetic fields are prescribed via the Darwin approximation to project out spurious light-wave time scales. Disparate time scales remain among the abundance of supported plasma waves. The resulting nonlinear, stiff hyperbolic PDE systems are effectively preconditioned using physics-based preconditioning ideas, whereby their linearized form is transformed into parabolic PDEs that target the fast wave behavior. These elliptic systems can be efficiently inverted by multigrid methods. We will demonstrate the effectiveness of the approach via numerical experiments. Work funded by LANL LDRD program.
On Rayleigh-Plesset based cavitation modelling of fluid film bearings using the Reynolds equation
NASA Astrophysics Data System (ADS)
Snyder, Troy A.; Braun, Minel J.; Pierson, Kristopher
2015-12-01
In the ‘universe’ of the general cavitation phenomena the issue of cavitation in bearings, due to its particular application and the mostly non-homogeneous working fluids associated with it, has presented a rather specialized challenge. The present paper models the phenomenon of pseudo-cavitation in fluid film bearings and offers a physics-based approach that conserves mass while solving the Reynolds (RE) and Rayleigh-Plesset (RP) equations in a coupled, fully transient environment. The RP solution calculates a time dependent void fraction synchronized with the RE transient solution, where density and viscosity are (re)calculated at every grid point of this homogeneous two-phase fluid. The growth and evolution of the cavitation zone expanse is physics-based and thus can accommodate evaporation, diffusion, or pseudocavitation as separate processes. This is a step beyond the present available cavitation models both for the RE and the Navier-Stokes equations.
Development Of Sputtering Models For Fluids-Based Plasma Simulation Codes
NASA Astrophysics Data System (ADS)
Veitzer, Seth; Beckwith, Kristian; Stoltz, Peter
2015-09-01
Rf-driven plasma devices such as ion sources and plasma processing devices for many industrial and research applications benefit from detailed numerical modeling. Simulation of these devices using explicit PIC codes is difficult due to inherent separations of time and spatial scales. One alternative type of model is fluid-based codes coupled with electromagnetics, that are applicable to modeling higher-density plasmas in the time domain, but can relax time step requirements. To accurately model plasma-surface processes, such as physical sputtering and secondary electron emission, kinetic particle models have been developed, where particles are emitted from a material surface due to plasma ion bombardment. In fluid models plasma properties are defined on a cell-by-cell basis, and distributions for individual particle properties are assumed. This adds a complexity to surface process modeling, which we describe here. We describe the implementation of sputtering models into the hydrodynamic plasma simulation code USim, as well as methods to improve the accuracy of fluids-based simulation of plasmas-surface interactions by better modeling of heat fluxes. This work was performed under the auspices of the Department of Energy, Office of Basic Energy Sciences Award #DE-SC0009585.
Adaptive registration of magnetic resonance images based on a viscous fluid model.
Chang, Herng-Hua; Tsai, Chih-Yuan
2014-11-01
This paper develops a new viscous fluid registration algorithm that makes use of a closed incompressible viscous fluid model associated with mutual information. In our approach, we treat the image pixels as the fluid elements of a viscous fluid governed by the nonlinear Navier-Stokes partial differential equation (PDE) that varies in both temporal and spatial domains. We replace the pressure term with an image-based body force to guide the transformation that is weighted by the mutual information between the template and reference images. A computationally efficient algorithm with staggered grids is introduced to obtain stable solutions of this modified PDE for transformation. The registration process of updating the body force, the velocity and deformation fields is repeated until the mutual information reaches a prescribed threshold. We have evaluated this new algorithm in a number of synthetic and medical images. As consistent with the theory of the viscous fluid model, we found that our method faithfully transformed the template images into the reference images based on the intensity flow. Experimental results indicated that the proposed scheme achieved stable registrations and accurate transformations, which is of potential in large-scale medical image deformation applications. PMID:25176596
Self-reconfigurable ship fluid-network modeling for simulation-based design
NASA Astrophysics Data System (ADS)
Moon, Kyungjin
Our world is filled with large-scale engineering systems, which provide various services and conveniences in our daily life. A distinctive trend in the development of today's large-scale engineering systems is the extensive and aggressive adoption of automation and autonomy that enable the significant improvement of systems' robustness, efficiency, and performance, with considerably reduced manning and maintenance costs, and the U.S. Navy's DD(X), the next-generation destroyer program, is considered as an extreme example of such a trend. This thesis pursues a modeling solution for performing simulation-based analysis in the conceptual or preliminary design stage of an intelligent, self-reconfigurable ship fluid system, which is one of the concepts of DD(X) engineering plant development. Through the investigations on the Navy's approach for designing a more survivable ship system, it is found that the current naval simulation-based analysis environment is limited by the capability gaps in damage modeling, dynamic model reconfiguration, and simulation speed of the domain specific models, especially fluid network models. As enablers of filling these gaps, two essential elements were identified in the formulation of the modeling method. The first one is the graph-based topological modeling method, which will be employed for rapid model reconstruction and damage modeling, and the second one is the recurrent neural network-based, component-level surrogate modeling method, which will be used to improve the affordability and efficiency of the modeling and simulation (M&S) computations. The integration of the two methods can deliver computationally efficient, flexible, and automation-friendly M&S which will create an environment for more rigorous damage analysis and exploration of design alternatives. As a demonstration for evaluating the developed method, a simulation model of a notional ship fluid system was created, and a damage analysis was performed. Next, the models
NASA Astrophysics Data System (ADS)
Sousa, Eder; Shumlak, Uri; Lin, Guang
2011-10-01
Modeling open boundaries is useful for truncating extended or infinite simulation domains to regions of greatest interest. However, artificial wave reflections at the boundaries can result for oblique wave intersections. The lacuna-based artificial boundary condition (ABC) method is applied to numerical simulations of the two-fluid plasma model on unbounded domains to avoid unphysical reflections. The method is temporally nonlocal and can handle arbitrary boundary shapes with no fitting needed nor accuracy loss. The algorithm is based on the presence of lacunae (aft fronts of the waves) in wave-type solutions in odd- dimensional space. The method is applied to Maxwell's equations of the two-fluid model. Placing error bounds on numerical simulations results is important for accurate comparisons, therefore, the multi-level Monte Carlo method is used to quantify the uncertainty of the two-fluid plasma model as applied to the GEM magnetic reconnection problem to study the sensitivity of the problem to uncertainty on the mass ratio, speed of light to Alfven speed ratio and the magnitude of the magnetic field initial perturbation.
NASA Astrophysics Data System (ADS)
Brown, M.; Fotheringham, J. D.; Hoyes, T. J.; Mortier, R. M.; Orszulik, S. T.; Randles, S. J.; Stroud, P. M.
The chemical nature and technology of the main synthetic lubricant base fluids is described, covering polyalphaolefins, alkylated aromatics, gas-to-liquid (GTL) base fluids, polybutenes, aliphatic diesters, polyolesters, polyalkylene glycols or PAGs and phosphate esters.Other synthetic lubricant base oils such as the silicones, borate esters, perfluoroethers and polyphenylene ethers are considered to have restricted applications due to either high cost or performance limitations and are not considered here.Each of the main synthetic base fluids is described for their chemical and physical properties, manufacture and production, their chemistry, key properties, applications and their implications when used in the environment.
Hariharan, Prasanna; D'Souza, Gavin; Horner, Marc; Malinauskas, Richard A; Myers, Matthew R
2015-09-01
As part of an ongoing effort to develop verification and validation (V&V) standards for using computational fluid dynamics (CFD) in the evaluation of medical devices, we have developed idealized flow-based verification benchmarks to assess the implementation of commonly cited power-law based hemolysis models in CFD. Verification process ensures that all governing equations are solved correctly and the model is free of user and numerical errors. To perform verification for power-law based hemolysis modeling, analytical solutions for the Eulerian power-law blood damage model (which estimates hemolysis index (HI) as a function of shear stress and exposure time) were obtained for Couette and inclined Couette flow models, and for Newtonian and non-Newtonian pipe flow models. Subsequently, CFD simulations of fluid flow and HI were performed using Eulerian and three different Lagrangian-based hemolysis models and compared with the analytical solutions. For all the geometries, the blood damage results from the Eulerian-based CFD simulations matched the Eulerian analytical solutions within ∼1%, which indicates successful implementation of the Eulerian hemolysis model. Agreement between the Lagrangian and Eulerian models depended upon the choice of the hemolysis power-law constants. For the commonly used values of power-law constants (α = 1.9-2.42 and β = 0.65-0.80), in the absence of flow acceleration, most of the Lagrangian models matched the Eulerian results within 5%. In the presence of flow acceleration (inclined Couette flow), moderate differences (∼10%) were observed between the Lagrangian and Eulerian models. This difference increased to greater than 100% as the beta exponent decreased. These simplified flow problems can be used as standard benchmarks for verifying the implementation of blood damage predictive models in commercial and open-source CFD codes. The current study only used power-law model as an illustrative example to emphasize the need
Kenkeremath, D.
1985-05-01
Numerical simulation models and data bases that were developed for DOE as part of a number of geothermal programs have been assessed with respect to their overall stage of development and usefulness. This report combines three separate studies that focus attention upon: (1) economic models related to geothermal energy; (2) physical geothermal system models pertaining to thermal energy and the fluid medium; and (3) geothermal energy data bases. Computerized numerical models pertaining to the economics of extracting and utilizing geothermal energy have been summarized and catalogued with respect to their availability, utility and function. The 19 models that are discussed in detail were developed for use by geothermal operators, public utilities, and lending institutions who require a means to estimate the value of a given resource, total project costs, and the sensitivity of these values to specific variables. A number of the models are capable of economically assessing engineering aspects of geothermal projects. Computerized simulations of heat distribution and fluid flow have been assessed and are presented for ten models. Five of the models are identified as wellbore simulators and five are described as reservoir simulators. Each model is described in terms of its operational characteristics, input, output, and other pertinent attributes. Geothermal energy data bases are reviewed with respect to their current usefulness and availability. Summaries of eight data bases are provided in catalogue format, and an overall comparison of the elements of each data base is included.
On the application of a physically based higher order fluid model for low-temperature plasmas
NASA Astrophysics Data System (ADS)
Garland, Nathan; White, Ron; Robson, Robert; Nicoletopoulos, Peter; Dujko, Sasa
2012-10-01
We present a high resolution, computationally efficient non-local fluid model of a low-temperature parallel plate plasma discharge. The non-local model uses low-order velocity moments of the Boltzmann equation representing particle, momentum and energy balance equations, coupled with Poisson's equations to determine space-charge fields. The system of equations is closed used a physically sound heat flux ansatz [1]. A new scheme is implemented for prescribing the relevant collisional terms in the balance equations, based on available electron swarm transport coefficients [2]. The model is applied to simulation of various configurations including the Gaseous Electronics Conference (GEC) reference cell and compared to previous models of the system. Results of the model yield spatial and temporal profiles of electron densities, flux and energy in addition to electric field distributions inside the GEC reference cell. In this paper, we highlight differences associated with local and non-local fluid equation treatments, as well as highlight the importance of correct implementation of electron swarm transport data. [1] R.E. Robson, R.D. White and Z. Lj. Petrovic, Rev. Mod. Phys. 77, 1303 (2005) [2] R.E. Robson, P. Nicoletopoulos, M. Hildebrandt and R.D. White, J. Chem. Phys. (sub
An earthquake instability model based on faults containing high fluid-pressure compartments
Lockner, D.A.; Byerlee, J.D.
1995-01-01
It has been proposed that large strike-slip faults such as the San Andreas contain water in seal-bounded compartments. Arguments based on heat flow and stress orientation suggest that in most of the compartments, the water pressure is so high that the average shear strength of the fault is less than 20 MPa. We propose a variation of this basic model in which most of the shear stress on the fault is supported by a small number of compartments where the pore pressure is relatively low. As a result, the fault gouge in these compartments is compacted and lithified and has a high undisturbed strength. When one of these locked regions fails, the system made up of the neighboring high and low pressure compartments can become unstable. Material in the high fluid pressure compartments is initially underconsolidated since the low effective confining pressure has retarded compaction. As these compartments are deformed, fluid pressure remains nearly unchanged so that they offer little resistance to shear. The low pore pressure compartments, however, are overconsolidated and dilate as they are sheared. Decompression of the pore fluid in these compartments lowers fluid pressure, increasing effective normal stress and shear strength. While this effect tends to stabilize the fault, it can be shown that this dilatancy hardening can be more than offset by displacement weakening of the fault (i.e., the drop from peak to residual strength). If the surrounding rock mass is sufficiently compliant to produce an instability, slip will propagate along the fault until the shear fracture runs into a low-stress region. Frictional heating and the accompanying increase in fluid pressure that are suggested to occur during shearing of the fault zone will act as additional destabilizers. However, significant heating occurs only after a finite amount of slip and therefore is more likely to contribute to the energetics of rupture propagation than to the initiation of the instability. We present
Predicting multidimensional annular flow with a locally based two-fluid model
Antal, S.P.; Edwards, D.P.; Strayer, T.D.
1998-06-01
The purpose of this work was to: develop a methodology to predict annular flows using a multidimensional four-field, two-fluid Computational Fluid Dynamics (CFD) computer code; develop closure models which use the CFD predicted local velocities, phasic volume fractions, etc...; implement a numerical method which allows the discretized equations to have the same characteristics as the differential form; and compare predicted results to local flow field data taken in a R-134a working fluid test section.
A case study of fluid flow in fractured rock mass based on 2-D DFN modeling
NASA Astrophysics Data System (ADS)
Han, Jisu; Noh, Young-Hwan; Um, Jeong-Gi; Choi, Yosoon
2014-05-01
A two dimensional steady-state fluid flow through fractured rock mass of an abandoned copper mine in Korea is addressed based on discrete fracture network modeling. An injection well and three observation wells were installed at the field site to monitor the variations of total heads induced by injection of fresh water. A series of packer tests were performed to estimate the rock mass permeability. First, the two dimensional stochastic fracture network model was built and validated for a granitic rock mass using the geometrical and statistical data obtained from surface exposures and borehole logs. This validated fracture network model was combined with the fracture data observed on boreholes to generate a stochastic-deterministic fracture network system. Estimated apertures for each of the fracture sets using permeability data obtained from borehole packer tests were discussed next. Finally, a systematic procedure for fluid flow modeling in fractured rock mass in two dimensional domain was presented to estimate the conductance, flow quantity and nodal head in 2-D conceptual linear pipe channel network. The results obtained in this study clearly show that fracture geometry parameters (orientation, density and size) play an important role in the hydraulic behavior of fractured rock masses.
Epstein, Joshua M.; Pankajakshan, Ramesh; Hammond, Ross A.
2011-01-01
We introduce a novel hybrid of two fields—Computational Fluid Dynamics (CFD) and Agent-Based Modeling (ABM)—as a powerful new technique for urban evacuation planning. CFD is a predominant technique for modeling airborne transport of contaminants, while ABM is a powerful approach for modeling social dynamics in populations of adaptive individuals. The hybrid CFD-ABM method is capable of simulating how large, spatially-distributed populations might respond to a physically realistic contaminant plume. We demonstrate the overall feasibility of CFD-ABM evacuation design, using the case of a hypothetical aerosol release in Los Angeles to explore potential effectiveness of various policy regimes. We conclude by arguing that this new approach can be powerfully applied to arbitrary population centers, offering an unprecedented preparedness and catastrophic event response tool. PMID:21687788
Fluid flow model of the Cerro Prieto Geothermal Field based on well log interpretation
Halfman, S.E.; Lippmann, M.J.; Zelwe, R.; Howard, J.H.
1982-08-10
The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine the direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.
Fluid flow model of the Cerro Prieto geothermal field based on well log interpretation
Halfman, S.E.; Lippmann, M.J.; Zelwer, R.; Howard, J.H.
1982-10-01
The subsurface geology of the Cerro Prieto geothermal field was analyzed using geophysical and lithologic logs. The distribution of permeable and relatively impermeable units and the location of faults are shown in a geologic model of the system. By incorporating well completion data and downhole temperature profiles into the geologic model, it was possible to determine he direction of geothermal fluid flow and the role of subsurface geologic features that control this movement.
Bedrock Channel and Cave Evolution Models Based on Computational Fluid Dynamics
NASA Astrophysics Data System (ADS)
Perne, M.; Covington, M. D.; Cooper, M.
2014-12-01
Models of bedrock channel cross-section evolution typically rely on simple approximations of boundary shear stress to calculate erosion rates across the channel. While such models provide a useful tool for gaining general insight into channel dynamics, they also exhibit a narrower range of behaviors than seen in nature and scale experiments. Recent computational advances enable use of computational fluid dynamics (CFD) to relax many of the assumptions used in these simple models by simulating the full 3D flow field and resulting erosion. We have developed a model of bedrock channel evolution at the reach scale, using CFD, that alternates flow simulation steps with channel evolution steps and evolves the channel in time according to shear stresses calculated from the CFD runs. Caves provide an ideal field setting for studying bedrock channel dynamics, because long records of incision are often preserved in the form of channel widths, meander patterns, and sculpted forms, such as scallops, that indicate flow velocity and direction. However, most existing numerical models of cave formation investigate processes on larger scales, treat conduits as simple shapes, such as cylinders, and deal with the early stages of speleogenesis when sediment transport and erosion mechanisms other than dissolution do not have to be taken into account. Therefore, initial applications of the CFD model focus on the dynamics of cave channels, and particularly on the controls of channel width. While discharge, base level, sediment supply, and the ratio of dissolution to mechanical erosion, are likely to play important roles in determining channel width, we lack a quantitative understanding for the importance of these various factors. Notches in passage walls are thought to result from lateral erosion during periods of increased sediment load when the bed is armored. Modeling is used to check the plausibility of this explanation, and examine whether other mechanisms may also produce notches
Simulation of single microorganism motion in fluid based on granular model
NASA Astrophysics Data System (ADS)
Viridi, S.; Nuraini, N.
2016-04-01
Microorganism model for simulating its motion is proposed in this work. It consists of granular particles which can interact to each other through linear spring mimicking microorganism muscles, which is simpler than other model. As a part of the organism organ is moving, while the other remains at its position, it will push the surrounding fluid through Stoke's force and as reaction the fluid pushes back the microorganism. Contracting force is used to change the distance between two points in the organ. Gravity influence is simply neglected in this work. All the considered forces are used to get motion parameters of organism through molecular dynamics method. It is observed that the use of contracting (push-pull) organ constructs slightly more effective model than shrink- and swell-organs as previously investigated, if weighted effectiveness formula is used as function of number of considered forces and involved particles.
Anderson, Debra F.; Cheung, Cecilia Y.
2014-01-01
Experimentation in late-gestation fetal sheep has suggested that regulation of amniotic fluid (AF) volume occurs primarily by modulating the rate of intramembranous transport of water and solutes across the amnion into underlying fetal blood vessels. In order to gain insight into intramembranous transport mechanisms, we developed a computer model that allows simulation of experimentally measured changes in AF volume and composition over time. The model included fetal urine excretion and lung liquid secretion as inflows into the amniotic compartment plus fetal swallowing and intramembranous absorption as outflows. By using experimental flows and solute concentrations for urine, lung liquid, and swallowed fluid in combination with the passive and active transport mechanisms of the intramembranous pathway, we simulated AF responses to basal conditions, intra-amniotic fluid infusions, fetal intravascular infusions, urine replacement, and tracheoesophageal occlusion. The experimental data are consistent with four intramembranous transport mechanisms acting in concert: 1) an active unidirectional bulk transport of AF with all dissolved solutes out of AF into fetal blood presumably by vesicles; 2) passive bidirectional diffusion of solutes, such as sodium and chloride, between fetal blood and AF; 3) passive bidirectional water movement between AF and fetal blood; and 4) unidirectional transport of lactate into the AF. Further, only unidirectional bulk transport is dynamically regulated. The simulations also identified areas for future study: 1) identifying intramembranous stimulators and inhibitors, 2) determining the semipermeability characteristics of the intramembranous pathway, and 3) characterizing the vesicles that are the primary mediators of intramembranous transport. PMID:25186112
Brace, Robert A; Anderson, Debra F; Cheung, Cecilia Y
2014-11-15
Experimentation in late-gestation fetal sheep has suggested that regulation of amniotic fluid (AF) volume occurs primarily by modulating the rate of intramembranous transport of water and solutes across the amnion into underlying fetal blood vessels. In order to gain insight into intramembranous transport mechanisms, we developed a computer model that allows simulation of experimentally measured changes in AF volume and composition over time. The model included fetal urine excretion and lung liquid secretion as inflows into the amniotic compartment plus fetal swallowing and intramembranous absorption as outflows. By using experimental flows and solute concentrations for urine, lung liquid, and swallowed fluid in combination with the passive and active transport mechanisms of the intramembranous pathway, we simulated AF responses to basal conditions, intra-amniotic fluid infusions, fetal intravascular infusions, urine replacement, and tracheoesophageal occlusion. The experimental data are consistent with four intramembranous transport mechanisms acting in concert: 1) an active unidirectional bulk transport of AF with all dissolved solutes out of AF into fetal blood presumably by vesicles; 2) passive bidirectional diffusion of solutes, such as sodium and chloride, between fetal blood and AF; 3) passive bidirectional water movement between AF and fetal blood; and 4) unidirectional transport of lactate into the AF. Further, only unidirectional bulk transport is dynamically regulated. The simulations also identified areas for future study: 1) identifying intramembranous stimulators and inhibitors, 2) determining the semipermeability characteristics of the intramembranous pathway, and 3) characterizing the vesicles that are the primary mediators of intramembranous transport. PMID:25186112
Jenny, Patrick Torrilhon, Manuel; Heinz, Stefan
2010-02-20
In this paper, a stochastic model is presented to simulate the flow of gases, which are not in thermodynamic equilibrium, like in rarefied or micro situations. For the interaction of a particle with others, statistical moments of the local ensemble have to be evaluated, but unlike in molecular dynamics simulations or DSMC, no collisions between computational particles are considered. In addition, a novel integration technique allows for time steps independent of the stochastic time scale. The stochastic model represents a Fokker-Planck equation in the kinetic description, which can be viewed as an approximation to the Boltzmann equation. This allows for a rigorous investigation of the relation between the new model and classical fluid and kinetic equations. The fluid dynamic equations of Navier-Stokes and Fourier are fully recovered for small relaxation times, while for larger values the new model extents into the kinetic regime. Numerical studies demonstrate that the stochastic model is consistent with Navier-Stokes in that limit, but also that the results become significantly different, if the conditions for equilibrium are invalid. The application to the Knudsen paradox demonstrates the correctness and relevance of this development, and comparisons with existing kinetic equations and standard solution algorithms reveal its advantages. Moreover, results of a test case with geometrically complex boundaries are presented.
NASA Astrophysics Data System (ADS)
Cui, Ke; Song, Yan-Ping; Chen, Huan-Long; Chen, Fu; Ooyama, Hiroharu
2016-07-01
A two-fluid model with the influence of inter-phase velocity-slip taken into account is proposed and a modified realizable k- ɛ turbulence model is put forward as well to make the equation set of two-fluid model closed. Based on this two-fluid model, numerical simulations are implemented on typical wet steam flow in different cases. Good consistency between numerical result and the experimental result implies that this two-fluid model is provided with high accuracy and wide applicability. The flow field analysis also shows that there exist several particular sites along the flow direction. These particular sites could illustrate the development mechanism of nucleation and droplet growing. In addition, further discussion about the flow in cascade then indicates that the presence of condensation has strong impact on the flow while the impact of inter-phase velocity-slip is relatively weaker. The composition of total pressure loss is present here, the majority of total pressure loss brought by condensation is about 8.78 % of inlet total pressure while the inter-phase velocity-slip just results in a small part of about 0.42 % of inlet total pressure, the rest of the total pressure loss is caused by pneumatic factors and this part is about 3.95 % of inlet total pressure.
Physical-based non-Newtonian fluid animation using SPH
NASA Astrophysics Data System (ADS)
Mao, Hai
Fluids are commonly seen in our daily lives. They exhibit a wide range of motions, which depend on their physical properties, and often result in amazing visual phenomena. Hence, fluid animation is a popular topic in computer graphics. The animation results not only enrich a computer-generated virtual world but have found applications in generating special effects in motion pictures and in computer games. The three-dimensional (3D) Navier-Stokes (NS) equation is a comprehensive mechanical description of the fluid motions. Smoothed Particle Hydrodynamics (SPH) is a popular particle-based fluid modeling formulation. In physical-based fluid animation, the fluid models are based on the 3D NS equation, which can be solved using SPH based methods. Non-Newtonian fluids form a rich class of fluids. Their physical behavior exhibits a strong and complex stress-strain relationship which falls outside the modeling range of Newtonian fluid mechanics. In physical-based fluid animation, most of the fluid models are based on Newtonian fluids, and hence they cannot realistically animate non-Newtonian fluid motions such as stretching, bending, and bouncing. Based on the 3D NS equation and SPH, three original contributions are presented in this dissertation, which address the following three aspects of fluid animation: (1) particle-based non-Newtonian fluids, (2) immiscible fluid-fluid collision, and (3) heating non-Newtonian fluids. Consequently, more varieties of non-Newtonian fluid motions can be animated, which include stretching, bending, and bouncing.
NASA Astrophysics Data System (ADS)
Guo, Xiaohui
Fluid and thermal problems are widely encountered in micro/nano-scale devices, the characteristic lengths of which are from hundreds of microns down to tens of nanometers. A great number of such devices involve fundamental components like microchannels, capillaries, membranes and cantilever beams. Continuum assumptions that lead to classical governing equations such as Navier-Stokes equations and Fourier Laws break down when the characteristic size shrinks by an order of millions. In addition, conventional sensors, actuators and controllers turn to be insufficient to depict the flow, thermal, or electrical fields in micro-devices without impacting the original conditions greatly. Therefore, the development of numerical methods becomes indispensable in design and performance analysis of micro-electro-mechanical systems (MEMS). The main goal of this PhD research is the development, implementation and application of comprehensive deterministic Boltzmann-ESBGK modeling framework to micro-scale fluid-thermal phenomena. Investigation of gas flows in short rectangular microchannels has been carried out to understand the rarefaction effects on the reduced mass-flow-rate as well as the non-equilibrium effects on the temperature components. At high Knudsen numbers, the reduced mass-flow-rate only depends on the pressure ratio and the temperature components deviate at the channel exit. For gas flows in long microchannels with and without constrictions, the Navier-Stokes equations with first-order slip boundary conditions are solved. Numerical results accurately predict the entrance pressure drop comparing to high-resolution experimental data using pressure-sensitive-paint (PSP). Simultions show clearly that the compressibility effects become less important than the rarefaction effects at low pressures. The coupled gas-phonon Boltzmann solver has been developed. The reduced distribution functions are used in the two-dimensional code to reduce the computational cost. The
Digital marbling: a multiscale fluid model.
Acar, Rüyam; Boulanger, Pierre
2006-01-01
This paper presents a multiscale fluid model based on mesoscale dynamics and viscous fluid equations as a generic tool for digital marbling purposes. The model uses an averaging technique on the adaptation of a stochastic mesoscale model to obtain the effect of fluctuations at different levels. It allows various user controls to simulate complex flow behaviors as in traditional marbling techniques, as well as laminar and turbulent flows. Material transport is based on an improved advection solution to be able to match the highly detailed, sharp fluid interfaces in marbling patterns. In the transport model, two reaction models are introduced to create different effects and to simulate density fluctuations. PMID:16805267
NASA Astrophysics Data System (ADS)
Varela-Jiménez, M. I.; Vargas Luna, J. L.; Cortés-Ramírez, J. A.; Song, G.
2015-04-01
Magnetorheological fluid (MRF) is a smart material whose rheological properties can be varied by a magnetic field; it has been applied in the development of semiactive dampers for a variety of applications. The material essentially consists of a suspension of magnetic particles in a nonmagnetic carrier fluid. It is important to understand the magnetic response of MRF and its dependence on several parameters for improving and designing MRF devices. The purpose of this work is to develop a constitutive model that describes the behavior of the shear yield stress of the material as function of the magnetic field and composition. Taking into account that the material changes its rheology and apparent viscosity according to magnetic field, a magnetically induced state transition is proposed; by the use of a state transition equation, a constitutive model for shear yield stress is defined, consisting of an expression that relates composition of the material and the stimulus applied, it also associates the volume fraction of particles, magnetic field and the material that composes the particles.
Stenroos, Matti; Nummenmaa, Aapo
2016-01-01
MEG/EEG source imaging is usually done using a three-shell (3-S) or a simpler head model. Such models omit cerebrospinal fluid (CSF) that strongly affects the volume currents. We present a four-compartment (4-C) boundary-element (BEM) model that incorporates the CSF and is computationally efficient and straightforward to build using freely available software. We propose a way for compensating the omission of CSF by decreasing the skull conductivity of the 3-S model, and study the robustness of the 4-C and 3-S models to errors in skull conductivity. We generated dense boundary meshes using MRI datasets and automated SimNIBS pipeline. Then, we built a dense 4-C reference model using Galerkin BEM, and 4-C and 3-S test models using coarser meshes and both Galerkin and collocation BEMs. We compared field topographies of cortical sources, applying various skull conductivities and fitting conductivities that minimized the relative error in 4-C and 3-S models. When the CSF was left out from the EEG model, our compensated, unbiased approach improved the accuracy of the 3-S model considerably compared to the conventional approach, where CSF is neglected without any compensation (mean relative error < 20% vs. > 40%). The error due to the omission of CSF was of the same order in MEG and compensated EEG. EEG has, however, large overall error due to uncertain skull conductivity. Our results show that a realistic 4-C MEG/EEG model can be implemented using standard tools and basic BEM, without excessive workload or computational burden. If the CSF is omitted, compensated skull conductivity should be used in EEG. PMID:27472278
Stenroos, Matti; Nummenmaa, Aapo
2016-01-01
MEG/EEG source imaging is usually done using a three-shell (3-S) or a simpler head model. Such models omit cerebrospinal fluid (CSF) that strongly affects the volume currents. We present a four-compartment (4-C) boundary-element (BEM) model that incorporates the CSF and is computationally efficient and straightforward to build using freely available software. We propose a way for compensating the omission of CSF by decreasing the skull conductivity of the 3-S model, and study the robustness of the 4-C and 3-S models to errors in skull conductivity. We generated dense boundary meshes using MRI datasets and automated SimNIBS pipeline. Then, we built a dense 4-C reference model using Galerkin BEM, and 4-C and 3-S test models using coarser meshes and both Galerkin and collocation BEMs. We compared field topographies of cortical sources, applying various skull conductivities and fitting conductivities that minimized the relative error in 4-C and 3-S models. When the CSF was left out from the EEG model, our compensated, unbiased approach improved the accuracy of the 3-S model considerably compared to the conventional approach, where CSF is neglected without any compensation (mean relative error < 20% vs. > 40%). The error due to the omission of CSF was of the same order in MEG and compensated EEG. EEG has, however, large overall error due to uncertain skull conductivity. Our results show that a realistic 4-C MEG/EEG model can be implemented using standard tools and basic BEM, without excessive workload or computational burden. If the CSF is omitted, compensated skull conductivity should be used in EEG. PMID:27472278
Tao, Chao; Jiang, Jack J.; Czerwonka, Lukasz
2011-01-01
The human vocal fold is treated as a continuous, transversally isotropic, porous solid saturated with liquid. A set of mathematical equations, based on the theory of fluid-saturated porous solids, is developed to formulate the vibration of the vocal fold tissue. As the fluid-saturated porous tissue model degenerates to the continuous elastic tissue model when the relative movement of liquid in the porous tissue is ignored, it can be considered a more general description of vocal fold tissue than the continuous, elastic model. Using the fluid-saturated porous tissue model, the vibration of a bunch of one-dimensional fibers in the vocal fold is analytically solved based on the small amplitude assumption. It is found that the vibration of the tissue will lead to the accumulation of excess liquid in the midmembranous vocal fold. The degree of liquid accumulation is positively proportional to the vibratory amplitude and frequency. The correspondence between the liquid distribution predicted by the porous tissue theory and the location of vocal nodules observed in clinical practice, provides theoretical evidence for the liquid accumulation hypothesis of vocal nodule formation (Jiang, Ph. D., dissertation, 1991, University of Iowa). PMID:19660905
Computational Fluid Dynamic Modeling of Rocket Based Combined Cycle Engine Flowfields
NASA Technical Reports Server (NTRS)
Daines, Russell L.; Merkle, Charles L.
1994-01-01
Computational Fluid Dynamic techniques are used to study the flowfield of a fixed geometry Rocket Based Combined Cycle engine operating in rocket ejector mode. Heat addition resulting from the combustion of injected fuel causes the subsonic engine flow to choke and go supersonic in the slightly divergent combustor-mixer section. Reacting flow computations are undertaken to predict the characteristics of solutions where the heat addition is determined by the flowfield. Here, adaptive gridding is used to improve resolution in the shear layers. Results show that the sonic speed is reached in the unheated portions of the flow first, while the heated portions become supersonic later. Comparison with results from another code show reasonable agreement. The coupled solutions show that the character of the combustion-based thermal choking phenomenon can be controlled reasonably well such that there is opportunity to optimize the length and expansion ratio of the combustor-mixer.
Measurement-based quantum lattice gas model of fluid dynamics in 2+1 dimensions.
Micci, Michael M; Yepez, Jeffrey
2015-09-01
Presented are quantum simulation results using a measurement-based quantum lattice gas algorithm for Navier-Stokes fluid dynamics in 2+1 dimensions. Numerical prediction of the kinematic viscosity was measured by the decay rate of an initial sinusoidal flow profile. Due to local quantum entanglement in the quantum lattice gas, the minimum kinematic viscosity in the measurement-based quantum lattice gas is lower than achievable in a classical lattice gas. The numerically predicted viscosities precisely match the theoretical predictions obtained with a mean field approximation. Uniform flow profile with double shear layers, on a 16K×8K lattice, leads to the Kelvin-Helmholtz instability, breaking up the shear layer into pairs of counter-rotating vortices that eventually merge via vortex fusion and dissipate because of the nonzero shear viscosity. PMID:26465581
Measurement-based quantum lattice gas model of fluid dynamics in 2+1 dimensions
NASA Astrophysics Data System (ADS)
Micci, Michael M.; Yepez, Jeffrey
2015-09-01
Presented are quantum simulation results using a measurement-based quantum lattice gas algorithm for Navier-Stokes fluid dynamics in 2+1 dimensions. Numerical prediction of the kinematic viscosity was measured by the decay rate of an initial sinusoidal flow profile. Due to local quantum entanglement in the quantum lattice gas, the minimum kinematic viscosity in the measurement-based quantum lattice gas is lower than achievable in a classical lattice gas. The numerically predicted viscosities precisely match the theoretical predictions obtained with a mean field approximation. Uniform flow profile with double shear layers, on a 16 K ×8 K lattice, leads to the Kelvin-Helmholtz instability, breaking up the shear layer into pairs of counter-rotating vortices that eventually merge via vortex fusion and dissipate because of the nonzero shear viscosity.
Thrust wedges and fluid overpressures: Sandbox models involving pore fluids
NASA Astrophysics Data System (ADS)
Mourgues, R.; Cobbold, P. R.
2006-05-01
The well-known model for the critical taper of an accretionary wedge includes overpressure as a first-order parameter. Fluid overpressures reduce frictional resistance at the base of a wedge but they also act as body forces on all material particles of the wedge, in addition to that of gravity. By means of sandbox modeling, many workers have tried to verify the predictions of the critical taper model, but few of them have so far incorporated true fluid pressures. We have used scaled experiments, in which compressed air flows through sand packs, so as to model the deformation of overpressured wedges. A new apparatus provides for a horizontally varying fluid pressure, for example, a linear variation, as in the critical taper model. We have done three series of experiments, involving horizontal shortening of homogeneous or multilayered sand models for various gradients of fluid pressure. As predicted by the critical taper model, the apical angle of the resulting wedge depends on the overpressure gradient. In homogeneous sand at a high overpressure gradient, deformation becomes diffuse and looks ductile. In multilayered models, detachments form beneath layers of low permeability, so that thrusts propagate rapidly toward the undeformed foreland. The efficiency of a detachment and its ability to propagate depend not only on the fluid pressure but also on the permeability ratios between the various layers.
NASA Astrophysics Data System (ADS)
Ovaysi, S.; Piri, M.
2009-12-01
We present a three-dimensional fully dynamic parallel particle-based model for direct pore-level simulation of incompressible viscous fluid flow in disordered porous media. The model was developed from scratch and is capable of simulating flow directly in three-dimensional high-resolution microtomography images of naturally occurring or man-made porous systems. It reads the images as input where the position of the solid walls are given. The entire medium, i.e., solid and fluid, is then discretized using particles. The model is based on Moving Particle Semi-implicit (MPS) technique. We modify this technique in order to improve its stability. The model handles highly irregular fluid-solid boundaries effectively. It takes into account viscous pressure drop in addition to the gravity forces. It conserves mass and can automatically detect any false connectivity with fluid particles in the neighboring pores and throats. It includes a sophisticated algorithm to automatically split and merge particles to maintain hydraulic connectivity of extremely narrow conduits. Furthermore, it uses novel methods to handle particle inconsistencies and open boundaries. To handle the computational load, we present a fully parallel version of the model that runs on distributed memory computer clusters and exhibits excellent scalability. The model is used to simulate unsteady-state flow problems under different conditions starting from straight noncircular capillary tubes with different cross-sectional shapes, i.e., circular/elliptical, square/rectangular and triangular cross-sections. We compare the predicted dimensionless hydraulic conductances with the data available in the literature and observe an excellent agreement. We then test the scalability of our parallel model with two samples of an artificial sandstone, samples A and B, with different volumes and different distributions (non-uniform and uniform) of solid particles among the processors. An excellent linear scalability is
NASA Astrophysics Data System (ADS)
Niu, Yang-Yao
2016-03-01
This paper is to continue our previous work in 2008 on solving a two-fluid model for compressible liquid-gas flows. We proposed a pressure-velocity based diffusion term original derived from AUSMD scheme of Wada and Liou in 1997 to enhance its robustness. The proposed AUSMD schemes have been applied to gas and liquid fluids universally to capture fluid discontinuities, such as the fluid interfaces and shock waves, accurately for the Ransom's faucet problem, air-water shock tube problems and 2D shock-water liquid interaction problems. However, the proposed scheme failed at computing liquid-gas interfaces in problems under large ratios of pressure, density and volume of fraction. The numerical instability has been remedied by Chang and Liou in 2007 using the exact Riemann solver to enhance the accuracy and stability of numerical flux across the liquid-gas interface. Here, instead of the exact Riemann solver, we propose a simple AUSMD type primitive variable Riemann solver (PVRS) which can successfully solve 1D stiffened water-air shock tube and 2D shock-gas interaction problems under large ratios of pressure, density and volume of fraction without the expensive cost of tedious computer time. In addition, the proposed approach is shown to deliver a good resolution of the shock-front, rarefaction and cavitation inside the evolution of high-speed droplet impact on the wall.
Two-fluid Hydrodynamic Model for Fluid-Flow Simulation in Fluid-Solids Systems
1994-06-20
FLUFIX is a two-dimensional , transient, Eulerian, and finite-difference program, based on a two-fluid hydrodynamic model, for fluid flow simulation in fluid-solids systems. The software is written in a modular form using the Implicit Multi-Field (IMF) numerical technique. Quantities computed are the spatial distribution of solids loading, gas and solids velocities, pressure, and temperatures. Predicted are bubble formation, bed frequencies, and solids recirculation. Applications include bubbling and circulating atmospheric and pressurized fluidized bed reactors, combustors,more » gasifiers, and FCC (Fluid Catalytic Cracker) reactors.« less
Zu, Y Q; He, S
2013-04-01
A lattice Boltzmann model (LBM) is proposed based on the phase-field theory to simulate incompressible binary fluids with density and viscosity contrasts. Unlike many existing diffuse interface models which are limited to density matched binary fluids, the proposed model is capable of dealing with binary fluids with moderate density ratios. A new strategy for projecting the phase field to the viscosity field is proposed on the basis of the continuity of viscosity flux. The new LBM utilizes two lattice Boltzmann equations (LBEs): one for the interface tracking and the other for solving the hydrodynamic properties. The LBE for interface tracking can recover the Chan-Hilliard equation without any additional terms; while the LBE for hydrodynamic properties can recover the exact form of the divergence-free incompressible Navier-Stokes equations avoiding spurious interfacial forces. A series of 2D and 3D benchmark tests have been conducted for validation, which include a rigid-body rotation, stationary and moving droplets, a spinodal decomposition, a buoyancy-driven bubbly flow, a layered Poiseuille flow, and the Rayleigh-Taylor instability. It is shown that the proposed method can track the interface with high accuracy and stability and can significantly and systematically reduce the parasitic current across the interface. Comparisons with momentum-based models indicate that the newly proposed velocity-based model can better satisfy the incompressible condition in the flow fields, and eliminate or reduce the velocity fluctuations in the higher-pressure-gradient region and, therefore, achieve a better numerical stability. In addition, the test of a layered Poiseuille flow demonstrates that the proposed scheme for mixture viscosity performs significantly better than the traditional mixture viscosity methods. PMID:23679542
NASA Astrophysics Data System (ADS)
Zu, Y. Q.; He, S.
2013-04-01
A lattice Boltzmann model (LBM) is proposed based on the phase-field theory to simulate incompressible binary fluids with density and viscosity contrasts. Unlike many existing diffuse interface models which are limited to density matched binary fluids, the proposed model is capable of dealing with binary fluids with moderate density ratios. A new strategy for projecting the phase field to the viscosity field is proposed on the basis of the continuity of viscosity flux. The new LBM utilizes two lattice Boltzmann equations (LBEs): one for the interface tracking and the other for solving the hydrodynamic properties. The LBE for interface tracking can recover the Chan-Hilliard equation without any additional terms; while the LBE for hydrodynamic properties can recover the exact form of the divergence-free incompressible Navier-Stokes equations avoiding spurious interfacial forces. A series of 2D and 3D benchmark tests have been conducted for validation, which include a rigid-body rotation, stationary and moving droplets, a spinodal decomposition, a buoyancy-driven bubbly flow, a layered Poiseuille flow, and the Rayleigh-Taylor instability. It is shown that the proposed method can track the interface with high accuracy and stability and can significantly and systematically reduce the parasitic current across the interface. Comparisons with momentum-based models indicate that the newly proposed velocity-based model can better satisfy the incompressible condition in the flow fields, and eliminate or reduce the velocity fluctuations in the higher-pressure-gradient region and, therefore, achieve a better numerical stability. In addition, the test of a layered Poiseuille flow demonstrates that the proposed scheme for mixture viscosity performs significantly better than the traditional mixture viscosity methods.
Guidelines for optimizing multilevel ECN using fluid-flow-based TCP model
NASA Astrophysics Data System (ADS)
Quet, Pierre-Francois; Chellappan, Sriram; Durresi, Arjan; Sridharan, Mukundan; Ozbay, Hitay; Jain, Raj
2002-07-01
Congestion avoidance on today's Internet is mainly provided by the combination of the TCP protocol and Active Queue Management (AQM) schemes such as the de facto standard RED (Random Early Detection). When used with ECN (Explicit Congestion Notification), these algorithms can be modeled as a feedback control system in which the feedback information is carried on a single bit. A modification of this scheme called MECN was proposed, where the marking information is carried using 2 bits. MECN conveys more accurate feedback about the network congestion to the source than the current 1-bit ECN. The TCP source reaction was modified so that it takes advantage of the extra information about congestion and adapts faster to the changing congestion scenario leading to a smoother decrease in the sending rates of the sources upon congestion detection and consequently resulting in an increase in the router's throughput. A linearized fluid flow model already developed for ECN is extended to our case. Using control theoretic tools we justify the performance obtained in using the MECN scheme and give guidelines for optimizing its parameters. We use ns simulations to illustrate the performance improvement from the point of better throughput and low level of oscillations in the queue.
Trajectory-based modeling of fluid transport in a medium with smoothly varying heterogeneity
NASA Astrophysics Data System (ADS)
Vasco, D. W.; Pride, Steven R.; Commer, Michael
2016-04-01
Using an asymptotic methodology, valid in the presence of smoothly varying heterogeneity and prescribed boundaries, we derive a trajectory-based solution for tracer transport. The analysis produces a Hamilton-Jacobi partial differential equation for the phase of the propagating tracer front. The trajectories follow from the characteristic equations that are equivalent to the Hamilton-Jacobi equation. The paths are determined by the fluid velocity field, the total porosity, and the dispersion tensor. Due to their dependence upon the local hydrodynamic dispersion, they differ from conventional streamlines. This difference is borne out in numerical calculations for both uniform and dipole flow fields. In an application to the computational X-ray imaging of a saline tracer test, we illustrate that the trajectories may serve as the basis for a form of tracer tomography. In particular, we use the onset time of a change in attenuation for each volume element of the X-ray image as a measure of the arrival time of the saline tracer. The arrival times are used to image the spatial variation of the effective hydraulic conductivity within the laboratory sample.
Nanodiamond-based thermal fluids.
Taha-Tijerina, Jose Jaime; Narayanan, Tharangattu Narayanan; Tiwary, Chandra Sekhar; Lozano, Karen; Chipara, Mircea; Ajayan, Pulickel M
2014-04-01
Dispersions of nanodiamond (average size ∼6 nm) within dielectric insulator mineral oil are reported for their enhanced thermal conductivity properties and potential applications in thermal management. Dynamic and kinematic viscosities-very important parameters in thermal management by nanofluids-are investigated. The dependence of the dynamic viscosity is well-described by the theoretical predictions of Einstein's model. The temperature dependence of the dynamic viscosity obeys an Arrhenius-like behavior, where the activation energy and the pre-exponential factor have an exponential dependence on the filler fraction of nanodiamonds. An enhancement in thermal conductivity up to 70% is reported for nanodiamond based thermal fluids. Additional electron microscopy, Raman spectroscopy and X-ray diffraction analysis support the experimental data and their interpretation. PMID:24650328
2010-01-01
Based on recently reported data that fructose ingestion is linked to arterial hypertension, a model of regulatory loops involving the colon role in maintenance of fluid and sodium homeostasis is proposed. In normal digestion of hyperosmolar fluids, also in cases of postprandial hypotension and in patients having the "dumping" syndrome after gastric surgery, any hyperosmolar intestinal content is diluted by water taken from circulation and being trapped in the bowel until reabsorption. High fructose corn sirup (HFCS) soft drinks are among common hyperosmolar drinks. Fructose is slowly absorbed through passive carrier-mediated facilitated diffusion, along the entire small bowel, thus preventing absorption of the trapped water for several hours. Here presented interpretation is that ingestion of hyperosmolar HFCS drinks due to a transient fluid shift into the small bowel increases renin secretion and sympathetic activity, leading to rise in ADH and aldosterone secretions. Their actions spare water and sodium in the large bowel and kidneys. Alteration of colon absorption due to hormone exposure depends on cell renewal and takes days to develop, so the momentary capacity of sodium absorption in the colon depends on the average aldosterone and ADH exposure during few previous days. This inertia in modulation of the colon function can make an individual that often takes HFCS drinks prone to sodium retention, until a new balance is reached with an expanded ECF pool and arterial hypertension. In individuals with impaired fructose absorption, even a higher risk of arterial hypertension can be expected. PMID:20579372
First Author = C.Z. Cheng; Jay R. Johnson
1998-07-10
A nonlinear kinetic-fluid model for high-beta plasmas with multiple ion species which can be applied to multiscale phenomena is presented. The model embeds important kinetic effects due to finite ion Larmor radius (FLR), wave-particle resonances, magnetic particle trapping, etc. in the framework of simple fluid descriptions. When further restricting to low frequency phenomena with frequencies less than the ion cyclotron frequency the kinetic-fluid model takes a simpler form in which the fluid equations of multiple ion species collapse into single-fluid density and momentum equations and a low frequency generalized Ohm's law. The kinetic effects are introduced via plasma pressure tensors for ions and electrons which are computed from particle distribution functions that are governed by the Vlasov equation or simplified plasma dynamics equations such as the gyrokinetic equation. The ion FLR effects provide a finite parallel electric field, a perpendicular velocity that modifies the ExB drift, and a gyroviscosity tensor, all of which are neglected in the usual one-fluid MHD description. Eigenmode equations are derived which include magnetosphere-ionosphere coupling effects for low frequency waves (e.g., kinetic/inertial Alfven waves and ballooning-mirror instabilities).
NASA Astrophysics Data System (ADS)
Hakkarainen, Elina; Tähtinen, Matti
2016-05-01
Demonstrations of direct steam generation (DSG) in linear Fresnel collectors (LFC) have given promising results related to higher steam parameters compared to the current state-of-the-art parabolic trough collector (PTC) technology using oil as heat transfer fluid (HTF). However, DSG technology lacks feasible solution for long-term thermal energy storage (TES) system. This option is important for CSP technology in order to offer dispatchable power. Recently, molten salts have been proposed to be used as HTF and directly as storage medium in both line-focusing solar fields, offering storage capacity of several hours. This direct molten salt (DMS) storage concept has already gained operational experience in solar tower power plant, and it is under demonstration phase both in the case of LFC and PTC systems. Dynamic simulation programs offer a valuable effort for design and optimization of solar power plants. In this work, APROS dynamic simulation program is used to model a DMS linear Fresnel solar field with two-tank TES system, and example simulation results are presented in order to verify the functionality of the model and capability of APROS for CSP modelling and simulation.
Comprehensive Mathematical Model Of Real Fluids
NASA Technical Reports Server (NTRS)
Anderson, Peter G.
1996-01-01
Mathematical model of thermodynamic properties of water, steam, and liquid and gaseous hydrogen and oxygen developed for use in computational simulations of flows of mass and heat in main engine of space shuttle. Similar models developed for other fluids and applications. Based on HBMS equation of state.
Wolf, Matthew B
2015-08-01
A mathematical model of whole-body acid-base and fluid-electrolyte balance was used to provide information leading to the diagnosis and fluid-therapy treatment in patients with complex acid-base disorders. Given a set of measured laboratory-chemistry values for a patient, a model of their unique, whole-body chemistry was created. This model predicted deficits or excesses in the masses of Na(+), K(+), Cl(-) and H2O as well as the plasma concentration of unknown or unmeasured species, such as ketoacids, in diabetes mellitus. The model further characterized the acid-base disorder by determining the patient's whole-body base excess and quantitatively partitioning it into ten components, each contributing to the overall disorder. The results of this study showed the importance of a complete set of laboratory measurements to obtain sufficient accuracy of the quantitative diagnosis; having only a minimal set, just pH and PCO2, led to a large scatter in the predicted results. A computer module was created that would allow a clinician to achieve this diagnosis at the bedside. This new diagnostic approach should prove to be valuable in the treatment of the critically ill. PMID:25281215
Martin, Kelly J; Picioreanu, Cristian; Nerenberg, Robert
2013-09-01
A two-dimensional, particle-based biofilm model coupled with mass transport and computational fluid dynamics was developed to simulate autotrophic denitrification in a spiral-wound membrane biofilm reactor (MBfR), where hydrogen is supplied via hollow-fiber membrane fabric. The spiral-wound configuration consists of alternating layers of plastic spacer net and membrane fabric that create rows of flow channels, with the top and bottom walls comprised of membranes. The transversal filaments of the spacer partially obstruct the channel flow, producing complex mixing and shear patterns that require multidimensional representation. This study investigated the effect of hydrogen and nitrate concentrations, as well as spacer configuration, on biofilm development and denitrification fluxes. The model results indicate that the cavity spacer filaments, which rest on the bottom membranes, cause uneven biofilm growth. Most biofilm resided on the bottom membranes, only in the wake of the filaments where low shear zones formed. In this way, filament configuration may help achieve a desired biofilm thickness. For the conditions tested in this study, the highest nitrate fluxes were attained by minimizing the filament diameter and maximizing the filament spacing. This lowered the shear stress at the top membranes, allowing for more biofilm growth. For the scenarios studied, biomass limitation at the top membranes hindered performance more significantly than diffusion limitation in the thick biofilms at the bottom membranes. The results also highlighted the importance of two-dimensional modeling to capture uneven biofilm growth on a substratum with geometrical complexity. PMID:23774188
VISCOPLASTIC FLUID MODEL FOR DEBRIS FLOW ROUTING.
Chen, Cheng-lung
1986-01-01
This paper describes how a generalized viscoplastic fluid model, which was developed based on non-Newtonian fluid mechanics, can be successfully applied to routing a debris flow down a channel. The one-dimensional dynamic equations developed for unsteady clear-water flow can be used for debris flow routing if the flow parameters, such as the momentum (or energy) correction factor and the resistance coefficient, can be accurately evaluated. The writer's generalized viscoplastic fluid model can be used to express such flow parameters in terms of the rheological parameters for debris flow in wide channels. A preliminary analysis of the theoretical solutions reveals the importance of the flow behavior index and the so-called modified Froude number for uniformly progressive flow in snout profile modeling.
NASA Technical Reports Server (NTRS)
Mavroidis, Constantinos; Pfeiffer, Charles; Paljic, Alex; Celestino, James; Lennon, Jamie; Bar-Cohen, Yoseph
2000-01-01
For many years, the robotic community sought to develop robots that can eventually operate autonomously and eliminate the need for human operators. However, there is an increasing realization that there are some tasks that human can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robot can be employed to perform these tasks. Remotely performing these types of tasks requires operating robots as human surrogates. While current "hand master" haptic systems are able to reproduce the feeling of rigid objects, they present great difficulties in emulating the feeling of remote/virtual stiffness. In addition, they tend to be heavy, cumbersome and usually they only allow limited operator workspace. In this paper a novel haptic interface is presented to enable human-operators to "feel" and intuitively mirror the stiffness/forces at remote/virtual sites enabling control of robots as human-surrogates. This haptic interface is intended to provide human operators intuitive feeling of the stiffness and forces at remote or virtual sites in support of space robots performing dexterous manipulation tasks (such as operating a wrench or a drill). Remote applications are referred to the control of actual robots whereas virtual applications are referred to simulated operations. The developed haptic interface will be applicable to IVA operated robotic EVA tasks to enhance human performance, extend crew capability and assure crew safety. The electrically controlled stiffness is obtained using constrained ElectroRheological Fluids (ERF), which changes its viscosity under electrical stimulation. Forces applied at the robot end-effector due to a compliant environment will be reflected to the user using this ERF device where a change in the system viscosity will occur proportionally to the force to be transmitted. In this paper, we will present the results of our modeling, simulation, and initial testing of such an
Method of recovering oil-based fluid
Brinkley, H.E.
1993-07-13
A method is described of recovering oil-based fluid, said method comprising the steps of: applying an oil-based fluid absorbent cloth of man-made fiber to an oil-based fluid, the cloth having at least a portion thereof that is napped so as to raise ends and loops of the man-made fibers and define voids; and absorbing the oil-based fluid into the napped portion of the cloth.
NASA Astrophysics Data System (ADS)
Ohta, J.; Tokunaga, T.
2012-12-01
In deep crust, it is considered that the solid phase tends to keep its polycrystalline structure while it flows as highly-viscous fluid, and that the fluid phase flows through polycrystalline solid as porous flow. Here, the solid-framework is considered to change its bulk volume due to the changes of fluid volumetric fraction. In addition, wettability of solid-liquid system, which is expressed as solid-liquid dihedral angle, is also considered to affect internal pore structure. Thus, the solid-framework deformation and wettability of solid-liquid system are considered to influence fluid migration. In this research, we firstly constructed the permeability model to formulate a relationship among solid-liquid dihedral angle, fluid fraction, and permeability based on the energetic and textural considerations of grain boundary interface. The permeability and the fluid fraction under minimum interfacial energy condition were expressed as functions of solid-liquid dihedral angle from this model. Then, we found that permeability can be written as functions of the fluid fraction and the permeability under minimum interfacial energy condition. Secondly, we formulated the deformation of solid-framework and fluid flow through the deforming framework. The governing equations included solid bulk viscosity and solid shear viscosity as necessary parameters to describe the behavior. Based on the derived governing equations, the one-dimensional numerical simulations were conducted with different solid viscosities. From the results where solid bulk/shear viscosity was set to be 1020 Pa×s, intervals with relatively high fluid fraction were formed and the intervals showed attenuated fluctuation of their fluid volume fraction. On the other hand, the results where solid bulk/shear viscosity was set to be 1019 Pa×s did not show such fluctuation. The complex interaction among fluid fraction, permeability, and solid viscosity could contribute to the observed phenomena, and further
Numerical modeling of materials processes with fluid-fluid interfaces
NASA Astrophysics Data System (ADS)
Yanke, Jeffrey Michael
A numerical model has been developed to study material processes that depend on the interaction between fluids with a large discontinuity in thermophysical properties. A base model capable of solving equations of mass, momentum, energy conservation, and solidification has been altered to enable tracking of the interface between two immiscible fluids and correctly predict the interface deformation using a volume of fluid (VOF) method. Two materials processes investigated using this technique are Electroslag Remelting (ESR) and plasma spray deposition. ESR is a secondary melting technique that passes an AC current through an electrically resistive slag to provide the heat necessary to melt the alloy. The simulation tracks the interface between the slag and metal. The model was validated against industrial scale ESR ingots and was able to predict trends in melt rate, sump depth, macrosegregation, and liquid sump depth. In order to better understand the underlying physics of the process, several constant current ESR runs simulated the effects of freezing slag in the model. Including the solidifying slag in the imulations was found to have an effect on the melt rate and sump shape but there is too much uncertainty in ESR slag property data at this time for quantitative predictions. The second process investigated in this work is the deposition of ceramic coatings via plasma spray deposition. In plasma spray deposition, powderized coating material is injected into a plasma that melts and carries the powder towards the substrate were it impacts, flattening out and freezing. The impacting droplets pile up to form a porous coating. The model is used to simulate this rain of liquid ceramic particles impacting the substrate and forming a coating. Trends in local solidification time and porosity are calculated for various particle sizes and velocities. The predictions of decreasing porosity with increasing particle velocity matches previous experimental results. Also, a
Parametric Modeling for Fluid Systems
NASA Technical Reports Server (NTRS)
Pizarro, Yaritzmar Rosario; Martinez, Jonathan
2013-01-01
Fluid Systems involves different projects that require parametric modeling, which is a model that maintains consistent relationships between elements as is manipulated. One of these projects is the Neo Liquid Propellant Testbed, which is part of Rocket U. As part of Rocket U (Rocket University), engineers at NASA's Kennedy Space Center in Florida have the opportunity to develop critical flight skills as they design, build and launch high-powered rockets. To build the Neo testbed; hardware from the Space Shuttle Program was repurposed. Modeling for Neo, included: fittings, valves, frames and tubing, between others. These models help in the review process, to make sure regulations are being followed. Another fluid systems project that required modeling is Plant Habitat's TCUI test project. Plant Habitat is a plan to develop a large growth chamber to learn the effects of long-duration microgravity exposure to plants in space. Work for this project included the design and modeling of a duct vent for flow test. Parametric Modeling for these projects was done using Creo Parametric 2.0.
Multi-fluid models of polymeric liquids
NASA Astrophysics Data System (ADS)
Tree, Douglas; Fredrickson, Glenn
Industrial processes for producing polymer-based materials often operate away from equilibrium, making the final microstructure - and thus the properties of the material - dependent on processing history. Current simulation methods struggle to accurately describe such processes. Traditional fluid dynamics is able to capture transport behavior, but lacks the complex phase behavior characteristic of many polymeric liquids. Coarse-grained particle models can handle the complexity, but are constrained by time and length scales. Consequently, we explore an alternative field-theoretic framework based on the ``two-fluid'' model originally proposed by Brochard and de Gennes. To demonstrate feasibility, we derive a model and develop an efficient numerical method for a ternary polymer solution. Subsequently, we use this model and method to examine the physics of the immersion precipitation process, used industrially to produce polymer membranes.
NASA Astrophysics Data System (ADS)
Nemčok, Michal; Henk, Andreas; Gayer, Rodney A.; Vandycke, Sara; Hathaway, Tanya M.
2002-12-01
We present a finite-element study of stress perturbation in evolving compressive and extensional strike-slip fault bridges. The results are compared with a fracture study of a compressive bridge at St Donats, UK. Horizontally interbedded calcareous mudstone and bioclastic calcilutite at St Donats have a distinct vertical permeability anisotropy. This sedimentary sequence behaves as a set of horizontal aquifers. The fluid flow in these aquifers is sensitive to mean stress gradients. Paleostress analysis of field fracture data, verified by finite-element modelling, indicates a rotation of σ1 towards parallelism with boundary faults inside the growing compressive bridge. Boundary faults and bridge faults recorded numerous fluid flow events. The modelled mean stress pattern shows a regional maximum within the bridge and local maxima/minima pairs at boundary fault tips. Finite-element modelling of an extensional bridge indicates that σ3 rotates towards parallelism with boundary faults. The mean stress pattern is similar to the pattern in compressive bridge but with maxima and minima locations interchanged. The stress patterns are reestablished by each stress build-up preceding the rupturation of the boundary faults throughout the development stages of strike-slip fault bridges. Mean stress gradients developed pre-failure control the fluid flow in fractures of the strike-slip fault system at and after the end of each stress build-up and the fluid flow in boundary faults post-failure. Fracture reactivation and new fracture generation within an evolving bridge is a process consisting of multiple successive events that retain the storage capacity of the bridge. Rupture and sealing of the main bounding-faults is a step-wise process that opens and closes fluid conduits between areas with different pressures.
Fluids and Combustion Facility: Fluids Integrated Rack Modal Model Correlation
NASA Technical Reports Server (NTRS)
McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.
2005-01-01
The Fluids Integrated Rack (FIR) is one of two racks in the Fluids and Combustion Facility on the International Space Station. The FIR is dedicated to the scientific investigation of space system fluids management supporting NASA s Exploration of Space Initiative. The FIR hardware was modal tested and FIR finite element model updated to satisfy the International Space Station model correlation criteria. The final cross-orthogonality results between the correlated model and test mode shapes was greater than 90 percent for all primary target modes.
A study of the variation of physical conditions in the cometary coma based on a 3D multi-fluid model
NASA Astrophysics Data System (ADS)
Shou, Y.; Combi, M. R.; Fougere, N.; Tenishev, V.; Toth, G.; Gombosi, T. I.; Huang, Z.; Jia, X.; Bieler, A. M.; Hansen, K. C.
2015-12-01
Physics-based numerical coma models are desirable whether to interpret the spacecraft observations of the inner coma or to compare with the ground-based observations of the outer coma. One example is Direct Simulation Monte Carlo (DSMC) method, which has been successfully adopted to simulate the coma under various complex conditions. However, for bright comets with large production rates, the time step in DSMC model has to be tiny to accommodate the small mean free path and the high collision frequency. In addition a truly time-variable 3D DSMC model would still be computationally difficult or even impossible under most circumstances. In this work, we develop a multi-neutral-fluid model based on BATS-R-US in the University of Michigan's SWMF (Space Weather Modeling Framework), which can serve as a useful alternative to DSMC methods to compute both the inner and the outer coma and to treat time-variable phenomena. This model treats H2O, OH, H2, O, H and CO2 as separate fluids and each fluid has its own velocity and temperature. But collisional interactions can also couple all fluids together. Collisional interactions tend to decrease the velocity differences and are also able to re-distribute the excess energy deposited by chemical reactions among all species. To compute the momentum and energy transfer caused by such interactions self-consistently, collisions between fluids, whose efficiency is proportional to the densities, are included as well as heating from various chemical reactions. By applying the model to comets with different production rates (i.e. 67P/Churyumov-Gerasimenko, 1P/Halley, etc.), we are able to study how the heating efficiency varies with cometocentric distances and production rates. The preliminary results and comparison are presented and discussed. This work has been partially supported by grant NNX14AG84G from the NASA Planetary Atmospheres Program, and US Rosetta contracts JPL #1266313, JPL #1266314 and JPL #1286489.
Standardization of Thermo-Fluid Modeling in Modelica.Fluid
Franke, Rudiger; Casella, Francesco; Sielemann, Michael; Proelss, Katrin; Otter, Martin; Wetter, Michael
2009-09-01
This article discusses the Modelica.Fluid library that has been included in the Modelica Standard Library 3.1. Modelica.Fluid provides interfaces and basic components for the device-oriented modeling of onedimensional thermo-fluid flow in networks containing vessels, pipes, fluid machines, valves and fittings. A unique feature of Modelica.Fluid is that the component equations and the media models as well as pressure loss and heat transfer correlations are decoupled from each other. All components are implemented such that they can be used for media from the Modelica.Media library. This means that an incompressible or compressible medium, a single or a multiple substance medium with one or more phases might be used with one and the same model as long as the modeling assumptions made hold. Furthermore, trace substances are supported. Modeling assumptions can be configured globally in an outer System object. This covers in particular the initialization, uni- or bi-directional flow, and dynamic or steady-state formulation of mass, energy, and momentum balance. All assumptions can be locally refined for every component. While Modelica.Fluid contains a reasonable set of component models, the goal of the library is not to provide a comprehensive set of models, but rather to provide interfaces and best practices for the treatment of issues such as connector design and implementation of energy, mass and momentum balances. Applications from various domains are presented.
NASA Technical Reports Server (NTRS)
White, R. J.
1973-01-01
A detailed description of Guyton's model and modifications are provided. Also included are descriptions of several typical experiments which the model can simulate to illustrate the model's general utility. A discussion of the problems associated with the interfacing of the model to other models such as respiratory and thermal regulation models which is prime importance since these stimuli are not present in the current model is also included. A user's guide for the operation of the model on the Xerox Sigma 3 computer is provided and two programs are described. A verification plan and procedure for performing experiments is also presented.
Modeling Strains Associated with Fluid Extraction
NASA Astrophysics Data System (ADS)
Barbour, A. J.; Agnew, D. C.; Wyatt, F. K.
2013-12-01
A class of strain signals found in data from a number of borehole strainmeters in the Plate Boundary Observatory network is believed to be associated with pumping of nearby water wells. In order to test the connection between fluid extraction and deformation, we have collected a multi- year record of the pump activity at two actively-pumped wells near the pair of strainmeters at the Pathfinder Ranch, a summer camp located in the Garner Valley in southern California. The data we have collected indicate strong correlations between (1) times of fluid extraction and the onset of significant strain and pore-fluid pressure changes, and (2) cumulative extraction volumes and the sizes of the pressure and strain perturbations. In order to model these observations, we use a sum of K autoregressive models to create a statistical description of the effect, and a poroelastic model to create a physical description. We show that for K = 2 the mixture model adequately preserves both long- and short-term effects, and can be used to construct a ';correction series' from the binary pumping series in a numerically efficient manner. Spatiotemporal strain and pore- fluid pressure fields associated with episodes of fluid extraction are simulated in a layered, radially extensive poroelastic medium. Based on the interpretations of our parameter exploration, the simplest model which fits the observed strains and pressures is a two layer model where rigid bedrock having relatively high diffusivity is overlain by roughly 100 meters of alluvium having slightly higher diffusivity and behaving as an unconfined aquifer system. The lack of a strong contrast in diffusivity between lithologic units suggests that the bedrock material has a relatively high density of hydraulically conductive fractures; borehole logging data and drillers' logs corroborate this. Further, the requirement that both layers have high conductivity helps explain the relatively low sensitivity of the aquifer system to dynamic
NASA Astrophysics Data System (ADS)
Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove
2016-04-01
Operation of fluid injection into and withdrawal from the subsurface for various purposes has been known to induce earthquakes. Such operations include hydraulic fracturing for shale gas extraction, hydraulic stimulation for Enhanced Geothermal System development and waste water disposal. Among these, several damaging earthquakes have been reported in the USA in particular in the areas of high-rate massive amount of wastewater injection [1] mostly with natural fault systems. Oil and gas production have been known to induce earthquake where pore fluid pressure decreases in some cases by several tens of Mega Pascal. One recent seismic event occurred in November 2013 near Azle, Texas where a series of earthquakes began along a mapped ancient fault system [2]. It was studied that a combination of brine production and waste water injection near the fault generated subsurface pressures sufficient to induced earthquakes on near-critically stressed faults. This numerical study aims at investigating the occurrence mechanisms of such earthquakes induced by fluid injection [3] and withdrawal by using hydro-geomechanical coupled dynamic simulator (Itasca's Particle Flow Code 2D). Generic models are setup to investigate the sensitivity of several parameters which include fault orientation, frictional properties, distance from the injection well to the fault, amount of fluid withdrawal around the injection well, to the response of the fault systems and the activation magnitude. Fault slip movement over time in relation to the diffusion of pore pressure is analyzed in detail. Moreover, correlations between the spatial distribution of pore pressure change and the locations of induced seismic events and fault slip rate are investigated. References [1] Keranen KM, Weingarten M, Albers GA, Bekins BA, Ge S, 2014. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection, Science 345, 448, DOI: 10.1126/science.1255802. [2] Hornbach MJ, DeShon HR
NASA Astrophysics Data System (ADS)
Leibs, Christopher A.
Efforts are currently being directed towards a fully implicit, electromagnetic, JFNK-based solver, motivating the necessity of developing a fluid-based, electromag- netic, preconditioning strategy. The two-fluid plasma (TFP) model is an ideal approximation to the kinetic Jacobian. The TFP model couples both an ion and an electron fluid with Maxwell's equations. The fluid equations consist of the conservation of momentum and number density. A Darwin approximation of Maxwell is used to eliminate light waves from the model in order to facilitate coupling to non-relativistic particle models. We analyze the TFP-Darwin system in the context of a stand-alone solver with consideration of preconditioning a kinetic-JFNK approach. The TFP-Darwin system is addressed numerically by use of nested iteration (NI) and a First-Order Systems Least Squares (FOSLS) discretization. An important goal of NI is to produce an approximation that is within the basis of attraction for Newton's method on a relatively coarse mesh and, thus, on all subsequent meshes. After scaling and modification, the TFP-Darwin model yields a nonlinear, first-order system of equa- tions whose Frechet derivative is shown to be uniformly H1-elliptic in a neighborhood of the exact solution. H1 ellipticity yields optimal finite element performance and lin- ear systems amenable to solution with Algebraic Multigrid (AMG). To efficiently focus computational resources, an adaptive mesh refinement scheme, based on the accuracy per computational cost, is leveraged. Numerical tests demonstrate the efficacy of the approach, yielding an approximate solution within discretization error in a relatively small number of computational work units.
A fluid model simulation of a simplified plasma limiter based on spectral-element time-domain method
Qian, Cheng; Ding, Dazhi Fan, Zhenhong; Chen, Rushan
2015-03-15
A simplified plasma limiter prototype is proposed and the fluid model coupled with Maxwell's equations is established to describe the operating mechanism of plasma limiter. A three-dimensional (3-D) simplified sandwich structure plasma limiter model is analyzed with the spectral-element time-domain (SETD) method. The field breakdown threshold of air and argon at different frequency is predicted and compared with the experimental data and there is a good agreement between them for gas microwave breakdown discharge problems. Numerical results demonstrate that the two-layer plasma limiter (plasma-slab-plasma) has better protective characteristics than a one-layer plasma limiter (slab-plasma-slab) with the same length of gas chamber.
NASA Astrophysics Data System (ADS)
Lee, H.; Min, D.; Lim, S.; Yang, J.; Kwon, B.; Yoo, H.
2009-12-01
In a conventional marine seismic data analysis, pressure data have been usually interpreted on the basis of acoustic wave equation. The acoustic wave equation, however, only deals with P-wave propagation, and it cannot correctly describe the wave propagation in acoustic-elastic (fluid-solid) coupled media. Recently, in 4C OBC survey (4-component ocean bottom cable), it is possible to acquire both pressure and 3-component displacements (measured at the sea-bottom). Combining pressure and displacement data allows us to interpret subsurface structures more accurately. In order to accurately simulate wave propagation in fluid-solid coupled media, we need an acoustic-elastic coupled modeling algorithm, which deals with displacements in elastic region and pressure in acoustic region. For waveform inversion and reverse-time migration that require a great number of forward modeling, it is essential to develop an efficient scheme that reduces computing time and computer core memory. In this study, we present a 3D time-domain acoustic-elastic coupled modeling algorithm on the basis of the cell-based finite difference method. The cell-based method has proven to properly describe the free-surface boundary, which indicates that it will also properly describe the fluid-solid interface boundaries. In the acoustic-elastic coupled modeling, we first compose cell-based finite differences individually for the 3D acoustic and elastic media, and then combine the differences using the fluid-solid interface boundary conditions. Considering that the 2D acoustic-elastic coupled modeling algorithm gives numerical solutions comparable to analytic solutions, we expect that the 3D acoustic-elastic coupled modeling will correctly describe wave propagation in the fluid-solid coupled media. We apply our algorithm to 3D horizontal two- and three-layer models. Numerical experiments show that the cell-based coupled modeling algorithm properly describes S- and converted waves as well as P-waves. The
Computational fluid dynamic modelling of cavitation
NASA Technical Reports Server (NTRS)
Deshpande, Manish; Feng, Jinzhang; Merkle, Charles L.
1993-01-01
Models in sheet cavitation in cryogenic fluids are developed for use in Euler and Navier-Stokes codes. The models are based upon earlier potential-flow models but enable the cavity inception point, length, and shape to be determined as part of the computation. In the present paper, numerical solutions are compared with experimental measurements for both pressure distribution and cavity length. Comparisons between models are also presented. The CFD model provides a relatively simple modification to an existing code to enable cavitation performance predictions to be included. The analysis also has the added ability of incorporating thermodynamic effects of cryogenic fluids into the analysis. Extensions of the current two-dimensional steady state analysis to three-dimensions and/or time-dependent flows are, in principle, straightforward although geometrical issues become more complicated. Linearized models, however offer promise of providing effective cavitation modeling in three-dimensions. This analysis presents good potential for improved understanding of many phenomena associated with cavity flows.
Fluid-solid modeling of lymphatic valves
NASA Astrophysics Data System (ADS)
Caulk, Alexander; Ballard, Matthew; Nepiyushchikh, Zhanna; Dixon, Brandon; Alexeev, Alexander
2015-11-01
The lymphatic system performs important physiological functions such as the return of interstitial fluid to the bloodstream to maintain tissue fluid balance, as well as the transport of immune cells in the body. It utilizes contractile lymphatic vessels, which contain valves that open and close to allow flow in only one direction, to directionally pump lymph against a pressure gradient. We develop a fluid-solid model of geometrically representative lymphatic valves. Our model uses a hybrid lattice-Boltzmann lattice spring method to capture fluid-solid interactions with two-way coupling between a viscous fluid and lymphatic valves in a lymphatic vessel. We use this model to investigate the opening and closing of lymphatic valves, and its effect on lymphatic pumping. This helps to broaden our understanding of the fluid dynamics of the lymphatic system.
[Kidney, Fluid, and Acid-Base Balance].
Shioji, Naohiro; Hayashi, Masao; Morimatsu, Hiroshi
2016-05-01
Kidneys play an important role to maintain human homeostasis. They contribute to maintain body fluid, electrolytes, and acid-base balance. Especially in fluid control, we, physicians can intervene body fluid balance using fluid resuscitation and diuretics. In recent years, one type of fluid resuscitation, hydroxyl ethyl starch has been extensively studied in the field of intensive care. Although their effects on fluid resuscitation are reasonable, serious complications such as kidney injury requiring renal replacement therapy occur frequently. Now we have to pay more attention to this important complication. Another topic of fluid management is tolvaptan, a selective vasopressin-2 receptor antagonist Recent randomized trial suggested that tolvaptan has a similar supportive effect for fluid control and more cost effective compared to carperitide. In recent years, Stewart approach is recognized as one important tool to assess acid-base balance in critically ill patients. This approach has great value, especially to understand metabolic components in acid-base balance. Even for assessing the effects of kidneys on acid-base balance, this approach gives us interesting insight. We should appropriately use this new approach to treat acid-base abnormality in critically ill patients. PMID:27319095
GUIDELINE FOR FLUID MODELING OF ATMOSPHERIC DIFFUSION
The fundamental principles for fluid modeling of flow and dispersion of pollutants in the atmospheric boundary layer are reviewed. The usefulness of fluid models are evaluated from both scientific and engineering viewpoints. Because many detailed decisions must be made during the...
Segregated Methods for Two-Fluid Models
Prosperetti, Andrea; Sundaresan, Sankaran; Pannala, Sreekanth; Zhang, Duan Z.
2007-01-01
The previous chapter, with its direct simulation of the fluid flow and a modeling approach to the particle phase, may be seen as a transition between the methods for a fully resolved simulation described in the first part of this book and those for a coarse grained description based on the averaging approach described in chapter ??. We now turn to the latter, which in practice are the only methods able to deal with the complex flows encountered in most situations of practical interest such as fluidized beds, pipelines, energy generation, sediment transport, and others. This chapter and the next one are devoted to numerical methods for so-called two-fluid models in which the phases are treated as inter-penetrating continua describing, e.g., a liquid and a gas, or a fluid and a suspended solid phase. These models can be extended to deal with more than two continua and, then, the denomination multi-fluid models might be more appropriate. For example, the commercial code OLGA (Bendiksen et al. 1991), widely used in the oil industry, recognizes three phases, all treated as interpenetrating continua: a continuous liquid, a gas, and a disperse liquid phase present as drops suspended in the gas phase. The more recent PeTra (Petroleum Transport, Larsen et al. 1997) also describes three phases, gas, oil, and water. Recent approaches to the description of complex boiling flows recognize four inter-penetrating phases: a liquid phase present both as a continuum and as a dispersion of droplets, and a gas/vapor phase also present as a continuum and a dispersion of bubbles. Methods for these multi-fluid models are based on those developed for the two-fluid model to which we limit ourselves.
In principle, one could simply take the model equations, discretize them, and solve them by a method suitable for non-linear problems, e.g. Newton-Raphson iteration. In practice, the computational cost of such a frontal attack is nearly always prohibitive in terms of storage requirement
Fluid casting of particle-based articles
Menchhofer, P.
1995-03-28
A method is disclosed for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with one aspect of the invention, a thermally settable slurry containing a relatively high concentration of the particles is introduced into an immiscible, heated fluid. The slurry sets hardens into a shape determined by the physical characteristics of the fluid and the manner of introduction of the slurry into the fluid. For example, the slurry is pulse injected into the fluid to provide spherical articles. The hardened spheres may then be sintered to consolidate the particles and provide a high density product. 1 figure.
Fluid casting of particle-based articles
Menchhofer, Paul
1995-01-01
A method for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with one aspect of the invention, a thermally settable slurry containing a relatively high concentration of the particles is introduced into an immiscible, heated fluid. The slurry sets or hardens into a shape determined by the physical characteristics of the fluid and the manner of introduction of the slurry into the fluid. For example, the slurry is pulse injected into the fluid to provide spherical articles. The hardened spheres may then be sintered to consolidate the particles and provide a high density product.
Liu, Huolong; Li, Mingzhong
2014-11-20
In this work a two-compartmental population balance model (TCPBM) was proposed to model a pulsed top-spray fluidized bed granulation. The proposed TCPBM considered the spatially heterogeneous granulation mechanisms of the granule growth by dividing the granulator into two perfectly mixed zones of the wetting compartment and drying compartment, in which the aggregation mechanism was assumed in the wetting compartment and the breakage mechanism was considered in the drying compartment. The sizes of the wetting and drying compartments were constant in the TCPBM, in which 30% of the bed was the wetting compartment and 70% of the bed was the drying compartment. The exchange rate of particles between the wetting and drying compartments was determined by the details of the flow properties and distribution of particles predicted by the computational fluid dynamics (CFD) simulation. The experimental validation has shown that the proposed TCPBM can predict evolution of the granule size and distribution within the granulator under different binder spray operating conditions accurately. PMID:25181553
Computational fluid dynamics modelling in cardiovascular medicine
Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2016-01-01
This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards ‘digital patient’ or ‘virtual physiological human’ representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges. PMID:26512019
Computational fluid dynamics modelling in cardiovascular medicine.
Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2016-01-01
This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards 'digital patient' or 'virtual physiological human' representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges. PMID:26512019
Geochemical modeling of fluid-fluid and fluid-mineral interactions during geological CO2 storage
NASA Astrophysics Data System (ADS)
Zhu, C.; Ji, X.; Lu, P.
2013-12-01
The long time required for effective CO2 storage makes geochemical modeling an indispensable tool for CCUS. One area of geochemical modeling research that is in urgent need is impurities in CO2 streams. Permitting impurities, such as H2S, in CO2 streams can lead to potential capital and energy savings. However, predicting the consequences of co-injection of CO2 and impurities into geological formations requires the understanding of the phase equilibrium and fluid-fluid interactions. To meet this need, we developed a statistical associating fluid theory (SAFT)-based equation of state (EOS) for the H2S-CO2-H2O-NaCl system at 373.15
Modelling natural convection of fluid in cuvette
NASA Astrophysics Data System (ADS)
Kucher, D.; Manukhin, B.; Andreeva, O.; Chivilikhin, S.
2014-09-01
Convection is a process of transfer liquid from a hot region to a cool region. This phenomenon is involved in many physical processes. The main characteristic of convection is a temperature field. Modelling of convection allows to get the information about temperature field at any time of process. In this paper the results of modelling natural convection of fluid in cuvette are presented. All results are approved by experimental data. For modelling the process of natural convection Navier-Stokes equations under Boussinesq approximation were used. An experimental setup based on digital holographic interferometry was developedin order to make an experiment. The results for three stadiums of convection, such as: jet initiation, initial jet formation, jet development with formation of mushroom-shaped convective stream, are presented.
Smart prosthetics based on magnetorheological fluids
NASA Astrophysics Data System (ADS)
Carlson, J. David; Matthis, Wilfried; Toscano, James R.
2001-06-01
One of the most exciting new applications for magnetorheological fluid technology is that of real-time controlled dampers for use in advanced prosthetic devices. In such systems a small magnetorheological fluid damper is used to control, in real-time, the motion of an artificial limb based on inputs from a group of sensors. A 'smart' prosthetic knee system based on a controllable magnetorheological fluid damper was commercially introduced to the orthopedics and prosthetics market in 2000. The benefit of such an artificial knee is a more natural gait that automatically adapts to changing gait conditions.
Direct modeling for computational fluid dynamics
NASA Astrophysics Data System (ADS)
Xu, Kun
2015-06-01
All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct
Fluid and Electrolyte Balance model (FEB)
NASA Technical Reports Server (NTRS)
Fitzjerrell, D. G.
1973-01-01
The effects of various oral input water loads on solute and water distribution throughout the body are presented in the form of a model. The model was a three compartment model; the three compartments being plasma, interstitial fluid and cellular fluid. Sodium, potassium, chloride and urea were the only major solutes considered explicitly. The control of body water and electrolyte distribution was affected via drinking and hormone levels.
Tactile dispay based on smart fluids
NASA Astrophysics Data System (ADS)
Liu, Y. J.; Davidson, R. I.; Taylor, P. M.
2007-07-01
A tactile display is programmable device to be detected by human touch. It has great potential applications in the field of virtual environment. The current research is the first step to develop a programmable tactile array based on ER/MR fluid technology. Prototypes of display incorporating controllable fluids such as electrrheological (ER) fluid and magnetorheological (MR) fluid have been developed and investigated. Surface force responses of these tactile displays under various electric/magnetic fields have been measured while a probe moving across the upper surface. As the applied external electric or magnetic field varied, the sensed surface profiles changed in synchronisation with the field strength. With the controllable fluid actuator, the displayed surface information is stable and repeatable.
Fiber bundle model under fluid pressure.
Amitrano, David; Girard, Lucas
2016-03-01
Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting. PMID:27078437
Fiber bundle model under fluid pressure
NASA Astrophysics Data System (ADS)
Amitrano, David; Girard, Lucas
2016-03-01
Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting.
Model of two-fluid reconnection.
Malyshkin, Leonid M
2009-12-01
A theoretical model of quasistationary, two-dimensional magnetic reconnection is presented in the framework of incompressible two-fluid magnetohydrodynamics. The results are compared with recent numerical simulations and experiment. PMID:20366155
Clay-based geothermal drilling fluids
Guven, N.; Carney, L.L.; Lee, L.J.; Bernhard, R.P.
1982-11-01
The rheological properties of fluids based on fibrous clays such as sepiolite and attapulgite have been systematically examined under conditions similar to those of geothermal wells, i.e. at elevated temperatures and pressures in environments with concentrated brines. Attapulgite- and sepiolite-based fluids have been autoclaved at temperatures in the range from 70 to 800/sup 0/F with the addition of chlorides and hydroxides of Na, K, Ca, and Mg. The rheological properties (apparent and plastic viscosity, fluid loss, gel strength, yield point, and cake thickness) of the autoclaved fluids have been studied and correlated with the chemical and physical changes that occur in the clay minerals during the autoclaving process.
Modeling quantum fluid dynamics at nonzero temperatures
Berloff, Natalia G.; Brachet, Marc; Proukakis, Nick P.
2014-01-01
The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluid model is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures. PMID:24704874
Transient Wellbore Fluid Flow Model
1982-04-06
WELBORE is a code to solve transient, one-dimensional two-phase or single-phase non-isothermal fluid flow in a wellbore. The primary thermodynamic variables used in solving the equations are the pressure and specific energy. An equation of state subroutine provides the density, quality, and temperature. The heat loss out of the wellbore is calculated by solving a radial diffusion equation for the temperature changes outside the bore. The calculation is done at each node point in themore » wellbore.« less
Theoretical models for supercritical fluid extraction.
Huang, Zhen; Shi, Xiao-Han; Jiang, Wei-Juan
2012-08-10
For the proper design of supercritical fluid extraction processes, it is essential to have a sound knowledge of the mass transfer mechanism of the extraction process and the appropriate mathematical representation. In this paper, the advances and applications of kinetic models for describing supercritical fluid extraction from various solid matrices have been presented. The theoretical models overviewed here include the hot ball diffusion, broken and intact cell, shrinking core and some relatively simple models. Mathematical representations of these models have been in detail interpreted as well as their assumptions, parameter identifications and application examples. Extraction process of the analyte solute from the solid matrix by means of supercritical fluid includes the dissolution of the analyte from the solid, the analyte diffusion in the matrix and its transport to the bulk supercritical fluid. Mechanisms involved in a mass transfer model are discussed in terms of external mass transfer resistance, internal mass transfer resistance, solute-solid interactions and axial dispersion. The correlations of the external mass transfer coefficient and axial dispersion coefficient with certain dimensionless numbers are also discussed. Among these models, the broken and intact cell model seems to be the most relevant mathematical model as it is able to provide realistic description of the plant material structure for better understanding the mass-transfer kinetics and thus it has been widely employed for modeling supercritical fluid extraction of natural matters. PMID:22560346
AFDM: An Advanced Fluid-Dynamics Model
Bohl, W.R.; Parker, F.R. ); Wilhelm, D. . Inst. fuer Neutronenphysik und Reaktortechnik); Berthier, J. ); Goutagny, L. . Inst. de Protection et de Surete Nucleaire); Ninokata,
1990-09-01
AFDM, or the Advanced Fluid-Dynamics Model, is a computer code that investigates new approaches simulating the multiphase-flow fluid-dynamics aspects of severe accidents in fast reactors. The AFDM formalism starts with differential equations similar to those in the SIMMER-II code. These equations are modified to treat three velocity fields and supplemented with a variety of new models. The AFDM code has 12 topologies describing what material contacts are possible depending on the presence or absence of a given material in a computational cell, on the dominant liquid, and on the continuous phase. Single-phase, bubbly, churn-turbulent, cellular, and dispersed flow regimes are permitted for the pool situations modeled. Virtual mass terms are included for vapor in liquid-continuous flow. Interfacial areas between the continuous and discontinuous phases are convected to allow some tracking of phenomenological histories. Interfacial areas are also modified by models of nucleation, dynamic forces, turbulence, flashing, coalescence, and mass transfer. Heat transfer is generally treated using engineering correlations. Liquid-vapor phase transitions are handled with the nonequilibrium, heat-transfer-limited model, whereas melting and freezing processes are based on equilibrium considerations. Convection is treated using a fractional-step method of time integration, including a semi-implicit pressure iteration. A higher-order differencing option is provided to control numerical diffusion. The Los Alamos SESAME equation-of-state has been implemented using densities and temperatures as the independent variables. AFDM programming has vectorized all computational loops consistent with the objective of producing an exportable code. 24 refs., 4 figs.
Non-Markovian coarse-grained modeling of polymeric fluids based on the Mori-Zwanzig formalism
NASA Astrophysics Data System (ADS)
Li, Zhen; Bian, Xin; Li, Xiantao; Karniadakis, George
The Mori-Zwanzig formalism for coarse-graining a complex dynamical system typically introduces memory effects. The Markovian assumption of delta-correlated fluctuating forces is often employed to simplify the formulation of coarse-grained (CG) models and numerical implementations. However, when the time scales of a system are not clearly separated, the memory effects become strong and the Markovian assumption becomes inaccurate. To this end, we incorporate memory effects into CG modeling by preserving non-Markovian interactions between CG variables based on the Mori-Zwanzig formalism. For a specific example, molecular dynamics (MD) simulations of star polymer melts are performed while the corresponding CG system is defined by grouping many bonded atoms into single clusters. Then, the effective interactions between CG clusters as well as the memory kernel are obtained from the MD simulations. The constructed CG force field with a memory kernel leads to a non-Markovian dissipative particle dynamics (NM-DPD). Quantitative comparisons on both static and dynamic properties between the CG models with Markovian and non-Markovian approximations will be presented. Supported by the DOE Center on Mathematics for Mesoscopic Modeling of Materials (CM4) and an INCITE grant.
NASA Technical Reports Server (NTRS)
Kandelman, A.; Nelson, D. J.
1977-01-01
Simplified mathematical model simulates large hydraulic systems on either analog or digital computers. Models of pumps, servoactuators, reservoirs, accumulators, and valves are connected generating systems containing six hundred elements.
Dinner, Stefanie; Borkowski, Julia; Stump-Guthier, Carolin; Ishikawa, Hiroshi; Tenenbaum, Tobias; Schroten, Horst; Schwerk, Christian
2016-01-01
The epithelial cells of the choroid plexus (CP), located in the ventricular system of the brain, form the blood-cerebrospinal fluid barrier (BCSFB). The BCSFB functions in separating the cerebrospinal fluid (CSF) from the blood and restricting the molecular exchange to a minimum extent. An in vitro model of the BCSFB is based on cells derived from a human choroid plexus papilloma (HIBCPP). HIBCPP cells display typical barrier functions including formation of tight junctions (TJs), development of a transepithelial electrical resistance (TEER), as well as minor permeabilities for macromolecules. There are several pathogens that can enter the central nervous system (CNS) via the BCSFB and subsequently cause severe disease like meningitis. One of these pathogens is Neisseria meningitidis (N. meningitidis), a human-specific bacterium. Employing the HIBCPP cells in an inverted cell culture filter insert system enables to study interactions of pathogens with cells of the BCSFB from the basolateral cell side, which is relevant in vivo. In this article, we describe seeding and culturing of HIBCPP cells on cell culture inserts. Further, infection of the cells with N. meningitidis along with analysis of invaded and adhered bacteria via double immunofluorescence is demonstrated. As the cells of the CP are also involved in other diseases, including neurodegenerative disorders like Alzheimer`s disease and Multiple Sclerosis, as well as during the brain metastasis of tumor cells, the model system can also be applied in other fields of research. It provides the potential to decipher molecular mechanisms and to identify novel therapeutic targets. PMID:27213495
Picciotto, Sally; Peters, Annette; Eisen, Ellen A.
2015-01-01
Occupational exposure to aerosolized particles of oil-based metalworking fluid was recently linked to deaths from ischemic heart disease. The current recommended exposure limits might be insufficient. Studying cardiovascular mortality is challenging because symptoms can induce sicker workers to reduce their exposure, causing healthy-worker survivor bias. G-estimation of accelerated failure time models reduces this bias and permits comparison of multiple exposure interventions. Michigan autoworkers from the United AutoWorkers–General Motors cohort (n = 38,666) were followed from 1941 through 1994. Separate binary variables indicated whether annual exposure exceeded a series of potential limits. Separate g-estimation analyses for each limit yielded the total number of life-years that could have been saved among persons who died from specific cardiovascular causes by enforcing that exposure limit. Banning oil-based fluids would have saved an estimated 4,003 (95% confidence interval: 2,200, 5,807) life-years among those who died of ischemic heart disease. Estimates for cardiovascular disease overall, acute myocardial infarction, and cerebrovascular disease were 3,500 (95% confidence interval: 1,350, 5,651), 2,932 (95% confidence interval: 1,587, 4,277), and 917 (95% confidence interval: −80, 1,913) life-years, respectively. A limit of 0.01 mg/m3 would have had a similar impact on cerebrovascular disease but one only half as great on ischemic heart disease. Analyses suggest that limiting exposure to metalworking fluids could have saved many life-years lost to cardiovascular diseases in this cohort. PMID:25816818
Fluid-dynamical model for antisurfactants
NASA Astrophysics Data System (ADS)
Conn, Justin J. A.; Duffy, Brian R.; Pritchard, David; Wilson, Stephen K.; Halling, Peter J.; Sefiane, Khellil
2016-04-01
We construct a fluid-dynamical model for the flow of a solution with a free surface at which surface tension acts. This model can describe both classical surfactants, which decrease the surface tension of the solution relative to that of the pure solvent, and antisurfactants (such as many salts when added to water, and small amounts of water when added to alcohol) which increase it. We demonstrate the utility of the model by considering the linear stability of an infinitely deep layer of initially quiescent fluid. In particular, we predict the occurrence of an instability driven by surface-tension gradients, which occurs for antisurfactant, but not for surfactant, solutions.
Electrorheological Fluid Based Force Feedback Device
NASA Technical Reports Server (NTRS)
Pfeiffer, Charles; Bar-Cohen, Yoseph; Mavroidis, Constantinos; Dolgin, Benjamin
1999-01-01
Parallel to the efforts to develop fully autonomous robots, it is increasingly being realized that there are applications where it is essential to have a fully controlled robot and "feel" its operating conditions, i.e. telepresence. This trend is a result of the increasing efforts to address tasks where humans can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robots can be employed to perform these tasks. Such robots need to be assisted by a human that remotely controls the operation. To address the goal of operating robots as human surrogates, the authors launched a study of mechanisms that provide mechanical feedback. For this purpose, electrorheological fluids (ERF) are being investigated for the potential application as miniature haptic devices. This family of electroactive fluids has the property of changing the viscosity during electrical stimulation. Consequently, ERF can be used to produce force feedback haptic devices for tele-operated control of medical and space robotic systems. Forces applied at the robot end-effector due to a compliant environment are reflected to the user using an ERF device where a change in the system viscosity will occur proportionally to the transmitted force. Analytical model and control algorithms are being developed taking into account the non-linearities of these type of devices. This paper will describe the concept and the developed mechanism of ERF based force feedback. The test process and the physical properties of this device will be described and the results of preliminary tests will be presented.
Two-fluid models of turbulence
NASA Technical Reports Server (NTRS)
Spalding, D. B.
1985-01-01
The defects of turbulence models are summarized and the importance of so-called nongradient diffusion in turbulent fluxes is discussed. The mathematical theory of the flow of two interpenetrating continua is reviewed, and the mathematical formulation of the two fluid model is outlined. Results from plane wake, axisymmetric jet, and combustion studies are shown.
Modeling the migration of fluids in subduction zones
NASA Astrophysics Data System (ADS)
Spiegelman, M.; Wilson, C. R.; van Keken, P. E.; Hacker, B. R.
2010-12-01
Fluids play a major role in the formation of arc volcanism and the generation of continental crust. Progressive dehydration reactions in the downgoing slab release fluids to the hot overlying mantle wedge, causing flux melting and the migration of melts to the volcanic front. While the qualitative concept is well established the quantitative details of fluid release and especially that of fluid migration and generation of hydrous melting in the wedge is still poorly understood. Here we present new models of the fluid migration through the mantle wedge for subduction zones that span the spectrum of arcs worldwide. We focus on the flow of water and use an existing set of high resolution thermal and metamorphic models (van Keken et al., JGR, in review) to predict the regions of water release from the sediments, upper and lower crust, and upper most mantle. We use this water flux as input for the fluid migration calculation based on new finite element models built on advanced computational libraries (FEniCS/PETSc) for efficient and flexible solution of coupled multi-physics problems. The first generation of these models solves for the evolution of porosity and fluid-pressure/flux throughout the slab and wedge given solid flow, viscosity and thermal fields from the existing thermal models. Fluid flow in the new models depends on both permeability and the rheology of the slab-wedge system as interaction with rheological variability can induce additional pressure gradients that affect the fluid flow pathways. We will explore the sensitivity of fluid flow paths for a range of subduction zones and fluid flow parameters with emphasis on variability of the location of the volcanic arc with respect to flow paths and expected degrees of hydrous melting which can be estimated given a variety of wet-melting parameterizations (e.g. Katz et al, 2003, Kelley et al, 2010). The current models just include dehydration reactions but work continues on the next generation of models which
Yield Stress Modeling of Electrorheological Fluids Using Neural Network
NASA Astrophysics Data System (ADS)
Wei, Kexiang; Meng, Guang
Electrorheological (ER) fluids are a kind of smart materials whose rheological properties can be rapidly changed by applied electric fields. Many potential industrial applications of ER technology have been proposed. In order to formulate better ER fluids and design ER devices, it is important to predict the yield stress of ER fluids based on the ER fluids components and the operating conditions. This paper proposes a new method for predicting the yield stress of ER fluids with neural network (NN). A multilayer perceptron with a single hidden layer of neurons is used to model the ER effect. The data for training and test were produced from the simulation of previous proposed mathematical models. The Levernberg-Marquardt back propagation algorithm was selected for fast learning. The results show the neural network model can well approximate the previous theoretical model, and the predicted outputs of NN agree nearly with the theoretical model values under the same input, all of which demonstrate that it is possible to generate a robust NN model for rapidly predicting the yield stress of ER fluids under different input parameters.
Schroth, Martin H.; Oostrom, Mart; Dobson, Richard; Zeyer, Josef
2008-08-01
Fluid/fluid interfacial areas are important in controlling the rate of mass and energy transfer between fluid phases in porous media. We present a modified thermodynamically based model (TBM) to predict fluid/fluid interfacial areas in porous media for arbitrary drainage/imbibition sequences. The TBM explicitly distinguishes between interfacial areas associated with continuous (free) and isolated (entrapped) nonwetting fluids. The model is restricted to two-fluid systems in which (1) no significant conversion of mechanical work into heat occurs, (2) the wetting fluid completely wets the porous medium’s solid surfaces, and (3) no changes in interfacial area due to mass transfer between phases occur. We show example calculations for two different drainage/imbibition sequences in two porous media: a highly uniform silica sand and a well-graded silt. The TBM’s predictions for interfacial area associated with free nonwetting-fluid are identical to those of a previously published geometry-based model (GBM). However, predictions for interfacial area associated with entrapped nonwetting-fluid are consistently larger in the TBM than in the GBM. Although a comparison of model predictions with experimental data is currently only possible to a limited extent, good general agreement was found for the TBM. As required model parameters are commonly used as inputs for or tracked during multifluid-flow simulations, the modified TBM may be easily incorporated in numerical codes.
Trajectory Tracking Control of Mobile Robot by Fluid Model
NASA Astrophysics Data System (ADS)
Miyata, Junichi; Murakami, Toshiyuki
This paper describes a fluid model based path planning of mobile robot. In the previous research, the authors have already proposed TBSA (Time Based Spline Approach) for smooth motion of industrial robots(1). The TBSA is a powerful method in industrial applications, but the future position and velocity commands must be known to use it. In the general applications of repeat motion, this assumption is acceptable. In the path planning of mobile robot, however, the future position and velocity commands are unknown. To address the above issue, a strategy to generate the path of mobile robot based on fluid model is proposed in this paper. The combination of the TBSA and the generated path by fluid model brings a smooth motion of mobile robots.
Modeling the Migration of Fluids in Subduction Zones
NASA Astrophysics Data System (ADS)
Wilson, C. R.; Spiegelman, M.; Van Keken, P. E.; Vrijmoed, J. C.; Hacker, B. R.
2011-12-01
Fluids play a major role in the formation of arc volcanism and the generation of continental crust. Progressive dehydration reactions in the downgoing slab release fluids to the hot overlying mantle wedge, causing flux melting and the migration of melts to the volcanic front. While the qualitative concept is well established, the quantitative details of fluid release and especially that of fluid migration and generation of hydrous melting in the wedge is still poorly understood. Here we present new models of the fluid migration through the mantle wedge for subduction zones. We use an existing set of high resolution metamorphic models (van Keken et al, 2010) to predict the regions of water release from the sediments, upper and lower crust, and upper most mantle. We use this water flux as input for the fluid migration calculation based on new finite element models built on advanced computational libraries (FEniCS/PETSc) for efficient and flexible solution of coupled multi-physics problems. The first generation of one-way coupled models solves for the evolution of porosity and fluid-pressure/flux throughout the slab and wedge given solid flow, viscosity and thermal fields from separate solutions to the incompressible Stokes and energy equations in the mantle wedge. These solutions are verified by comparing to previous benchmark studies (van Keken et al, 2008) and global suites of thermal subduction models (Syracuse et al, 2010). Fluid flow depends on both permeability and the rheology of the slab-wedge system as interaction with rheological variability can induce additional pressure gradients that affect the fluid flow pathways. These non-linearities have been shown to explain laboratory-scale observations of melt band orientation in labratory experiments and numerical simulations of melt localization in shear bands (Katz et al 2006). Our second generation of models dispense with the pre-calculation of incompressible mantle flow and fully couple the now compressible
De Boever, Wesley; Bultreys, Tom; Derluyn, Hannelore; Van Hoorebeke, Luc; Cnudde, Veerle
2016-06-01
In this paper, we examine the possibility to use on-site permeability measurements for cultural heritage applications as an alternative for traditional laboratory tests such as determination of the capillary absorption coefficient. These on-site measurements, performed with a portable air permeameter, were correlated with the pore network properties of eight sandstones and one granular limestone that are discussed in this paper. The network properties of the 9 materials tested in this study were obtained from micro-computed tomography (μCT) and compared to measurements and calculations of permeability and the capillary absorption rate of the stones under investigation, in order to find the correlation between pore network characteristics and fluid management characteristics of these sandstones. Results show a good correlation between capillary absorption, permeability and network properties, opening the possibility of using on-site permeability measurements as a standard method in cultural heritage applications. PMID:26950624
Tröbs, Monique; Achenbach, Stephan; Röther, Jens; Redel, Thomas; Scheuering, Michael; Winneberger, David; Klingenbeck, Klaus; Itu, Lucian; Passerini, Tiziano; Kamen, Ali; Sharma, Puneet; Comaniciu, Dorin; Schlundt, Christian
2016-01-01
Invasive fractional flow reserve (FFRinvasive), although gold standard to identify hemodynamically relevant coronary stenoses, is time consuming and potentially associated with complications. We developed and evaluated a new approach to determine lesion-specific FFR on the basis of coronary anatomy as visualized by invasive coronary angiography (FFRangio): 100 coronary lesions (50% to 90% diameter stenosis) in 73 patients (48 men, 25 women; mean age 67 ± 9 years) were studied. On the basis of coronary angiograms acquired at rest from 2 views at angulations at least 30° apart, a PC-based computational fluid dynamics modeling software used personalized boundary conditions determined from 3-dimensional reconstructed angiography, heart rate, and blood pressure to derive FFRangio. The results were compared with FFRinvasive. Interobserver variability was determined in a subset of 25 narrowings. Twenty-nine of 100 coronary lesions were hemodynamically significant (FFRinvasive ≤ 0.80). FFRangio identified these with an accuracy of 90%, sensitivity of 79%, specificity of 94%, positive predictive value of 85%, and negative predictive value of 92%. The area under the receiver operating characteristic curve was 0.93. Correlation between FFRinvasive (mean: 0.84 ± 0.11) and FFRangio (mean: 0.85 ± 0.12) was r = 0.85. Interobserver variability of FFRangio was low, with a correlation of r = 0.88. In conclusion, estimation of coronary FFR with PC-based computational fluid dynamics modeling on the basis of lesion morphology as determined by invasive angiography is possible with high diagnostic accuracy compared to invasive measurements. PMID:26596195
NASA Technical Reports Server (NTRS)
Spirka, T. A.; Myers, J. G.; Setser, R. M.; Halliburton, S. S.; White, R. D.; Chatzimavroudis, G. P.
2005-01-01
A priority of NASA is to identify and study possible risks to astronauts health during prolonged space missions [l]. The goal is to develop a procedure for a preflight evaluation of the cardiovascular system of an astronaut and to forecast how it will be affected during the mission. To predict these changes, a computational cardiovascular model must be constructed. Although physiology data can be used to make a general model, a more desirable subject-specific model requires anatomical, functional, and flow data from the specific astronaut. MRI has the unique advantage of providing images with all of the above information, including three-directional velocity data which can be used as boundary conditions in a computational fluid dynamics (CFD) program [2,3]. MRI-based CFD is very promising for reproduction of the flow patterns of a specific subject and prediction of changes in the absence of gravity. The aim of this study was to test the feasibility of this approach by reconstructing the geometry of MRI-scanned arterial models and reproducing the MRI-measured velocities using CFD simulations on these geometries.
Molecular Modeling of Solid Fluid Phase Behavior
Peter A. Monson
2007-12-20
This report gives a summary of the achievements under DOE contract No. DOE/ER/14150 during the period September 1, 1990 to December 31, 2007. This project was concerned with the molecular modeling of solid-fluid equilibrium. The focus was on understanding how solid-fluid and solid-solid phase behavior are related to molecular structure, and the research program made a seminal contribution in this area. The project led to 34 journal articles, including a comprehensive review article published in Advances in Chemical Physics. The DOE funding supported the work of 5 Ph.D. students, 2 M.S. students and 5 postdoctoral researchers.
NASA Astrophysics Data System (ADS)
Lou, Wentao; Zhu, Miaoyong
2014-10-01
A computation fluid dynamics-simultaneous reaction model (CFD-SRM) coupled model has been proposed to describe the desulfurization behavior in a gas-stirred ladle. For the desulfurization thermodynamics, different models were investigated to determine sulfide capacity and oxygen activity. For the desulfurization kinetic, the effect of bubbly plume flow, as well as oxygen absorption and oxidation reactions in slag eyes are considered. The thermodynamic and kinetic modification coefficients are proposed to fit the measured data, respectively. Finally, the effects of slag basicity and gas flow rate on the desulfurization efficiency are investigated. The results show that as the interfacial reactions (Al2O3)-(FeO)-(SiO2)-(MnO)-[S]-[O] simultaneous kinetic equilibrium is adopted to determine the oxygen activity, and the Young's model with the modification coefficient R th of 1.5 is adopted to determine slag sulfide capacity, the predicted sulfur distribution ratio LS agrees well with the measured data. With an increase of the gas blowing time, the predicted desulfurization rate gradually decreased, and when the modification parameter R k is 0.8, the predicted sulfur content changing with time in ladle agrees well with the measured data. If the oxygen absorption and oxidation reactions in slag eyes are not considered in this model, then the sulfur removal rate in the ladle would be overestimated, and this trend would become more obvious with an increase of the gas flow rate and decrease of the slag layer height. With the slag basicity increasing, the total desulfurization ratio increases; however, the total desulfurization ratio changes weakly as the slag basicity exceeds 7. With the increase of the gas flow rate, the desulfurization ratio first increases and then decreases. When the gas flow rate is 200 NL/min, the desulfurization ratio reaches a maximum value in an 80-ton gas-stirred ladle.
Comparing fluid mechanics models with experimental data.
Spedding, G R
2003-01-01
The art of modelling the physical world lies in the appropriate simplification and abstraction of the complete problem. In fluid mechanics, the Navier-Stokes equations provide a model that is valid under most circumstances germane to animal locomotion, but the complexity of solutions provides strong incentive for the development of further, more simplified practical models. When the flow organizes itself so that all shearing motions are collected into localized patches, then various mathematical vortex models have been very successful in predicting and furthering the physical understanding of many flows, particularly in aerodynamics. Experimental models have the significant added convenience that the fluid mechanics can be generated by a real fluid, not a model, provided the appropriate dimensionless groups have similar values. Then, analogous problems can be encountered in making intelligible but independent descriptions of the experimental results. Finally, model predictions and experimental results may be compared if, and only if, numerical estimates of the likely variations in the tested quantities are provided. Examples from recent experimental measurements of wakes behind a fixed wing and behind a bird in free flight are used to illustrate these principles. PMID:14561348
NASA Technical Reports Server (NTRS)
Chatzimavroudis, George P.; Spirka, Thomas A.; Setser, Randolph M.; Myers, Jerry G.
2004-01-01
One of NASA's objectives is to be able to perform a complete, pre-flight, evaluation of cardiovascular changes in astronauts scheduled for prolonged space missions. Computational fluid dynamics (CFD) has shown promise as a method for estimating cardiovascular function during reduced gravity conditions. For this purpose, MRI can provide geometrical information, to reconstruct vessel geometries, and measure all spatial velocity components, providing location specific boundary conditions. The objective of this study was to investigate the reliability of MRI-based model reconstruction and measured boundary conditions for CFD simulations. An aortic arch model and a carotid bifurcation model were scanned in a 1.5T Siemens MRI scanner. Axial MRI acquisitions provided images for geometry reconstruction (slice thickness 3 and 5 mm; pixel size 1x1 and 0.5x0.5 square millimeters). Velocity acquisitions provided measured inlet boundary conditions and localized three-directional steady-flow velocity data (0.7-3.0 L/min). The vessel walls were isolated using NIH provided software (ImageJ) and lofted to form the geometric surface. Constructed and idealized geometries were imported into a commercial CFD code for meshing and simulation. Contour and vector plots of the velocity showed identical features between the MRI velocity data, the MRI-based CFD data, and the idealized-geometry CFD data, with less than 10% differences in the local velocity values. CFD results on models reconstructed from different MRI resolution settings showed insignificant differences (less than 5%). This study illustrated, quantitatively, that reliable CFD simulations can be performed with MRI reconstructed models and gives evidence that a future, subject-specific, computational evaluation of the cardiovascular system alteration during space travel is feasible.
Modeling of a magnetorheological fluid damper with parallel plate behavior
NASA Astrophysics Data System (ADS)
Falah, Abdulazim H.; Clark, William W.; Phule, Pradeep P.
1998-06-01
This paper presents the modeling and experimental testing of a magnetorheological (MR) fluid damper. The damper consists of a main cylinder and piston rod that pushes MR fluid through a very small clearance between the piston and the sidewalls of the cylinder. Magnetic coils are wrapped outside the cylinder to create the magnetic field. The damper model is developed based on parallel plate analysis by using both Newtonian and Bingham shear flow mechanisms. Empirical data was used to find the required parameter for a Bingham model that is the dynamic yield stress. These empirical data show the shear stress vs. shear strain at different values of magnetic flux density (B). The dynamic yield stress of MR fluid is a function of magnetic field. Finally, the model is validated through experimental testing of the damper.
Experimental Evaluation of Equivalent-Fluid Models for Melamine Foam
NASA Technical Reports Server (NTRS)
Allen, Albert R.; Schiller, Noah H.
2016-01-01
Melamine foam is a soft porous material commonly used in noise control applications. Many models exist to represent porous materials at various levels of fidelity. This work focuses on rigid frame equivalent fluid models, which represent the foam as a fluid with a complex speed of sound and density. There are several empirical models available to determine these frequency dependent parameters based on an estimate of the material flow resistivity. Alternatively, these properties can be experimentally educed using an impedance tube setup. Since vibroacoustic models are generally sensitive to these properties, this paper assesses the accuracy of several empirical models relative to impedance tube measurements collected with melamine foam samples. Diffuse field sound absorption measurements collected using large test articles in a laboratory are also compared with absorption predictions determined using model-based and measured foam properties. Melamine foam slabs of various thicknesses are considered.
Lattice Boltzmann model for compressible fluids
NASA Technical Reports Server (NTRS)
Alexander, F. J.; Chen, H.; Chen, S.; Doolen, G. D.
1992-01-01
A lattice Boltzmann model is derived which simulates compressible fluids. By choosing the parameters of the equilibrium distribution appropriately, the sound speed (which may be set arbitrarily low), bulk viscosity, and kinematic viscosity can be selected. This model simulates compressible flows and can include shocks. With a proper rescaling and zero-sound speed, this model simulates Burgers's equation. The viscosity determined by a Chapman-Enskog expansion compares well with that measured form simulations. The exact solutions of Burgers's equation on the unit circle are compared to solutions of lattice Boltzmann model finding reasonable agreement.
NASA Astrophysics Data System (ADS)
Stacey, W. M.
2016-06-01
A fluid model for the tokamak edge pressure profile required by the conservation of particles, momentum and energy in the presence of specified heating and fueling sources and electromagnetic and geometric parameters has been developed. Kinetics effects of ion orbit loss are incorporated into the model. The use of this model as a "transport" constraint together with a "Peeling-Ballooning (P-B)" instability constraint to achieve a prediction of edge pressure pedestal heights and widths in future tokamaks is discussed.
Corley, Richard A; Kabilan, Senthil; Kuprat, Andrew P; Carson, James P; Jacob, Richard E; Minard, Kevin R; Teeguarden, Justin G; Timchalk, Charles; Pipavath, Sudhakar; Glenny, Robb; Einstein, Daniel R
2015-07-01
Computational fluid dynamics (CFD) modeling is well suited for addressing species-specific anatomy and physiology in calculating respiratory tissue exposures to inhaled materials. In this study, we overcame prior CFD model limitations to demonstrate the importance of realistic, transient breathing patterns for predicting site-specific tissue dose. Specifically, extended airway CFD models of the rat and human were coupled with airway region-specific physiologically based pharmacokinetic (PBPK) tissue models to describe the kinetics of 3 reactive constituents of cigarette smoke: acrolein, acetaldehyde and formaldehyde. Simulations of aldehyde no-observed-adverse-effect levels for nasal toxicity in the rat were conducted until breath-by-breath tissue concentration profiles reached steady state. Human oral breathing simulations were conducted using representative aldehyde yields from cigarette smoke, measured puff ventilation profiles and numbers of cigarettes smoked per day. As with prior steady-state CFD/PBPK simulations, the anterior respiratory nasal epithelial tissues received the greatest initial uptake rates for each aldehyde in the rat. However, integrated time- and tissue depth-dependent area under the curve (AUC) concentrations were typically greater in the anterior dorsal olfactory epithelium using the more realistic transient breathing profiles. For human simulations, oral and laryngeal tissues received the highest local tissue dose with greater penetration to pulmonary tissues than predicted in the rat. Based upon lifetime average daily dose comparisons of tissue hot-spot AUCs (top 2.5% of surface area-normalized AUCs in each region) and numbers of cigarettes smoked/day, the order of concern for human exposures was acrolein > formaldehyde > acetaldehyde even though acetaldehyde yields were 10-fold greater than formaldehyde and acrolein. PMID:25858911
Corley, Richard A.; Kabilan, Senthil; Kuprat, Andrew P.; Carson, James P.; Jacob, Richard E.; Minard, Kevin R.; Teeguarden, Justin G.; Timchalk, Charles; Pipavath, Sudhakar; Glenny, Robb; Einstein, Daniel R.
2015-01-01
Computational fluid dynamics (CFD) modeling is well suited for addressing species-specific anatomy and physiology in calculating respiratory tissue exposures to inhaled materials. In this study, we overcame prior CFD model limitations to demonstrate the importance of realistic, transient breathing patterns for predicting site-specific tissue dose. Specifically, extended airway CFD models of the rat and human were coupled with airway region-specific physiologically based pharmacokinetic (PBPK) tissue models to describe the kinetics of 3 reactive constituents of cigarette smoke: acrolein, acetaldehyde and formaldehyde. Simulations of aldehyde no-observed-adverse-effect levels for nasal toxicity in the rat were conducted until breath-by-breath tissue concentration profiles reached steady state. Human oral breathing simulations were conducted using representative aldehyde yields from cigarette smoke, measured puff ventilation profiles and numbers of cigarettes smoked per day. As with prior steady-state CFD/PBPK simulations, the anterior respiratory nasal epithelial tissues received the greatest initial uptake rates for each aldehyde in the rat. However, integrated time- and tissue depth-dependent area under the curve (AUC) concentrations were typically greater in the anterior dorsal olfactory epithelium using the more realistic transient breathing profiles. For human simulations, oral and laryngeal tissues received the highest local tissue dose with greater penetration to pulmonary tissues than predicted in the rat. Based upon lifetime average daily dose comparisons of tissue hot-spot AUCs (top 2.5% of surface area-normalized AUCs in each region) and numbers of cigarettes smoked/day, the order of concern for human exposures was acrolein > formaldehyde > acetaldehyde even though acetaldehyde yields were 10-fold greater than formaldehyde and acrolein. PMID:25858911
Discrete models of fluids: spatial averaging, closure and model reduction
Panchenko, Alexander; Tartakovsky, Alexandre M.; Cooper, Kevin
2014-04-15
We consider semidiscrete ODE models of single-phase fluids and two-fluid mixtures. In the presence of multiple fine-scale heterogeneities, the size of these ODE systems can be very large. Spatial averaging is then a useful tool for reducing computational complexity of the problem. The averages satisfy exact balance equations of mass, momentum, and energy. These equations do not form a satisfactory continuum model because evaluation of stress and heat flux requires solving the underlying ODEs. To produce continuum equations that can be simulated without resolving microscale dynamics, we recently proposed a closure method based on the use of regularized deconvolution. Here we continue the investigation of deconvolution closure with the long term objective of developing consistent computational upscaling for multiphase particle methods. The structure of the fine-scale particle solvers is reminiscent of molecular dynamics. For this reason we use nonlinear averaging introduced for atomistic systems by Noll, Hardy, and Murdoch-Bedeaux. We also consider a simpler linear averaging originally developed in large eddy simulation of turbulence. We present several simple but representative examples of spatially averaged ODEs, where the closure error can be analyzed. Based on this analysis we suggest a general strategy for reducing the relative error of approximate closure. For problems with periodic highly oscillatory material parameters we propose a spectral boosting technique that augments the standard deconvolution and helps to correctly account for dispersion effects. We also conduct several numerical experiments, one of which is a complete mesoscale simulation of a stratified two-fluid flow in a channel. In this simulation, the operation count per coarse time step scales sublinearly with the number of particles.
Two Dimensional Fluid Flow Models Offshore Southwestern Taiwan
NASA Astrophysics Data System (ADS)
Chen, L. W.; Wu, S. K.; Chi, W. C.; Liu, C. S.; Shyu, C. T.; Wang, Y. S.
2012-04-01
Fluid migration rates are important parameters for understanding the structural characteristics and evolution of the crustal tectonics and hydrocarbon exploration. However, they are difficult to measure on the seafloor. Dense distribution of bottom-simulating reflectors (BSRs) as the index of fluid existence to shed light on our study of the fluid migration. In this study, We acquired 2D fluid flow patterns in two potential gas hydrate prospect sites offshore southwestern Taiwan, and respectively modeled across Yung-An and Formosa ridge in N-S and E-W direction southwestern Taiwan. Temperature field in the shallow crust is used as a tracer to examine the fluid flow patterns. We use thermal information directly measured by thermal probes and topography data to develop the theoretical 2D temperature field using a thermal conduction model, which was derived from a finite element method. The discrepancy between the observed temperature data and the conductive model is attributed to advection heat transfer due to fluid migration. For Yung-An Ridge, we found the BSR-based temperatures are about 2oC higher than the conduction model in the following zones: (1) near a fault zone, (2) on the eastern flank where there are strong seismic reflectors in a pseudo 3D seismic dataset, (3) a seismic chimney zone. We interpret that there is possible active dewatering inside the accretionary prism to allow fluid to migrate upward here. For Formosa Ridge in the passive margin, the BSR-based temperatures are about 2oC colder than the theoretical model, especially on the flanks. We interpret that cold seawater is moving into the ridge from the flanks, cooling the ridge, and then some of the fluid is expelled at the ridge top. The shallow temperature fields are strongly affected by 2D or even 3D bathymetry effects. But we can still gain much information regarding fluid flow patterns through modeling. In the near future, we will extend such study into 3D. Keywords: fluid migration
COMPUTATIONAL FLUID DYNAMICS MODELING ANALYSIS OF COMBUSTORS
Mathur, M.P.; Freeman, Mark; Gera, Dinesh
2001-11-06
In the current fiscal year FY01, several CFD simulations were conducted to investigate the effects of moisture in biomass/coal, particle injection locations, and flow parameters on carbon burnout and NO{sub x} inside a 150 MW GEEZER industrial boiler. Various simulations were designed to predict the suitability of biomass cofiring in coal combustors, and to explore the possibility of using biomass as a reburning fuel to reduce NO{sub x}. Some additional CFD simulations were also conducted on CERF combustor to examine the combustion characteristics of pulverized coal in enriched O{sub 2}/CO{sub 2} environments. Most of the CFD models available in the literature treat particles to be point masses with uniform temperature inside the particles. This isothermal condition may not be suitable for larger biomass particles. To this end, a stand alone program was developed from the first principles to account for heat conduction from the surface of the particle to its center. It is envisaged that the recently developed non-isothermal stand alone module will be integrated with the Fluent solver during next fiscal year to accurately predict the carbon burnout from larger biomass particles. Anisotropy in heat transfer in radial and axial will be explored using different conductivities in radial and axial directions. The above models will be validated/tested on various fullscale industrial boilers. The current NO{sub x} modules will be modified to account for local CH, CH{sub 2}, and CH{sub 3} radicals chemistry, currently it is based on global chemistry. It may also be worth exploring the effect of enriched O{sub 2}/CO{sub 2} environment on carbon burnout and NO{sub x} concentration. The research objective of this study is to develop a 3-Dimensional Combustor Model for Biomass Co-firing and reburning applications using the Fluent Computational Fluid Dynamics Code.
Mathematical modeling of fluid-electrolyte alterations during weightlessness
NASA Technical Reports Server (NTRS)
Leonard, J. I.
1984-01-01
Fluid electrolyte metabolism and renal endocrine control as it pertains to adaptation to weightlessness were studied. The mathematical models that have been particularly useful are discussed. However, the focus of the report is on the physiological meaning of the computer studies. A discussion of the major ground based analogs of weightlessness are included; for example, head down tilt, water immersion, and bed rest, and a comparison of findings. Several important zero g phenomena are described, including acute fluid volume regulation, blood volume regulation, circulatory changes, longer term fluid electrolyte adaptations, hormonal regulation, and body composition changes. Hypotheses are offered to explain the major findings in each area and these are integrated into a larger hypothesis of space flight adaptation. A conceptual foundation for fluid electrolyte metabolism, blood volume regulation, and cardiovascular regulation is reported.
Winer, Jesse L; Kramer, Daniel R; Robison, Richard A; Ohiorhenuan, Ifije; Minneti, Michael; Giannotta, Steven; Zada, Gabriel
2015-11-01
Cadaveric surgical simulation carries the advantage of realistic anatomy and haptic feedback but has been historically difficult to model for intraventricular approaches given the need for active flow of CSF. This feasibility study was designed to simulate intraventricular neuroendoscopic approaches and techniques by reconstituting natural CSF flow in a cadaveric model. In 10 fresh human cadavers, a simple cervical laminectomy and dural opening were made, and a 12-gauge arterial catheter was introduced. Saline was continuously perfused at physiological CSF pressures to reconstitute the subarachnoid space and ventricles. A neuroendoscope was subsequently inserted via a standard right frontal bur hole. In 8 of the 10 cadavers, adequate reconstitution and endoscopic access of the lateral and third ventricles were achieved. In 2 cadavers, ventricular access was not feasible, perhaps because of a small ventricle size and/or deteriorated tissue quality. In all 8 cadavers with successful CSF flow reconstitution and endoscopic access, identifying the foramen of Monro was possible, as was performing septum pellucidotomy and endoscopic third ventriculostomy. Furthermore, navigation of the cerebral aqueduct, fourth ventricle, prepontine cistern, and suprasellar cistern via the lamina terminalis was possible, providing a complementary educational paradigm for resident education that cannot typically be performed in live surgery. Surgical simulation plays a critical and increasingly prominent role in surgical education, particularly for techniques with steep learning curves including intraventricular neuroendoscopic procedures. This novel model provides feasible and realistic surgical simulation of neuroendoscopic intraventricular procedures and approaches. PMID:25859805
Modeling of Non-Isothermal Cryogenic Fluid Sloshing
NASA Technical Reports Server (NTRS)
Agui, Juan H.; Moder, Jeffrey P.
2015-01-01
A computational fluid dynamic model was used to simulate the thermal destratification in an upright self-pressurized cryostat approximately half-filled with liquid nitrogen and subjected to forced sinusoidal lateral shaking. A full three-dimensional computational grid was used to model the tank dynamics, fluid flow and thermodynamics using the ANSYS Fluent code. A non-inertial grid was used which required the addition of momentum and energy source terms to account for the inertial forces, energy transfer and wall reaction forces produced by the shaken tank. The kinetics-based Schrage mass transfer model provided the interfacial mass transfer due to evaporation and condensation at the sloshing interface. The dynamic behavior of the sloshing interface, its amplitude and transition to different wave modes, provided insight into the fluid process at the interface. The tank pressure evolution and temperature profiles compared relatively well with the shaken cryostat experimental test data provided by the Centre National D'Etudes Spatiales.
SPH modeling of fluid-solid interaction for dynamic failure analysis of fluid-filled thin shells
NASA Astrophysics Data System (ADS)
Caleyron, F.; Combescure, A.; Faucher, V.; Potapov, S.
2013-05-01
This work concerns the prediction of failure of a fluid-filled tank under impact loading, including the resulting fluid leakage. A water-filled steel cylinder associated with a piston is impacted by a mass falling at a prescribed velocity. The cylinder is closed at its base by an aluminum plate whose characteristics are allowed to vary. The impact on the piston creates a pressure wave in the fluid which is responsible for the deformation of the plate and, possibly, the propagation of cracks. The structural part of the problem is modeled using Mindlin-Reissner finite elements (FE) and Smoothed Particle Hydrodynamics (SPH) shells. The modeling of the fluid is also based on an SPH formulation. The problem involves significant fluid-structure interactions (FSI) which are handled through a master-slave-based method and the pinballs method. Numerical results are compared to experimental data.
Cremers, Thomas I F H; Flik, Gunnar; Folgering, Joost H A; Rollema, Hans; Stratford, Robert E
2016-05-01
Administration of bupropion [(±)-2-(tert-butylamino)-1-(3-chlorophenyl)propan-1-one] and its preformed active metabolite, hydroxybupropion [(±)-1-(3-chlorophenyl)-2-[(1-hydroxy-2-methyl-2-propanyl)amino]-1-propanone], to rats with measurement of unbound concentrations by quantitative microdialysis sampling of plasma and brain extracellular fluid was used to develop a compartmental pharmacokinetics model to describe the blood-brain barrier transport of both substances. The population model revealed rapid equilibration of both entities across the blood-brain barrier, with resultant steady-state brain extracellular fluid/plasma unbound concentration ratio estimates of 1.9 and 1.7 for bupropion and hydroxybupropion, respectively, which is thus indicative of a net uptake asymmetry. An overshoot of the brain extracellular fluid/plasma unbound concentration ratio at early time points was observed with bupropion; this was modeled as a time-dependent uptake clearance of the drug across the blood-brain barrier. Translation of the model was used to predict bupropion and hydroxybupropion exposure in human brain extracellular fluid after twice-daily administration of 150 mg bupropion. Predicted concentrations indicate that preferential inhibition of the dopamine and norepinephrine transporters by the metabolite, with little to no contribution by bupropion, would be expected at this therapeutic dose. Therefore, these results extend nuclear imaging studies on dopamine transporter occupancy and suggest that inhibition of both transporters contributes significantly to bupropion's therapeutic efficacy. PMID:26916207
Variable flexure-based fluid filter
Brown, Steve B.; Colston, Jr., Billy W.; Marshall, Graham; Wolcott, Duane
2007-03-13
An apparatus and method for filtering particles from a fluid comprises a fluid inlet, a fluid outlet, a variable size passage between the fluid inlet and the fluid outlet, and means for adjusting the size of the variable size passage for filtering the particles from the fluid. An inlet fluid flow stream is introduced to a fixture with a variable size passage. The size of the variable size passage is set so that the fluid passes through the variable size passage but the particles do not pass through the variable size passage.
Soleimani, Sajjad; Dubini, Gabriele; Pennati, Giancarlo
2016-06-01
It is important to thoroughly remove the thrombus within the course of aspiration thrombectomy; otherwise, it may lead to further embolization. The performance of the aspiration thrombectomy device with a generic geometry is studied through the computational approach. In order to model the thrombus aspiration, a real left coronary artery is chosen while thrombi with various sizes are located at the bifurcation area of the coronary artery and, depending on the size of the thrombus, it is stretched toward the side branches. The thrombus occupies the artery resembling the blood current obstruction in the coronary vessel similar to the situation that leads to heart attack. It is concluded that the aspiration ability of the thrombectomy device is not linked to the thrombus size; it is rather linked to the aspiration pressure and thrombus age (organized versus fresh thrombus). However, the aspiration time period correlates to the thrombus size. The minimum applicable aspiration pressure is also investigated in this study. PMID:26351782
Method of recovering oil-based fluid and apparatus
Brinkley, H.E.
1993-07-20
A method is described for recovering oil-based fluid from a surface having oil-based fluid thereon comprising the steps of: applying to the oil-based fluid on the surface an oil-based fluid absorbent cloth of man-made fibers, the cloth having at least one napped surface that defines voids therein, the nap being formed of raised ends or loops of the fibers; absorbing, with the cloth, oil-based fluid; feeding the cloth having absorbed oil-based fluid to a means for applying a force to the cloth to recover oil-based fluid; and applying force to the cloth to recover oil-based fluid therefrom using the force applying means.
Landau Fluid Models for Magnetized Plasmas
Sulem, P. L.; Passot, T.; Marradi, L.
2008-10-15
A Landau fluid model for a magnetized plasma, that retains a linear description of low-frequency kinetic effects involving transverse scales significantly smaller than the ion Larmor radius, is discussed and validated in the context of nonlinear wave dynamics. Preliminary simulations of the turbulent regime are presented in one space dimension, as a first step towards more realistic three-dimensional computations, aimed to analyze the combined effect of dispersion and collisionless dissipation on the energy cascade.
A preliminary study to Assess Model Uncertainties in Fluid Flows
Marc Oliver Delchini; Jean C. Ragusa
2009-09-01
The goal of this study is to assess the impact of various flow models for a simplified primary coolant loop of a light water nuclear reactor. The various fluid flow models are based on the Euler equations with an additional friction term, gravity term, momentum source, and energy source. The geometric model is purposefully chosen simple and consists of a one-dimensional (1D) loop system in order to focus the study on the validity of various fluid flow approximations. The 1D loop system is represented by a rectangle; the fluid is heated up along one of the vertical legs and cooled down along the opposite leg. A pressurizer and a pump are included in the horizontal legs. The amount of energy transferred and removed from the system is equal in absolute value along the two vertical legs. The various fluid flow approximations are compressible vs. incompressible, and complete momentum equation vs. Darcy’s approximation. The ultimate goal is to compute the fluid flow models’ uncertainties and, if possible, to generate validity ranges for these models when applied to reactor analysis. We also limit this study to single phase flows with low-Mach numbers. As a result, sound waves carry a very small amount of energy in this particular case. A standard finite volume method is used for the spatial discretization of the system.
Yang, Chun; Tang, Dalin; Atluri, Satya
2011-01-01
Previously, we introduced a computational procedure based on three-dimensional meshless generalized finite difference (MGFD) method and serial magnetic resonance imaging (MRI) data to quantify patient-specific carotid atherosclerotic plaque growth functions and simulate plaque progression. Structure-only models were used in our previous report. In this paper, fluid-stricture interaction (FSI) was added to improve on prediction accuracy. One participating patient was scanned three times (T1, T2, and T3, at intervals of about 18 months) to obtain plaque progression data. Blood flow was assumed to laminar, Newtonian, viscous and incompressible. The Navier-Stokes equations with arbitrary Lagrangian-Eulerian (ALE) formulation were used as the governing equations. Plaque material was assumed to be uniform, homogeneous, isotropic, linear, and nearly incompressible. The linear elastic model was used. The 3D FSI plaque model was discretized and solved using a meshless generalized finite difference (GFD) method. Growth functions with a) morphology alone; b) morphology and plaque wall stress (PWS); morphology and flow shear stress (FSS), and d) morphology, PWS and FSS were introduced to predict future plaque growth based on previous time point data. Starting from the T2 plaque geometry, plaque progression was simulated by solving the FSI model and adjusting plaque geometry using plaque growth functions iteratively until T3 is reached. Numerically simulated plaque progression agreed very well with the target T3 plaque geometry with errors ranging from 8.62%, 7.22%, 5.77% and 4.39%, with the growth function including morphology, plaque wall stress and flow shear stress terms giving the best predictions. Adding flow shear stress term to the growth function improved the prediction error from 7.22% to 4.39%, a 40% improvement. We believe this is the first time 3D plaque progression FSI simulation based on multi-year patient-tracking data was reported. Serial MRI-based progression
NASA Astrophysics Data System (ADS)
Yang, Xiaochen; Zhang, Qinghe; Hao, Linnan
2015-03-01
A water-fluid mud coupling model is developed based on the unstructured grid finite volume coastal ocean model (FVCOM) to investigate the fluid mud motion. The hydrodynamics and sediment transport of the overlying water column are solved using the original three-dimensional ocean model. A horizontal two-dimensional fluid mud model is integrated into the FVCOM model to simulate the underlying fluid mud flow. The fluid mud interacts with the water column through the sediment flux, current, and shear stress. The friction factor between the fluid mud and the bed, which is traditionally determined empirically, is derived with the assumption that the vertical distribution of shear stress below the yield surface of fluid mud is identical to that of uniform laminar flow of Newtonian fluid in the open channel. The model is validated by experimental data and reasonable agreement is found. Compared with numerical cases with fixed friction factors, the results simulated with the derived friction factor exhibit the best agreement with the experiment, which demonstrates the necessity of the derivation of the friction factor.
Numerical Modeling of Fluid Transient in Cryogenic Fluid Network of Rocket Propulsion System
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Flachbart, Robin
2003-01-01
Fluid transients, also known as water hammer, can have a significant impact on the design and operation of both spacecraft and launch vehicles propulsion systems. These transients often occur at system activation and shut down. For ground safety reasons, many spacecrafts are launched with the propellant lines dry. These lines are often evacuated by the time the spacecraft reaches orbit. When the propellant isolation valve opens during propulsion system activation, propellant rushes into lines creating a pressure surge. During propellant system shutdown, a pressure surge is created due to sudden closure of a valve. During both activation and shutdown, pressure surges must be predicted accurately to ensure structural integrity of the propulsion system fluid network. The method of characteristics is the most widely used method of calculating fluid transients in pipeline [ 1,2]. The method of characteristics, however, has limited applications in calculating flow distribution in complex flow circuits with phase change, heat transfer and rotational effects. A robust cryogenic propulsion system analyzer must have the capability to handle phase change, heat transfer, chemical reaction, rotational effects and fluid transients in conjunction with subsystem flow model for pumps, valves and various pipe fittings. In recent years, such a task has been undertaken at Marshall Space Flight Center with the development of the Generalized Fluid System Simulation Program (GFSSP), which is based on finite volume method in fluid network [3]. GFSSP has been extensively verified and validated by comparing its predictions with test data and other numerical methods for various applications such as internal flow of turbo-pump [4], propellant tank pressurization [5,6], chilldown of cryogenic transfer line [7] and squeeze film damper rotordynamics [8]. The purpose of the present paper is to investigate the applicability of the finite volume method to predict fluid transient in cryogenic flow
Draft: Modeling Two-Phase Flow in Porous Media Including Fluid-Fluid Interfacial Area
Crandall, Dustin; Niessner, Jennifer; Hassanizadeh, S Majid
2008-01-01
We present a new numerical model for macro-scale twophase flow in porous media which is based on a physically consistent theory of multi-phase flow.The standard approach for modeling the flow of two fluid phases in a porous medium consists of a continuity equation for each phase, an extended form of Darcy’s law as well as constitutive relationships for relative permeability and capillary pressure. This approach is known to have a number of important shortcomings and, in particular, it does not account for the presence and role of fluid - fluid interfaces. An alternative is to use an extended model which is founded on thermodynamic principles and is physically consistent. In addition to the standard equations, the model uses a balance equation for specific interfacial area. The constitutive relationship for capillary pressure involves not only saturation, but also specific interfacial area. We show how parameters can be obtained for the alternative model using experimental data from a new kind of flow cell and present results of a numerical modeling study
Performance of magnetorheological fluids beyond the chain based shear limit
NASA Astrophysics Data System (ADS)
Sherman, Stephen G.; Wereley, Norman M.
2014-05-01
Magnetorheological (MR) fluids consist of magnetizable particles suspended in a carrier fluid, and upon application of a magnetic field, the particles form chains, and the so-called MR effect occurs, causing the fluid to develop a yield stress. However, calculations have shown that as the Mason number rises, the maximum stable chain length falls, and above a critical Mason number, no stable chains can form in the fluid, implying an upper limit on the existence of the MR effect. Using a standard simulation model for MR fluids, we find a significant reduction in fluid stress at the predicted Mason numbers for low volume fraction fluids.
A mathematical model of peritoneal fluid absorption in tissue.
Stachowska-Pietka, Joanna; Waniewski, Jacek; Flessner, Michael F; Lindholm, Bengt
2005-01-01
To investigate how water flow and interstitial pressure change in tissue during a peritoneal dwell with isotonic fluid, we developed a mathematical model of water transport in the tissue. Transport through muscle alone (M) and through muscle with intact skin (MS) were considered for the rat abdominal wall, using various parameters for muscle and skin. Based on the concept of distributed capillary and lymphatic systems, two main transport barriers were taken into account. capillary membrane and interstitium. We calculated the tissue hydrostatic pressure profiles and compared them with experimental data. The theoretic steady-state pressure distribution for model M is in good agreement with the experimental data. In model MS, the theoretic distribution diverges from the data in the subcutaneous layer. The transient times for fluid flow in the tissue for both model simulations are rather long (40 minutes in model M and 95 minutes in model MS) and depend on intraperitoneal pressure. The fraction of fluid absorbed from the tissue by the lymphatics increases with time from 10% to 97% of fluid flow from the peritoneal cavity. PMID:16686276
On the coupling between fluid flow and mesh motion in the modelling of fluid structure interaction
NASA Astrophysics Data System (ADS)
Dettmer, Wulf G.; Perić, Djordje
2008-12-01
Partitioned Newton type solution strategies for the strongly coupled system of equations arising in the computational modelling of fluid solid interaction require the evaluation of various coupling terms. An essential part of all ALE type solution strategies is the fluid mesh motion. In this paper, we investigate the effect of the terms which couple the fluid flow with the fluid mesh motion on the convergence behaviour of the overall solution procedure. We show that the computational efficiency of the simulation of many fluid solid interaction processes, including fluid flow through flexible pipes, can be increased significantly if some of these coupling terms are calculated exactly.
A Two-Fluid, MHD Coronal Model
NASA Technical Reports Server (NTRS)
Suess, Steven T.; Wang, A.-H.; Wu, S. T.; Poletto, G.; McComas, D. J.
1998-01-01
We describe first results from a numerical two-fluid MHD model of the global structure of the solar corona. The model is two-fluid in the sense that it accounts for the collisional energy exchange between protons and electrons. As in our single-fluid model, volumetric heat and momentum sources are required to produce high speed wind from coronal holes, low speed wind above streamers, and mass fluxes similar to the empirical solar wind. By specifying different proton and electron heating functions we obtain a high proton temperature in the coronal hole and a relatively low proton temperature in the streamer (in comparison with the electron temperature). This is consistent with inferences from SOHO/UVCS, and with the Ulysses/SWOOPS proton and electron temperature measurements which we show from the fast latitude scan. The density in the coronal hole between 2 solar radii and 5 solar radii (2RS and 5RS) is similar to the density reported from SPARTAN 201-01 measurements by Fisher and Guhathakurta. The proton mass flux scaled to 1 AU is 2.4 x 10(exp 8)/sq cm s, which is consistent with Ulysses observations. Inside the closed field region, the density is sufficiently high so that the simulation gives equal proton and electron temperatures due to the high collision rate. In open field regions (in the coronal hole and above the streamer) the proton and electron temperatures differ by varying amounts. In the streamer, the temperature and density are similar to those reported empirically by Li et al and the plasma beta is larger than unity everywhere above approx. 1.5 R(sub s), as it is in all other MHD coronal streamer models.
Wu, Binxin
2010-12-01
In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester. PMID:21047058
Reduced order modeling of fluid/structure interaction.
Barone, Matthew Franklin; Kalashnikova, Irina; Segalman, Daniel Joseph; Brake, Matthew Robert
2009-11-01
This report describes work performed from October 2007 through September 2009 under the Sandia Laboratory Directed Research and Development project titled 'Reduced Order Modeling of Fluid/Structure Interaction.' This project addresses fundamental aspects of techniques for construction of predictive Reduced Order Models (ROMs). A ROM is defined as a model, derived from a sequence of high-fidelity simulations, that preserves the essential physics and predictive capability of the original simulations but at a much lower computational cost. Techniques are developed for construction of provably stable linear Galerkin projection ROMs for compressible fluid flow, including a method for enforcing boundary conditions that preserves numerical stability. A convergence proof and error estimates are given for this class of ROM, and the method is demonstrated on a series of model problems. A reduced order method, based on the method of quadratic components, for solving the von Karman nonlinear plate equations is developed and tested. This method is applied to the problem of nonlinear limit cycle oscillations encountered when the plate interacts with an adjacent supersonic flow. A stability-preserving method for coupling the linear fluid ROM with the structural dynamics model for the elastic plate is constructed and tested. Methods for constructing efficient ROMs for nonlinear fluid equations are developed and tested on a one-dimensional convection-diffusion-reaction equation. These methods are combined with a symmetrization approach to construct a ROM technique for application to the compressible Navier-Stokes equations.
Aland, Sebastian; Lowengrub, John; Voigt, Axel
2012-10-01
Colloid particles that are partially wetted by two immiscible fluids can become confined to fluid-fluid interfaces. At sufficiently high volume fractions, the colloids may jam and the interface may crystallize. The fluids together with the interfacial colloids form an emulsion with interesting material properties and offer an important route to new soft materials. A promising approach to simulate these emulsions was presented in Aland et al. [Phys. Fluids 23, 062103 (2011)], where a Navier-Stokes-Cahn-Hilliard model for the macroscopic two-phase fluid system was combined with a surface phase-field-crystal model for the microscopic colloidal particles along the interface. Unfortunately this model leads to spurious velocities which require very fine spatial and temporal resolutions to accurately and stably simulate. In this paper we develop an improved Navier-Stokes-Cahn-Hilliard-surface phase-field-crystal model based on the principles of mass conservation and thermodynamic consistency. To validate our approach, we derive a sharp interface model and show agreement with the improved diffuse interface model. Using simple flow configurations, we show that the new model has much better properties and does not lead to spurious velocities. Finally, we demonstrate the solid-like behavior of the crystallized interface by simulating the fall of a solid ball through a colloid-laden multiphase fluid. PMID:23214691
NASA Astrophysics Data System (ADS)
Aland, Sebastian; Lowengrub, John; Voigt, Axel
2012-10-01
Colloid particles that are partially wetted by two immiscible fluids can become confined to fluid-fluid interfaces. At sufficiently high volume fractions, the colloids may jam and the interface may crystallize. The fluids together with the interfacial colloids form an emulsion with interesting material properties and offer an important route to new soft materials. A promising approach to simulate these emulsions was presented in Aland [Phys. FluidsPHFLE61070-663110.1063/1.3584815 23, 062103 (2011)], where a Navier-Stokes-Cahn-Hilliard model for the macroscopic two-phase fluid system was combined with a surface phase-field-crystal model for the microscopic colloidal particles along the interface. Unfortunately this model leads to spurious velocities which require very fine spatial and temporal resolutions to accurately and stably simulate. In this paper we develop an improved Navier-Stokes-Cahn-Hilliard-surface phase-field-crystal model based on the principles of mass conservation and thermodynamic consistency. To validate our approach, we derive a sharp interface model and show agreement with the improved diffuse interface model. Using simple flow configurations, we show that the new model has much better properties and does not lead to spurious velocities. Finally, we demonstrate the solid-like behavior of the crystallized interface by simulating the fall of a solid ball through a colloid-laden multiphase fluid.
A numerical model for dynamic crustal-scale fluid flow
NASA Astrophysics Data System (ADS)
Sachau, Till; Bons, Paul; Gomez-Rivas, Enrique; Koehn, Daniel
2015-04-01
Fluid flow in the crust is often envisaged and modeled as continuous, yet minimal flow, which occurs over large geological times. This is a suitable approximation for flow as long as it is solely controlled by the matrix permeability of rocks, which in turn is controlled by viscous compaction of the pore space. However, strong evidence (hydrothermal veins and ore deposits) exists that a significant part of fluid flow in the crust occurs strongly localized in both space and time, controlled by the opening and sealing of hydrofractures. We developed, tested and applied a novel computer code, which considers this dynamic behavior and couples it with steady, Darcian flow controlled by the matrix permeability. In this dual-porosity model, fractures open depending on the fluid pressure relative to the solid pressure. Fractures form when matrix permeability is insufficient to accommodate fluid flow resulting from compaction, decompression (Staude et al. 2009) or metamorphic dehydration reactions (Weisheit et al. 2013). Open fractures can close when the contained fluid either seeps into the matrix or escapes by fracture propagation: mobile hydrofractures (Bons, 2001). In the model, closing and sealing of fractures is controlled by a time-dependent viscous law, which is based on the effective stress and on either Newtonian or non-Newtonian viscosity. Our simulations indicate that the bulk of crustal fluid flow in the middle to lower upper crust is intermittent, highly self-organized, and occurs as mobile hydrofractures. This is due to the low matrix porosity and permeability, combined with a low matrix viscosity and, hence, fast sealing of fractures. Stable fracture networks, generated by fluid overpressure, are restricted to the uppermost crust. Semi-stable fracture networks can develop in an intermediate zone, if a critical overpressure is reached. Flow rates in mobile hydrofractures exceed those in the matrix porosity and fracture networks by orders of magnitude
Phase-separation models for swimming enhancement in complex fluids
NASA Astrophysics Data System (ADS)
Man, Yi; Lauga, Eric
2015-08-01
Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results.
Phase-separation models for swimming enhancement in complex fluids.
Man, Yi; Lauga, Eric
2015-08-01
Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results. PMID:26382500
The Chemical Behavior of Fluids Released during Deep Subduction Based on Fluid Inclusions
NASA Astrophysics Data System (ADS)
Frezzotti, M. L.; Ferrando, S.
2014-12-01
We present a review of current research on fluid inclusions in (HP-) UHP metamorphic rocks that, combined with existing experimental research and thermodynamic models, allow us to investigate the chemical and physical properties of fluids released during deep subduction, their solvent and element transport capacity, and the subsequent implications for the element recycling in the mantle wedge. An impressive number of fluid inclusion studies indicate three main populations of fluid inclusions in HP and UHP metamorphic rocks: i) aqueous and/or non-polar gaseous fluid inclusions (FI), ii) multiphase solid inclusions (MSI), and iii) melt inclusions (MI). Chemical data from preserved fluid inclusions in rocks match with and implement "model" fluids by experiments and thermodynamics, revealing a continuity behind the extreme variations of physico-chemical properties of subduction-zone fluids. From fore-arc to sub-arc depths, fluids released by progressive devolatilization reactions from slab lithologies change from relatively diluted chloride-bearing aqueous solutions (± N2), mainly influenced by halide ligands, to (alkali) aluminosilicate-rich aqueous fluids, in which polymerization probably governs the solubility and transport of major (e.g., Si and Al) and trace elements (including C). Fluid inclusion data implement the petrological models explaining deep volatile liberation in subduction zones, and their flux into the mantle wedge.
Eylenceoğlu, E.; Rafatov, I.; Kudryavtsev, A. A.
2015-01-15
Two-dimensional hybrid Monte Carlo–fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model.
Structural stability of a 1D compressible viscoelastic fluid model
NASA Astrophysics Data System (ADS)
Huo, Xiaokai; Yong, Wen-An
2016-07-01
This paper is concerned with a compressible viscoelastic fluid model proposed by Öttinger. Although the model has a convex entropy, the Hessian matrix of the entropy does not symmetrize the system of first-order partial differential equations due to the non-conservative terms in the constitutive equation. We show that the corresponding 1D model is symmetrizable hyperbolic and dissipative and satisfies the Kawashima condition. Based on these, we prove the global existence of smooth solutions near equilibrium and justify the compatibility of the model with the Navier-Stokes equations.
Modelling non-dust fluids in cosmology
Christopherson, Adam J.; Hidalgo, Juan Carlos; Malik, Karim A. E-mail: juan.hidalgo@port.ac.uk
2013-01-01
Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or 'dust', this approach gives the correct results for scales much smaller than the cosmological horizon, but for scenarios in which the fluid has pressure this is no longer the case. In this article, we present the correspondence of perturbations in Newtonian and cosmological perturbation theory, showing exact mathematical equivalence for pressureless matter, and giving the relativistic corrections for matter with pressure. As an example, we study the case of scalar field dark matter which features non-zero pressure perturbations. We discuss some problems which may arise when evolving the perturbations in this model with Newtonian numerical simulations and with CMB Boltzmann codes.
Design and development of magnetorheological fluid-based passive actuator.
Shokrollahi, Elnaz; Price, Karl; Drake, James M; Goldenberg, Andrew A
2015-08-01
We present the design and experimental validation of a magnetorheological (MR) fluid-based passive actuator for tele-robotic bone biopsy procedures. With Finite Element Method Magnet (FEMM) software, the required uniform magnetic field circuit design was simulated. An 1100 turn 24 AWG copper wire coil wrapped around a magnetic core was used to create a magnetic field. The field strength was measured with a Hall effect sensor, and compared to the simulation. The maximum magnetic field flux produced by a constant current of 1.4 A was 0.2 T, similar to the simulation results. A series of quasi-static experiments were conducted to characterize the forces generated by the MR fluid-based actuator under various currents up to 12 N. An analytical model was developed to validate the measurements from the passive actuator. PMID:26737387
NASA Astrophysics Data System (ADS)
Septiani, Eka Lutfi; Widiyastuti, W.; Winardi, Sugeng; Machmudah, Siti; Nurtono, Tantular; Kusdianto
2016-02-01
Flame assisted spray dryer are widely uses for large-scale production of nanoparticles because of it ability. Numerical approach is needed to predict combustion and particles production in scale up and optimization process due to difficulty in experimental observation and relatively high cost. Computational Fluid Dynamics (CFD) can provide the momentum, energy and mass transfer, so that CFD more efficient than experiment due to time and cost. Here, two turbulence models, k-ɛ and Large Eddy Simulation were compared and applied in flame assisted spray dryer system. The energy sources for particle drying was obtained from combustion between LPG as fuel and air as oxidizer and carrier gas that modelled by non-premixed combustion in simulation. Silica particles was used to particle modelling from sol silica solution precursor. From the several comparison result, i.e. flame contour, temperature distribution and particle size distribution, Large Eddy Simulation turbulence model can provide the closest data to the experimental result.
Numerical simulation of continuum models for fluid-fluid interface dynamics
NASA Astrophysics Data System (ADS)
Gross, S.; Reusken, A.
2013-05-01
This paper is concerned with numerical methods for two-phase incompressible flows assuming a sharp interface model for interfacial stresses. Standard continuum models for the fluid dynamics in the bulk phases, for mass transport of a solute between the phases and for surfactant transport on the interface are given. We review some recently developed finite element methods for the appropriate discretization of such models, e. g., a pressure extended finite element (XFE) space which is suitable to represent the pressure jump, a space-time extended finite element discretization for the mass transport equation of a solute and a surface finite element method (SurFEM) for surfactant transport. Numerical experiments based on level set interface capturing and adaptive multilevel finite element discretization are presented for rising droplets with a clean interface model and a spherical droplet in a Poisseuille flow with a Boussinesq-Scriven interface model.
AIR INGRESS ANALYSIS: COMPUTATIONAL FLUID DYNAMIC MODELS
Chang H. Oh; Eung S. Kim; Richard Schultz; Hans Gougar; David Petti; Hyung S. Kang
2010-08-01
The Idaho National Laboratory (INL), under the auspices of the U.S. Department of Energy, is performing research and development that focuses on key phenomena important during potential scenarios that may occur in very high temperature reactors (VHTRs). Phenomena Identification and Ranking Studies to date have ranked an air ingress event, following on the heels of a VHTR depressurization, as important with regard to core safety. Consequently, the development of advanced air ingress-related models and verification and validation data are a very high priority. Following a loss of coolant and system depressurization incident, air will enter the core of the High Temperature Gas Cooled Reactor through the break, possibly causing oxidation of the in-the core and reflector graphite structure. Simple core and plant models indicate that, under certain circumstances, the oxidation may proceed at an elevated rate with additional heat generated from the oxidation reaction itself. Under postulated conditions of fluid flow and temperature, excessive degradation of the lower plenum graphite can lead to a loss of structural support. Excessive oxidation of core graphite can also lead to the release of fission products into the confinement, which could be detrimental to a reactor safety. Computational fluid dynamic model developed in this study will improve our understanding of this phenomenon. This paper presents two-dimensional and three-dimensional CFD results for the quantitative assessment of the air ingress phenomena. A portion of results of the density-driven stratified flow in the inlet pipe will be compared with results of the experimental results.
Fluid mechanical model of the Helmholtz resonator
NASA Technical Reports Server (NTRS)
Hersh, A. S.; Walker, B.
1977-01-01
A semi-empirical fluid mechanical model of the acoustic behavior of Helmholtz resonators is presented which predicts impedance as a function of the amplitude and frequency of the incident sound pressure field and resonator geometry. The model assumes that the particle velocity approaches the orifice in a spherical manner. The incident and cavity sound fields are connected by solving the governing oscillating mass and momentum conservation equations. The model is in agreement with the Rayleigh slug-mass model at low values of incident sound pressure level. At high values, resistance is predicted to be independent of frequency, proportional to the square root of the amplitude of the incident sound pressure field, and virtually independent of resonator geometry. Reactance is predicted to depend in a very complicated way upon resonator geometry, incident sound pressure level, and frequency. Nondimensional parameters are defined that divide resonator impedance into three categories corresponding to low, moderately low, and intense incident sound pressure amplitudes. The two-microphone method was used to measure the impedance of a variety of resonators. The data were used to refine and verify the model.
Zimmerman, Jonathan A.; Wong, Bryan Matthew; Jones, Reese E.; Templeton, Jeremy Alan; Lee, Jonathan
2010-11-01
Understanding charge transport processes at a molecular level using computational techniques is currently hindered by a lack of appropriate models for incorporating anisotropic electric fields, as occur at charged fluid/solid interfaces, in molecular dynamics (MD) simulations. In this work, we develop a model for including electric fields in MD using an atomistic-to-continuum framework. Our model represents the electric potential on a finite element mesh satisfying a Poisson equation with source terms determined by the distribution of the atomic charges. The method is verified using simulations where analytical solutions are known or comparisons can be made to existing techniques. A Calculation of a salt water solution in a silicon nanochannel is performed to demonstrate the method in a target scientific application.
Discrete Models of Fluids: Spatial Averaging, Closure, and Model Reduction
Panchenko, Alexander; Tartakovsky, Alexandre; Cooper, Kevin
2014-03-06
The main question addressed in the paper is how to obtain closed form continuum equations governing spatially averaged dynamics of semi-discrete ODE models of fluid flow. In the presence of multiple small scale heterogeneities, the size of these ODE systems can be very large. Spatial averaging is then a useful tool for reducing computational complexity of the problem. The averages satisfy balance equations of mass, momentum and energy. These equations are exact, but they do not form a continuum model in the true sense of the word because calculation of stress and heat flux requires solving the underlying ODE system. To produce continuum equations that can be simulated without resolving micro-scale dynamics, we developed a closure method based on the use of regularized deconvolutions. We mostly deal with non-linear averaging suitable for Lagrangian particle solvers, but consider Eulerian linear averaging where appropriate. The results of numerical experiments show good agreement between our closed form flux approximations and their exact counterparts.
Template Matching Using a Fluid Flow Model
NASA Astrophysics Data System (ADS)
Newman, William Curtis
Template matching is successfully used in machine recognition of isolated spoken words. In these systems a word is broken into frames (20 millisecond time slices) and the spectral characteristics of each frame are found. Thus, each word is represented as a 2-dimensional (2-D) function of spectral characteristic and frame number. An unknown word is recognized by matching its 2-D representation to previously stored example words, or templates, also in this 2-D form. A new model for this matching step will be introduced. The 2-D representations of the template and unknown are used to determine the shape of a volume of viscous fluid. This volume is broken up into many small elements. The unknown is changed into the template by allowing flows between the element boundaries. Finally the match between the template and unknown is determined by calculating a weighted squared sum of the flow values. The model also allows the relative flow resistance between the element boundaries to be changed. This is useful for characterizing the important features of a given template. The flow resistances are changed according to the gradient of a simple performance function. This performance function is evaluated using a set of training samples provided by the user. The model is applied to isolated word and single character recognition tasks. Results indicate the applications where this model works best.
Dimension reduction method for ODE fluid models
Tartakovsky, Alexandre M.; Panchenko, Alexander; Ferris, Kim F.
2011-09-20
We develop a dimension reduction method for large size ODE systems obtained from a dis- cretization of partial differential equations of viscous fluid flow of nearly constant density. The method is also applicable to other large size classical particle systems with negligibly small variations of concentration. We propose a new computational closure for mesoscale balance equations based on numerical iterative deconvolution. To illustrate the computa- tional advantages of the proposed reduction method we use it to solve a system of Smoothed Particle Hydrodynamic ODEs describing Poiseuille flows driven by uniform and periodic (in space) body forces. For the Poiseuille flow driven by the uniform force the coarse solution was obtained with the zero-order deconvolution. For the flow driven by the periodic body force, the first-order deconvolution was necessary to obtain a sufficiently accurate solution.
Edison, John R.; Monson, Peter A.
2014-07-14
Recently we have developed a dynamic mean field theory (DMFT) for lattice gas models of fluids in porous materials [P. A. Monson, J. Chem. Phys. 128(8), 084701 (2008)]. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable states for fluids in pores and is especially useful for studying system exhibiting adsorption/desorption hysteresis. In this paper we discuss the extension of the theory to higher order by means of the path probability method (PPM) of Kikuchi and co-workers. We show that this leads to a treatment of the dynamics that is consistent with thermodynamics coming from the Bethe-Peierls or Quasi-Chemical approximation for the equilibrium or metastable equilibrium states of the lattice model. We compare the results from the PPM with those from DMFT and from dynamic Monte Carlo simulations. We find that the predictions from PPM are qualitatively similar to those from DMFT but give somewhat improved quantitative accuracy, in part due to the superior treatment of the underlying thermodynamics. This comes at the cost of greater computational expense associated with the larger number of equations that must be solved.
State-of-the-art review of computational fluid dynamics modeling for fluid-solids systems
NASA Astrophysics Data System (ADS)
Lyczkowski, R. W.; Bouillard, J. X.; Ding, J.; Chang, S. L.; Burge, S. W.
1994-05-01
As the result of 15 years of research (50 staff years of effort) Argonne National Laboratory (ANL), through its involvement in fluidized-bed combustion, magnetohydrodynamics, and a variety of environmental programs, has produced extensive computational fluid dynamics (CFD) software and models to predict the multiphase hydrodynamic and reactive behavior of fluid-solids motions and interactions in complex fluidized-bed reactors (FBR's) and slurry systems. This has resulted in the FLUFIX, IRF, and SLUFIX computer programs. These programs are based on fluid-solids hydrodynamic models and can predict information important to the designer of atmospheric or pressurized bubbling and circulating FBR, fluid catalytic cracking (FCC) and slurry units to guarantee optimum efficiency with minimum release of pollutants into the environment. This latter issue will become of paramount importance with the enactment of the Clean Air Act Amendment (CAAA) of 1995. Solids motion is also the key to understanding erosion processes. Erosion rates in FBR's and pneumatic and slurry components are computed by ANL's EROSION code to predict the potential metal wastage of FBR walls, intervals, feed distributors, and cyclones. Only the FLUFIX and IRF codes will be reviewed in the paper together with highlights of the validations because of length limitations. It is envisioned that one day, these codes with user-friendly pre- and post-processor software and tailored for massively parallel multiprocessor shared memory computational platforms will be used by industry and researchers to assist in reducing and/or eliminating the environmental and economic barriers which limit full consideration of coal, shale, and biomass as energy sources; to retain energy security; and to remediate waste and ecological problems.
A coupled model of fluid flow in jointed rock
Swenson, Daniel; Martineau, Rick; James, Mark; Brown, Don
1991-01-01
We present a fully coupled model of fluid flow in jointed rock, where the fluid flow depends on the joint openings and the joint openings depend on the fluid pressure. The joints and rock blocks are modeled discretely using the finite element method. Solutions for the fluid and rock are obtained and iteration is performed until both solutions converge. Example applications include an examination of the effects of back-pressure on flow in a geothermal reservoir and transient fluid injection into a reservoir.
High quality water base fracturing fluid
Chen, L.D.; Chen, G.Y.; Zi, X.X.
1982-01-01
A new fracturing fluid is presented that contains partially hydrolyzed polymethylene acrylamide crosslinked with polyvalent metal ions as a thickening and friction reducing agent and persulfate, hydrogen peroxide, perborate or hydragine as a gel breaking agent. This fluid offers a number of advantages over conventional fracturing materials as it is free from any residues and possesses better thickening ability, shear stability, salt resistance, temperature-viscosity properties, etc. The new fluid was successfully used for hydraulic fracturing operations in low-permeable formations. 5 refs.
Modelling couplings between reaction, fluid flow and deformation: Kinetics
NASA Astrophysics Data System (ADS)
Malvoisin, Benjamin; Podladchikov, Yury Y.; Connolly, James A. D.
2016-04-01
Mineral assemblages out of equilibrium are commonly found in metamorphic rocks testifying of the critical role of kinetics for metamorphic reactions. As experimentally determined reaction rates in fluid-saturated systems generally indicate complete reaction in less than several years, i.e. several orders of magnitude faster than field-based estimates, metamorphic reaction kinetics are generally thought to be controlled by transport rather than by processes at the mineral surface. However, some geological processes like earthquakes or slow-slip events have shorter characteristic timescales, and transport processes can be intimately related to mineral surface processes. Therefore, it is important to take into account the kinetics of mineral surface processes for modelling fluid/rock interactions. Here, a model coupling reaction, fluid flow and deformation was improved by introducing a delay in the achievement of equilibrium. The classical formalism for dissolution/precipitation reactions was used to consider the influence of the distance from equilibrium and of temperature on the reaction rate, and a dependence on porosity was introduced to model evolution of reacting surface area during reaction. The fitting of experimental data for three reactions typically occurring in metamorphic systems (serpentine dehydration, muscovite dehydration and calcite decarbonation) indicates a systematic faster kinetics close from equilibrium on the dehydration side than on the hydration side. This effect is amplified through the porosity term in the reaction rate since porosity is formed during dehydration. Numerical modelling indicates that this difference in reaction rate close from equilibrium plays a key role in microtextures formation. The developed model can be used in a wide variety of geological systems where couplings between reaction, deformation and fluid flow have to be considered.
Modelling Transcapillary Transport of Fluid and Proteins in Hemodialysis Patients
Pietribiasi, Mauro; Waniewski, Jacek; Załuska, Alicja; Załuska, Wojciech; Lindholm, Bengt
2016-01-01
Background The kinetics of protein transport to and from the vascular compartment play a major role in the determination of fluid balance and plasma refilling during hemodialysis (HD) sessions. In this study we propose a whole-body mathematical model describing water and protein shifts across the capillary membrane during HD and compare its output to clinical data while evaluating the impact of choosing specific values for selected parameters. Methods The model follows a two-compartment structure (vascular and interstitial space) and is based on balance equations of protein mass and water volume in each compartment. The capillary membrane was described according to the three-pore theory. Two transport parameters, the fractional contribution of large pores (αLP) and the total hydraulic conductivity (LpS) of the capillary membrane, were estimated from patient data. Changes in the intensity and direction of individual fluid and solute flows through each part of the transport system were analyzed in relation to the choice of different values of small pores radius and fractional conductivity, lymphatic sensitivity to hydraulic pressure, and steady-state interstitial-to-plasma protein concentration ratio. Results The estimated values of LpS and αLP were respectively 10.0 ± 8.4 mL/min/mmHg (mean ± standard deviation) and 0.062 ± 0.041. The model was able to predict with good accuracy the profiles of plasma volume and serum total protein concentration in most of the patients (average root-mean-square deviation < 2% of the measured value). Conclusions The applied model provides a mechanistic interpretation of fluid transport processes induced by ultrafiltration during HD, using a minimum of tuned parameters and assumptions. The simulated values of individual flows through each kind of pore and lymphatic absorption rate yielded by the model may suggest answers to unsolved questions on the relative impact of these not-measurable quantities on total vascular refilling and
Fluid Structure Modelling of Blood Flow in Vessels.
Moatamedi, M; Souli, M; Al-Bahkali, E
2014-12-01
This paper describes the capabilities of fluid structure interaction based multi-physics numerical modelling in solving problems related to vascular biomechanics. In this research work, the onset of a pressure pulse was simulated at the entrance of a three dimensional straight segment of the blood vessel like circular tube and the resulting dynamic response in the form of a propagating pulse wave through the wall was analysed and compared. Good agreement was found between the numerical results and the theoretical description of an idealized artery. Work has also been done on implementing the material constitutive models specific for vascular applications. PMID:26336693
Computational fluid dynamic modeling of fluidized-bed polymerization reactors
Rokkam, Ram
2012-01-01
Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.
Momentum transfer across fluid-fluid interfaces in porous media: A network model
Goode, P.A.; Ramakrishnan, T.S. )
1993-07-01
Two-phase flow in porous media is described based on the extended form of Darcy's law, which ignores momentum transfer at fluid-fluid interfaces. Two forms of corrections to this simple description have been proposed in the literature: on the relative permeability dependence on viscosity ratio; the other on the velocities assumed to be proportional to both phase pressure gradients and so introducing an additional saturation-dependent cross coefficient. In this article, to identify the correct form of transport equations, a simple cubic network model of 30 x 30 x 30 bonds is used. The cross section of the bonds is that of a four-cusp duct. The fluid interface in each duct is located by capillary equilibrium. The duct hydraulic conductances are then obtained as a function of viscosity ratio and phase volume fraction using a finite element calculation. These individual duct results are used in the network calculations for which a percolation algorithm is applied to simulate nonwetting phase displacing wetting phase, a process also known as initial drainage. Flow calculations show that both the nonwetting-phase relative permeability and the cross coefficient are strong functions of saturation and viscosity ratio. Also, the off-diagonal terms may contribute to a nonnegligible fraction of the flow. The proposed generalization of the Darcy equations is applicable to all problems involving multiphase flow in porous media. The current practices for relative permeability measurements and reservoir simulation may have to be reexamined in the context of the proposed transport equations.
Tribological and Rheological Properties of a Synovial Fluid Model
NASA Astrophysics Data System (ADS)
Klossner, Rebecca; Liang, Jing; Krause, Wendy
2010-03-01
Hyaluronic acid (HA) and the plasma proteins, albumin and globulins, are the most abundant macromolecules in synovial fluid, the fluid that lubricates freely moving joints. In previous studies, bovine synovial fluid, a synovial fluid model (SFM) and albumin in phosphate buffered saline (PBS) were observed to be rheopectic---viscosity increases over time under constant shear. Additionally, steady shear experiments have a strong shear history dependence in protein-containing solutions, whereas samples of HA in PBS behaved as a ``typical'' polyelectrolyte. The observed rheopexy and shear history dependence are indicative of structure building in solution, which is most likely caused by protein aggregation. The tribology of the SFM was also investigated using nanoindenter-based scratch tests. The coefficient of frictions (μ) between the diamond nanoindenter tip and a polyethylene surface was measured in the presence of the SFM and solutions with varied protein and HA concentrations. The lowest μ is observed in the SFM, which most closely mimics a healthy joint. Finally, an anti-inflammatory drug, hydroxychloroquine, was shown to inhibit protein interactions in the SFM in rheological studies, and thus the tribological response was examined. We hypothesize that the rheopectic behavior is important in lubrication regimes and therefore, the rheological and tribological properties of these solutions will be correlated.
Simulation and modeling techniques for parachute fluid-structure interactions
NASA Astrophysics Data System (ADS)
Stein, Keith Robert
This thesis is on advanced flow simulation and modeling techniques for fluid-structure interactions (FSI) encountered in parachute systems. The main fluid dynamics solver is based on the Deforming-Spatial-Domain/Stabilized Space-Time (DSD/SST) finite element formulation of the Navier-Stokes equations of incompressible flows. The DSD/SST formulation, which was introduced earlier for flow computations involving moving boundaries and interfaces, gives us the capability to handle parachute structural deformations. The structural dynamics solver is based on a total Lagrangian finite element formulation of the equilibrium equations for a "tension structure" composed of membranes, cables, and concentrated masses. The fluid and structure are coupled iteratively within a nonlinear iteration loop, with multiple nonlinear iterations improving the convergence of the coupled system. Unstructured mesh generation and mesh moving techniques for handling of parachute deformations are developed and/or adapted to address the challenges posed by the coupled problem. The FSI methodology was originally implemented on the Thinking Machines CM-5 supercomputer and is now actively used on the CRAY T3E-1200. Applications to a variety of round and cross parachutes used by the US Army are presented, and different stages of the parachute operations, including inflation and terminal descent, are modeled.
NASA Technical Reports Server (NTRS)
Sinha, Neeraj; Brinckman, Kevin; Jansen, Bernard; Seiner, John
2011-01-01
A method was developed of obtaining propulsive base flow data in both hot and cold jet environments, at Mach numbers and altitude of relevance to NASA launcher designs. The base flow data was used to perform computational fluid dynamics (CFD) turbulence model assessments of base flow predictive capabilities in order to provide increased confidence in base thermal and pressure load predictions obtained from computational modeling efforts. Predictive CFD analyses were used in the design of the experiments, available propulsive models were used to reduce program costs and increase success, and a wind tunnel facility was used. The data obtained allowed assessment of CFD/turbulence models in a complex flow environment, working within a building-block procedure to validation, where cold, non-reacting test data was first used for validation, followed by more complex reacting base flow validation.
Modeling of Fluid-Membrane Interaction in Cellular Microinjection Process
NASA Astrophysics Data System (ADS)
Karzar-Jeddi, Mehdi; Diaz, Jhon; Olgac, Nejat; Fan, Tai-Hsi
2009-11-01
Cellular microinjection is a well-accepted method to deliver matters such as sperm, nucleus, or macromolecules into biological cells. To improve the success rate of in vitro fertilization and to establish the ideal operating conditions for a novel computer controlled rotationally oscillating intracytoplasmic sperm injection (ICSI) technology, we investigate the fluid-membrane interactions in the ICSI procedure. The procedure consists of anchoring the oocyte (a developing egg) using a holding pipette, penetrating oocyte's zona pellucida (the outer membrane) and the oolemma (the plasma or inner membrane) using an injection micropipette, and finally to deliver sperm into the oocyte for fertilization. To predict the large deformation of the oocyte membranes up to the piercing of the oolemma and the motion of fluids across both membranes, the dynamic fluid-pipette-membrane interactions are formulated by the coupled Stokes' equations and the continuum membrane model based on Helfrich's energy theory. A boundary integral model is developed to simulate the transient membrane deformation and the local membrane stress induced by the longitudinal motion of the injection pipette. The model captures the essential features of the membranes shown on optical images of ICSI experiments, and is capable of suggesting the optimal deformation level of the oolemma to start the rotational oscillations for piercing into the oolemma.
A THC Simulator for Modeling Fluid-Rock Interactions
NASA Astrophysics Data System (ADS)
Hamidi, Sahar; Galvan, Boris; Heinze, Thomas; Miller, Stephen
2014-05-01
Fluid-rock interactions play an essential role in many earth processes, from a likely influence on earthquake nucleation and aftershocks, to enhanced geothermal system, carbon capture and storage (CCS), and underground nuclear waste repositories. In THC models, two-way interactions between different processes (thermal, hydraulic and chemical) are present. Fluid flow influences the permeability of the rock especially if chemical reactions are taken into account. On one hand solute concentration influences fluid properties while, on the other hand, heat can affect further chemical reactions. Estimating heat production from a naturally fractured geothermal systems remains a complex problem. Previous works are typically based on a local thermal equilibrium assumption and rarely consider the salinity. The dissolved salt in fluid affects the hydro- and thermodynamical behavior of the system by changing the hydraulic properties of the circulating fluid. Coupled thermal-hydraulic-chemical models (THC) are important for investigating these processes, but what is needed is a coupling to mechanics to result in THMC models. Although similar models currently exist (e.g. PFLOTRAN), our objective here is to develop algorithms for implementation using the Graphics Processing Unit (GPU) computer architecture to be run on GPU clusters. To that aim, we present a two-dimensional numerical simulation of a fully coupled non-isothermal non-reactive solute flow. The thermal part of the simulation models heat transfer processes for either local thermal equilibrium or nonequilibrium cases, and coupled to a non-reactive mass transfer described by a non-linear diffusion/dispersion model. The flow process of the model includes a non-linear Darcian flow for either saturated or unsaturated scenarios. For the unsaturated case, we use the Richards' approximation for a mixture of liquid and gas phases. Relative permeability and capillary pressure are determined by the van Genuchten relations
Physicochemical properties of magnetic fluids based on synthetic oils
NASA Astrophysics Data System (ADS)
Korolev, V. V.; Ramazanova, A. G.; Yashkova, V. I.; Balmasova, O. V.
2013-04-01
A technique for synthesizing magnetic fluids based on Alkaren synthetic oil is described. The optimum synthesis conditions for the magnetite are selected, and the magnetic phase-stabilizer quantitative ratio is calculated. A magnetic fluid based on synthetic hydrocarbon oil is synthesized, and its physicochemical characteristics are determined.
ANFIS modeling for prediction of particle motions in fluid flows
NASA Astrophysics Data System (ADS)
Safdari, Arman; Kim, Kyung Chun
2015-11-01
Accurate dynamic analysis of parcel of solid particles driven in fluid flow system is of interest for many natural and industrial applications such as sedimentation process, study of cloud particles in atmosphere, etc. In this paper, numerical modeling of solid particles in incompressible flow using Eulerian-Lagrangian approach is carried out to investigate the dynamic behavior of particles in different flow conditions; channel and cavity flow. Although modern computers have been well developed, the high computational time and costs for this kind of problems are still demanded. The Lattice Boltzmann Method (LBM) is used to simulate fluid flows and combined with the Lagrangian approach to predict the motion of particles in the range of masses. Some particles are selected, and subjected to Adaptive-network-based fuzzy inference system (ANFIS) to predict the trajectory of moving solid particles. Using a hybrid learning procedure from computational particle movement, the ANFIS can construct an input-output mapping based on fuzzy if-then rules and stipulated computational fluid dynamics prediction pairs. The obtained results from ANFIS algorithm is validated and compared with the set of benchmark data provided based on point-like approach coupled with the LBM method.
Model reduction for parametric instability analysis in shells conveying fluid
NASA Astrophysics Data System (ADS)
Kochupillai, Jayaraj; Ganesan, N.; Padmanabhan, Chandramouli
2003-05-01
Flexible pipes conveying fluid are often subjected to parametric excitation due to time-periodic flow fluctuations. Such systems are known to exhibit complex instability phenomena such as divergence and coupled-mode flutter. Investigators have typically used weighted residual techniques, to reduce the continuous system model into a discrete model, based on approximation functions with global support, for carrying out stability analysis. While this approach is useful for straight pipes, modelling based on FEM is needed for the study of complicated piping systems, where the approximation functions used are local in support. However, the size of the problem is now significantly larger and for computationally efficient stability analysis, model reduction is necessary. In this paper, model reduction techniques are developed for the analysis of parametric instability in flexible pipes conveying fluids under a mean pressure. It is shown that only those linear transformations which leave the original eigenvalues of the linear time invariant system unchanged are admissible. The numerical technique developed by Friedmann and Hammond (Int. J. Numer. Methods Eng. Efficient 11 (1997) 1117) is used for the stability analysis. One of the key research issues is to establish criteria for deciding the basis vectors essential for an accurate stability analysis. This paper examines this issue in detail and proposes new guidelines for their selection.
Hoi, Yiemeng; Ionita, Ciprian N.; Tranquebar, Rekha V.; Hoffmann, Kenneth R.; Woodward, Scott, H.; Taulbee, Dale B.; Meng, Hui; Rudin, Stephen
2011-01-01
An asymmetric stent with low porosity patch across the intracranial aneurysm neck and high porosity elsewhere is designed to modify the flow to result in thrombogenesis and occlusion of the aneurysm and yet to reduce the possibility of also occluding adjacent perforator vessels. The purposes of this study are to evaluate the flow field induced by an asymmetric stent using both numerical and digital subtraction angiography (DSA) methods and to quantify the flow dynamics of an asymmetric stent in an in vivo aneurysm model. We created a vein-pouch aneurysm model on the canine carotid artery. An asymmetric stent was implanted at the aneurysm, with 25% porosity across the aneurysm neck and 80% porosity elsewhere. The aneurysm geometry, before and after stent implantation, was acquired using cone beam CT and reconstructed for computational fluid dynamics (CFD) analysis. Both steady-state and pulsatile flow conditions using the measured waveforms from the aneurysm model were studied. To reduce computational costs, we modeled the asymmetric stent effect by specifying a pressure drop over the layer across the aneurysm orifice where the low porosity patch was located. From the CFD results, we found the asymmetric stent reduced the inflow into the aneurysm by 51%, and appeared to create a stasis-like environment which favors thrombus formation. The DSA sequences also showed substantial flow reduction into the aneurysm. Asymmetric stents may be a viable image guided intervention for treating intracranial aneurysms with desired flow modification features. PMID:21666881
A fluid model of cancer progression and treatment
NASA Astrophysics Data System (ADS)
Wise, Steven; Cristini, Vittorio; Lowengrub, John; Zheng, Xiaoming
2003-11-01
In this talk, we will present recent progress on a computer simulator of cancer based on a fluid model of tumor growth. The tumor is represented as an incompressible fluid with a source that represents cell-proliferation. Angiogenesis and its complex nonlinear interplay with cell-growth are included as well as the effects of traditional and new therapies. We find that tumors while growing develop shape instabilities that lead to tissue invasion and possible metastasization. In addition, traditional therapy may have a two-fold effect while causing a tumor to shrink by killing the tumor cells, a shape instability may occur leading to tumor fragmentation leading to migration of small cell-clusters through the external tissue and blood vessels thus enhancing the potential for mestastasization.
Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova
James Glimm
2009-06-04
The three year plan for this project was to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (Direct Numerical Simulation (DNS), Large Eddy Simulations (LES), full two fluid simulations and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We model 2D and 3D perturbations of planar or circular interfaces. We compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. Multiple layers and reshock are considered here.
MHD results from a collisionless fluid model
NASA Astrophysics Data System (ADS)
Ramos, J. J.
2002-11-01
A non-conventional closure ansatz for collisionless MHD has been proposed in Ref.[1]. The truncation of the set of fluid moment equations is suggested by a comparison between the standard non-relativistic set and the non-relativistic limit of the relativistic set derived in Ref.[2]. The resulting model is a closed system of evolution equations in conservation form for the particle, momentum and energy densities, and the energy flux, allowing for pressure anisotropy and parallel heat flux. The static equilibrium condition is the same as in the Chew-Goldberger-Low theory, supplemented by the condition that the parallel energy flux be constant along the magnetic field. We study the linear perturbations about such static equilibria to derive the MHD wave dispersion relations in a homogeneous background and the perturbed potential energy associated with a stability energy principle. [1] J.J. Ramos, 2002 International Sherwood Theory Meeting, Rochester, NY, paper 1D25. [2] R.D. Hazeltine and S.M. Mahajan, Ap. J. 567, 1262 (2002).
Modelling of reactive fluid transport in deformable porous rocks
NASA Astrophysics Data System (ADS)
Yarushina, V. M.; Podladchikov, Y. Y.
2009-04-01
One outstanding challenge in geology today is the formulation of an understanding of the interaction between rocks and fluids. Advances in such knowledge are important for a broad range of geologic settings including partial melting and subsequent migration and emplacement of a melt into upper levels of the crust, or fluid flow during regional metamorphism and metasomatism. Rock-fluid interaction involves heat and mass transfer, deformation, hydrodynamic flow, and chemical reactions, thereby necessitating its consideration as a complex process coupling several simultaneous mechanisms. Deformation, chemical reactions, and fluid flow are coupled processes. Each affects the others. Special effort is required for accurate modelling of the porosity field through time. Mechanical compaction of porous rocks is usually treated under isothermal or isoentropic simplifying assumptions. However, joint consideration of both mechanical compaction and reactive porosity alteration requires somewhat greater than usual care about thermodynamic consistency. Here we consider the modelling of multi-component, multi-phase systems, which is fundamental to the study of fluid-rock interaction. Based on the conservation laws for mass, momentum, and energy in the form adopted in the theory of mixtures, we derive a thermodynamically admissible closed system of equations describing the coupling of heat and mass transfer, chemical reactions, and fluid flow in a deformable solid matrix. Geological environments where reactive transport is important are located at different depths and accordingly have different rheologies. In the near surface, elastic or elastoplastic properties would dominate, whereas viscoplasticity would have a profound effect deeper in the lithosphere. Poorly understood rheologies of heterogeneous porous rocks are derived from well understood processes (i.e., elasticity, viscosity, plastic flow, fracturing, and their combinations) on the microscale by considering a
Microscope-Based Fluid Physics Experiments in the Fluids and Combustion Facility on ISS
NASA Technical Reports Server (NTRS)
Doherty, Michael P.; Motil, Susan M.; Snead, John H.; Malarik, Diane C.
2000-01-01
At the NASA Glenn Research Center, the Microgravity Science Program is planning to conduct a large number of experiments on the International Space Station in both the Fluid Physics and Combustion Science disciplines, and is developing flight experiment hardware for use within the International Space Station's Fluids and Combustion Facility. Four fluids physics experiments that require an optical microscope will be sequentially conducted within a subrack payload to the Fluids Integrated Rack of the Fluids and Combustion Facility called the Light Microscopy Module, which will provide the containment, changeout, and diagnostic capabilities to perform the experiments. The Light Microscopy Module is planned as a fully remotely controllable on-orbit microscope facility, allowing flexible scheduling and control of experiments within International Space Station resources. This paper will focus on the four microscope-based experiments, specifically, their objectives and the sample cell and instrument hardware to accommodate their requirements.
Complex fluid flow modeling with SPH on GPU
NASA Astrophysics Data System (ADS)
Bilotta, Giuseppe; Hérault, Alexis; Del Negro, Ciro; Russo, Giovanni; Vicari, Annamaria
2010-05-01
We describe an implementation of the Smoothed Particle Hydrodynamics (SPH) method for the simulation of complex fluid flows. The algorithm is entirely executed on Graphic Processing Units (GPUs) using the Compute Unified Device Architecture (CUDA) developed by NVIDIA and fully exploiting their computational power. An increase of one to two orders of magnitude in simulation speed over equivalent CPU code is achieved. A complete modeling of the flow of a complex fluid such as lava is challenging from the modelistic, numerical and computational points of view. The natural topography irregularities, the dynamic free boundaries and phenomena such as solidification, presence of floating solid bodies or other obstacles and their eventual fragmentation make the problem difficult to solve using traditional numerical methods (finite volumes, finite elements): the need to refine the discretization grid in correspondence of high gradients, when possible, is computationally expensive and with an often inadequate control of the error; for real-world applications, moreover, the information needed by the grid refinement may not be available (e.g. because the Digital Elevation Models are too coarse); boundary tracking is also problematic with Eulerian discretizations, more so with complex fluids due to the presence of internal boundaries given by fluid inhomogeneity and presence of solidification fronts. An alternative approach is offered by mesh-free particle methods, that solve most of the problems connected to the dynamics of complex fluids in a natural way. Particle methods discretize the fluid using nodes which are not forced on a given topological structure: boundary treatment is therefore implicit and automatic; the movement freedom of the particles also permits the treatment of deformations without incurring in any significant penalty; finally, the accuracy is easily controlled by the insertion of new particles where needed. Our team has developed a new model based on the
NASA Astrophysics Data System (ADS)
Edwards, R.; Doster, F.; Celia, M. A.; Bandilla, K.
2015-12-01
The process of hydraulic fracturing in shale gas formations typically involves the injection of large quantities of water-based fluid (2×107L typical) into the shale formations in order to fracture the rock. A large proportion of the fracturing fluids injected into shale gas wells during hydraulic fracturing does not return out of the well once production begins. The percentage of water returning varies within and between different shale plays, but is generally around 30%. The large proportion of the fluid that does not return raises the possibility that it could migrate out of the target shale formation and potentially toward aquifers and the surface through pathways such as the created hydraulic fractures, faults and adjacent wells. A leading hypothesis for the fate of the remaining fracturing fluid is that it is spontaneously imbibed from the hydraulic fractures into the shale rock matrix due to the low water saturation and very high capillary pressure in the shale. The imbibition hypothesis is assessed using numerical modeling of the two-phase flow of fracturing fluid and gas in the shale during injection. The model incorporates relevant two-phase physical phenomena such as capillarity and relative permeability, including hysteretic behavior in both. Modeling scenarios for fracturing fluid injection were assessed under varying conditions for shale reservoir parameters and spatial heterogeneities in permeability and wettability. The results showed that the unaccounted fracturing fluid may plausibly be imbibed into the shale matrix under certain conditions, and that significant small-scale spatial heterogeneity in the shale permeability likely plays an important role in imbibing the fracturing fluid.
A review is given of recent fluid modeling studies conducted at the EPA Fluid Modeling Facility of flow and diffusion in complex terrain. Estimates are given for the ratio of the maximum concentration on a hill surface to the maximum concentration in the absence of the hill. The ...
Properties of forced convection experimental with silicon carbide based nano-fluids
NASA Astrophysics Data System (ADS)
Soanker, Abhinay
With the advent of nanotechnology, many fields of Engineering and Science took a leap to the next level of advancements. The broad scope of nanotechnology initiated many studies of heat transfer and thermal engineering. Nano-fluids are one such technology and can be thought of as engineered colloidal fluids with nano-sized colloidal particles. There are different types of nano-fluids based on the colloidal particle and base fluids. Nano-fluids can primarily be categorized into metallic, ceramics, oxide, magnetic and carbon based. The present work is a part of investigation of the thermal and rheological properties of ceramic based nano-fluids. alpha-Silicon Carbide based nano-fluid with Ethylene Glycol and water mixture 50-50% volume concentration was used as the base fluid here. This work is divided into three parts; Theoretical modelling of effective thermal conductivity (ETC) of colloidal fluids, study of Thermal and Rheological properties of alpha-SiC nano-fluids, and determining the Heat Transfer properties of alpha-SiC nano-fluids. In the first part of this work, a theoretical model for effective thermal conductivity (ETC) of static based colloidal fluids was formulated based on the particle size, shape (spherical), thermal conductivity of base fluid and that of the colloidal particle, along with the particle distribution pattern in the fluid. A MATLAB program is generated to calculate the details of this model. The model is specifically derived for least and maximum ETC enhancement possible and thereby the lower and upper bounds was determined. In addition, ETC is also calculated for uniform colloidal distribution pattern. Effect of volume concentration on ETC was studied. No effect of particle size was observed for particle sizes below a certain value. Results of this model were compared with Wiener bounds and Hashin- Shtrikman bounds. The second part of this work is a study of thermal and rheological properties of alpha-Silicon Carbide based nano-fluids
Development of Efficient Real-Fluid Model in Simulating Liquid Rocket Injector Flows
NASA Technical Reports Server (NTRS)
Cheng, Gary; Farmer, Richard
2003-01-01
The characteristics of propellant mixing near the injector have a profound effect on the liquid rocket engine performance. However, the flow features near the injector of liquid rocket engines are extremely complicated, for example supercritical-pressure spray, turbulent mixing, and chemical reactions are present. Previously, a homogeneous spray approach with a real-fluid property model was developed to account for the compressibility and evaporation effects such that thermodynamics properties of a mixture at a wide range of pressures and temperatures can be properly calculated, including liquid-phase, gas- phase, two-phase, and dense fluid regions. The developed homogeneous spray model demonstrated a good success in simulating uni- element shear coaxial injector spray combustion flows. However, the real-fluid model suffered a computational deficiency when applied to a pressure-based computational fluid dynamics (CFD) code. The deficiency is caused by the pressure and enthalpy being the independent variables in the solution procedure of a pressure-based code, whereas the real-fluid model utilizes density and temperature as independent variables. The objective of the present research work is to improve the computational efficiency of the real-fluid property model in computing thermal properties. The proposed approach is called an efficient real-fluid model, and the improvement of computational efficiency is achieved by using a combination of a liquid species and a gaseous species to represent a real-fluid species.
Pulmonary fluid flow challenges for experimental and mathematical modeling.
Levy, Rachel; Hill, David B; Forest, M Gregory; Grotberg, James B
2014-12-01
Modeling the flow of fluid in the lungs, even under baseline healthy conditions, presents many challenges. The complex rheology of the fluids, interaction between fluids and structures, and complicated multi-scale geometry all add to the complexity of the problem. We provide a brief overview of approaches used to model three aspects of pulmonary fluid and flow: the surfactant layer in the deep branches of the lung, the mucus layer in the upper airway branches, and closure/reopening of the airway. We discuss models of each aspect, the potential to capture biological and therapeutic information, and open questions worthy of further investigation. We hope to promote multi-disciplinary collaboration by providing insights into mathematical descriptions of fluid-mechanics in the lung and the kinds of predictions these models can make. PMID:25096289
Pulmonary Fluid Flow Challenges for Experimental and Mathematical Modeling
Levy, Rachel; Hill, David B.; Forest, M. Gregory; Grotberg, James B.
2014-01-01
Modeling the flow of fluid in the lungs, even under baseline healthy conditions, presents many challenges. The complex rheology of the fluids, interaction between fluids and structures, and complicated multi-scale geometry all add to the complexity of the problem. We provide a brief overview of approaches used to model three aspects of pulmonary fluid and flow: the surfactant layer in the deep branches of the lung, the mucus layer in the upper airway branches, and closure/reopening of the airway. We discuss models of each aspect, the potential to capture biological and therapeutic information, and open questions worthy of further investigation. We hope to promote multi-disciplinary collaboration by providing insights into mathematical descriptions of fluid-mechanics in the lung and the kinds of predictions these models can make. PMID:25096289
Modeling the relaxation dynamics of fluids in nanoporous materials
NASA Astrophysics Data System (ADS)
Edison, John R.
Mesoporous materials are being widely used in the chemical industry in various environmentally friendly separation processes and as catalysts. Our research can be broadly described as an effort to understand the behavior of fluids confined in such materials. More specifically we try to understand the influence of state variables like temperature and pore variables like size, shape, connectivity and structural heterogeneity on both the dynamic and equilibrium behavior of confined fluids. The dynamic processes associated with the approach to equilibrium are largely unexplored. It is important to look into the dynamic behavior for two reasons. First, confined fluids experience enhanced metastabilities and large equilibration times in certain classes of mesoporous materials, and the approach to the metastable/stable equilibrium is of tremendous interest. Secondly, understanding the transport resistances in a microscopic scale will help better engineer heterogeneous catalysts and separation processes. Here we present some of our preliminary studies on dynamics of fluids in ideal pore geometries. The tool that we have used extensively to investigate the relaxation dynamics of fluids in pores is the dynamic mean field theory (DMFT) as developed by Monson [P. A. Monson, J. Chem. Phys., 128, 084701 (2008)]. The theory is based on a lattice gas model of the system and can be viewed as a highly computationally efficient approximation to the dynamics averaged over an ensemble of Kawasaki dynamics Monte Carlo trajectories of the system. It provides a theory of the dynamics of the system consistent with the thermodynamics in mean field theory. The nucleation mechanisms associated with confined fluid phase transitions are emergent features in the calculations. We begin by describing the details of the theory and then present several applications of DMFT. First we present applications to three model pore networks (a) a network of slit pores with a single pore width; (b) a network
Surface tension driven flow in glass melts and model fluids
NASA Technical Reports Server (NTRS)
Mcneil, T. J.; Cole, R.; Subramanian, R. S.
1982-01-01
Surface tension driven flow has been investigated analytically and experimentally using an apparatus where a free column of molten glass or model fluids was supported at its top and bottom faces by solid surfaces. The glass used in the experiments was sodium diborate, and the model fluids were silicone oils. In both the model fluid and glass melt experiments, conclusive evidence was obtained to prove that the observed flow was driven primarily by surface tension forces. The experimental observations are in qualitative agreement with predictions from the theoretical model.
NASA Astrophysics Data System (ADS)
Bird, M. B.; Butler, S. L.; Hawkes, C. D.; Kotzer, T.
2014-12-01
The use of numerical simulations to model physical processes occurring within subvolumes of rock samples that have been characterized using advanced 3D imaging techniques is becoming increasingly common. Not only do these simulations allow for the determination of macroscopic properties like hydraulic permeability and electrical formation factor, but they also allow the user to visualize processes taking place at the pore scale and they allow for multiple different processes to be simulated on the same geometry. Most efforts to date have used specialized research software for the purpose of simulations. In this contribution, we outline the steps taken to use commercial software Avizo to transform a 3D synchrotron X-ray-derived tomographic image of a rock core sample to an STL (STereoLithography) file which can be imported into the commercial multiphysics modeling package COMSOL. We demonstrate that the use of COMSOL to perform fluid and electrical current flow simulations through the pore spaces. The permeability and electrical formation factor of the sample are calculated and compared with laboratory-derived values and benchmark calculations. Although the simulation domains that we were able to model on a desk top computer were significantly smaller than representative elementary volumes, and we were able to establish Kozeny-Carman and Archie's Law trends on which laboratory measurements and previous benchmark solutions fall. The rock core samples include a Fountainebleau sandstone used for benchmarking and a marly dolostone sampled from a well in the Weyburn oil field of southeastern Saskatchewan, Canada. Such carbonates are known to have complicated pore structures compared with sandstones, yet we are able to calculate reasonable macroscopic properties. We discuss the computing resources required.
Clarysse, Sarah; Brouwers, Joachim; Tack, Jan; Annaert, Pieter; Augustijns, Patrick
2011-07-17
The purpose of this study was to validate both existing fasted and fed state simulated intestinal fluids (FaSSIF and FeSSIF), and simpler, alternative media for predicting intraluminal drug solubility during drug discovery and early drug development. For 17 model drugs, the solubilizing capacity of FaSSIF(c) and FeSSIF(c) (subscript indicates the use of crude taurocholate) and different concentrations of D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) in phosphate buffer were correlated with the solubilizing capacity of human intestinal fluids (HIF) in the fasted and the early postprandial state. A good correlation between solubility in fasted HIF and FaSSIF(c) and between solubility in fed HIF and FeSSIF(c) was obtained, indicated by R(2) values of 0.91 and 0.86, respectively. Comparable values were obtained for 0.1% TPGS for the fasted state (R(2)=0.84) and 2% TPGS for the fed state (R(2)=0.84). Direct estimation of intestinal drug solubility by the measured solubilities in FaSSIF(c) and FeSSIF(c) was acceptable. However, better estimates were obtained by calculating solubilities based on the equations describing the relationship between solubilities in FaSSIF(c) and FeSSIF(c) as function of observed solubilities in HIF. Using this approach, the predictive value of the TPGS-based solvent system was also acceptable and comparable to that of FaSSIF(c) and FeSSIF(c). In conclusion, FaSSIF(c) and FeSSIF(c) can be considered biorelevant media for intestinal solubility estimation. A simpler TPGS-based system may be a valuable alternative with improved stability and lower cost. PMID:21570465
Modeling Tools Predict Flow in Fluid Dynamics
NASA Technical Reports Server (NTRS)
2010-01-01
"Because rocket engines operate under extreme temperature and pressure, they present a unique challenge to designers who must test and simulate the technology. To this end, CRAFT Tech Inc., of Pipersville, Pennsylvania, won Small Business Innovation Research (SBIR) contracts from Marshall Space Flight Center to develop software to simulate cryogenic fluid flows and related phenomena. CRAFT Tech enhanced its CRUNCH CFD (computational fluid dynamics) software to simulate phenomena in various liquid propulsion components and systems. Today, both government and industry clients in the aerospace, utilities, and petrochemical industries use the software for analyzing existing systems as well as designing new ones."
Nonlinear multimodal model for TLD of irregular tank geometry and small fluid depth
NASA Astrophysics Data System (ADS)
Love, J. S.; Tait, M. J.
2013-11-01
Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy. TLDs of irregular or complex tank geometry may be required in practice to avoid tank interference with fixed structural or mechanical components. The literature offers few analytical models to predict the response of this type of TLD, particularly when the fluid depth is small. In this paper, a multimodal model is developed utilizing a Boussinesq-type modal theory which is valid for small TLD fluid depths. The Bateman-Luke variational principle is employed to develop a system of coupled nonlinear ordinary differential equations which describe the fluid response when the tank is subjected to base excitation. Energy dissipation is incorporated into the model from the inclusion of damping screens. The fluid model is used to describe the response of a 2D structure-TLD system when the structure is subjected to external loading and the TLD tank geometry is irregular.
Lateral fluid percussion: model of traumatic brain injury in mice.
Alder, Janet; Fujioka, Wendy; Lifshitz, Jonathan; Crockett, David P; Thakker-Varia, Smita
2011-01-01
Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes (1,2). Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement (3,4). The resulting hematomas and lacerations cause a vascular response (3,5), and the morphological and functional damage of the white matter leads to diffuse axonal injury (6-8). Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure (9). Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals (10-12), which ultimately result in long-term neurological disabilities (13,14). Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair. Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration (1). The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue (1,15). Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure (16,17). The weight drop/impact model is characterized by the fall of a rod with a specific
Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice
Alder, Janet; Fujioka, Wendy; Lifshitz, Jonathan; Crockett, David P.; Thakker-Varia, Smita
2011-01-01
Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair. Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed
Lateral (Parasagittal) Fluid Percussion Model of Traumatic Brain Injury.
Van, Ken C; Lyeth, Bruce G
2016-01-01
Fluid percussion was first conceptualized in the 1940s and has evolved into one of the leading laboratory methods for studying experimental traumatic brain injury (TBI). Over the decades, fluid percussion has been used in numerous species and today is predominantly applied to the rat. The fluid percussion technique rapidly injects a small volume of fluid, such as isotonic saline, through a circular craniotomy onto the intact dura overlying the brain cortex. In brief, the methods involve surgical production of a circular craniotomy, attachment of a fluid-filled conduit between the dura overlying the cortex and the outlet port of the fluid percussion device. A fluid pulse is then generated by the free-fall of a pendulum striking a piston on the fluid-filled cylinder of the device. The fluid enters the cranium, producing a compression and displacement of the brain parenchyma resulting in a sharp, high magnitude elevation of intracranial pressure that is propagated diffusely through the brain. This results in an immediate and transient period of traumatic unconsciousness as well as a combination of focal and diffuse damage to the brain, which is evident upon histological and behavioral analysis. Numerous studies have demonstrated that the rat fluid percussion model reproduces a wide range of pathological features associated with human TBI. PMID:27604722
Numerical modeling of fluid migration in subduction zones
NASA Astrophysics Data System (ADS)
Walter, M. J.; Quinteros, J.; Sobolev, S. V.
2015-12-01
It is well known that fluids play a crucial role in subduction evolution. For example, mechanical weakening along tectonic interfaces, due to high fluid pressure, may enable oceanic subduction. Hence, the fluid content seems to be a critical parameter for subduction initiation. Studies have also shown a correlation between the location of slab dehydration and intermediate seismic activity. Furthermore, expelled fluids from the subduction slab affect the melting temperature, consequently, contributing to partial melting in the wedge above the down-going plate and extensive volcanism. In summary, fluids have a great impact on tectonic processes and therefore should be incorporated into geodynamic numerical models. Here we use existing approaches to couple and solve fluid flow equations in the SLIM-3D thermo-mechanical code. SLIM-3D is a three-dimensional thermo-mechanical code capable of simulating lithospheric deformation with elasto-visco-plastic rheology. It has been successfully applied to model geodynamic processes at different tectonic settings, including subduction zones. However, although SLIM-3D already includes many features, fluid migration has not been incorporated into the model yet. To this end, we coupled solid and fluid flow assuming that fluids flow through a porous and deformable solid. Thereby, we introduce a two-phase flow into the model, in which the Stokes flow is coupled with the Darcy law for fluid flow. Ultimately, the evolution of porosity is governed by a compaction pressure and the advection of the porous solid. We show the details of our implementation of the fluid flow into the existing thermo-mechanical finite element code and present first results of benchmarks and experiments. We are especially interested in the coupling of subduction processes and the evolution of the magmatic arc. Thereby, we focus on the key factors controlling magma emplacement and its influence on subduction processes.
Particle Modelling of Fluid Phenomena in Three -
NASA Astrophysics Data System (ADS)
Mahmoudi, Mohsen
A new, numerical approach is developed to simulate fluid phenomena by means of molecular type behavior. First, consider the large number of molecules to be approximated by a smaller number of aggregates called particles. Then, let the particles interact with each other according to a classical molecular type force vec F whose magnitude F is given (Hirchfelder, Curtiss and Bird (1954)) by: F = rm -{Gover r^{p}} + {Hover r^{q}}, in which G, H, p, q, are positive constants and r is the distance between two particles. The acceleration of each particle is related to the force by the Newtonian dynamical equations vec F = m vec a. Displacement, velocity, and acceleration of each particle are then approximated by the "Leap Frog" formulas. The CRAY X-MP/24 is used to solve numerically the resulting large system of nonlinear, ordinary differential equations. We then study fluid phenomena in the following order. Part 1. Generation of particle fluids in a cylindrical region. Part 2. Verification of basic fluid properties. Part 3. Simulation of surface motion. In this part, we simulate three phenomena, which can be observed physically, by dropping a small object into a container filled with liquid. First, there is a backdrop. Then, a wave will be generated and going outward from the point of entry of the object into the container. Last, a reaction which can be recorded only with a high speed camera (Trefethen (1972)) is that very small drops of the container fluid may actually pinch off from the backdrop. Part 4. Simulation of surface tension. This phenomena can be observed by performing the following experiment. A small needle placed gently upon a water surface will not be sunk but will be supported by the molecular forces in the liquid surface. The molecules in the surface are depressed slightly in the process.
Development and mathematical modeling of biomagnetic fluid dynamics
NASA Astrophysics Data System (ADS)
Haik, Yousef
In this study the human blood as a biomagnetic fluid and the blood flow under the influence of magnetic field is investigated. Experiments were performed to examine the effect of magnetic field on blood flow. The blood flow in a straight pipe when aligned to the magnetic field lines was reduced by 28% when the field strength was 10 tesla. The sedimentation rate of red blood cells in the stagnant container due to gravity was reduced when the whole blood was subjected to a horizontally imposed magnetic field from a permanent magnet of 1.2 tesla. The physical properties of whole blood under the influence of high magnetic field were also investigated. It was found that the magnetic susceptibility of whole blood is in the order of 10-6 when deoxygenated and 10-7 when oxygenated. In the present study the whole blood is treated as a single fluid. The governing equations for the flow under magnetic field are derived based on the modified Stokes' principle. The model coefficients were obtained by performing experiments on the whole blood. The mathematical model is simplified based on the equilibrium approximation and the experimental observations. Numerical simulations were obtained for the situations such as acceleration and retardation of blood flow, removal of blood thrombus from the vein wall by increasing the shear rate and the behavior of the blood in the aneurysm in the vicinity of a magnetic field. It is shown that the blood flow characteristic can change dramatically when the fluid is subjected to magnetic field. Finally different biomagnetic applications are proposed. Among these proposed applications is a device to separate the red blood cells from the whole blood for possible treatment of the white cells. Another proposed application is the Magnetic MEMS. Magnetic micro delivery systems that utilizes the magnetic force to deliver a micro machine to a specific site and magnetic micro rotary systems that uses the magnetic torque to drive the micromachine are
Hydraulic fracturing fluid migration in the subsurface: A review and expanded modeling results
NASA Astrophysics Data System (ADS)
Birdsell, Daniel T.; Rajaram, Harihar; Dempsey, David; Viswanathan, Hari S.
2015-09-01
Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated. Topographically driven flow, overpressured shale reservoirs, permeable pathways such as faults or leaky wellbores, the increased formation pressure due to HF fluid injection, and the density contrast of the HF fluid to the surrounding brine can encourage upward HF fluid migration. In contrast, the very low shale permeability and capillary imbibition of water into partially saturated shale may sequester much of the HF fluid, and well production will remove HF fluid from the subsurface. We review the literature on important aspects of HF fluid migration. Single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore with flowback and produced water, how much reaches overlying aquifers, and how much is permanently sequestered by capillary imbibition, which is treated as a sink term based on a semianalytical, one-dimensional solution for two-phase flow. These simulations include all of the important aspects of HF fluid migration identified in the literature review and are performed in five stages to faithfully represent the typical operation of a hydraulically fractured well. No fracturing fluid reaches the aquifer without a permeable pathway. In the presence of a permeable pathway, 10 times more fracturing fluid reaches the aquifer if well production and capillary imbibition are not included in the model.
NASA Astrophysics Data System (ADS)
Tang, Z. B.; Deng, Y. D.; Su, C. Q.; Yuan, X. H.
2015-06-01
In this study, a numerical model has been employed to analyze the internal flow field distribution in a heat exchanger applied for an automotive thermoelectric generator based on computational fluid dynamics. The model simulates the influence of factors relevant to the heat exchanger, including the automotive waste heat mass flow velocity, temperature, internal fins, and back pressure. The result is in good agreement with experimental test data. Sensitivity analysis of the inlet parameters shows that increase of the exhaust velocity, compared with the inlet temperature, makes little contribution (0.1 versus 0.19) to the heat transfer but results in a detrimental back pressure increase (0.69 versus 0.21). A configuration equipped with internal fins is proved to offer better thermal performance compared with that without fins. Finally, based on an attempt to improve the internal flow field, a more rational structure is obtained, offering a more homogeneous temperature distribution, higher average heat transfer coefficient, and lower back pressure.
Dielectric breakdown in mineral oil ITO 100 based magnetic fluid
NASA Astrophysics Data System (ADS)
Kudelcik, J.; Bury, P.; Kopcansky, P.; Timko, M.
The development of dielectric breakdown and the DC dielectric breakdown voltage of magnetic fluids based on inhibited transformer oil ITO 100 were investigated in parallel orientations of external magnetic field. It was shown that the breakdown voltage is strongly influenced by the magnetic nanoparticles. The magnetic fluids with the volume concentration 1and 0.2% had better dielectric properties than pure transformer oil. The increase of breakdown voltage was interpreted on the base of the bubble theory of breakdown.
Computational fluid dynamics modeling for emergency preparedness and response
Lee, R.L.; Albritton, J.R.; Ermak, D.L.; Kim, J.
1995-02-01
Computational fluid dynamics (CFD) has (CFD) has played an increasing in the improvement of atmospheric dispersion modeling. This is because many dispersion models are now driven by meteorological fields generated from CFD models or, in numerical weather prediction`s terminology, prognostic models. Whereas most dispersion models typically involve one or a few scalar, uncoupled equations, the prognostic equations are a set of highly-couple equations whose solution requires a significant level of computational power. Recent advances in computer hardware and software have enabled modestly-priced, high performance, workstations to exhibit the equivalent computation power of some mainframes. Thus desktop-class machines that were limited to performing dispersion calculations driven by diagnostic wind fields may now be used to calculate complex flows using prognostic CFD models. The Release and Advisory Capability (ARAC) program at Lawrence Livermore National Laboratory (LLNL) has, for the past several years, taken advantage of the improvements in hardware technology to develop a national emergency response capability based on executing diagnostic models on workstations. Diagnostic models that provide wind fields are, in general, simple to implement, robust and require minimal time for execution. Because these models typically contain little physics beyond mass-conservation, their performance is extremely sensitive to the quantity and quality of input meteorological data and, in spite of their utility, can be applied with confidence to only modestly complex flows. We are now embarking on a development program to incorporate prognostic models to generate, in real-time, the meteorological fields for the dispersion models. In contrast to diagnostic models, prognostic models are physically-based and are capable of incorporating many physical processes to treat highly complex flow scenarios.
GEOSIM: A numerical model for geophysical fluid flow simulation
NASA Technical Reports Server (NTRS)
Butler, Karen A.; Miller, Timothy L.; Lu, Huei-Iin
1991-01-01
A numerical model which simulates geophysical fluid flow in a wide range of problems is described in detail, and comparisons of some of the model's results are made with previous experimental and numerical studies. The model is based upon the Boussinesq Navier-Stokes equations in spherical coordinates, which can be reduced to a cylindrical system when latitudinal walls are used near the pole and the ratio of latitudinal length to the radius of the sphere is small. The equations are approximated by finite differences in the meridional plane and spectral decomposition in the azimuthal direction. The user can specify a variety of boundary and initial conditions, and there are five different spectral truncation options. The results of five validation cases are presented: (1) the transition between axisymmetric flow and baroclinic wave flow in the side heated annulus; (2) the steady baroclinic wave of the side heated annulus; (3) the wave amplitude vacillation of the side heated annulus; (4) transition to baroclinic wave flow in a bottom heated annulus; and (5) the Spacelab Geophysical Fluid Flow Cell (spherical) experiment.
Dynamic Dielectrophoresis Model of Multi-Phase Ionic Fluids
Yan, Ying; Luo, Jing; Guo, Dan; Wen, Shizhu
2015-01-01
Ionic-based dielectrophoretic microchips have attracted significant attention due to their wide-ranging applications in electro kinetic and biological experiments. In this work, a numerical method is used to simulate the dynamic behaviors of ionic droplets in a microchannel under the effect of dielectrophoresis. When a discrete liquid dielectric is encompassed within a continuous fluid dielectric placed in an electric field, an electric force is produced due to the dielectrophoresis effect. If either or both of the fluids are ionic liquids, the magnitude and even the direction of the force will be changed because the net ionic charge induced by an electric field can affect the polarization degree of the dielectrics. However, using a dielectrophoresis model, assuming ideal dielectrics, results in significant errors. To avoid the inaccuracy caused by the model, this work incorporates the electrode kinetic equation and defines a relationship between the polarization charge and the net ionic charge. According to the simulation conditions presented herein, the electric force obtained in this work has an error exceeding 70% of the actual value if the false effect of net ionic charge is not accounted for, which would result in significant issues in the design and optimization of experimental parameters. Therefore, there is a clear motivation for developing a model adapted to ionic liquids to provide precise control for the dielectrophoresis of multi-phase ionic liquids. PMID:25699513
A two-fluid model for avalanche and debris flows.
Pitman, E Bruce; Le, Long
2005-07-15
Geophysical mass flows--debris flows, avalanches, landslides--can contain O(10(6)-10(10)) m(3) or more of material, often a mixture of soil and rocks with a significant quantity of interstitial fluid. These flows can be tens of meters in depth and hundreds of meters in length. The range of scales and the rheology of this mixture presents significant modelling and computational challenges. This paper describes a depth-averaged 'thin layer' model of geophysical mass flows containing a mixture of solid material and fluid. The model is derived from a 'two-phase' or 'two-fluid' system of equations commonly used in engineering research. Phenomenological modelling and depth averaging combine to yield a tractable set of equations, a hyperbolic system that describes the motion of the two constituent phases. If the fluid inertia is small, a reduced model system that is easier to solve may be derived. PMID:16011934
Finite Element Modelling of Fluid Coupling in the Coiled Cochlea
NASA Astrophysics Data System (ADS)
Ni, Guangjian; Elliott, S. J.; Lineton, B.; Saba, R.
2011-11-01
A finite element model is first used to calculate the modal pressure difference for a box model of the cochlea, which shows that the number of fluid elements across the width of the cochlea determines the accuracy with which the near field, or short wavenumber, component of the fluid coupling is reproduced. Then results are compared with the analytic results to validate the accuracy of the FE model. It is, however, the far field, or long wavelength, component of the fluid coupling that is most affected by the geometry. A finite element model of the coiled cochlea is then used to calculate fluid coupling in this case, which has similar characteristics to the uncoiled model.
A reexamination of two-fluid solar wind models
NASA Technical Reports Server (NTRS)
Nerney, S.; Barnes, A.
1977-01-01
The two-fluid solar-wind equations have been solved by a method which is approximately 50 times faster than any previously developed, through the use of asymptotic expansions which are self-consistently iterated upon to find a solution that passes through the critical point. The energy assumptions in two-fluid solar-wind models are reexamined, and the conclusions are as follows: (1) proton thermal conduction may not be neglected, (2) the Coulomb logarithm must be calculated as a function of radius, and (3) the electron and proton temperatures at the base need not be equal, even when the time scale for energy exchange between the species is an order of magnitude smaller than the expansion time at the base. It is possible to reproduce reasonable quiet-time solar-wind parameters at 1 AU, but only if the proton temperature is approximately twice the electron temperature at 1 solar radius. This may indicate that extended proton heating is important in the outer solar corona. Winds with velocities at 1 AU of 450 km/s are generated without nonthermal energy deposition but require high proton temperatures as well as very low densities at the base. Higher-velocity solutions are not possible in a spherically symmetric geometry for reasonable particle fluxes at 1 AU, and it is suggested that these higher-velocity states probably require additional heating, acceleration mechanisms, or nonradial flow.
Multiscale modeling for fluid transport in nanosystems.
Lee, Jonathan W.; Jones, Reese E.; Mandadapu, Kranthi Kiran; Templeton, Jeremy Alan; Zimmerman, Jonathan A.
2013-09-01
Atomistic-scale behavior drives performance in many micro- and nano-fluidic systems, such as mircrofludic mixers and electrical energy storage devices. Bringing this information into the traditionally continuum models used for engineering analysis has proved challenging. This work describes one such approach to address this issue by developing atomistic-to-continuum multi scale and multi physics methods to enable molecular dynamics (MD) representations of atoms to incorporated into continuum simulations. Coupling is achieved by imposing constraints based on fluxes of conserved quantities between the two regions described by one of these models. The impact of electric fields and surface charges are also critical, hence, methodologies to extend finite-element (FE) MD electric field solvers have been derived to account for these effects. Finally, the continuum description can have inconsistencies with the coarse-grained MD dynamics, so FE equations based on MD statistics were derived to facilitate the multi scale coupling. Examples are shown relevant to nanofluidic systems, such as pore flow, Couette flow, and electric double layer.
Pipes Conveying Fluid: A Model Dynamical Problem
NASA Astrophysics Data System (ADS)
Païdoussis, M. P.; Li, G. X.
1993-02-01
This paper reviews the dynamics of pipes conveying fluid and presents a selective review of the research undertaken on it. It is endeavoured to show that this system is fast becoming a new paradigm in dynamics, on a par with, for instance, the classical problem of the column subjected to compressive loading, but one capable of displaying much richer dynamical behaviour. The dynamics of pipes with supported ends, cantilevered pipes or with unusual boundary conditions; continuously flexible pipes or articulated ones; pipe conveying incompressible or compressible fluid, with steady or unsteady flow velocity; pipes thin enough to be treated as thin shells; linear, nonlinear and chaotic dynamics; these and many more are some of the aspects of the problem considered. An Appendix is provided for those unfamiliar with the modern methods of nonlinear analysis.
A fully coupled porous flow and geomechanics model for fluid driven cracks: a peridynamics approach
NASA Astrophysics Data System (ADS)
Ouchi, Hisanao; Katiyar, Amit; York, Jason; Foster, John T.; Sharma, Mukul M.
2015-03-01
A state-based non-local peridynamic formulation is presented for simulating fluid driven fractures in an arbitrary heterogeneous poroelastic medium. A recently developed peridynamic formulation of porous flow has been coupled with the existing peridynamic formulation of solid and fracture mechanics resulting in a peridynamic model that for the first time simulates poroelasticity and fluid-driven fracture propagation. This coupling is achieved by modeling the role of pore pressure on the deformation of porous media and vice versa through porosity variation with medium deformation, pore pressure and total mean stress. The poroelastic model is verified by simulating the one-dimensional consolidation of fluid saturated rock. An additional porous flow equation with material permeability dependent on fracture width is solved to simulate fluid flow in the fractured region. Finally, single fluid-driven fracture propagation with a two-dimensional plane strain assumption is simulated and verified against the corresponding classical analytical solution.
The effect of Fe3O4 nanoparticles on the thermal conductivities of various base fluids.
Altan, Cem L; Bucak, Seyda
2011-07-15
Conventional heat transfer fluids have intrinsically poor heat transfer properties compared to solids. Enhancing the efficiency of heat transfer is of great interest for various industrial applications. Suspending solid particles in a fluid increases the thermal conductivity of the resulting suspension and enhances the heat transfer properties. In this work, changes in thermal conductivities of fluids upon the addition of magnetic nanoparticles have been investigated. Fe(3)O(4) nanoparticles are synthesized using different synthesis methods and are suspended in various oils. The effect of the base fluid and the type of magnetic particle on the thermal conductivity is investigated in detail. Up to 28% increase in the thermal conductivity is obtained with 2.5 wt% magnetic particles in hexane. The thermal conductivity enhancement is found to depend on the particle concentration, method of preparation and base fluid. The enhancements obtained are higher than those estimated using any theoretical model present in the literature. PMID:21659690
The effect of Fe3O4 nanoparticles on the thermal conductivities of various base fluids
NASA Astrophysics Data System (ADS)
Altan, Cem L.; Bucak, Seyda
2011-07-01
Conventional heat transfer fluids have intrinsically poor heat transfer properties compared to solids. Enhancing the efficiency of heat transfer is of great interest for various industrial applications. Suspending solid particles in a fluid increases the thermal conductivity of the resulting suspension and enhances the heat transfer properties. In this work, changes in thermal conductivities of fluids upon the addition of magnetic nanoparticles have been investigated. Fe3O4 nanoparticles are synthesized using different synthesis methods and are suspended in various oils. The effect of the base fluid and the type of magnetic particle on the thermal conductivity is investigated in detail. Up to 28% increase in the thermal conductivity is obtained with 2.5 wt% magnetic particles in hexane. The thermal conductivity enhancement is found to depend on the particle concentration, method of preparation and base fluid. The enhancements obtained are higher than those estimated using any theoretical model present in the literature.
Babchin, A J; Bentsen, R; Faybishenko, B; Geilikman, M B
2016-07-01
The objective of the current paper is to extend the theoretical approach and an analytical solution, which was proposed by Babchin and Faybishenko (2014), for the evaluation of a capillary pressure (Pc) curve in porous media based on the apparent specific surface area, using an explicit combination of the relative permeability functions for the wetting and nonwetting phases. Specifically, in the current paper, the authors extended this approach by the application of two types of capillary bundle models with different formulations of effective capillary radius formulae. The application of the new models allowed the authors to improve the results of calculations of the effective average contact angle given in the paper by Babchin and Faybishenko (2014). The validation of the new models for calculations of the Pc curve is also given in this paper using the results of a specifically designed core experiment, which was originally conducted by Ayub and Bentsen (2001). PMID:26211849
Development of an analytical model for organic-fluid fouling
Panchal, C.B.; Watkinson, A.P.
1994-10-01
The research goal of this project is to determine ways to effectively mitigate fouling in organic fluids: hydrocarbons and derived fluids. The fouling research focuses on the development of methodology for determining threshold conditions for fouling. Initially, fluid containing chemicals known to produce foulant is analyzed; subsequently, fouling of industrial fluids is investigated. The fouling model developed for determining the effects of physical parameters is the subject of this report. The fouling model is developed on the premise that the chemical reaction for generation of precursor can take place in the bulk fluid, in the thermal-boundary layer, or at the fluid/wall interface, depending upon the interactive effects of fluid dynamics, heat and mass transfer, and the controlling chemical reaction. In the analysis, the experimental data are examined for fouling deposition of polyperoxide produced by autoxidation of indene in kerosene. The effects of fluid and wall temperatures for two flow geometries are analyzed. The results show that the relative effects of physical parameters on the fouling rate differ for the three fouling mechanisms. Therefore, to apply the closed-flow-loop data to industrial conditions, the controlling mechanism must be identified.
Two-fluid model for heavy electron physics
NASA Astrophysics Data System (ADS)
Yang, Yi-feng
2016-07-01
The two-fluid model is a phenomenological description of the gradual change of the itinerant and local characters of f-electrons with temperature and other tuning parameters and has been quite successful in explaining many unusual and puzzling experimental observations in heavy electron materials. We review some of these results and discuss possible implications of the two-fluid model in understanding the microscopic origin of heavy electron physics.
Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion
NASA Technical Reports Server (NTRS)
Nastula, Jolanta; Salstein, David A.; Gross, Richard
2011-01-01
By analyzing geophysical fluids geographic distribution, we can isolate the regional provenance for some of the important signals in polar motion. An understanding of such will enable us to determine whether certain climate signals can have an impact on polar motion. Here we have compared regional patterns of three surficial fluids: the atmosphere, ocean and land-based hydrosphere. The oceanic excitation function of polar motion was estimated with the ECCO/JPL data - assimilating model, and the atmospheric excitation function was determined from NCEP/NCAR reanalyses. The excitation function due to land hydrology was estimated from the Gravity Recovery and Climate Experiment (GRACE) data by an indirect approach that determines water thickness. Our attention focuses on the regional distribution of atmospheric and oceanic excitation of the annual and Chandler wobbles during 1993-2010, and on hydrologic excitation of these wobbles during 2002.9-2011.5. It is found that the regions of maximum fractional covariance (those exceeding a value of 3 .10 -3) for the annual band are over south Asia, southeast Asia and south central Indian ocean, for hydrology, atmosphere and ocean respectively; and for the Chandler period, areas over North America, Asia, and South America; and scattered across the southern oceans for the atmosphere and oceans respectively
Attenuation of numerical artefacts in the modelling of fluid interfaces
NASA Astrophysics Data System (ADS)
Evrard, Fabien; van Wachem, Berend G. M.; Denner, Fabian
2015-11-01
Numerical artefacts in the modelling of fluid interfaces, such as parasitic currents or spurious capillary waves, present a considerable problem in two-phase flow modelling. Parasitic currents result from an imperfect evaluation of the interface curvature and can severely affect the flow, whereas spatially underresolved (spurious) capillary waves impose strict limits on the time-step and, hence, dictate the required computational resources for surface-tension-dominated flows. By applying an additional shear stress term at the fluid interface, thereby dissipating the surface energy associated with small wavelengths, we have been able to considerably reduce the adverse impact of parasitic currents and mitigate the time-step limit imposed by capillary waves. However, a careful choice of the applied interface viscosity is crucial, since an excess of additional dissipation compromises the accuracy of the solution. We present the derivation of the additional interfacial shear stress term, explain the underlying physical mechanism and discuss the impact on parasitic currents and interface instabilities based on a variety of numerical experiments. We acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) through Grant No. EP/M021556/1 and from PETROBRAS.
Modelling fluid flow in a reciprocating compressor
NASA Astrophysics Data System (ADS)
Tuhovcak, Jan; Hejčík, Jiří; Jícha, Miroslav
2015-05-01
Efficiency of reciprocating compressor is strongly dependent on the valves characteristics, which affects the flow through the suction and discharge line. Understanding the phenomenon inside the compressor is necessary step in development process. Commercial CFD tools offer wide capabilities to simulate the flow inside the reciprocating compressor, however they are too complicated in terms of computational time and mesh creation. Several parameters describing compressor could be therefore examined without the CFD analysis, such is valve characteristic, flow through the cycle and heat transfer. The aim of this paper is to show a numerical tool for reciprocating compressor based on the energy balance through the cycle, which provides valve characteristics, flow through the cycle and heat losses from the cylinder. Spring-damping-mass model was used for the valve description. Boundary conditions were extracted from the performance test of 4-cylinder semihermetic compressor and numerical tool validation was performed with indicated p-V diagram comparison.
Implementation of a model of bodily fluids regulation.
Fontecave-Jallon, Julie; Thomas, S Randall
2015-09-01
The classic model of blood pressure regulation by Guyton et al. (Annu Rev Physiol 34:13-46, 1972a; Ann Biomed Eng 1:254-281, 1972b) set a new standard for quantitative exploration of physiological function and led to important new insights, some of which still remain the focus of debate, such as whether the kidney plays the primary role in the genesis of hypertension (Montani et al. in Exp Physiol 24:41-54, 2009a; Exp Physiol 94:382-388, 2009b; Osborn et al. in Exp Physiol 94:389-396, 2009a; Exp Physiol 94:388-389, 2009b). Key to the success of this model was the fact that the authors made the computer code (in FORTRAN) freely available and eventually provided a convivial user interface for exploration of model behavior on early microcomputers (Montani et al. in Int J Bio-med Comput 24:41-54, 1989). Ikeda et al. (Ann Biomed Eng 7:135-166, 1979) developed an offshoot of the Guyton model targeting especially the regulation of body fluids and acid-base balance; their model provides extended renal and respiratory functions and would be a good basis for further extensions. In the interest of providing a simple, useable version of Ikeda et al.'s model and to facilitate further such extensions, we present a practical implementation of the model of Ikeda et al. (Ann Biomed Eng 7:135-166, 1979), using the ODE solver Berkeley Madonna. PMID:25935135
Using record player demonstrations as analog models for geophysical fluids
NASA Astrophysics Data System (ADS)
Grannan, A. M.; Cheng, J. S.; Hawkins, E. K.; Ribeiro, A.; Aurnou, J. M.
2015-12-01
All celestial bodies, including stars, planets, satellites, and asteroids, rotate. The influence of rotation on the fluid layers in these bodies plays an important and diverse role, affecting many processes including oceanic and atmospheric circulation at the surface and magnetic field generation occurring in the interior. To better understand these large-scale processes, record players and containers of water are used as analog models to demonstrate the basic interplay between rotation and fluid motions. To contrast between rotating and non-rotating fluid motions, coffee creamer and food coloring are used as fluid tracers to provide a hands-on method of understanding the influence of rotation on the shapes of the planets, weather patterns, and the alignment of magnetic fields with rotational axes. Such simple demonstrations have been successfully employed for children in public outreach events and for adults in graduate level fluid dynamics courses.
Dispersant for water-based solids-containing fluids and a drilling fluid
Branch, H. III
1986-04-08
A dispersant is described for water-based, solids-containing fluids comprising a copolymer of a solufonated styrene monomer and a second monomer neutralized into having an amide substituent and being originally selected from the group consisting of maleic anhydride, maleimide and dimethyl maleate, the copolymer having from 2 to 100 monomer units.
An efficient fully atomistic potential model for dense fluid methane
NASA Astrophysics Data System (ADS)
Jiang, Chuntao; Ouyang, Jie; Zhuang, Xin; Wang, Lihua; Li, Wuming
2016-08-01
A fully atomistic model aimed to obtain a general purpose model for the dense fluid methane is presented. The new optimized potential for liquid simulation (OPLS) model is a rigid five site model which consists of five fixed point charges and five Lennard-Jones centers. The parameters in the potential model are determined by a fit of the experimental data of dense fluid methane using molecular dynamics simulation. The radial distribution function and the diffusion coefficient are successfully calculated for dense fluid methane at various state points. The simulated results are in good agreement with the available experimental data shown in literature. Moreover, the distribution of mean number hydrogen bonds and the distribution of pair-energy are analyzed, which are obtained from the new model and other five reference potential models. Furthermore, the space-time correlation functions for dense fluid methane are also discussed. All the numerical results demonstrate that the new OPLS model could be well utilized to investigate the dense fluid methane.
Multi-fluid pipe flow model for analysis of wellbore dynamics
NASA Astrophysics Data System (ADS)
Krasnopolsky, B.; Starostin, A.; Osiptsov, A.
2012-09-01
We present the results of developing a multi-fluid model for a transient multiphase flow in a pipe with application to oil and gas well cleanup after drilling or hydraulic fracturing. The model is an extension of the earlier work on multi-fluid models for near-horizontal pipes to cover any inclination angle and include additional phases. The 1D multi-fluid model governs a transient isothermal flow of three compressible fluids in a horizontal, deviated, or a vertical pipe. The multi-fluid model research code is based on well-known SIMPLE schemes, and features implementation of either a geometry or a mass conservation based algorithms. The multi-fluid model is able to predict the flow regimes with a single interface between gas and liquid mixture: stratified flow, flow with rolling waves, and flow with slugs. The code is validated against an analytical solutions and flow pattern maps. Agreement with theory is found in predicting the transition between the regimes. The final application of the model will be in transient wellbore dynamics with flow regime transitions.
Validation of an All-Pressure Fluid Drop Model: Heptane Fluid Drops in Nitrogen
NASA Technical Reports Server (NTRS)
Harstad, K.; Bellan, J.; Bulzan, Daniel L. (Technical Monitor)
2000-01-01
Despite the fact that supercritical fluids occur both in nature and in industrial situations, the fundamentals of their behavior is poorly understood because supercritical fluids combine the characteristics of both liquids and gases, and therefore their behavior is not intuitive. There are several specific reasons for the lack of understanding: First, data from (mostly optical) measurements can be very misleading because regions of high density thus observed are frequently identified with liquids. A common misconception is that if in an experiment one can optically identify "drops" and "ligaments", the observed fluid must be in a liquid state. This inference is incorrect because in fact optical measurements detect any large change (i.e. gradients) in density. Thus, the density ratio may be well below Omicron(10(exp 3)) that characterizes its liquid/gas value, but the measurement will still identify a change in the index of refraction providing that the change is sudden (steep gradients). As shown by simulations of supercritical fluids, under certain conditions the density gradients may remain large during the supercritical binary fluids mixing, thus making them optically identifiable. Therefore, there is no inconsistency between the optical observation of high density regions and the fluids being in a supercritical state. A second misconception is that because a fluid has a liquid-like density, it is appropriate to model it as a liquid. However, such fluids may have liquid-like densities while their transport properties differ from those of a liquid. Considering that the critical pressure of most fuel hydrocarbons used in Diesel and gas turbine engines is in the range of 1.5 - 3 MPa, and the fact that the maximum pressure attained in these engines is about 6 Mps, it is clear that the fuel in the combustion chamber will experience both subcritical and supercritical conditions. Studies of drop behavior over a wide range of pressures were performed in the past
Computational fluid dynamics framework for aerodynamic model assessment
NASA Astrophysics Data System (ADS)
Vallespin, D.; Badcock, K. J.; Da Ronch, A.; White, M. D.; Perfect, P.; Ghoreyshi, M.
2012-07-01
This paper reviews the work carried out at the University of Liverpool to assess the use of CFD methods for aircraft flight dynamics applications. Three test cases are discussed in the paper, namely, the Standard Dynamic Model, the Ranger 2000 jet trainer and the Stability and Control Unmanned Combat Air Vehicle. For each of these, a tabular aerodynamic model based on CFD predictions is generated along with validation against wind tunnel experiments and flight test measurements. The main purpose of the paper is to assess the validity of the tables of aerodynamic data for the force and moment prediction of realistic aircraft manoeuvres. This is done by generating a manoeuvre based on the tables of aerodynamic data, and then replaying the motion through a time-accurate computational fluid dynamics calculation. The resulting forces and moments from these simulations were compared with predictions from the tables. As the latter are based on a set of steady-state predictions, the comparisons showed perfect agreement for slow manoeuvres. As manoeuvres became more aggressive some disagreement was seen, particularly during periods of large rates of change in attitudes. Finally, the Ranger 2000 model was used on a flight simulator.
Computational fluid dynamics modeling for emergency preparedness & response
Lee, R.L.; Albritton, J.R.; Ermak, D.L.; Kim, J.
1995-07-01
Computational fluid dynamics (CFD) has played an increasing role in the improvement of atmospheric dispersion modeling. This is because many dispersion models are now driven by meteorological fields generated from CFD models or, in numerical weather prediction`s terminology, prognostic models. Whereas most dispersion models typically involve one or a few scalar, uncoupled equations, the prognostic equations are a set of highly-coupled, nonlinear equations whose solution requires a significant level of computational power. Until recently, such computer power could be found only in CRAY-class supercomputers. Recent advances in computer hardware and software have enabled modestly-priced, high performance, workstations to exhibit the equivalent computation power of some mainframes. Thus desktop-class machines that were limited to performing dispersion calculations driven by diagnostic wind fields may now be used to calculate complex flows using prognostic CFD models. The Atmospheric Release and Advisory Capability (ARAC) program at Lawrence Livermore National Laboratory (LLNL) has, for the past several years, taken advantage of the improvements in hardware technology to develop a national emergency response capability based on executing diagnostic models on workstations. Diagnostic models that provide wind fields are, in general, simple to implement, robust and require minimal time for execution. Such models have been the cornerstones of the ARAC operational system for the past ten years. Kamada (1992) provides a review of diagnostic models and their applications to dispersion problems. However, because these models typically contain little physics beyond mass-conservation, their performance is extremely sensitive to the quantity and quality of input meteorological data and, in spite of their utility, can be applied with confidence to only modestly complex flows.
Soy Protein Isolate As Fluid Loss Additive in Bentonite-Water-Based Drilling Fluids.
Li, Mei-Chun; Wu, Qinglin; Song, Kunlin; Lee, Sunyoung; Jin, Chunde; Ren, Suxia; Lei, Tingzhou
2015-11-11
Wellbore instability and formation collapse caused by lost circulation are vital issues during well excavation in the oil industry. This study reports the novel utilization of soy protein isolate (SPI) as fluid loss additive in bentonite-water based drilling fluids (BT-WDFs) and describes how its particle size and concentration influence on the filtration property of SPI/BT-WDFs. It was found that high pressure homogenization (HPH)-treated SPI had superior filtration property over that of native SPI due to the improved ability for the plugging pore throat. HPH treatment also caused a significant change in the surface characteristic of SPI, leading to a considerable surface interaction with BT in aqueous solution. The concentration of SPI had a significant impact on the dispersion state of SPI/BT mixtures in aquesous solution. At low SPI concentrations, strong aggregations were created, resulting in the formation of thick, loose, high-porosity and high-permeability filter cakes and high fluid loss. At high SPI concentrations, intercatlated/exfoliated structures were generated, resulting in the formation of thin, compact, low-porosity and low-permeability filter cakes and low fluid loss. The SPI/BT-WDFs exhibited superior filtration property than pure BT-WDFs at the same solid concentraion, demonstrating the potential utilization of SPI as an effective, renewable, and biodegradable fluid loss reducer in well excavation applications. PMID:26492498
A magnetorheological fluid based orthopedic active knee brace
NASA Astrophysics Data System (ADS)
Zite, Jamaal L.; Ahmadkhanlou, Farzad; Neelakantan, Vijay A.; Washington, Gregory N.
2006-03-01
The disadvantage of current knee braces ranges from high cost for customization to a loss in physical mobility and limited rehabilitative value. One approach to solving this problem is to use a Magnetorheological (MR) device to make the knee brace have a controllable resistance. Our design solution is to replace the manufacturer's joint with an rotary MR fluid based shear damper. The device is designed based on a maximum yield stress, a corresponding magnetic field, a torque and the MR fluid viscosity. The analytical and experimental results show the advantages and the feasibility of using the proposed MR based controllable knee braces.
Self-consistent gyroviscous fluid model of rotational discontinuities
Hau, L.N.; Sonnerup, B.U.O. )
1991-09-01
One-dimensional steady state equilibrium structures of rotational discontinuities (RDs) have been constructed by use of a nondissipative gyroviscous two-fluid model in which electron inertia is neglected. The gyroviscous two-fluid RDs presented in this paper satisfy the MHD jump conditions for RDs exactly, i.e., all plasma properties as well as the magnetic field magnitude are identical and uniform on both sides of the layer, and v{sub x}, the normal flow speed there, is equal to the Alfven speed based on the normal magnetic field component B{sub x}. A necessary condition for the existence of RD solutions is derived by performing fixed-point analysis at the possible upstream and downstream states of RDs. This analysis shows that in the B{sub y}B{sub z} plane the magnetic structure near the fixed point is either a center or a saddle point. For those upstream conditions that give rise to a center point, no RD structure exists; when the fixed point examined is a saddle point, numerical integration of the one-dimension, steady state, nonlinear gyroviscous two-fluid equations indicates that self-consistent complete RD structures may sometimes (but not always) exist. These structures involve a rotation of the tangential magnetic field by an angle {phi} that is determined by the angle {theta} between the upstream (or downstream) magnetic field and the vector normal to the discontinuity, by the plasma beta value, {beta} = 2{mu}{sub o}p/B{sup 2}, and by the electron to ion temperature ratio T{sub e}/T{sub i}. Only electron-polarized structures have been found to date: within these discontinuities the field magnitude {vert bar}B{vert bar} always displays a maximum. If ion-polarized RDs exist, they would contain a minimum in {vert bar}B{vert bar}. However, no such structures have been found.
Development Of Simulation Model For Fluid Catalytic Cracking
NASA Astrophysics Data System (ADS)
Ghosh, Sobhan
2010-10-01
Fluid Catalytic Cracking (FCC) is the most widely used secondary conversion process in the refining industry, for producing gasoline, olefins, and middle distillate from heavier petroleum fractions. There are more than 500 units in the world with a total processing capacity of about 17 to 20% of the crude capacity. FCC catalyst is the highest consumed catalyst in the process industry. On one hand, FCC is quite flexible with respect to it's ability to process wide variety of crudes with a flexible product yield pattern, and on the other hand, the interdependence of the major operating parameters makes the process extremely complex. An operating unit is self balancing and some fluctuations in the independent parameters are automatically adjusted by changing the temperatures and flow rates at different sections. However, a good simulation model is very useful to the refiner to get the best out of the process, in terms of selection of the best catalyst, to cope up with the day to day changing of the feed quality and the demands of different products from FCC unit. In addition, a good model is of great help in designing the process units and peripherals. A simple empirical model is often adequate to monitor the day to day operations, but they are not of any use in handling the other problems such as, catalyst selection or, design / modification of the plant. For this, a kinetic based rigorous model is required. Considering the complexity of the process, large number of chemical species undergoing "n" number of parallel and consecutive reactions, it is virtually impossible to develop a simulation model based on the kinetic parameters. The most common approach is to settle for a semi empirical model. We shall take up the key issues for developing a FCC model and the contribution of such models in the optimum operation of the plant.
Hybrid fluid/kinetic model for parallel heat conduction
Callen, J.D.; Hegna, C.C.; Held, E.D.
1998-12-31
It is argued that in order to use fluid-like equations to model low frequency ({omega} < {nu}) phenomena such as neoclassical tearing modes in low collisionality ({nu} < {omega}{sub b}) tokamak plasmas, a Chapman-Enskog-like approach is most appropriate for developing an equation for the kinetic distortion (F) of the distribution function whose velocity-space moments lead to the needed fluid moment closure relations. Further, parallel heat conduction in a long collision mean free path regime can be described through a combination of a reduced phase space Chapman-Enskog-like approach for the kinetics and a multiple-time-scale analysis for the fluid and kinetic equations.
Viscous quark-gluon plasma model through fluid QCD approach
Djun, T. P.; Soegijono, B.; Mart, T.; Handoko, L. T. E-mail: Laksana.tri.handoko@lipi.go.id
2014-09-25
A Lagrangian density for viscous quark-gluon plasma has been constructed within the fluid-like QCD framework. Gauge symmetry is preserved for all terms inside the Lagrangian, except for the viscous term. The transition mechanism from point particle field to fluid field, and vice versa, are discussed. The energy momentum tensor that is relevant to the gluonic plasma having the nature of fluid bulk of gluon sea is derived within the model. By imposing conservation law in the energy momentum tensor, shear viscosity appears as extractable from the equation.
Numerical modeling of fluid migration in subduction zones
NASA Astrophysics Data System (ADS)
Walter, Marius J.; Quinteros, Javier; Sobolev, Stephan V.
2015-04-01
It is well known that fluids play a crucial role in subduction evolution. For example, excess mechanical weakening along tectonic interfaces, due to excess fluid pressure, may enable oceanic subduction. Hence, the fluid content seems to be a critical parameter for subduction initiation. Studies have also shown a correlation between the location of slab dehydration and intermediate seismic activity. Furthermore, expelled fluids from the subduction slab affect the melting temperature, consequently, contributing to partial melting in the wedge above the downgoing plate, and resulting in chemical changes in earth interior and extensive volcanism. In summary, fluids have a great impact on tectonic processes and therefore should be incorporated into geodynamic numerical models. Here we use existing approaches to couple and solve fluid flow equations in the SLIM-3D thermo-mechanical code. SLIM-3D is a three-dimensional thermo-mechanical code capable of simulating lithospheric deformation with elasto-visco-plastic rheology. It incorporates an arbitrary Lagrangian Eulerian formulation, free surface, and changes in density and viscosity, due to endothermic and exothermic phase transitions. It has been successfully applied to model geodynamic processes at different tectonic settings, including subduction zones. However, although SLIM-3D already includes many features, fluid migration has not been incorporated into the model yet. To this end, we coupled solid and fluid flow assuming that fluids flow through a porous and deformable solid. Thereby, we introduce a two-phase flow into the model, in which the Stokes flow is coupled with the Darcy law for fluid flow. This system of equations becomes, however, nonlinear, because the rheology and permeability are depended on the porosity (fluid fraction of the matrix). Ultimately, the evolution of porosity is governed by the compaction pressure and the advection of the porous solid. We show the details of our implementation of the
NASA Technical Reports Server (NTRS)
Muszynska, Agnes; Bently, Donald E.
1991-01-01
Perturbation techniques used for identification of rotating system dynamic characteristics are described. A comparison between two periodic frequency-swept perturbation methods applied in identification of fluid forces of rotating machines is presented. The description of the fluid force model identified by inputting circular periodic frequency-swept force is given. This model is based on the existence and strength of the circumferential flow, most often generated by the shaft rotation. The application of the fluid force model in rotor dynamic analysis is presented. It is shown that the rotor stability is an entire rotating system property. Some areas for further research are discussed.
A computational model for doctoring fluid films in gravure printing
NASA Astrophysics Data System (ADS)
Hariprasad, Daniel S.; Grau, Gerd; Schunk, P. Randall; Tjiptowidjojo, Kristianto
2016-04-01
The wiping, or doctoring, process in gravure printing presents a fundamental barrier to resolving the micron-sized features desired in printed electronics applications. This barrier starts with the residual fluid film left behind after wiping, and its importance grows as feature sizes are reduced, especially as the feature size approaches the thickness of the residual fluid film. In this work, various mechanical complexities are considered in a computational model developed to predict the residual fluid film thickness. Lubrication models alone are inadequate, and deformation of the doctor blade body together with elastohydrodynamic lubrication must be considered to make the model predictive of experimental trends. Moreover, model results demonstrate that the particular form of the wetted region of the blade has a significant impact on the model's ability to reproduce experimental measurements.
Paradigms of Complexity in Modelling of Fluid and Kinetic Processes
NASA Astrophysics Data System (ADS)
Diamond, P. H.
2006-10-01
The need to discuss and compare a wide variety of models of fluid and kinetic processes is motivated by the astonishing wide variety of complex physical phenomena which occur in plasmas in nature. Such phenomena include, but are not limited to: turbulence, turbulent transport and mixing, reconnection and structure formation. In this talk, I will review how various fluid and kinetic models come to grips with the essential physics of these phenomena. For example, I will discuss how the idea of a turbulent cascade and the concept of an ``eddy'' are realized quite differently in fluid and Vlasov models. Attention will be placed primarily on physical processes, the physics content of various models, and the consequences of choices in model construction, rather than on the intrinsic mathematical structure of the theories. Examples will be chosen from fusion, laboratory, space and astrophysical plasmas.
Greg Weirs; Hyung Lee
2011-09-01
V&V and UQ are the primary means to assess the accuracy and reliability of M&S and, hence, to establish confidence in M&S. Though other industries are establishing standards and requirements for the performance of V&V and UQ, at present, the nuclear industry has not established such standards or requirements. However, the nuclear industry is beginning to recognize that such standards are needed and that the resources needed to support V&V and UQ will be very significant. In fact, no single organization has sufficient resources or expertise required to organize, conduct and maintain a comprehensive V&V and UQ program. What is needed is a systematic and standardized approach to establish and provide V&V and UQ resources at a national or even international level, with a consortium of partners from government, academia and industry. Specifically, what is needed is a structured and cost-effective knowledge base that collects, evaluates and stores verification and validation data, and shows how it can be used to perform V&V and UQ, leveraging collaboration and sharing of resources to support existing engineering and licensing procedures as well as science-based V&V and UQ processes. The Nuclear Energy Knowledge base for Advanced Modeling and Simulation (NE-KAMS) is being developed at the Idaho National Laboratory in conjunction with Bettis Laboratory, Sandia National Laboratories, Argonne National Laboratory, Utah State University and others with the objective of establishing a comprehensive and web-accessible knowledge base to provide V&V and UQ resources for M&S for nuclear reactor design, analysis and licensing. The knowledge base will serve as an important resource for technical exchange and collaboration that will enable credible and reliable computational models and simulations for application to nuclear power. NE-KAMS will serve as a valuable resource for the nuclear industry, academia, the national laboratories, the U.S. Nuclear Regulatory Commission (NRC) and
Hole-cleaning capabilities of an ester-based drilling fluid system
Kenny, P.; Hemphill, T.
1996-03-01
Well 33/9-C02, located in the Statfjord field in the Norwegian sector of the North Sea, held the world record in extended-reach drilling from 1993--95. To successfully drill a well of this type, an efficient drilling fluid is required to suspend the weighting material and provide good carrying capacity. The ester-based mud system used in the 12{1/4}- and 8{1/2}-in. hole sections of this well exhibited excellent hole-cleaning capabilities. This paper describes the fluid`s performance in the field and in the laboratory where the fluid was tested under down-hole conditions. Fluid rheological behavior is described with the more accurate yield-power law. (YPL) (Herschel-Bulkley) model.
NASA Astrophysics Data System (ADS)
Konrad-Schmolke, Matthias; Halama, Ralf
2014-11-01
Quantitative geochemical modeling is today applied in a variety of geological environments from the petrogenesis of igneous rocks to radioactive waste disposal. In addition, the development of thermodynamic databases and computer programs to calculate equilibrium phase diagrams has greatly advanced our ability to model geodynamic processes. Combined with experimental data on elemental partitioning and isotopic fractionation, thermodynamic forward modeling unfolds enormous capacities that are far from exhausted. In metamorphic petrology the combination of thermodynamic and trace element forward modeling can be used to study and to quantify processes at spatial scales from μm to km. The thermodynamic forward models utilize Gibbs energy minimization to quantify mineralogical changes along a reaction path of a chemically open fluid/rock system. These results are combined with mass balanced trace element calculations to determine the trace element distribution between rock and melt/fluid during the metamorphic evolution. Thus, effects of mineral reactions, fluid-rock interaction and element transport in metamorphic rocks on the trace element and isotopic composition of minerals, rocks and percolating fluids or melts can be predicted. Here we illustrate the capacities of combined thermodynamic-geochemical modeling based on two examples relevant to mass transfer during metamorphism. The first example focuses on fluid-rock interaction in and around a blueschist-facies shear zone in felsic gneisses, where fluid-induced mineral reactions and their effects on boron (B) concentrations and isotopic compositions in white mica are modeled. In the second example, fluid release from a subducted slab, the associated transport of B as well as variations in B concentrations and isotopic compositions in liberated fluids and residual rocks are modeled. We compare the modeled results of both examples to geochemical data of natural minerals and rocks and demonstrate that the combination
Phantom model of physiologic intracranial pressure and cerebrospinal fluid dynamics.
Bottan, Simone; Poulikakos, Dimos; Kurtcuoglu, Vartan
2012-06-01
We describe herein a novel life-size phantom model of the intracranial cavity and its validation. The cerebrospinal fluid (CSF) domains including ventricular, cysternal, and subarachnoid spaces were derived via magnetic resonance imaging. Brain mechanical properties and cranio-spinal compliance were set based on published data. Both bulk and pulsatile physiologic CSF flow were modeled. Model validation was carried out by comparisons of flow and pressure measurements in the phantom with published in vivo data of healthy subjects. Physiologic intracranial pressure with 10 mmHg mean and 0.4 mmHg peak pulse amplitude was recorded in the ventricles. Peak CSF flow rates of 0.2 and 2 ml/s were measured in the cerebral aqueduct and subarachnoid space, respectively. The phantom constitutes a first-of-its-kind approach to modeling physiologic intracranial dynamics in vitro. Herein, we describe the phantom design and manufacturing, definition and implementation of its operating parameters, as well as the validation of the modeled dynamics. PMID:22333981
NASA Astrophysics Data System (ADS)
Chang, Gary Han; Modarres-Sadeghi, Yahya
2015-11-01
In this work, a reduced-order model (ROM) is constructed to study fluid-structure interaction of thin shell structures conveying fluid. The method of snapshot Proper Orthogonal Decomposition (POD) is used to construct the reduced-order bases based on a series of CFD results, which then are improved using a QR-factorization technique to satisfy the various boundary conditions in physiological flow problems. In the process, two sets of POD modes are extracted: those due to the shell wall's motion and those due to the pulsatile flow. The Modal Assurance Criterion (MAC) technique is used for selecting the final POD modes used in the reduced-order model. The structure model is solved by Galerkin's method and the FSI coupling is done by adapting a coupled momentum method. The results show that the dynamic behavior of thin shells conveying fluid is closely related to the distribution of the shell's Gaussian curvature, the existence of imperfections and the physiological flow conditions. This method can effectively construct a computationally efficient FSI model, which allows us to examine a wide range of parameters which exist in real-life physiological problems.
Numerical Modeling of Conjugate Heat Transfer in Fluid Network
NASA Technical Reports Server (NTRS)
Majumdar, Alok
2004-01-01
Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.
Microfluidic flow switching design using volume of fluid model.
Chein, Reiyu; Tsai, S H
2004-03-01
In this study, a volume of fluid (VOF) model was employed for microfluidic switch design. The VOF model validity in predicting the interface between fluid streams with different viscosities co-flowing in a microchannel was first verified by experimental observation. It was then extended to microfluidic flow switch design. Two specific flow switches, one with a guided fluid to one of five desired outlet ports, and another with a guided fluid flows into one, two, or three outlet ports equally distributed along the outlet channel of a Y-shaped channel. The flow switching was achieved by controlling the flow rate ratios between tested and buffer fluids. The numerical results showed that the VOF model could successfully predict the flow switching phenomena in these flow switches. The numerical results also showed that the flow rate ratio required for flow switching depends on the viscosity ratio between the tested and buffer fluids. The numerical simulation was verified by experimental study and the agreement was good. PMID:15307449
Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed
Zhongyi Deng; Rui Xiao; Baosheng Jin; He Huang; Laihong Shen; Qilei Song; Qianjun Li
2008-05-15
Computational fluid dynamics (CFD) modeling, which has recently proven to be an effective means of analysis and optimization of energy-conversion processes, has been extended to coal gasification in this paper. A 3D mathematical model has been developed to simulate the coal gasification process in a pressurized spout-fluid bed. This CFD model is composed of gas-solid hydrodynamics, coal pyrolysis, char gasification, and gas phase reaction submodels. The rates of heterogeneous reactions are determined by combining Arrhenius rate and diffusion rate. The homogeneous reactions of gas phase can be treated as secondary reactions. A comparison of the calculated and experimental data shows that most gasification performance parameters can be predicted accurately. This good agreement indicates that CFD modeling can be used for complex fluidized beds coal gasification processes. 37 refs., 7 figs., 5 tabs.
Magnetic wire-based sensors for the microrheology of complex fluids.
Chevry, L; Sampathkumar, N K; Cebers, A; Berret, J-F
2013-12-01
We propose a simple microrheology technique to evaluate the viscoelastic properties of complex fluids. The method is based on the use of magnetic wires of a few microns in length submitted to a rotational magnetic field. In this work, the method is implemented on a surfactant wormlike micellar solution that behaves as an ideal Maxwell fluid. With increasing frequency, the wires undergo a transition between a steady and a hindered rotation regime. The study shows that the average rotational velocity and the amplitudes of the oscillations obey scaling laws with well-defined exponents. From a comparison between model predictions and experiments, the rheological parameters of the fluid are determined. PMID:24483443
Modeling surface tension using a ghost fluid technique within a volume of fluid formulation
Francois, M. M.; Kothe, D. B.; Cummins, S. J.
2004-01-01
Ghost fluid methods (GFM) are a viable approach for imposing sharp boundary conditions on interfaces that are arbitrarily embedded within the computational mesh. All GFM to date are formulated with an interface distance function that resides within a level-set (LS) framework. Recently we proposed a technique for reconstructing distance functions from volume fractions. This technique enables the exploitation of GFM within a volume of fluid formulation for modeling an interfacial phenomenon like surface tension. Combining GFM with a volume of fluid (VOF) formulation is attractive because of the VOF method's superior mass conservation and because of the ability of GFM to maintain sharp jump conditions. The continuum surface tension force (CSF) method, however, has the propensity to produce smooth jump. In the following, the combined VOF-GFM and more classical VOF-CSF formulations are compared and contrasted. Static and dynamic numerical results are used to illustrate our findings and support our claims.
A Generalized Fluid System Simulation Program to Model Flow Distribution in Fluid Networks
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Bailey, John W.; Schallhorn, Paul; Steadman, Todd
1998-01-01
This paper describes a general purpose computer program for analyzing steady state and transient flow in a complex network. The program is capable of modeling phase changes, compressibility, mixture thermodynamics and external body forces such as gravity and centrifugal. The program's preprocessor allows the user to interactively develop a fluid network simulation consisting of nodes and branches. Mass, energy and specie conservation equations are solved at the nodes; the momentum conservation equations are solved in the branches. The program contains subroutines for computing "real fluid" thermodynamic and thermophysical properties for 33 fluids. The fluids are: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutane, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride and ammonia. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. Seventeen different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include: pipe flow, flow through a restriction, non-circular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct, labyrinth seal, parallel plates, common fittings and valves, pump characteristics, pump power, valve with a given loss coefficient, and a Joule-Thompson device. The system of equations describing the fluid network is solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods. This paper also illustrates the application and verification of the code by comparison with Hardy Cross method for steady state flow and analytical solution for unsteady flow.
Aptamer-Based Screens of Human Body Fluids for Biomarkers
Albaba, Dania; Soomro, Sanam; Mohan, Chandra
2015-01-01
In recent years, aptamers have come to replace antibodies in high throughput multiplexed experiments. The aptamer-based biomarker screening technology, which kicked off in 2010, is capable of interrogating thousands of proteins in a very small sample volume. With this new technology, researchers hope to find clinically appropriate biomarkers for a myriad of illnesses by screening human body fluids. In this work, we have reviewed a total of eight studies utilizing aptamer-based biomarker screens of human body fluids, and have highlighted novel protein biomarkers discovered. PMID:27600232
Reconstruction of modified gravity with perfect fluid cosmological models
NASA Astrophysics Data System (ADS)
Singh, C. P.; Singh, Vijay
2014-04-01
In this paper we present the cosmological viability of reconstruction of an alternative gravitational theory, namely, the modified gravity, where is the Ricci scalar curvature and the trace of stress energy momentum tensor. A functional form of is chosen for the reconstruction in perfect fluid flat Friedmann-Robertson-Walker model. The gravitational field equations contain two fluid sources, one is perfect fluid and other is due to modified gravity which is to be considered as an exotic fluid. This allows us for derivation and analysis of a set of new cosmological solutions for gravity by considering these two fluids as a non-interacting. Two known forms of scale factor (de Sitter and power-law) are considered for the explicit and successful reconstruction. The equation of state parameter (EoS) of exotic matter and the effective EoS parameter have been discussed. In de Sitter solution we find that the fluid behaves as phantom dark energy when the usual matter (perfect fluid) shows the behavior between decelerated phase to accelerated phase. In the absence of usual matter it behaves as a cosmological constant. In case of power -law cosmology two different cases are discussed and analyzed the behavior of different phases of the universe accordingly through the equation of state and density parameters.
CO2-based mixtures as working fluids for geothermal turbines.
Wright, Steven Alan; Conboy, Thomas M.; Ames, David E.
2012-01-01
Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for application to a variety of heat sources, including geothermal, solar, fossil, and nuclear power. This work is centered on the supercritical CO{sub 2} (S-CO{sub 2}) power conversion cycle, which has the potential for high efficiency in the temperature range of interest for these heat sources and is very compact-a feature likely to reduce capital costs. One promising approach is the use of CO{sub 2}-based supercritical fluid mixtures. The introduction of additives to CO{sub 2} alters the equation of state and the critical point of the resultant mixture. A series of tests was carried out using Sandia's supercritical fluid compression loop that confirmed the ability of different additives to increase or lower the critical point of CO{sub 2}. Testing also demonstrated that, above the modified critical point, these mixtures can be compressed in a turbocompressor as a single-phase homogenous mixture. Comparisons of experimental data to the National Institute of Standards and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties (REFPROP) Standard Reference Database predictions varied depending on the fluid. Although the pressure, density, and temperature (p, {rho}, T) data for all tested fluids matched fairly well to REFPROP in most regions, the critical temperature was often inaccurate. In these cases, outside literature was found to provide further insight and to qualitatively confirm the validity of experimental findings for the present investigation.
Fully Coupled Well Models for Fluid Injection and Production
White, Mark D.; Bacon, Diana H.; White, Signe K.; Zhang, Z. F.
2013-08-05
Wells are the primary engineered component of geologic sequestration systems with deep subsurface reservoirs. Wells provide a conduit for injecting greenhouse gases and producing reservoirs fluids, such as brines, natural gas, and crude oil, depending on the target reservoir. Well trajectories, well pressures, and fluid flow rates are parameters over which well engineers and operators have control during the geologic sequestration process. Current drilling practices provided well engineers flexibility in designing well trajectories and controlling screened intervals. Injection pressures and fluids can be used to purposely fracture the reservoir formation or to purposely prevent fracturing. Numerical simulation of geologic sequestration processes involves the solution of multifluid transport equations within heterogeneous geologic media. These equations that mathematically describe the flow of fluid through the reservoir formation are nonlinear in form, requiring linearization techniques to resolve. In actual geologic settings fluid exchange between a well and reservoir is a function of local pressure gradients, fluid saturations, and formation characteristics. In numerical simulators fluid exchange between a well and reservoir can be specified using a spectrum of approaches that vary from totally ignoring the reservoir conditions to fully considering reservoir conditions and well processes. Well models are a numerical simulation approach that account for local conditions and gradients in the exchange of fluids between the well and reservoir. As with the mathematical equations that describe fluid flow in the reservoir, variation in fluid properties with temperature and pressure yield nonlinearities in the mathematical equations that describe fluid flow within the well. To numerically simulate the fluid exchange between a well and reservoir the two systems of nonlinear multifluid flow equations must be resolved. The spectrum of numerical approaches for resolving
Desbonnets, Quentin; Broc, Daniel
2012-07-01
It is well known that a fluid may strongly influence the dynamic behaviour of a structure. Many different physical phenomena may take place, depending on the conditions: fluid flow, fluid at rest, little or high displacements of the structure. Inertial effects can take place, with lower vibration frequencies, dissipative effects also, with damping, instabilities due to the fluid flow (Fluid Induced Vibration). In this last case the structure is excited by the fluid. Tube bundles structures are very common in the nuclear industry. The reactor cores and the steam generators are both structures immersed in a fluid which may be submitted to a seismic excitation or an impact. In this case the structure moves under an external excitation, and the movement is influence by the fluid. The main point in such system is that the geometry is complex, and could lead to very huge sizes for a numerical analysis. Homogenization models have been developed based on the Euler equations for the fluid. Only inertial effects are taken into account. A next step in the modelling is to build models based on the homogenization of the Navier-Stokes equations. The papers presents results on an important step in the development of such model: the analysis of the fluid flow in a oscillating tube bundle. The analysis are made from the results of simulations based on the Navier-Stokes equations for the fluid. Comparisons are made with the case of the oscillations of a single tube, for which a lot of results are available in the literature. Different fluid flow pattern may be found, depending in the Reynolds number (related to the velocity of the bundle) and the Keulegan Carpenter number (related to the displacement of the bundle). A special attention is paid to the quantification of the inertial and dissipative effects, and to the forces exchanges between the bundle and the fluid. The results of such analysis will be used in the building of models based on the homogenization of the Navier
3D Fluid-Structure Modeling of a Monofin
NASA Astrophysics Data System (ADS)
Monier, L.; Razafimahery, F.; Rakotomanana, L.
2010-10-01
The purpose of this paper is to develop a numerical modelisation for the behaviour of a monofin. We have developped a fluid struture model simulating the movement of a fin in a swimming pool. We first present the geometry and the equations and then proceed to different numerical experiments in order to validate the model.
Two-Fluid Models and Interfacial Area Transport in Microgravity Condition
NASA Technical Reports Server (NTRS)
Ishii, Mamoru; Sun, Xiao-Dong; Vasavada, Shilp
2004-01-01
The objective of the present study is to develop a two-fluid model formulation with interfacial area transport equation applicable for microgravity conditions. The new model is expected to make a leapfrog improvement by furnishing the constitutive relations for the interfacial interaction terms with the interfacial area transport equation, which can dynamically model the changes of the interfacial structures. In the first year of this three-year project supported by the U.S. NASA, Office of Biological and Physics Research, the primary focus is to design and construct a ground-based, microgravity two-phase flow simulation facility, in which two immiscible fluids with close density will be used. In predicting the two-phase flow behaviors in any two-phase flow system, the interfacial transfer terms are among the most essential factors in the modeling. These interfacial transfer terms in a two-fluid model specify the rate of phase change, momentum exchange, and energy transfer at the interface between the two phases. For the two-phase flow under the microgravity condition, the stability of the fluid particle interface and the interfacial structures are quite different from those under normal gravity condition. The flow structure may not reach an equilibrium condition and the two fluids may be loosely coupled such that the inertia terms of each fluid should be considered separately by use of the two-fluid model. Previous studies indicated that, unless phase-interaction terms are accurately modeled in the two-fluid model, the complex modeling does not necessarily warrant an accurate solution.
Modeling anomalous diffusion of dense fluids in carbon nanotubes
NASA Astrophysics Data System (ADS)
Wang, Gerald; Hadjiconstantinou, Nicolas
2015-11-01
Molecular diffusive mechanisms exhibited under nanoconfinement can differ considerably from the Fickian self-diffusion expected in a bulk fluid. We propose a theoretical description of this phenomenon in a nanofluidic system of considerable interest - namely, a dense fluid confined within a carbon nanotube (CNT). We show that the anomalous diffusion reported in the literature is closely related to the fluid layering widely observed in this system and recently theoretically described [Wang and Hadjiconstantinou, Physics of Fluids, 052006, 2015]. In particular, we find that the key to describing the anomalous molecular diffusion (within sufficiently large CNTs) lies in recognizing that the diffusion mechanism is spatially dependent: while fluid in the center of the nanotube (at least three molecular diameters away from the wall) exhibits Fickian diffusion, fluid near the CNT wall can demonstrate non-Fickian diffusive behavior. The previously reported anomalous diffusive behavior can be reproduced, to a good approximation level, by appropriately combining the bulk and near-wall behavior to form a model for the overall diffusion rate within the nanotube. Such models produce results in quantitative agreement with molecular dynamics simulations.
40 CFR Appendix 3 to Subpart A of... - Procedure for Mixing Base Fluids With Sediments
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Procedure for Mixing Base Fluids With... Subcategory Pt. 435, Subpt. A, App. 3 Appendix 3 to Subpart A of Part 435—Procedure for Mixing Base Fluids...) sediments with the base fluids that are used to formulate synthetic-based drilling fluids and other...
40 CFR Appendix 3 to Subpart A of... - Procedure for Mixing Base Fluids With Sediments
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Procedure for Mixing Base Fluids With... Subcategory Pt. 435, Subpt. A, App. 3 Appendix 3 to Subpart A of Part 435—Procedure for Mixing Base Fluids...) sediments with the base fluids that are used to formulate synthetic-based drilling fluids and other...
New hydrologic model of fluid migration in deep porous media
NASA Astrophysics Data System (ADS)
Dmitrievsky, A.; Balanyuk, I.
2009-04-01
The authors present a new hydrological model of mantle processes that effect on formation of oil-and-gas bearing basins, fault tectonics and thermal convection. Any fluid migration is initially induced by lateral stresses in the crust and lithosphere which result from global geodynamic processes related to the mantle convection. The global processes are further transformed into regional movements in weakness zones. Model of porous media in deep fractured zones and idea of self-oscillation processes in mantle layers and fractured zones of the crust at different depths was used as the basis for developed concept. The content of these notions resides in the fact that there are conditions of dynamic balance in mantle layers originating as a result of combination and alternate actions of compaction and dilatance mechanisms. These mechanisms can be manifested in different combinations and under different conditions as well as can be complemented by other processes influencing on regime of fluid migration. They can act under condition of passive margin, ocean rift and ocean subduction zones as well as in consolidated platform and sheet. Self-oscillation regime, sub vertical direction of fluid flows, anomalously high layer pressure, and high level of anomalies of various geophysical fields are common for them. A certain class of fluid dynamic models describing consolidation of sedimentary basins, free oscillation processes slow and quick (at the final stage) fluid dynamic processes of the evolution of a sedimentary basin in subduction zones is considered for the first time. The last model of quick fluid dynamic processes reflects the process of formation of hydrocarbon deposits in the zones of collision of lithosphere plates. The results of numerical simulation and diagrams reflecting consecutive stages of the gas-fluid dynamic front propagation are assessed of the Pri-Caspian depression as the example. Calculations with this model will simultaneously be carried out for
Hydromechanical Modeling of Fluid Flow in the Lower Crust
NASA Astrophysics Data System (ADS)
Connolly, J.
2011-12-01
The lower crust lies within an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguity has allowed two schools of thought to develop concerning the nature of fluid flow in the lower crust. The classical school holds that lower crustal rocks are inviscid and that any fluid generated by metamorphic devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school, permeability is a dynamic property and fluid flow is upward. In contrast, the modern school uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that it is reflected by inference from field studies, offers some support to both schools. In particular, evidence of significant lateral and channelized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid-rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models of lower crustal fluid flow that rocks are neither inviscid nor rigid, but compact by viscous mechanisms on a finite time-scale. This presentation will review the principle consequences of, and obstacles to, incorporating compaction in such models. The role of viscous compaction in the lower crust is extraordinarily uncertain, but ignoring this uncertainty in models of lower crustal fluid flow does not make the models any more certain. Models inevitably invoke an initial steady state hydraulic regime. This initial steady state is critical to model outcomes because it
Salt tectonics and shallow subseafloor fluid convection: models of coupled fluid-heat-salt transport
Wilson, A.; Ruppel, C.
2007-01-01
Thermohaline convection associated with salt domes has the potential to drive significant fluid flow and mass and heat transport in continental margins, but previous studies of fluid flow associated with salt structures have focused on continental settings or deep flow systems of importance to petroleum exploration. Motivated by recent geophysical and geochemical observations that suggest a convective pattern to near-seafloor pore fluid flow in the northern Gulf of Mexico (GoMex), we devise numerical models that fully couple thermal and chemical processes to quantify the effects of salt geometry and seafloor relief on fluid flow beneath the seafloor. Steady-state models that ignore halite dissolution demonstrate that seafloor relief plays an important role in the evolution of shallow geothermal convection cells and that salt at depth can contribute a thermal component to this convection. The inclusion of faults causes significant, but highly localized, increases in flow rates at seafloor discharge zones. Transient models that include halite dissolution show the evolution of flow during brine formation from early salt-driven convection to later geothermal convection, characteristics of which are controlled by the interplay of seafloor relief and salt geometry. Predicted flow rates are on the order of a few millimeters per year or less for homogeneous sediments with a permeability of 10−15 m2, comparable to compaction-driven flow rates. Sediment permeabilities likely fall below 10−15 m2 at depth in the GoMex basin, but such thermohaline convection can drive pervasive mass transport across the seafloor, affecting sediment diagenesis in shallow sediments. In more permeable settings, such flow could affect methane hydrate stability, seafloor chemosynthetic communities, and the longevity of fluid seeps.
Particle hopping vs. fluid-dynamical models for traffic flow
Nagel, K.
1995-12-31
Although particle hopping models have been introduced into traffic science in the 19509, their systematic use has only started recently. Two reasons for this are, that they are advantageous on modem computers, and that recent theoretical developments allow analytical understanding of their properties and therefore more confidence for their use. In principle, particle hopping models fit between microscopic models for driving and fluiddynamical models for traffic flow. In this sense, they also help closing the conceptual gap between these two. This paper shows connections between particle hopping models and traffic flow theory. It shows that the hydrodynamical limits of certain particle hopping models correspond to the Lighthill-Whitham theory for traffic flow, and that only slightly more complex particle hopping models produce already the correct traffic jam dynamics, consistent with recent fluid-dynamical models for traffic flow. By doing so, this paper establishes that, on the macroscopic level, particle hopping models are at least as good as fluid-dynamical models. Yet, particle hopping models have at least two advantages over fluid-dynamical models: they straightforwardly allow microscopic simulations, and they include stochasticity.
Multi-fluid plasma modeling with Braginskii collisional transport processes
NASA Astrophysics Data System (ADS)
Ho, A.; Shumlak, U.; Miller, S. T.
2015-11-01
Magnetohydrodynamics (MHD) works well where transport processes are primarily advective. Extensions of the MHD model are capable of capturing some collisional phenomena such as electrical resistivity, which are important in systems with mean free paths less than the characteristic length. However, MHD models have difficulties resolving systems where the Debye length cannot be assumed to approach zero. These systems arise in low density, hot plasmas. By modeling the ions and electrons as distinct fluids, the 5-moment multi-fluid plasma model is able to capture these short-range transport processes that are not accounted for in MHD. To model the transport processes the Braginskii transport terms are added to the 5-moment model, which introduces viscosity, heat conduction, and binary species interactions. These transport properties are affected by strong magnetic fields, resulting in anisotropic collisional effects. The multi-fluid equations are evolved explicitly and are coupled with Maxwell's equations. This research extends the University of Washington's WARPXM code to include the Braginskii terms with the 5-moment multi-fluid plasma model. The implementation is validated against theoretical results from a Hartmann flow benchmark problem. This work is supported by a grant from the United States Air Force Office of Scientific Research.
Coupled Hydro-Mechanical Modeling of Fluid Geological Storage
NASA Astrophysics Data System (ADS)
Castelletto, N.; Garipov, T.; Tchelepi, H. A.
2013-12-01
The accurate modeling of the complex coupled physical processes occurring during the injection and the post-injection period is a key factor for assessing the safety and the feasibility of anthropogenic carbon dioxide (CO2) sequestration in subsurface formations. In recent years, it has become widely accepted the importance of the coupling between fluid flow and geomechanical response in constraining the sustainable pressure buildup caused by fluid injection relative to the caprock sealing capacity, induced seismicity effects and ground surface stability [e.g., Rutqvist, 2012; Castelletto et al., 2013]. Here, we present a modeling approach based on a suitable combination of Finite Volumes (FVs) and Finite Elements (FEs) to solve the coupled system of partial differential equations governing the multiphase flow in a deformable porous medium. Specifically, a FV method is used for the flow problem while the FE method is adopted to address the poro-elasto-plasticity equations. The aim of the present work is to compare the performance and the robustness of unconditionally stable sequential-implicit schemes [Kim et al., 2011] and the fully-implicit method in solving the algebraic systems arising from the discretization of the governing equations, for both normally conditioned and severely ill-conditioned problems. The two approaches are tested against well-known analytical solutions and experimented with in a realistic application of CO2 injection in a synthetic aquifer. References: - Castelletto N., G. Gambolati, and P. Teatini (2013), Geological CO2 sequestration in multi-compartment reservoirs: Geomechanical challenges, J. Geophys. Res. Solid Earth, 118, 2417-2428, doi:10.1002/jgrb.50180. - Kim J., H. A. Tchelepi, and R. Juanes (2011), Stability, accuracy and efficiency of sequential methods for coupled flow and geomechanics, SPE J., 16(2), 249-262. - Rutqvist J. (2012), The geomechanics of CO2 storage in deep sedimentary formations, Geotech. Geol. Eng., 30, 525-551.
Computational Fluid Dynamics Model for Saltstone Vault 4 Vapor Sapce
Lee, Si Young
2005-06-27
Computational fluid dynamics (CFD) methods have been used to estimate the flow patterns for vapor space inside the Saltstone Vault No.4 under different operating scenarios. The purpose of this work is to examine the gas motions inside the vapor space under the current vault configurations. A CFD model took three-dimensional transient momentum-energy coupled approach for the vapor space domain of the vault. The modeling calculations were based on prototypic vault geometry and expected normal operating conditions as defined by Waste Solidification Engineering. The modeling analysis was focused on the air flow patterns near the ventilated corner zones of the vapor space inside the Saltstone vault. The turbulence behavior and natural convection mechanism used in the present model were benchmarked against the literature information and theoretical results. The verified model was applied to the Saltstone vault geometry for the transient assessment of the air flow patterns inside the vapor space of the vault region using the boundary conditions as provided by the customer. The present model considered two cases for the estimations of the flow patterns within the vapor space. One is the reference baseline case. The other is for the negative temperature gradient between the roof inner and top grout surface temperatures intended for the potential bounding condition. The flow patterns of the vapor space calculated by the CFD model demonstrate that the ambient air comes into the vapor space of the vault through the lower-end ventilation hole, and it gets heated up by the Benard-cell type circulation before leaving the vault via the higher-end ventilation hole. The calculated results are consistent with the literature information.
Direct pore-level modeling of incompressible fluid flow in porous media
Ovaysi, Saeed; Piri, Mohammad
2010-09-20
We present a dynamic particle-based model for direct pore-level modeling of incompressible viscous fluid flow in disordered porous media. The model is capable of simulating flow directly in three-dimensional high-resolution micro-CT images of rock samples. It is based on moving particle semi-implicit (MPS) method. We modify this technique in order to improve its stability for flow in porous media problems. Using the micro-CT image of a rock sample, the entire medium, i.e., solid and fluid, is discretized into particles. The incompressible Navier-Stokes equations are then solved for each particle using the MPS summations. The model handles highly irregular fluid-solid boundaries effectively. An algorithm to split and merge fluid particles is also introduced. To handle the computational load, we present a parallel version of the model that runs on distributed memory computer clusters. The accuracy of the model is validated against the analytical, numerical, and experimental data available in the literature. The validated model is then used to simulate both unsteady- and steady-state flow of an incompressible fluid directly in a representative elementary volume (REV) size micro-CT image of a naturally-occurring sandstone with 3.398 {mu}m resolution. We analyze the quality and consistency of the predicted flow behavior and calculate absolute permeability using the steady-state flow rate.
[Exposure to vegetal esters based metal cutting fluids: health effects].
Riva, M M; Bellini, M; Leghissa, P; Gambini, D; Mosconi, G
2012-01-01
The aim of our research is to study respiratory and dermatologic diseases (irritative and allergic) in a cohort of workers exposed to vegetal esters based metal cutting fluids of the latest generation. A cohort of 81 workers (mean age 34.5 years, seniority 17.4 years), with mean exposure to vegetal esters based metal cutting fluids of 2.8 years, has been subjected to clinical evaluations. The investigation did not reveal any disease or disorder of the respiratory system, any folluculitis or any allergic contact dermatitis caused by sensitization to vegetal esters based metal cutting fluids. On the contrary we documented 5 cases of irritant contact dermatitis, even if favored by an improper use of protection devices. According to early results, the introduction of vegetal esters based metal cutting fluids seems to reduce the risk to the worker's health. A longitudinal surveillance is still needed to confirm that even in the medium and long-term sensitizations will not occur. PMID:23405602
Good modelling practice in applying computational fluid dynamics for WWTP modelling.
Wicklein, Edward; Batstone, Damien J; Ducoste, Joel; Laurent, Julien; Griborio, Alonso; Wicks, Jim; Saunders, Stephen; Samstag, Randal; Potier, Olivier; Nopens, Ingmar
2016-01-01
Computational fluid dynamics (CFD) modelling in the wastewater treatment (WWT) field is continuing to grow and be used to solve increasingly complex problems. However, the future of CFD models and their value to the wastewater field are a function of their proper application and knowledge of their limits. As has been established for other types of wastewater modelling (i.e. biokinetic models), it is timely to define a good modelling practice (GMP) for wastewater CFD applications. An International Water Association (IWA) working group has been formed to investigate a variety of issues and challenges related to CFD modelling in water and WWT. This paper summarizes the recommendations for GMP of the IWA working group on CFD. The paper provides an overview of GMP and, though it is written for the wastewater application, is based on general CFD procedures. A forthcoming companion paper to provide specific details on modelling of individual wastewater components forms the next step of the working group. PMID:26942517
Quantum free-electron laser: A fluid model
NASA Astrophysics Data System (ADS)
Monteiro, L. F.; Serbeto, A.; Tsui, K. H.
2012-02-01
Free-Electron Lasers (FELs) are today a very important area of research. Such devices can generate short pulses of high-power coherent radiation in wavelengths that are unreachable to conventional molecular lasers, such as X-Rays, and are based on the radiation emitted by a relativistic electron beam that performs a waving movement induced by an alternating electromagnetic field. They can be described by classical or quantum models. Classical models are simpler than the last, but they are valid only if the one-photon momentum recoil is not greater than the beam momentum spread, where the FEL operates in a new Quantum regime, and quantum models should be used. It is the case for high-energy fotons and low-energy electron beams. In this work we present a hydrodynamical model which incorporates quantum effects. Starting from Poisson equation and a Schrödinger-like equation deduced from the total relativistic energy of the electron under the action of a ponderomotive potential V associated with the combined wiggle and radiation fields, we obtain, by performing a Madelung transformation to the electron wave function, a set of fluid equations (continuity and momentum) to the beam dynamics, where a Bohm potential accumulates the quantum information. By coupling the wave equation, under the SVEA hypothesis, we get a set of nonlinear PDE system which describes the quantum-FEL as a three-wave interaction phenomena, where the amplified radiation is seen as Compton or Raman backscattered radiation. Our model is simpler than previous quantum models, and can be used in laser amplification theory as well.
A fluid model for Helicobacter pylori
NASA Astrophysics Data System (ADS)
Reigh, Shang-Yik; Lauga, Eric
2015-11-01
Swimming microorganisms and self-propelled nanomotors are often found in confined environments. The bacterium Helicobacter pylori survives in the acidic environment of the human stomach and is able to penetrate gel-like mucus layers and cause infections by locally changing the rheological properties of the mucus from gel-like to solution-like. In this talk we propose an analytical model for the locomotion of Helicobacter pylori as a confined spherical squirmer which generates its own confinement. We solve analytically the flow field around the swimmer, and derive the swimming speed and energetics. The role of the boundary condition in the outer wall is discussed. An extension of our model is also proposed for other biological and chemical swimmers. Newton Trust.
Fluid mechanics in stented arterial model
NASA Astrophysics Data System (ADS)
Bernad, S. I.; Totorean, A.; Bosioc, A.; Crainic, N.; Hudrea, C.; Bernad, E. S.
2015-12-01
Local hemodynamic factors are known affect the natural history of the restenosis critically after coronary stenting of atherosclerosis. Stent-induced flows disturbance magnitude dependent directly on the strut design. Strut shape, strut thickness and the distance between consecutive struts have been associated clinically with the with post-intervention clinical outcomes. Hemodynamically favorable designs according to computational modeling can reduced in-stent restenosis after coronary stenting intervention.
Thermodynamic micellization model of asphaltene precipitation from petroleum fluids
Victorov, A.I.; Firoozabadi, A.
1996-06-01
A thermodynamic micellization model is proposed for the description of asphaltene precipitation from petroleum fluids. It describes the solubilization of asphaltene polar species by resin bipolar molecules in the micelles. A simple form of the standard Gibbs free energy of micellization is used. The petroleum fluid is assumed to be a dilute solution with respect to the monomeric asphaltenes, resins, and micelles. The Peng-Robinson equation of state (PR-EOS) is applied to describe the fugacity of monomeric asphaltene in the bulk of the petroleum fluid. Intermicellar interactions as well as osmotic pressure effects are neglected. The proposed model shows promising results to describe asphaltene deposition from crude mixtures. It predicts the change in precipitation power of different alkane precipitants and the effect of pressure on asphaltene precipitation. The amount and the onset of predicted asphaltene precipitation are sensitive to the amount of resins in the crude. All these results are in line with laboratory observations and oil-field data.
Modeling of fluid and heat flow in fractured geothermal reservoirs
Pruess, K.
1988-08-01
In most geothermal reservoirs large-scale permeability is dominated by fractures, while most of the heat and fluid reserves are stored in the rock matrix. Early-time fluid production comes mostly from the readily accessible fracture volume, while reservoir behavior at later time depends upon the ease with which fluid and heat can be transferred from the rock matrix to the fractures. Methods for modeling flow in fractured porous media must be able to deal with this matrix-fracture exchange, the so-called interporosity flow. This paper reviews recent work at Lawrence Berkeley Laboratory on numerical modeling of nonisothermal multiphase flow in fractured porous media. We also give a brief summary of simulation applications to problems in geothermal production and reinjection. 29 refs., 1 fig.
NASA Astrophysics Data System (ADS)
Azma, Sahra; Rezazadeh, Ghader; Shabani, Rasoul; Alizadeh-Haghighi, Elnaz
2016-06-01
Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In micro-resonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated.
NASA Astrophysics Data System (ADS)
Azma, Sahra; Rezazadeh, Ghader; Shabani, Rasoul; Alizadeh-Haghighi, Elnaz
2016-02-01
Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In micro-resonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated.
A vorticity based approach to handle the fluid-structure interaction problems
NASA Astrophysics Data System (ADS)
Farahbakhsh, Iman; Ghassemi, Hassan; Sabetghadam, Fereidoun
2016-02-01
A vorticity based approach for the numerical solution of the fluid-structure interaction problems is introduced in which the fluid and structure(s) can be viewed as a continuum. Retrieving the vorticity field and recalculating a solenoidal velocity field, specially at the fluid-structure interface, are the kernel of the proposed algorithm. In the suggested method, a variety of constitutive equations as a function of left Cauchy-Green deformation tensor can be applied for modeling the structure domain. A nonlinear Mooney-Rivlin and Saint Venant-Kirchhoff model are expressed in terms of the left Cauchy-Green deformation tensor and the presented method is able to model the behavior of a visco-hyperelastic structure in the incompressible flow. Some numerical experiments, with considering the neo-Hookean model for structure domain, are executed and the results are validated via the available results from literature.
[Determination of body fluid based on analysis of nucleic acids].
Korabečná, Marie
2015-01-01
Recent methodological approaches of molecular genetics allow isolation of nucleic acids (DNA and RNA) from negligible forensic samples. Analysis of these molecules may be used not only for individual identification based on DNA profiling but also for the detection of origin of the body fluid which (alone or in mixture with other body fluids) forms the examined biological trace. Such an examination can contribute to the evaluation of procedural, technical and tactical value of the trace. Molecular genetic approaches discussed in the review offer new possibilities in comparison with traditional spectrum of chemical, immunological and spectroscopic tests especially with regard to the interpretation of mixtures of biological fluids and to the confirmatory character of the tests. Approaches based on reverse transcription of tissue specific mRNA and their subsequent polymerase chain reaction (PCR) and fragmentation analysis are applicable on samples containing minimal amounts of biological material. Methods for body fluid discrimination based on examination of microRNA in samples provided so far confusing results therefore further development in this field is needed. The examination of tissue specific methylation of nucleotides in selected gene sequences seems to represent a promising enrichment of the methodological spectrum. The detection of DNA sequences of tissue related bacteria has been established and it provides satisfactory results mainly in combination with above mentioned methodological approaches. PMID:26419517
A new approach for fluid dynamics simulation: The Short-lived Water Cuboid Particle model
NASA Astrophysics Data System (ADS)
Qiao, Changjian; Li, Jiansong; Tian, Zongshun
2016-09-01
There are many researches to simulate the fluid which adopt the traditional particle-based approach and the grid-based approach. However, it needs massive storage in the traditional particle-based approach and it is very complicated to design the grid-based approach with the Navier-Stokes Equations or the Shallow Water Equations (SWEs) because of the difficulty of solving equations. This paper presents a new model called the Short-lived Water Cuboid Particle model. It updates the fluid properties (mass and momentum) recorded in the fixed Cartesian grids by computing the weighted sum of the water cuboid particles with a time step life. Thus it is a two-type-based approach essentially, which not only owns efficient computation and manageable memory like the grid-based approach, but also deals with the discontinuous water surface (wet/dry fronts, boundary conditions, etc.) with high accuracy as well as the particle-based approach. The proposed model has been found capable to simulate the fluid excellently for three laboratory experimental cases and for the field case study of the Malpasset dam-break event occurred in France in 1959. The obtained results show that the model is proved to be an alternative approach to simulate the fluid dynamics with a fair accuracy.
Particle-based simulation of hydraulic fracture and fluid/heat flow in geothermal reservoirs
NASA Astrophysics Data System (ADS)
Mora, Peter; Wang, Yucang; Alonso-Marroquin, Fernando
2013-06-01
Realizing the potential of geothermal energy as a cheap, green, sustainable resource to provide for the planet's future energy demands that a key geophysical problem be solved first: how to develop and maintain a network of multiple fluid flow pathways for the time required to deplete the heat within a given region. We present the key components for micro-scale particle-based numerical modeling of hydraulic fracture, and fluid and heat flow in geothermal reservoirs. They are based on the latest developments of ESyS-Particle - the coupling of the Lattice Solid Model (LSM) to simulate the nonlinear dynamics of complex solids with the Lattice Boltzmann Method (LBM) applied to the nonlinear dynamics of coupled fluid and heat flow in the complex solid-fluid system. The coupled LSM/LBM can be used to simulate development of fracture systems in discontinuous media, elastic stress release, fluid injection and the consequent slip at joint surfaces, and hydraulic fracturing; heat exchange between hot rocks and water within flow pathways created through hydraulic fracturing; and fluid flow through complex, narrow, compact and gouge-or powder-filled fracture and joint systems. We demonstrate the coupled LSM/LBM to simulate the fundamental processes listed above, which are all components for the generation and sustainability of the hot-fractured rock geothermal energy fracture systems required to exploit this new green-energy resource.
NASA Astrophysics Data System (ADS)
Liu, Yu-Liang; Zhu, Jie; Luo, Xiao-Shu
2009-09-01
Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified.
Inhomogeneous generalizations of Bianchi type VIh models with perfect fluid
NASA Astrophysics Data System (ADS)
Roy, S. R.; Prasad, A.
1991-07-01
Inhomogeneous universes admitting an Abelian G2 of isometry and filled with perfect fluid have been derived. These contain as special cases exact homogeneous universes of Bianchi type VIh. Many of these universes asymptotically tend to homogeneous Bianchi VIh universes. The models have been discussed for their physical and kinematical behaviors.
ASTP fluid transfer measurement experiment. [using breadboard model
NASA Technical Reports Server (NTRS)
Fogal, G. L.
1974-01-01
The ASTP fluid transfer measurement experiment flight system design concept was verified by the demonstration and test of a breadboard model. In addition to the breadboard effort, a conceptual design of the corresponding flight system was generated and a full scale mockup fabricated. A preliminary CEI specification for the flight system was also prepared.
OpenFLUID: an open-source software environment for modelling fluxes in landscapes
NASA Astrophysics Data System (ADS)
Fabre, Jean-Christophe; Rabotin, Michaël; Crevoisier, David; Libres, Aline; Dagès, Cécile; Moussa, Roger; Lagacherie, Philippe; Raclot, Damien; Voltz, Marc
2013-04-01
Integrative landscape functioning has become a common concept in environmental management. Landscapes are complex systems where many processes interact in time and space. In agro-ecosystems, these processes are mainly physical processes, including hydrological-processes, biological processes and human activities. Modelling such systems requires an interdisciplinary approach, coupling models coming from different disciplines, developed by different teams. In order to support collaborative works, involving many models coupled in time and space for integrative simulations, an open software modelling platform is a relevant answer. OpenFLUID is an open source software platform for modelling landscape functioning, mainly focused on spatial fluxes. It provides an advanced object-oriented architecture allowing to i) couple models developed de novo or from existing source code, and which are dynamically plugged to the platform, ii) represent landscapes as hierarchical graphs, taking into account multi-scale, spatial heterogeneities and landscape objects connectivity, iii) run and explore simulations in many ways : using the OpenFLUID software interfaces for users (command line interface, graphical user interface), or using external applications such as GNU R through the provided ROpenFLUID package. OpenFLUID is developed in C++ and relies on open source libraries only (Boost, libXML2, GLib/GTK, OGR/GDAL, …). For modelers and developers, OpenFLUID provides a dedicated environment for model development, which is based on an open source toolchain, including the Eclipse editor, the GCC compiler and the CMake build system. OpenFLUID is distributed under the GPLv3 open source license, with a special exception allowing to plug existing models licensed under any license. It is clearly in the spirit of sharing knowledge and favouring collaboration in a community of modelers. OpenFLUID has been involved in many research applications, such as modelling of hydrological network
A gravitational test of wave reinforcement versus fluid density models
NASA Technical Reports Server (NTRS)
Johnson, Jacqueline Umstead
1990-01-01
Spermatozoa, protozoa, and algae form macroscopic patterns somewhat analogous to thermally driven convection cells. These bioconvective patterns have attracted interest in the fluid dynamics community, but whether in all cases these waves were gravity driven was unknown. There are two conflicting theories, one gravity dependent (fluid density model), the other gravity independent (wave reinforcement theory). The primary objectives of the summer faculty fellows were to: (1) assist in sample collection (spermatozoa) and preparation for the KC-135 research airplane experiment; and (2) to collaborate on ground testing of bioconvective variables such as motility, concentration, morphology, etc., in relation to their macroscopic patterns. Results are very briefly given.
A model of attractive interactions to account for fluid-fluid phase separation of protein solutions
NASA Astrophysics Data System (ADS)
Malfois, Marc; Bonneté, Françoise; Belloni, Luc; Tardieu, Annette
1996-08-01
Concentrated γ-crystallin and lysozyme solutions have been reported to undergo a fluid-fluid phase separation when cooled below a critical temperature. This behavior is under control of the weak forces acting in solution between macromolecules. We have used small angle x-ray scattering at the synchrotron radiation facility LURE (Orsay, France) to analyze the interaction potentials. A model of attractive interactions which depends upon three parameters, protein diameter, potential depth, and range, is able to account for both the x-ray structure factors measured at high temperature and for the low temperature phase separation. Although van der Waals forces could be at the origin of the attractive interaction potentials, other more specific effects also contribute to the protein phase diagrams.
NASA Astrophysics Data System (ADS)
Biyanto, Totok R.
2016-06-01
Fouling in a heat exchanger in Crude Preheat Train (CPT) refinery is an unsolved problem that reduces the plant efficiency, increases fuel consumption and CO2 emission. The fouling resistance behavior is very complex. It is difficult to develop a model using first principle equation to predict the fouling resistance due to different operating conditions and different crude blends. In this paper, Artificial Neural Networks (ANN) MultiLayer Perceptron (MLP) with input structure using Nonlinear Auto-Regressive with eXogenous (NARX) is utilized to build the fouling resistance model in shell and tube heat exchanger (STHX). The input data of the model are flow rates and temperatures of the streams of the heat exchanger, physical properties of product and crude blend data. This model serves as a predicting tool to optimize operating conditions and preventive maintenance of STHX. The results show that the model can capture the complexity of fouling characteristics in heat exchanger due to thermodynamic conditions and variations in crude oil properties (blends). It was found that the Root Mean Square Error (RMSE) are suitable to capture the nonlinearity and complexity of the STHX fouling resistance during phases of training and validation.
A fluid mechanical model for current-generating-feeding jellyfish
NASA Astrophysics Data System (ADS)
Peng, Jifeng; Dabiri, John
2008-11-01
Many jellyfish species, e.g. moon jellyfish Aurelia aurita, use body motion to generate fluid currents which carry their prey to the vicinity of their capture appendages. In this study, a model was developed to understand the fluid mechanics for this current-generating-feeding mode of jellyfish. The flow generated by free-swimming Aurelia aurita was measured using digital particle image velocimetry. The dynamics of prey (e.g., brine shrimp Artemia) in the flow field were described by a modified Maxey-Riley equation which takes into consideration the inertia of prey and the escape forces, which prey exert in the presence of predator. A Lagrangian analysis was used to identify the region of the flow in which prey can be captured by the jellyfish and the clearance rate was quantified. The study provides a new methodology to study biological current-generating-feeding and the transport and mixing of particles in fluid flow in general.
NASA Astrophysics Data System (ADS)
Shervais, John W.; Jean, Marlon M.
2012-10-01
Enrichment of the mantle wedge above subduction zones with fluid mobile elements is thought to represent a fundamental process in the origin of arc magmas. This "subduction factory" is typically modeled as a mass balance of inputs (from the subducted slab) and outputs (arc volcanics). We present here a new method to model fluid mobile elements, based on the composition of peridotites associated with supra-subduction ophiolites, which form by melt extraction and fluid enrichment in the mantle wedge above nascent subduction zones. The Coast Range ophiolite (CRO), California, is a Jurassic supra-subduction zone ophiolite that preserves mantle lithologies formed in response to hydrous melting. We use high-precision laser ablation ICP-MS analyses of relic pyroxenes from these peridotites to document fluid-mobile element (FME) concentrations, along with a suite of non-fluid mobile elements that includes rare earth and high-field strength elements. In the CRO, fluid-mobile elements are enriched by factors of up to 100× DMM, whereas fluid immobile elements are progressively depleted by melt extraction. The high concentrations of fluid mobile elements in supra-subduction peridotite pyroxene can be attributed to a flux of aqueous fluid or fluid-rich melt phase derived from the subducting slab. To model this enrichment, we derive a new algorithm that calculates the concentration of fluid mobile elements added to the source: C=[C/[[D/(D-PF)]∗[1-(PF/D)
Fluid coupling in a discrete model of cochlear mechanics.
Elliott, Stephen J; Lineton, Ben; Ni, Guangjian
2011-09-01
A discrete model of cochlear mechanics is introduced that includes a full, three-dimensional, description of fluid coupling. This formulation allows the fluid coupling and basilar membrane dynamics to be analyzed separately and then coupled together with a simple piece of linear algebra. The fluid coupling is initially analyzed using a wavenumber formulation and is separated into one component due to one-dimensional fluid coupling and one comprising all the other contributions. Using the theory of acoustic waves in a duct, however, these two components of the pressure can also be associated with a far field, due to the plane wave, and a near field, due to the evanescent, higher order, modes. The near field components are then seen as one of a number of sources of additional longitudinal coupling in the cochlea. The effects of non-uniformity and asymmetry in the fluid chamber areas can also be taken into account, to predict both the pressure difference between the chambers and the mean pressure. This allows the calculation, for example, of the effect of a short cochlear implant on the coupled response of the cochlea. PMID:21895085
NASA Astrophysics Data System (ADS)
Inderbitzen, K. E.; Wheat, C. G.; Baker, P. A.; Fisher, A. T.
2014-12-01
Currently, fluid circulation patterns and the evolution of rock/fluid compositions as circulation occurs in subseafloor hydrothermal systems are poorly constrained. Sedimented spreading centers provide a unique opportunity to study subsurface flow because sediment acts as an insulating blanket that traps heat from the cooling magma body and limits: (a) potential flow paths for seawater to recharge the aquifer in permeable upper basaltic basement and (b) points of altered fluid egress. This also allows for a range of thermal and geochemical gradients to exist near the sediment-water interface. Models of fluid circulation patterns in this type of hydrologic setting have been generated (eg. Stein and Fisher, 2001); however fluid chemistry datasets have not previously been used to test the model's viability. We address this issue by integrating the existing circulation model with fluid compositional data collected from sediment pore waters and high temperature hydrothermal vents located in Middle Valley on the Juan de Fuca Ridge. Middle Valley hosts a variety of hydrologic regimes: including areas of fluid recharge (Site 855), active venting (Site 858/1036; Dead Dog vent field), recent venting (Site 856/1035; Bent Hill Massive Sulfide deposit) and a section of heavily sedimented basement located between recharge and discharge sites (Site 857). We will present new results based on thermal and geochemical data from the area of active venting (Sites 858 and 1036), that was collected during Ocean Drilling Program Legs 139 and 169 and a subsequent heat flow/gravity coring effort. These results illuminate fine scale controls on secondary recharge and fluid flow within the sediment section at Site 858/1036. The current status of high temperature vents in this area (based on observations made in July, 2014) will also be outlined.
Meakin, Paul; Tartakovsky, Alexandre M.
2009-07-14
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
Paul Meakin; Alexandre Tartakovsky
2009-07-01
In the subsurface fluids play a critical role by transporting dissolved minerals, colloids and contaminants (sometimes over long distances), by mediating dissolution and precipitation processes and enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone, water/oil, water/gas, gas/oil and water/oil/gas in oil reservoirs, water/air/non-aqueous phase liquids (NAPL) in contaminated vadose zone systems and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines, and its impact on dynamic contact angles, must also be taken into account, and coupled with the fluid flow. Pore network models and simple statistical physics based models such as the invasion percolation and diffusion-limited aggregation models have been used quite extensively. However, these models for multiphase fluid flow are based on simplified models for pore space geometries and simplified physics. Other methods such a lattice Boltzmann and lattice gas models, molecular dynamics, Monte Carlo methods, and particle methods such as dissipative particle dynamics and smoothed particle hydrodynamics are based more firmly on first principles, and they do not require simplified pore and/or fracture geometries. However, they are less (in some cases very much less) computationally efficient that pore network and statistical physics models. Recently a combination of continuum computation fluid dynamics, fluid-fluid interface tracking or capturing and simple models for the dependence of contact angles on fluid velocity
Unifying binary fluid diffuse-interface models in the sharp-interface limit
NASA Astrophysics Data System (ADS)
Sibley, David; Nold, Andreas; Kalliadasis, Serafim
2013-11-01
Flows involving free boundaries occur widely in both nature and technological applications, existing at liquid-gas interfaces (e.g. between liquid water and water vapour) or between different immiscible fluids (e.g. oil and water, and termed a binary fluid). To understand the asymptotic behaviour near a contact line, a liquid-gas diffuse-interface model has been investigated recently. In contrast, here we investigate the behaviour between two ostensibly immiscible fluids, a binary fluid, using related models where the interface has a thin but finite thickness. Quantities such as the mass fraction of the two fluid components are modelled as varying smoothly but rapidly in the interfacial region. There has been a wide variety of models used for this situation, based on Cahn-Hilliard or Allen-Cahn theories coupled to hydrodynamic equations, and we consider the effect of these differences using matched asymptotic methods in the important sharp-interface limit, where the interface thickness goes to zero. Our aim is to understand which models represent better the classical hydrodynamic model and associated free-surface boundary conditions.
Freezable Radiator Model Correlation Improvements and Fluids Study
NASA Technical Reports Server (NTRS)
Lillibridge, Sean; Navarro, Moses
2011-01-01
Freezable radiators offer an attractive solution to the issue of thermal control system scalability. As thermal environments change, a freezable radiator will effectively scale the total heat rejection it is capable of as a function of the thermal environment and flow rate through the radiator. Scalable thermal control systems are a critical technology for spacecraft that will endure missions with widely varying thermal requirements. These changing requirements are a result of the space craft s surroundings and because of different thermal rejection requirements during different mission phases. However, freezing and thawing (recovering) a radiator is a process that has historically proven very difficult to predict through modeling, resulting in highly inaccurate predictions of recovery time. To attempt to improve this, tests were conducted in 2009 to determine whether the behavior of a simple stagnating radiator could be predicted or emulated in a Thermal Desktop(trademark) numerical model. A 50-50 mixture of DowFrost HD and water was used as the working fluid. Efforts to scale this model to a full scale design, as well as efforts to characterize various thermal control fluids at low temperatures are also discussed. Previous testing and modeling efforts showed that freezable radiators could be operated as intended, and be fairly, if not perfectly predicted by numerical models. This paper documents the improvements made to the numerical model, and outcomes of fluid studies that were determined necessary to go forward with further radiator testing.
Fluids and Combustion Facility: Combustion Integrated Rack Modal Model Correlation
NASA Technical Reports Server (NTRS)
McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.
2005-01-01
The Fluids and Combustion Facility (FCF) is a modular, multi-user, two-rack facility dedicated to combustion and fluids science in the US Laboratory Destiny on the International Space Station. FCF is a permanent facility that is capable of accommodating up to ten combustion and fluid science investigations per year. FCF research in combustion and fluid science supports NASA's Exploration of Space Initiative for on-orbit fire suppression, fire safety, and space system fluids management. The Combustion Integrated Rack (CIR) is one of two racks in the FCF. The CIR major structural elements include the International Standard Payload Rack (ISPR), Experiment Assembly (optics bench and combustion chamber), Air Thermal Control Unit (ATCU), Rack Door, and Lower Structure Assembly (Input/Output Processor and Electrical Power Control Unit). The load path through the rack structure is outlined. The CIR modal survey was conducted to validate the load path predicted by the CIR finite element model (FEM). The modal survey is done by experimentally measuring the CIR frequencies and mode shapes. The CIR model was test correlated by updating the model to represent the test mode shapes. The correlated CIR model delivery is required by NASA JSC at Launch-10.5 months. The test correlated CIR flight FEM is analytically integrated into the Shuttle for a coupled loads analysis of the launch configuration. The analysis frequency range of interest is 0-50 Hz. A coupled loads analysis is the analytical integration of the Shuttle with its cargo element, the Mini Payload Logistics Module (MPLM), in the Shuttle cargo bay. For each Shuttle launch configuration, a verification coupled loads analysis is performed to determine the loads in the cargo bay as part of the structural certification process.
Agent-Based Chemical Plume Tracing Using Fluid Dynamics
NASA Technical Reports Server (NTRS)
Zarzhitsky, Dimitri; Spears, Diana; Thayer, David; Spears, William
2004-01-01
This paper presents a rigorous evaluation of a novel, distributed chemical plume tracing algorithm. The algorithm is a combination of the best aspects of the two most popular predecessors for this task. Furthermore, it is based on solid, formal principles from the field of fluid mechanics. The algorithm is applied by a network of mobile sensing agents (e.g., robots or micro-air vehicles) that sense the ambient fluid velocity and chemical concentration, and calculate derivatives. The algorithm drives the robotic network to the source of the toxic plume, where measures can be taken to disable the source emitter. This work is part of a much larger effort in research and development of a physics-based approach to developing networks of mobile sensing agents for monitoring, tracking, reporting and responding to hazardous conditions.
Light-responsive viscoelastic fluids based on anionic wormlike micelles.
Lu, Yechang; Zhou, Tengfei; Fan, Qing; Dong, Jinfeng; Li, Xuefeng
2013-12-15
A new class of light-responsive viscoelastic fluids based on anionic wormlike micelles is reported. The key components are sodium oleate (NaOA) and a cationic azobenzene dye, 1-[2-(4-phenylazo-phenoxy)-ethyl]-3-methylimidazolium bromide (C0AZOC2IMB). These binary systems are gel-like fluids at certain concentration ratios of [C0AZOC2IMB]/[NaOA], e.g. 35/100, owing to the formation of long, entangled wormlike micelles. The viscosity of these fluids can be controlled reversibly by light due to photo isomerization between trans-C0AZOC2IMB and cis-C0AZOC2IMB. For example, the zero-shear viscosity (η0) of an originally gel-like sample is high up to ~1300 Pa s when C0AZOC2IMB is in its trans from, whereas the mixture becomes a Newtonian fluid with η0 about 0.01 Pa s after UV light irradiation. For the post-irradiated cis-C0AZOC2IMB, short cylindrical micelles form, hence accounting for the lower viscosity. Evidence for the structural transition is provided by UV-vis spectra, rheology, (1)H NMR and cryo-transmission electronic microscopy measurements. PMID:24144381
Ferromagnetic Fluid as a Model of Social Impact
NASA Astrophysics Data System (ADS)
Fronczak, Piotr; Fronczak, Agata; Hołyst, Janusz A.
The paper proposes a new model of spin dynamics which can be treated as a model of sociological coupling between individuals. Our approach takes into account two different human features: Gregariousness and individuality. We will show how they affect a psychological distance between individuals and how the distance changes the opinion formation in a social group. Apart from its sociological aplications the model displays the variety of other interesting phenomena like self-organizing ferromagnetic state or a second order phase transition and can be studied from different points of view, e.g., as a model of ferromagnetic fluid, complex evolving network or multiplicative random process.
A Landau fluid model for dissipative trapped electron modes
Hedrick, C.L.; Leboeuf, J.N.; Sidikman, K.L.
1995-09-01
A Landau fluid model for dissipative trapped electron modes is developed which focuses on an improved description of the ion dynamics. The model is simple enough to allow nonlinear calculations with many harmonics for the times necessary to reach saturation. The model is motivated by a discussion that starts with the gyro-kinetic equation and emphasizes the importance of simultaneously including particular features of magnetic drift resonance, shear, and Landau effects. To ensure that these features are simultaneously incorporated in a Landau fluid model with only two evolution equations, a new approach to determining the closure coefficients is employed. The effect of this technique is to reduce the matching of fluid and kinetic responses to a single variable, rather than two, and to allow focusing on essential features of the fluctuations in question, rather than features that are only important for other types of fluctuations. Radially resolved nonlinear calculations of this model, advanced in time to reach saturation, are presented to partially illustrate its intended use. These calculations have a large number of poloidal and toroidal harmonics to represent the nonlinear dynamics in a converged steady state which includes cascading of energy to both short and long wavelengths.
An Extended Equation of State Modeling Method I. Pure Fluids
NASA Astrophysics Data System (ADS)
Scalabrin, G.; Bettio, L.; Marchi, P.; Piazza, L.; Richon, D.
2006-09-01
A new technique is proposed here to represent the thermodynamic surface of a pure fluid in the fundamental Helmholtz energy form. The peculiarity of the present method is the extension of a generic equation of state for the target fluid, which is assumed as the basic equation, through the distortion of its independent variables by individual shape functions, which are represented by a neural network used as function approximator. The basic equation of state for the target fluid can have the simple functional form of a cubic equation, as, for instance, the Soave-Redlich-Kwong equation assumed in the present study. A set of nine fluids including hydrocarbons, haloalkane refrigerants, and strongly polar substances has been considered. For each of them the model has been regressed and then validated against volumetric and caloric properties generated in the vapor, liquid, and supercritical regions from highly accurate dedicated equations of state. In comparison with the underlying cubic equation of state, the prediction accuracy is improved by a factor between 10 and 100, depending on the property and on the region. It has been verified that about 100 density experimental points, together with from 10 to 20 coexistence data, are sufficient to guarantee high prediction accuracy for different thermodynamic properties. The method is a promising modeling technique for the heuristic development of multiparameter dedicated equations of state from experimental data.
Fluid-solid interaction model for hydraulic reciprocating O-ring seals
NASA Astrophysics Data System (ADS)
Liao, Chuanjun; Huang, Weifeng; Wang, Yuming; Suo, Shuangfu; Liu, Ying
2013-01-01
Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.
NASA Astrophysics Data System (ADS)
Wang, Ya; Masoumi, Masoud; Gaucher-Petitdemange, Matthias
2015-03-01
Passive structural damping treatments have been applied with the use of high-viscosity fillings (in practice) and have been the focus of numerous research studies and papers. However, internal viscoelastic fluid leading to passive damping of flexible cantilever beams, has not yet been investigated in the literature. Although structures containing internal fluid channels provide multifunctional solutions to many engineering issues, they also raise damping control requests caused by unacceptable vibrations due to ambient environmental changes. In this paper, we examine ambient effects on damping properties of flexible cantilever beams, each conveying an internal high-viscosity fluid channel. Experiments are conducted to investigate how the internal fluids provide damping to the system under varied temperatures, frequencies and base-acceleration levels. While the vibration analysis of pipes conveying internal flow has been extensively studied, internal high-viscosity fluids in relation to passive damping of flexible cantilever beams and their ambient, environment-dependent behaviors have not been well-investigated. Originally motivated by research, which uses internal fluid channels to provide the cooling of multifunctional composite structures, we aim to research the damping behaviors of cantilever beams. We will conduct an experimental study and modeling analysis, examining the vibrations and frequency responses of the cantilever beams when filled with three types of internal fluids.
NASA Astrophysics Data System (ADS)
Pfunt, Helena; Houben, Georg; Himmelsbach, Thomas
2016-04-01
Gas production from shale formations by hydraulic fracturing has raised concerns about the effects on the quality of fresh groundwater. The migration of injected fracking fluids towards the surface was investigated in the North German Basin, based on the known standard lithology. This included cases with natural preferential pathways such as permeable fault zones and fracture networks. Conservative assumptions were applied in the simulation of flow and mass transport triggered by a high pressure boundary of up to 50 MPa excess pressure. The results show no significant fluid migration for a case with undisturbed cap rocks and a maximum of 41 m vertical transport within a permeable fault zone during the pressurization. Open fractures, if present, strongly control the flow field and migration; here vertical transport of fracking fluids reaches up to 200 m during hydraulic fracturing simulation. Long-term transport of the injected water was simulated for 300 years. The fracking fluid rises vertically within the fault zone up to 485 m due to buoyancy. Progressively, it is transported horizontally into sandstone layers, following the natural groundwater flow direction. In the long-term, the injected fluids are diluted to minor concentrations. Despite the presence of permeable pathways, the injected fracking fluids in the reported model did not reach near-surface aquifers, either during the hydraulic fracturing or in the long term. Therefore, the probability of impacts on shallow groundwater by the rise of fracking fluids from a deep shale-gas formation through the geological underground to the surface is small.
Micro-poromechanics model of fluid-saturated chemically active fibrous media
Misra, Anil; Parthasarathy, Ranganathan; Singh, Viraj; Spencer, Paulette
2014-01-01
We have developed a micromechanics based model for chemically active saturated fibrous media that incorporates fiber network microstructure, chemical potential driven fluid flow, and micro-poromechanics. The stress-strain relationship of the dry fibrous media is first obtained by considering the fiber behavior. The constitutive relationships applicable to saturated media are then derived in the poromechanics framework using Hill’s volume averaging. The advantage of this approach is that the resultant continuum model accounts for the discrete nature of the individual fibers while retaining a form suitable for porous materials. As a result, the model is able to predict the influence of micro-scale phenomena, such as the fiber pre-strain caused by osmotic effects and evolution of fiber network structure with loading, on the overall behavior and in particular, on the poromechanics parameters. Additionally, the model can describe fluid-flow related rate-dependent behavior under confined and unconfined conditions and varying chemical environments. The significance of the approach is demonstrated by simulating unconfined drained monotonic uniaxial compression under different surrounding fluid bath molarity, and fluid-flow related creep and relaxation at different loading-levels and different surrounding fluid bath molarity. The model predictions conform to the experimental observations for saturated soft fibrous materials. The method can potentially be extended to other porous materials such as bone, clays, foams and concrete. PMID:25755301
Interstellar turbulence model : A self-consistent coupling of plasma and neutral fluids
Shaikh, Dastgeer; Zank, Gary P.; Pogorelov, Nikolai
2006-09-26
We present results of a preliminary investigation of interstellar turbulence based on a self-consistent two-dimensional fluid simulation model. Our model describes a partially ionized magnetofluid interstellar medium (ISM) that couples a neutral hydrogen fluid to a plasma through charge exchange interactions and assumes that the ISM turbulent correlation scales are much bigger than the shock characteristic length-scales, but smaller than the charge exchange mean free path length-scales. The shocks have no influence on the ISM turbulent fluctuations. We find that nonlinear interactions in coupled plasma-neutral ISM turbulence are influenced substantially by charge exchange processes.
A coupled fluid flow, deformation and heat transfer model for a twin roll caster
Bradbury, P.J.; Hunt, J.D.
1995-12-31
A numerical model of coupled fluid flow, solidification and plastic deformation for the twin roll casting process has been developed. Non-orthogonal curvilinear coordinates are used to provide a more realistic description of the roll bite geometry while a variable heat transfer coefficient based on the normal pressure at the strip/roll interface, is incorporated through the roll bite.
NASA Astrophysics Data System (ADS)
Heinze, Thomas; Galvan, Boris; Miller, Stephen
2013-04-01
Fluid-rock interactions are mechanically fundamental to many earth processes, including fault zones and hydrothermal/volcanic systems, and to future green energy solutions such as enhanced geothermal systems and carbon capture and storage (CCS). Modeling these processes is challenging because of the strong coupling between rock fracture evolution and the consequent large changes in the hydraulic properties of the system. In this talk, we present results of a numerical model that includes poro-elastic plastic rheology (with hardening, softening, and damage), and coupled to a non-linear diffusion model for fluid pressure propagation and two-phase fluid flow. Our plane strain model is based on the poro- elastic plastic behavior of porous rock and is advanced with hardening, softening and damage using the Mohr- Coulomb failure criteria. The effective stress model of Biot (1944) is used for coupling the pore pressure and the rock behavior. Frictional hardening and cohesion softening are introduced following Vermeer and de Borst (1984) with the angle of internal friction and the cohesion as functions of the principal strain rates. The scalar damage coefficient is assumed to be a linear function of the hardening parameter. Fluid injection is modeled as a two phase mixture of water and air using the Richards equation. The theoretical model is solved using finite differences on a staggered grid. The model is benchmarked with experiments on the laboratory scale in which fluid is injected from below in a critically-stressed, dry sandstone (Stanchits et al. 2011). We simulate three experiments, a) the failure a dry specimen due to biaxial compressive loading, b) the propagation a of low pressure fluid front induced from the bottom in a critically stressed specimen, and c) the failure of a critically stressed specimen due to a high pressure fluid intrusion. Comparison of model results with the fluid injection experiments shows that the model captures most of the experimental
NASA Astrophysics Data System (ADS)
Catania, Giuseppe; Sorrentino, Silvio
2015-01-01
The design of hydraulic transmission systems for control and actuation requires accurate knowledge of their dynamic response: some standard techniques are known to obtain a consistent dynamic model of a fluid line, including the contribution of inertia, compressibility and friction. In this paper an efficient procedure is developed for simulating the dynamic response of a fluid line in both the frequency and time domains, focusing the attention on the modal analysis of a discretized model, in view of coupling with mechanical systems. A bi-dimensional approach is adopted, and the laminar flow frequency-dependent friction is modeled using non-integer order differential laws, which may improve the accuracy of the simulated responses in comparison with more traditional Newtonian models.
Base fluid in improving heat transfer for EV car battery
NASA Astrophysics Data System (ADS)
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
Fluid-based radon mitigation technology development for industrial applications
Liu, K.V.; Gabor, J.D.; Holtz, R.E.; Gross, K.C.
1996-06-01
The objective of the radon mitigation technology development effort is to develop an efficient and economical radon gas removal technology based on a fluid absorption process. The technology must be capable of cleaning up a wide range of radon gas stream concentrations to a level that meets EPA gas emission standards for residential and industrial applications. Argonne has recently identified a phenomenon that offers the possibility of radon recovery from the atmosphere with high efficiency at room temperature, and radon release at slightly elevated temperatures (50-60 degrees C.) such a device would offer numerous substantial advantages over conventional cryogenic charcoal systems for the removal of radon. Controlled sources of radon in Argonne`s radon research facility are being used to quantitatively assess the performance of a selected class of absorbing fluids over a range of radon concentrations. This paper will discuss the design of laboratory- and engineering-scale radon absorption units and present some preliminary experimental test results.
Analog model for quantum gravity effects: phonons in random fluids.
Krein, G; Menezes, G; Svaiter, N F
2010-09-24
We describe an analog model for quantum gravity effects in condensed matter physics. The situation discussed is that of phonons propagating in a fluid with a random velocity wave equation. We consider that there are random fluctuations in the reciprocal of the bulk modulus of the system and study free phonons in the presence of Gaussian colored noise with zero mean. We show that, in this model, after performing the random averages over the noise function a free conventional scalar quantum field theory describing free phonons becomes a self-interacting model. PMID:21230759
Lennard-Jones and lattice models of driven fluids.
Díez-Minguito, M; Garrido, P L; Marro, J
2005-08-01
We introduce a nonequilibrium off-lattice model for anisotropic phenomena in fluids. This is a Lennard-Jones generalization of the driven lattice-gas model in which the particles' spatial coordinates vary continuously. A comparison between the two models allows us to discuss some exceptional, hardly realistic features of the original discrete system--which has been considered a prototype for nonequilibrium anisotropic phase transitions. We thus help to clarify open issues, and discuss on the implications of our observations for future investigation of anisotropic phase transitions. PMID:16196640
Approaches to Validation of Models for Low Gravity Fluid Behavior
NASA Technical Reports Server (NTRS)
Chato, David J.; Marchetta, Jeffery; Hochstein, John I.; Kassemi, Mohammad
2005-01-01
This paper details the author experiences with the validation of computer models to predict low gravity fluid behavior. It reviews the literature of low gravity fluid behavior as a starting point for developing a baseline set of test cases. It examines authors attempts to validate their models against these cases and the issues they encountered. The main issues seem to be that: Most of the data is described by empirical correlation rather than fundamental relation; Detailed measurements of the flow field have not been made; Free surface shapes are observed but through thick plastic cylinders, and therefore subject to a great deal of optical distortion; and Heat transfer process time constants are on the order of minutes to days but the zero-gravity time available has been only seconds.
Extended fluid models: Pressure tensor effects and equilibria
Cerri, S. S.; Henri, P.; Califano, F.; Pegoraro, F.; Del Sarto, D.; Faganello, M.
2013-11-15
We consider the use of “extended fluid models” as a viable alternative to computationally demanding kinetic simulations in order to manage the global large scale evolution of a collisionless plasma while accounting for the main effects that come into play when spatial micro-scales of the order of the ion inertial scale d{sub i} and of the thermal ion Larmor radius ρ{sub i} are formed. We present an extended two-fluid model that retains finite Larmor radius (FLR) corrections to the ion pressure tensor while electron inertia terms and heat fluxes are neglected. Within this model we calculate analytic FLR plasma equilibria in the presence of a shear flow and elucidate the role of the magnetic field asymmetry. Using a Hybrid Vlasov code, we show that these analytic equilibria offer a significant improvement with respect to conventional magnetohydrodynamic shear-flow equilibria when initializing kinetic simulations.
A 2D electrohydrodynamic model for electrorotation of fluid drops.
Feng, James Q
2002-02-01
A theoretical analysis of spontaneous electrorotation of deformable fluid drops in a DC electric field is presented with a 2D electrohydrodynamic model. The fluids in the system are assumed to be leaky dielectric and Newtonian. If the rotating flow is dominant over the cellular convection type of electrohydrodynamic flow, closed-form solutions for drops of small deformations can be obtained. Because the governing equations are in general nonlinear even when drop deformations are ignored, the general solution for even undeformed drop takes a form of infinite series and can only be evaluated by numerical means. Both closed-form solutions for special cases and numerical solutions for more general cases are obtained here to describe steady-state field variables and first-order drop deformations. In a DC electric field of strength beyond the threshold value, spontaneous electrorotation of a drop is shown to occur when charge relaxation in the surrounding fluid is faster than the fluid inside the drop. With increasing the strength of the applied electric field from the threshold for onset of electrorotation, the axis of drop contraction deviates from from that of the applied electric field in the direction of the rotating flow with an angle increasing with the field strength. PMID:16290391
Modeling interfacial area transport in multi-fluid systems
Yarbro, S.L.
1996-11-01
Many typical chemical engineering operations are multi-fluid systems. They are carried out in distillation columns (vapor/liquid), liquid-liquid contactors (liquid/liquid) and other similar devices. An important parameter is interfacial area concentration, which determines the rate of interfluid heat, mass and momentum transfer and ultimately, the overall performance of the equipment. In many cases, the models for determining interfacial area concentration are empirical and can only describe the cases for which there is experimental data. In an effort to understand multiphase reactors and the mixing process better, a multi-fluid model has been developed as part of a research effort to calculate interfacial area transport in several different types of in-line static mixers. For this work, the ensemble-averaged property conservation equations have been derived for each fluid and for the mixture. These equations were then combined to derive a transport equation for the interfacial area concentration. The final, one-dimensional model was compared to interfacial area concentration data from two sizes of Kenics in-line mixer, two sizes of concurrent jet and a Tee mixer. In all cases, the calculated and experimental data compared well with the highest scatter being with the Tee mixer comparison.
Fluid-Structure interaction modeling in deformable porous arteries
NASA Astrophysics Data System (ADS)
Zakerzadeh, Rana; Zunino, Paolo
2015-11-01
A computational framework is developed to study the coupling of blood flow in arteries interacting with a poroelastic arterial wall featuring possibly large deformations. Blood is modeled as an incompressible, viscous, Newtonian fluid using the Navier-Stokes equations and the arterial wall consists of a thick material which is modeled as a Biot system that describes the mechanical behavior of a homogeneous and isotropic elastic skeleton, and connecting pores filled with fluid. Discretization via finite element method leads to the system of nonlinear equations and a Newton-Raphson scheme is adopted to solve the resulting nonlinear system through consistent linearization. Moreover, interface conditions are imposed on the discrete level via mortar finite elements or Nitsche's coupling. The discrete linearized coupled FSI system is solved by means of a splitting strategy, which allows solving the Navier-Stokes and Biot equations separately. The numerical results investigate the effects of proroelastic parameters on the pressure wave propagation in arteries, filtration of incompressible fluids through the porous media, and the structure displacement. The fellowship support from the Computational Modeling & Simulation PhD program at University of Pittsburgh for Rana Zakerzadeh is gratefully acknowledged.
NASA Astrophysics Data System (ADS)
Gangwar, Rahul Kumar; Bhardwaj, Vanita; Singh, Vinod Kumar
2016-02-01
We reported the modeling result of selectively magnetic fluid infiltrated dual-core photonic crystal fiber based magnetic field sensor. Inside the cross-section of the designed photonic crystal fiber, the two fiber cores filled with magnetic fluid (Fe3O4) form two independent waveguides with mode coupling. The mode coupling under different magnetic field strengths is investigated theoretically. The sensitivity of the sensor as a function of the structural parameters of the photonic crystal fiber is calculated. The result shows that the proposed sensing device with 1 cm photonic crystal fiber length has a large sensitivity of 305.8 pm/Oe.
Fluid particle diffusion in a semidilute suspension of model micro-organisms
NASA Astrophysics Data System (ADS)
Ishikawa, Takuji; Locsei, J. T.; Pedley, T. J.
2010-08-01
We calculate non-Brownian fluid particle diffusion in a semidilute suspension of swimming micro-organisms. Each micro-organism is modeled as a spherical squirmer, and their motions in an infinite suspension otherwise at rest are computed by the Stokesian-dynamics method. In calculating the fluid particle motions, we propose a numerical method based on a combination of the boundary element technique and Stokesian dynamics. We present details of the numerical method and examine its accuracy. The limitation of semidiluteness is required to ensure accuracy of the fluid particle velocity calculation. In the case of a suspension of non-bottom-heavy squirmers the spreading of fluid particles becomes diffusive in a shorter time than that of the squirmers, and the diffusivity of fluid particles is smaller than that of squirmers. It is confirmed that the probability density distribution of fluid particles also shows diffusive properties. The effect of tracer particle size is investigated by inserting some inert spheres of the same radius as the squirmers, instead of fluid particles, into the suspension. The diffusivity for inert spheres is not less than one tenth of that for fluid particles, even though the particle size is totally different. Scaling analysis indicates that the diffusivity of fluid particles and inert spheres becomes proportional to the volume fraction of squirmers in the semidilute regime provided that there is no more than a small recirculation region around a squirmer, which is confirmed numerically. In the case of a suspension of bottom-heavy squirmers, horizontal diffusivity decreases considerably even with small values of the bottom heaviness, which indicates the importance of bottom heaviness in the diffusion phenomena. We believe that these fundamental findings will enhance our understanding of the basic mechanics of a suspension of swimming micro-organisms.
Spherically symmetric Einstein-aether perfect fluid models
NASA Astrophysics Data System (ADS)
Coley, Alan A.; Leon, Genly; Sandin, Patrik; Latta, Joey
2015-12-01
We investigate spherically symmetric cosmological models in Einstein-aether theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic inhomogeneous cosmological models and astrophysical objects with values for the parameters which are consistent with current constraints. In particular, we consider dust models in (β-) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field.
Fluid-Rock Interaction Models: Code Release and Results
NASA Astrophysics Data System (ADS)
Bolton, E. W.
2006-12-01
Numerical models our group has developed for understanding the role of kinetic processes during fluid-rock interaction will be released free to the public. We will also present results that highlight the importance of kinetic processes. The author is preparing manuals describing the numerical methods used, as well as "how-to" guides for using the models. The release will include input files, full in-line code documentation of the FORTRAN source code, and instructions for use of model output for visualization and analysis. The aqueous phase (weathering) and supercritical (mixed-volatile metamorphic) fluid flow and reaction models for porous media will be released separately. These codes will be useful as teaching and research tools. The codes may be run on current generation personal computers. Although other codes are available for attacking some of the problems we address, unique aspects of our codes include sub-grid-scale grain models to track grain size changes, as well as dynamic porosity and permeability. Also, as the flow field can change significantly over the course of the simulation, efficient solution methods have been developed for the repeated solution of Poisson-type equations that arise from Darcy's law. These include sparse-matrix methods as well as the even more efficient spectral-transform technique. Results will be presented for kinetic control of reaction pathways and for heterogeneous media. Codes and documentation for modeling intra-grain diffusion of trace elements and isotopes, and exchange of these between grains and moving fluids will also be released. The unique aspect of this model is that it includes concurrent diffusion and grain growth or dissolution for multiple mineral types (low-diffusion regridding has been developed to deal with the moving-boundary problem at the fluid/mineral interface). Results for finite diffusion rates will be compared to batch and fractional melting models. Additional code and documentation will be released
Magnetorheology of dimorphic magnetorheological fluids based on nanofibers
NASA Astrophysics Data System (ADS)
Bombard, Antonio J. F.; Gonçalves, Flavia R.; Morillas, Jose R.; de Vicente, Juan
2014-12-01
We report a systematic experimental investigation on the use of nanofibers to enhance the magnetorheological (MR) effect in conventional (microsphere-based) MR fluids formulated in polyalphaolefin oil/1-octanol. Two kinds of nanofibers are employed that have very similar morphology but very different magnetic properties. On the one hand we use non-magnetic goethite nanofibers. On the other hand we employ magnetic chromium dioxide nanofibers. For appropriate concentrations the on-state relative yield stress increases up to 80% when incorporating the nanofibers in the formulation. A similar yield stress enhancement is found for both nanofibers investigated (magnetic and non-magnetic) suggesting that the main factor behind this MR enhancement is the particle shape anisotropy. The relative yield stresses obtained by partial substitution of carbonyl iron particles with nanofibers are significantly larger than those measured in previous works on MR fluids formulated by partial substitution with non-magnetic micronsized spherical particles. We also demonstrate that these dimorphic MR fluids also exhibit remarkably larger long-term sedimentation stability while keeping the same penetration and redispersibility characteristics.
Plate-like iron particles based bidisperse magnetorheological fluid
NASA Astrophysics Data System (ADS)
Shah, Kruti; Oh, Jong-Seok; Choi, Seung-Bok; Upadhyay, R. V.
2013-12-01
Magnetorheological (MR) properties are experimentally investigated for bi-dispersion suspension of plate-like iron magnetic particles dispersed in carrier liquid to see the influence of small size particle on large size MR fluid. As a first step, structural, magnetic, and morphology of two different micron size magnetic particles are described in details. The three different weight fractions of MR fluid samples are then prepared, followed by measuring their magneto-viscous and visco-elastic properties. In the steady-state shear, the Bingham yield stress obtained by extrapolating the shear stress to the zero shear rate increases by augmenting the weight fraction of small micron size magnetic particles and the strength of magnetic field. In the oscillatory strain sweep test at an angular frequency of 10 rad s-1, a transition from visco-elastic solid to visco-elastic liquid is observed and a strong chain formation is proposed to explain the mechanism for transition. The storage modulus also increases with increasing weight fraction. From the frequency sweep test, the storage modulus is seen as independent of frequency, but depends on the magnetic field strength and weight fraction. The magneto-viscous sweep test indicates that both shear modulus and complex viscosity are independent with weight fraction at a high magnetic field. This experimental study reveals some very important physical parameters, rheological properties, and storage modulus of the plate-like iron particles based on MR fluid. The formation of less compact because of the anisotropy in iron particle creates weak sedimentation and good redispersibility of MR fluid. The results presented in this work are the key factors for devising how mechanical applications operated under static and dynamic conditions.
Radiant heat transfer modeling in electrorheological fluids: Treatment as an absorbing medium
Hargrove, J.B.; Lloyd, J.R.; Radcliffe, C.J.
1996-12-31
Radiation heat transfer control utilizing the unique properties of electrorheological (ER) fluids has recently been the subject of considerable interest as an innovative new area of research. While much work has been done to demonstrate the concept and show the potential for radiation transmittance control, little has been done to specifically identify the fundamental radiation transport mechanism involved. This paper identifies particle absorption as the dominant mode for attenuation of radiant energy from the range of 500 nm to 800 nm incident upon an ER fluid made of micron sized zeolite particles. Furthermore, appropriate models are developed based on absorption theory to predict radiation heat transfer through a composite window featuring a layer of ER fluid. The levels of extinction predicted by these models are compared to data obtained by experimental measurement, with excellent agreement shown.
A two-phase solid/fluid model for dense granular flows including dilatancy effects
NASA Astrophysics Data System (ADS)
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Koné, El-Hadj; Narbona-Reina, Gladys
2016-04-01
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [{Iverson et al.}, 2010]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure [{Bouchut et al.}, 2016]. The model is derived from a 3D two-phase model proposed by {Jackson} [2000] based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work [{Bouchut et al.}, 2015]. In particular, {Pitman and Le} [2005] replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's model by closing the mixture equations by a weak compressibility relation following {Roux and Radjai} [1998]. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To
NASA Astrophysics Data System (ADS)
Nader, Fadi; Bachaud, Pierre; Michel, Anthony
2015-04-01
Quantitative assessment of fluid-rock interactions and their impact on carbonate host-rocks has recently become a very attractive research topic within academic and industrial realms. Today, a common operational workflow that aims at predicting the relevant diagenetic processes on the host rocks (i.e. fluid-rock interactions) consists of three main stages: i) constructing a conceptual diagenesis model including inferred preferential fluids pathways; ii) quantifying the resulted diagenetic phases (e.g. depositing cements, dissolved and recrystallized minerals); and iii) numerical modelling of diagenetic processes. Most of the concepts of diagenetic processes operate at the larger, basin-scale, however, the description of the diagenetic phases (products of such processes) and their association with the overall petrophysical evolution of sedimentary rocks remain at reservoir (and even outcrop/ well core) scale. Conceptual models of diagenetic processes are thereafter constructed based on studying surface-exposed rocks and well cores (e.g. petrography, geochemistry, fluid inclusions). We are able to quantify the diagenetic products with various evolving techniques and on varying scales (e.g. point-counting, 2D and 3D image analysis, XRD, micro-CT and pore network models). Geochemical modelling makes use of thermodynamic and kinetic rules as well as data-bases to simulate chemical reactions and fluid-rock interactions. This can be through a 0D model, whereby a certain process is tested (e.g. the likelihood of a certain chemical reaction to operate under specific conditions). Results relate to the fluids and mineral phases involved in the chemical reactions. They could be used as arguments to support or refute proposed outcomes of fluid-rock interactions. Coupling geochemical modelling with transport (reactive transport model; 1D, 2D and 3D) is another possibility, attractive as it provides forward simulations of diagenetic processes and resulting phases. This
Application of Ester based Drilling Fluid for Shale Gas Drilling
NASA Astrophysics Data System (ADS)
Sauki, Arina; Safwan Zazarli Shah, Mohamad; Bakar, Wan Zairani Wan
2015-05-01
Water based mud is the most commonly used mud in drilling operation. However, it is ineffective when dealing with water-sensitive shale that can lead to shale hydration, consequently wellbore instability is compromised. The alternative way to deal with this kind of shale is using synthetic-based mud (SBM) or oil-based mud (OBM). OBM is the best option in terms of technical requirement. Nevertheless, it is toxic and will create environmental problems when it is discharged to onshore or offshore environment. SBM is safer than the OBM. The aim of this research is to formulate a drilling mud system that can carry out its essential functions for shale gas drilling to avoid borehole instability. Ester based SBM has been chosen for the mud formulation. The ester used is methyl-ester C12-C14 derived from palm oil. The best formulation of ester-based drilling fluid was selected by manipulating the oil-water ratio content in the mud which are 70/30, 80/20 and 90/10 respectively. The feasibility of using this mud for shale gas drilling was investigated by measuring the rheological properties, shale reactivity and toxicity of the mud and the results were compared with a few types of OBM and WBM. The best rheological performance can be seen at 80/20 oil-water ratio of ester based mud. The findings revealed that the rheological performance of ester based mud is comparable with the excellent performance of sarapar based OBM and about 80% better than the WBM in terms of fluid loss. Apart from that, it is less toxic than other types of OBM which can maintain 60% prawn's survival even after 96 hours exposure in 100,000 ppm of mud concentration in artificial seawater.
Acoustic intensity calculations for axisymmetrically modeled fluid regions
NASA Technical Reports Server (NTRS)
Hambric, Stephen A.; Everstine, Gordon C.
1992-01-01
An algorithm for calculating acoustic intensities from a time harmonic pressure field in an axisymmetric fluid region is presented. Acoustic pressures are computed in a mesh of NASTRAN triangular finite elements of revolution (TRIAAX) using an analogy between the scalar wave equation and elasticity equations. Acoustic intensities are then calculated from pressures and pressure derivatives taken over the mesh of TRIAAX elements. Intensities are displayed as vectors indicating the directions and magnitudes of energy flow at all mesh points in the acoustic field. A prolate spheroidal shell is modeled with axisymmetric shell elements (CONEAX) and submerged in a fluid region of TRIAAX elements. The model is analyzed to illustrate the acoustic intensity method and the usefulness of energy flow paths in the understanding of the response of fluid-structure interaction problems. The structural-acoustic analogy used is summarized for completeness. This study uncovered a NASTRAN limitation involving numerical precision issues in the CONEAX stiffness calculation causing large errors in the system matrices for nearly cylindrical cones.
Magnetic Capture of a Molecular Biomarker from Synovial Fluid in a Rat Model of Knee Osteoarthritis.
Yarmola, Elena G; Shah, Yash; Arnold, David P; Dobson, Jon; Allen, Kyle D
2016-04-01
Biomarker development for osteoarthritis (OA) often begins in rodent models, but can be limited by an inability to aspirate synovial fluid from a rodent stifle (similar to the human knee). To address this limitation, we have developed a magnetic nanoparticle-based technology to collect biomarkers from a rodent stifle, termed magnetic capture. Using a common OA biomarker--the c-terminus telopeptide of type II collagen (CTXII)--magnetic capture was optimized in vitro using bovine synovial fluid and then tested in a rat model of knee OA. Anti-CTXII antibodies were conjugated to the surface of superparamagnetic iron oxide-containing polymeric particles. Using these anti-CTXII particles, magnetic capture was able to estimate the level of CTXII in 25 μL aliquots of bovine synovial fluid; and under controlled conditions, this estimate was unaffected by synovial fluid viscosity. Following in vitro testing, anti-CTXII particles were tested in a rat monoiodoacetate model of knee OA. CTXII could be magnetically captured from a rodent stifle without the need to aspirate fluid and showed tenfold changes in CTXII levels from OA-affected joints relative to contralateral control joints. Combined, these data demonstrate the ability and sensitivity of magnetic capture for post-mortem analysis of OA biomarkers in the rat. PMID:26136062
Composition dependence of fluid thermophysical properties: Theory and modeling
Ely, J.F.
1993-03-29
Objectives are studies of equilibrium/nonequilibrium properties of asymmetric fluid mixtures through computer simulation (CS), development of predictive theories of mixture equilibrium properties, development and application of selection algorithm methodology for mixture equations of state, and use of theory to develop new engineering design models for fluid mixtures. Kirwood charging method CS of Lennard-Jones mixtures with large size ratios verified the Kirkwood-Buff/Baxter method of calculating chemical potentials. CS of n-butane showed that the rheology is not a function of system size. A modified stepwise regression algorithm was developed and applied to HFC R134a. An analytical expression was developed for conformal solution size correction for mixtures. The extended corresponding states theory (ECST) can be applied to systems having large polarity differences; an accurate representation was developed of bulk phase properties of water-hydrocarbon systems. It was found how to force ECST to reach the correct virial limit.
Green Algae as Model Organisms for Biological Fluid Dynamics
NASA Astrophysics Data System (ADS)
Goldstein, Raymond E.
2015-01-01
In the past decade, the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimeters), their geometric regularity, the ease with which they can be cultured, and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms.
A mathematical model of post-instability in fluid mechanics
NASA Technical Reports Server (NTRS)
Zak, M. A.
1982-01-01
Postinstability of fluids is eliminated in numerical models by introducing multivalued velocity fields after discarding the principle of impenetrability. Smooth functions are shown to be incapable of keeping the derivatives from going towards infinity when iterating solutions for the governing equations such as those defined by Navier-Stokes. Enlarging the class of functions is shown to be necessary to eliminate the appearance of imaginary characteristic roots in the systems of arbitrary partial differential equations, a condition which leads to physically impossible motions. The enlarging is demonstrated to be achievable by allowing several individual particles with different velocities to appear at the same point of space, and the subsequent multivaluedness of the solutions is purely a mathematical concern, rather than one of actual physical existence. Applications are provided for an inviscid fluid and for turbulence.
Green Algae as Model Organisms for Biological Fluid Dynamics*
Goldstein, Raymond E.
2015-01-01
In the past decade the volvocine green algae, spanning from the unicellular Chlamydomonas to multicellular Volvox, have emerged as model organisms for a number of problems in biological fluid dynamics. These include flagellar propulsion, nutrient uptake by swimming organisms, hydrodynamic interactions mediated by walls, collective dynamics and transport within suspensions of microswimmers, the mechanism of phototaxis, and the stochastic dynamics of flagellar synchronization. Green algae are well suited to the study of such problems because of their range of sizes (from 10 μm to several millimetres), their geometric regularity, the ease with which they can be cultured and the availability of many mutants that allow for connections between molecular details and organism-level behavior. This review summarizes these recent developments and highlights promising future directions in the study of biological fluid dynamics, especially in the context of evolutionary biology, that can take advantage of these remarkable organisms. PMID:26594068
Fault zone architecture and fluid flow: Insights from field data and numerical modeling
NASA Astrophysics Data System (ADS)
Caine, Jonathan Saul; Forster, Craig B.
Fault zones in the upper crust are typically composed of complex fracture networks and discrete zones of comminuted and geochemically altered fault rocks. Determining the patterns and rates of fluid flow in these distinct structural discontinuities is a three-dimensional problem. A series of numerical simulations of fluid flow in a set of three-dimensional discrete fracture network models aids in identifying the primary controlling parameters of fault-related fluid flow, and their interactions, throughout episodic deformation. Four idealized, but geologically realistic, fault zone architectural models are based on fracture data collected along exposures of the Stillwater Fault Zone in Dixie Valley, Nevada and geometric data from a series of normal fault zones in east Greenland. The models are also constrained by an Andersonian model for mechanically compatible fracture networks associated with normal faulting. Fluid flow in individual fault zone components, such as a fault core and damage zone, and full outcrop scale model domains are simulated using a finite element routine. Permeability contrasts between components and permeability anisotropy within components are identified as the major controlling factors in fault-related fluid flow. Additionally, the structural and hydraulic variations in these components are also major controls of flow at the scale of the full model domains. The four models can also be viewed as a set of snapshots in the mechanical evolution of a single fault zone. Changes in the hydraulic parameters within the models mimic the evolution of the permeability structure of each model through a single deformation cycle. The model results demonstrate that small changes in the architecture and hydraulic parameters of individual fault zone components can have very large impacts, up to five orders of magnitude, on the permeability structure of the full model domains. Closure of fracture apertures in each fault zone magnifies the magnitude and
Rotating-fluid experiments with an atmospheric general circulation model
NASA Technical Reports Server (NTRS)
Geisler, J. E.; Pitcher, E. J.; Malone, R. C.
1983-01-01
In order to determine features of rotating fluid flow that are dependent on the geometry, rotating annulus-type experiments are carried out with a numerical model in spherical coordinates. Rather than constructing and testing a model expressly for this purpose, it is found expedient to modify an existing general circulation model of the atmosphere by removing the model physics and replacing the lower boundary with a uniform surface. A regime diagram derived from these model experiments is presented; its major features are interpreted and contrasted with the major features of rotating annulus regime diagrams. Within the wave regime, a narrow region is found where one or two zonal wave numbers are dominant. The results reveal no upper symmetric regime; wave activity at low rotation rates is thought to be maintained by barotropic rather than baroclinic processes.
Parallel technology for numerical modeling of fluid dynamics problems by high-accuracy algorithms
NASA Astrophysics Data System (ADS)
Gorobets, A. V.
2015-04-01
A parallel computation technology for modeling fluid dynamics problems by finite-volume and finite-difference methods of high accuracy is presented. The development of an algorithm, the design of a software implementation, and the creation of parallel programs for computations on large-scale computing systems are considered. The presented parallel technology is based on a multilevel parallel model combining various types of parallelism: with shared and distributed memory and with multiple and single instruction streams to multiple data flows.
One-dimensional cloud fluid model for propagating star formation
NASA Technical Reports Server (NTRS)
Titus, Timothy N.; Struck-Marcell, Curtis
1990-01-01
The aim of this project was to study the propagation of star formation (SF) with a self-consistent deterministic model for the interstellar gas. The questions of under what conditions does star formation propagate in this model and what are the mechanisms of the propagation are explored. Here, researchers used the deterministic Oort-type cloud fluid model of Scalo and Struck-Marcell (1984, also see the review of Struck-Marcell, Scalo and Appleton 1987). This cloud fluid approach includes simple models for the effects of cloud collisional coalescence or disruption, collisional energy dissipation, and cloud disruption and acceleration as the result of young star winds, HII regions and supernovae. An extensive one-zone parameter study is presented in Struck-Marcell and Scalo (1987). To answer the questions above, researchers carried out one-dimensional calculations for an annulus within a galactic disk, like the so-called solar neighborhood of the galactic chemical evolution. In the calculations the left-hand boundary is set equal to the right hand boundary. The calculation is obviously idealized; however, it is computationally convenient to study the first order effects of propagating star formation. The annulus was treated as if it were at rest, i.e., in the local rotating frame. This assumption may remove some interesting effects of a supersonic gas flow, but was necessary to maintain a numerical stability in the annulus. The results on the one-dimensional propagation of SF in the Oort cloud fluid model follow: (1) SF is propagated by means of hydrodynamic waves, which can be generated by external forces or by the pressure generated by local bursts. SF is not effectively propagated via diffusion or variation in cloud interaction rates without corresponding density and velocity changes. (2) The propagation and long-range effects of SF depend on how close the gas density is to the critical threshold value, i.e., on the susceptibility of the medium.
NASA Astrophysics Data System (ADS)
Nguyen, Desmond
Arguably the most important prerequisite to a good primary cementing job is mud displacement. In order to have effective mud displacement, complete removal of drilled cuttings from the well bore is required. This becomes more challenging in highly-deviated to horizontal wells where the casing tends to lie on the low side of the well bore creating an eccentric annular flow geometry. In this study, a theoretical approach based on the theory of particles transport and fluid mechanics is adopted to develop two new mathematical models: (1) cuttings transport; and (2) drilling fluid displacement by cement slurry in horizontal wells. Two computer algorithms are developed based on these models. The effects of various operational conditions, hole geometry and fluid properties are simulated using these computer models. The results compare favourably with those obtained by previous investigators. These simulated examples demonstrate that the two models can be used to analyse the sensitivity of the cuttings transport and displacement processes to changes in the operational conditions, hole geometry and fluid properties. Hence, they can potentially be used as design and/or analysis tools for the optimisation of these processes in highly- deviated to horizontal wells.
NASA Technical Reports Server (NTRS)
Majumdar, Alok K.; LeClair, Andre C.; Hedayat, Ali
2016-01-01
This paper presents a numerical model of pressurization of a cryogenic propellant tank for the Integrated Vehicle Fluid (IVF) system using the Generalized Fluid System Simulation Program (GFSSP). The IVF propulsion system, being developed by United Launch Alliance, uses boiloff propellants to drive thrusters for the reaction control system as well as to run internal combustion engines to develop power and drive compressors to pressurize propellant tanks. NASA Marshall Space Flight Center (MSFC) has been running tests to verify the functioning of the IVF system using a flight tank. GFSSP, a finite volume based flow network analysis software developed at MSFC, has been used to develop an integrated model of the tank and the pressurization system. This paper presents an iterative algorithm for converging the interface boundary conditions between different component models of a large system model. The model results have been compared with test data.
Forward-in-time differencing for fluids: Nonhydrostatic modeling of fluid motions on a sphere
Smolarkiewicz, P.K.; Grubisic, V.; Margolin, L.G.; Wyszogrodzki, A.A.
1998-12-31
Traditionally, numerical models for simulating planetary scale weather and climate employ the hydrostatic primitive equations--an abbreviated form of Navier-Stokes` equations that neglect vertical accelerations and use simplified Coriolis forces. Although there is no evidence so far that including nonhydrostatic effects in global models has any physical significance for large scale solutions, there is an emerging trend in the community toward restoring Navier-Stokes` equations (or at least their less constrained forms) in global models of atmospheres and oceans. The primary motivation is that state-of-the-art computers already admit resolutions where local nonhydrostatic effects become noticeable. much of this present research aims to improve the design of a high-performance numerical model for simulating the flows of moist (and precipitating), rotating, stratified fluids past a specified time-dependent irregular lower boundary. This model is representative of a class of nonhydrostatic atmospheric codes that employs the anelastic equations of motion in a terrain-following curvilinear framework, and contains parallel implementations of semi-Lagrangian and Eulerian approximations selectable by the user. The model has been employed in a variety of application; the quality of results suggest that modern nonoscillatory forward-in-time (NFT) methods are superior to the more traditional centered-in-time-and-space schemes, in terms of accuracy, computational efficiency, flexibility and robustness. The authors have extended the Cartesian NFT model to a mountainous sphere and, consequently, have dispensed with the traditional geophysical simplifications of hydrostaticity, gentle terrain slopes, and weak rotation. In this paper, they discuss the algorithmic design, relative efficiency and accuracy of several different variants (hydrostatic, nonhydrostatic, implicit, explicit, etc.) of the NFT global model. They substantiate their theoretical discussions with the results of
Particle-fluid two-phase flow modeling
NASA Astrophysics Data System (ADS)
Mortensen, G. A.; Trapp, J. A.
This paper describes a numerical scheme and computer program, DISCON, for the calculation of two-phase flows that does not require the use of flow regime maps. This model is intermediate between-thermal instantaneous and the averaged two-fluid model. It solves the Eulerian continuity, momentum, and energy equations for each liquid control volume, and the Lagrangian mass, momentum, energy, and position equations for each bubble. The bubbles are modeled individually using a large representative number of bubbles, thus, avoiding the numerical diffusion associated with Eulerian models. DISCON has been used to calculate the bubbling of air through a column of water and the subcooled boiling of water in a flow channel. The results of these calculations are presented.
Particle-fluid two-phase flow modeling
Mortensen, G.A. ); Trapp, J.A. Idaho National Engineering Lab., Idaho Falls, ID )
1992-01-01
This paper describes a numerical scheme and computer program, DISCON, for the calculation of two-phase flows that does not require the use of flow regime maps. This model is intermediate between-thermal instantaneous and the averaged two-fluid model. It solves the Eulerian continuity, momentum, and energy equations for each liquid control volume, and the Lagrangian mass, momentum, energy, and position equations for each bubble. The bubbles are modeled individually using a large representative number of bubbles thus avoiding the numerical diffusion associated with Eulerian models. DISCON has been used to calculate the bubbling of air through a column of water and the subcooled boiling of water in a flow channel. The results of these calculations are presented.
Particle-fluid two-phase flow modeling
Mortensen, G.A.; Trapp, J.A. |
1992-09-01
This paper describes a numerical scheme and computer program, DISCON, for the calculation of two-phase flows that does not require the use of flow regime maps. This model is intermediate between-thermal instantaneous and the averaged two-fluid model. It solves the Eulerian continuity, momentum, and energy equations for each liquid control volume, and the Lagrangian mass, momentum, energy, and position equations for each bubble. The bubbles are modeled individually using a large representative number of bubbles thus avoiding the numerical diffusion associated with Eulerian models. DISCON has been used to calculate the bubbling of air through a column of water and the subcooled boiling of water in a flow channel. The results of these calculations are presented.
An Anisotropic Fluid-Solid Model of the Mouse Heart
Carson, James P.; Kuprat, Andrew P.; Jiao, Xiangmin; del Pin, Facundo; Einstein, Daniel R.
2010-01-01
A critical challenge in biomechanical simulations is the spatial discretization of complex fluid-solid geometries created from imaging. This is especially important when dealing with Lagrangian interfaces, as there must be at a minimum both geometric and topological compatibility between fluid and solid phases, with exact matching of the interfacial nodes being highly desirable. We have developed a solution to this problem and applied the approach to the creation of a 3D fluidsolid mesh of the mouse heart. First, a 50 micron isotropic MRI dataset of a perfusion-fixed mouse heart was segmented into blood, tissue, and background using a customized multimaterial connected fuzzy thresholding algorithm. Then, a multimaterial marching cubes algorithm was applied to produce two compatible isosurfaces, one for the blood-tissue boundary and one for the tissue-background boundary. A multimaterial smoothing algorithm that rigorously conserves volume for each phase simultaneously smoothed the isosurfaces. Next we applied novel automated meshing algorithms to generate anisotropic hybrid meshes with the number of layers and the desired element anisotropy for each material as the only input parameters. As the meshes are scale-invariant within a material and include boundary layer prisms, fluid-structure interaction computations would have a relative error equilibrated over the entire mesh. The resulting model is highly detailed mesh representation of the mouse heart, including features such as chordae and coronary vasculature, that is also maximally efficient to produce the best simulation results for the computational resources available
Computational modeling of fluid structural interaction in arterial stenosis
NASA Astrophysics Data System (ADS)
Bali, Leila; Boukedjane, Mouloud; Bahi, Lakhdar
2013-12-01
Atherosclerosis affects the arterial blood vessels causing stenosis because of which the artery hardens resulting in loss of elasticity in the affected region. In this paper, we present: an approach to model the fluid-structure interaction through such an atherosclerosis affected region of the artery, The blood is assumed as an incompressible Newtonian viscous fluid, and the vessel wall was treated as a thick-walled, incompressible and isotropic material with uniform mechanical properties. The numerical simulation has been studied in the context of The Navier-Stokes equations for an interaction with an elastic solid. The study of fluid flow and wall motion was initially carried out separately, Discretized forms of the transformed wall and flow equations, which are coupled through the boundary conditions at their interface, are obtained by control volume method and simultaneously to study the effects of wall deformability, solutions are obtained for both rigid and elastic walls. The results indicate that deformability of the wall causes an increase in the time average of pressure drop, but a decrease in the maximum wall shear stress. Displacement and stress distributions in the wall are presented.
Beyond poiseuille: preservation fluid flow in an experimental model.
Singh, Saurabh; Randle, Lucy V; Callaghan, Paul T; Watson, Christopher J E; Callaghan, Chris J
2013-01-01
Poiseuille's equation describes the relationship between fluid viscosity, pressure, tubing diameter, and flow, yet it is not known if cold organ perfusion systems follow this equation. We investigated these relationships in an ex vivo model and aimed to offer some rationale for equipment selection. Increasing the cannula size from 14 to 20 Fr increased flow rate by a mean (SD) of 13 (12)%. Marshall's hyperosmolar citrate was three times less viscous than UW solution, but flows were only 45% faster. Doubling the bag pressure led to a mean (SD) flow rate increase of only 19 (13)%, not twice the rate. When external pressure devices were used, 100 mmHg of continuous pressure increased flow by a mean (SD) of 43 (17)% when compared to the same pressure applied initially only. Poiseuille's equation was not followed; this is most likely due to "slipping" of preservation fluid within the plastic tubing. Cannula size made little difference over the ranges examined; flows are primarily determined by bag pressure and fluid viscosity. External infusor devices require continuous pressurisation to deliver high flow. Future studies examining the impact of perfusion variables on graft outcomes should include detailed equipment descriptions. PMID:24062943
Beyond Poiseuille: Preservation Fluid Flow in an Experimental Model
Singh, Saurabh; Randle, Lucy V.; Callaghan, Paul T.; Watson, Christopher J. E.; Callaghan, Chris J.
2013-01-01
Poiseuille's equation describes the relationship between fluid viscosity, pressure, tubing diameter, and flow, yet it is not known if cold organ perfusion systems follow this equation. We investigated these relationships in an ex vivo model and aimed to offer some rationale for equipment selection. Increasing the cannula size from 14 to 20 Fr increased flow rate by a mean (SD) of 13 (12)%. Marshall's hyperosmolar citrate was three times less viscous than UW solution, but flows were only 45% faster. Doubling the bag pressure led to a mean (SD) flow rate increase of only 19 (13)%, not twice the rate. When external pressure devices were used, 100 mmHg of continuous pressure increased flow by a mean (SD) of 43 (17)% when compared to the same pressure applied initially only. Poiseuille's equation was not followed; this is most likely due to “slipping” of preservation fluid within the plastic tubing. Cannula size made little difference over the ranges examined; flows are primarily determined by bag pressure and fluid viscosity. External infusor devices require continuous pressurisation to deliver high flow. Future studies examining the impact of perfusion variables on graft outcomes should include detailed equipment descriptions. PMID:24062943
Co-Extrusion Instabilities Modeled with a Single Fluid
NASA Astrophysics Data System (ADS)
Reis, T.; Sahin, M.; Wilson, H.
2008-07-01
Industrial processes involving co-extrusion of multiple fluids to produce multi-layered products are rife with instabilities. We consider a simple indicative instance of co-extrusion, in which there is only a single fluid involved in the flow, but two different channel branches impose differing flow histories on it. The channels merge and, ideally, a smooth film is extruded with two layers having different stress histories. In experimental studies a wavelike instability is observed with a well defined wavelength in the flow direction and a `zig-zag' like structure, indicating that the extra flow caused by the instability is three-dimensional. Suggested mechanisms for instabilities in co-extrusion include a jump in viscosity and/or first normal stress difference across a flat interface, and a coupling of normal stresses with streamline curvature in the region where the two streams merge. Using a numerical linear stability tool we investigate this instability (using a single mode fluid model throughout) and explore which of the known mechanisms is the most likely culprit here.
A New Method Based on the F-Curve for Characterizing Fluid Flow in Continuous Casting Tundishes
NASA Astrophysics Data System (ADS)
Li, Dongxia; Cui, Heng; Liu, Yang; Tian, Enhua; Du, Jianxin
2016-04-01
"Combined Model" is often applied to characterize the fluid flow in tundishes. There are different ways to manage the calculation of this model, while the most recently used is introduced by SAHAI and EMI. But this approach may lead to incorrect results in some special cases. In this paper, a new method based on the F-Curve is proposed to analyze the fluid flow in tundishes, and the relationship between E-Curve and F-Curve is concerned. In the end, their application to tundish fluid flow has been outlined. The dead volume calculated by the new method is much close to the results of dye experiment and the numerical simulation.
Equivalent Liénard-type models for a fluid transmission line
NASA Astrophysics Data System (ADS)
Torres, Lizeth; Aguiñaga, Jorge Alejandro Delgado; Besançon, Gildas; Verde, Cristina; Begovich, Ofelia
2016-08-01
The main contribution of this paper is the derivation of spatiotemporal Liénard-type models for expressing the dynamical behavior of a fluid transmission line. The derivation is carried out from a quasilinear hyperbolic system made of a momentum equation and a continuity one. An advantage of these types of models is that they are suitable for formulating estimation algorithms. This claim is confirmed in the present paper for the case of fluid dynamics, since the article presents the conception and evaluation of a Liénard model-based observer that estimates the parameters of a pipeline such as the friction factor, the equivalent length and the wave speed. To show the potentiality of the approach, results based on some simulation and experimental tests are presented. xml:lang="fr"
Oral fluid-based biomarkers in periodontal disease - part 2. Gingival crevicular fluid.
AlRowis, Raed; AlMoharib, Hani S; AlMubarak, Abdulrahman; Bhaskardoss, Jagankumar; Preethanath, R S; Anil, Sukumaran
2014-09-01
Periodontal diagnosis and treatment plan are based on the assessment of probing depth, clinical attachment level, plaque index, gingival index, bleeding on probing, suppuration, furcation involvement, mobility, and radiographic findings. However, these clinical parameters are not sufficiently sensitive and specific to identify disease activity in individual sites or to predict future attachment loss. Hence, attention is focused on the development of diagnostic tools that could screen and differentiate the active inflamed sites and predict future tissue destruction. Gingival crevicular fluid (GCF), has gained great interest on possible diagnostic value in periodontal disease. It contains a large number of proteins and peptides derived from inflamed host tissues. The analysis of the GCF components can reflect the disease status of individual sites and thus, identify potential biomarkers of periodontitis. A literature search was carried out to find out all the available tests that indicate periodontal disease markers in GCF. All major databases were searched to compile the information on published reports between 1999 and 2014. The list of GCF-biomarkers available to date is compiled and presented in a table format. Based on the available literature on GCF biomarkers, it can be concluded that several sensitive and reliable markers are present to detect the presence, severity, and response to treatment. Further studies are warranted to analyze the sensitivity and reliability of these indicators which might help in developing noninvasive tests that could help in the diagnosis of periodontal disease. PMID:25395809
NASA Astrophysics Data System (ADS)
Yoon, Jeoung Seok; Zang, Arno; Zimmermann, Günter; Stephansson, Ove; Min, Ki-Bok
2015-04-01
This paper presents discrete element based numerical model which is applied to simulation of multiple stage hydraulic fracturing in crystalline granitic geothermal reservoir. Target site modeled locates in south of state of Saxony Germany. Particle Flow Code 2D (Itasca) is used in which fluid flow algorithm and moment tensor based seismicity computation algorithm are implemented. Crystalline rock layer to be stimulated locates at 4-6 km depth with relative low density of pre-existing joints and faults. Hydraulic stimulation is modeled with five stages of fluid injection with distance of several hundreds of meters. Hydraulic fracturing is done on the stages from toe to heel direction along a series of sub-horizontally drilled wellbore with constant rate of fluid injection. Fracture propagation paths and induced seismic events are documented based on their time of occurrence and their magnitude. In addition to the evolution of the fracture propagation path and distribution of the induced events, migration of the injected fluid is investigated in space and time. This is to see how the results relate to the fluid migration front in low permeability crystalline reservoir subjected to multiple stage hydraulic fracturing. Moreover, this paper addresses advantages and disadvantages of the inclined drilling of the wellbore in low permeability reservoir and multi-stage fracturing setting. We try to seek an optimum inclination of the drilling in relation to the gradients and magnitudes of the in situ stresses, which are horizontal minimum and vertical stresses. Preliminary modeling results show that inclination angle of the drilling has a significant effect on lowering of the stress shadow effect and level of induced seismicity in terms of total number, magnitudes and the Gutenberg-Richter relation.
NASA Astrophysics Data System (ADS)
Hurlbatt, A.; O’Connell, D.; Gans, T.
2016-08-01
Analytical and numerical models allow investigation of complicated discharge phenomena and the interplay that makes plasmas such a complex environment. Global models are quick to implement and can have almost negligible computation cost, but provide only bulk or spatially averaged values. Full fluid models take longer to develop, and can take days to solve, but provide accurate spatio-temporal profiles of the whole plasma. The work presented here details a different type of model, analytically similar to fluid models, but computationally closer to a global model, and able to give spatially resolved solutions for the challenging environment of electronegative plasmas. Included are non-isothermal electrons, gas heating, and coupled neutral dynamics. Solutions are reached in seconds to minutes, and spatial profiles are given for densities, fluxes, and temperatures. This allows the semi-analytical model to fill the gap that exists between global and full fluid models, extending the tools available to researchers. The semi-analytical model can perform broad parameter sweeps that are not practical with more computationally expensive models, as well as exposing non-trivial trends that global models cannot capture. Examples are given for a low pressure oxygen CCP. Excellent agreement is shown with a full fluid model, and comparisons are drawn with the corresponding global model.
Knowledge-based zonal grid generation for computational fluid dynamics
NASA Technical Reports Server (NTRS)
Andrews, Alison E.
1988-01-01
Automation of flow field zoning in two dimensions is an important step towards reducing the difficulty of three-dimensional grid generation in computational fluid dynamics. Using a knowledge-based approach makes sense, but problems arise which are caused by aspects of zoning involving perception, lack of expert consensus, and design processes. These obstacles are overcome by means of a simple shape and configuration language, a tunable zoning archetype, and a method of assembling plans from selected, predefined subplans. A demonstration system for knowledge-based two-dimensional flow field zoning has been successfully implemented and tested on representative aerodynamic configurations. The results show that this approach can produce flow field zonings that are acceptable to experts with differing evaluation criteria.
NASA Astrophysics Data System (ADS)
Zhang, L.; Ning, F.; Jiang, G.; Wu, N.; Wu, D.
2009-12-01
Oceanic gas hydrate-bearing sediment is usually porous media, with the temperature and pressure closer to the curve of hydrate phase equilibrium than those in the permafrost region. In the case of near-balanced or over-balanced drilling through this sediment, the water-based drilling fluid used invades into this sediment, and hydrates decompose with heat transfer between drilling fluid and this sediment. During these processes, there are inevitably energy and mass exchanges between drilling fluid and the sediment, which will affect the logging response, borehole stability and reservoir evaluation. When drilling fluid invades into this sediment, solid and liquid phases of drilling fluid permeate into the wellbore and displace original fluids and solids, and water content of formation increases. With the temperature and pressure changing, gas hydrates in the sediment decompose into gas and water, and water content of formation further changes. When the filter cakes form, the invasion of drilling fluid is weakened. This process is accompanied by the heat and mass transfer within the range from wellbore to undisturbed area, including heat conduction of rock matrix, the convective heat transfer of fluids invaded, the heat absorbing of hydrate decomposition and the mass exchange between fluids invaded and the gas and water generated by hydrate decomposition. As a result, dynamic balance is built up and there are generally four different regions from wellbore to undisturbed area, i.e. filter cakes region, filter liquor region, water/free gas region, and water/free gas/hydrate region. According to the analysis on the invasion of drilling fuild into sediment, the whole invasion process can be described as an anisothermal and unstable displacement and diffusion process coupled with phase change. Refering to models of drilling fuilds invasion into normal oil and gas formation and natrual gas production from hydrate deposit by heating, the model of the invasion of drilling
Null controllability in a fluid-solid structure model
NASA Astrophysics Data System (ADS)
Raymond, J.-P.; Vanninathan, M.
We consider a system coupling the Stokes equations in a two-dimensional domain with a structure equation which is a system of ordinary differential equations corresponding to a finite dimensional approximation of equations modeling deformations of an elastic body or vibrations of a rigid body. For that system we establish a null controllability result for localized distributed controls acting only in the fluid equations and there is no control in the solid part. This controllability result follows from a Carleman inequality that we prove for the adjoint system.
Numerical modelling of the impact of a liquid drop on the surface of a two-phase fluid system
NASA Astrophysics Data System (ADS)
Sochan, Agata; Lamorski, Krzysztof; Bieganowski, Andrzej; Ryżak, Magdalena
2014-05-01
The aim of the study was validation of a numerical model of the impact of a liquid drop on the surface of a two-phase system of immiscible fluids. The drop impact phenomenon was recorded using a high-speed camera (Vision Research MIRO M310) and the data were recorded at 2000 frames per second. The numerical calculations were performed with the Finite Volume Method (FVM) solving the three-dimensional Navier-Stokes equations for three phases: air and two selected immiscible fluids. The Volume of Fluid (VOF) technique was employed for modelling of the boundaries between the phases. Numerical modelling was done with the Finite Volume Method using an available OpenFOAM software. The experiment was based on three variables: • the height from which the drop of the selected fluids fell (the speed of the drop), • the thickness of the layers of the two selected immiscible fluids (a thin layer of the fluid with a lower density was spread over the higher-density fluid), • the size of the fluid droplet. The velocity and radius of the falling drop was calculated based on the recorded images. The used parameters allowed adequate projection of the impact of fluid droplets on a system of two immiscible liquids. Development of the numerical model of splash may further have practical applications in environmental protection (spraying of hazardous fluids, spread of fuels and other hazardous substances as a result of disasters, spraying (water cooling) of hot surfaces), and in agriculture (prevention of soil erosion). The study was partially funded from the National Science Centre (Poland) based on the decision no. DEC-2012/07/N/ST10/03280.
Modeling Dark Energy Through AN Ising Fluid with Network Interactions
NASA Astrophysics Data System (ADS)
Luongo, Orlando; Tommasini, Damiano
2014-12-01
We show that the dark energy (DE) effects can be modeled by using an Ising perfect fluid with network interactions, whose low redshift equation of state (EoS), i.e. ω0, becomes ω0 = -1 as in the ΛCDM model. In our picture, DE is characterized by a barotropic fluid on a lattice in the equilibrium configuration. Thus, mimicking the spin interaction by replacing the spin variable with an occupational number, the pressure naturally becomes negative. We find that the corresponding EoS mimics the effects of a variable DE term, whose limiting case reduces to the cosmological constant Λ. This permits us to avoid the introduction of a vacuum energy as DE source by hand, alleviating the coincidence and fine tuning problems. We find fairly good cosmological constraints, by performing three tests with supernovae Ia (SNeIa), baryonic acoustic oscillation (BAO) and cosmic microwave background (CMB) measurements. Finally, we perform the Akaike information criterion (AIC) and Bayesian information criterion (BIC) selection criteria, showing that our model is statistically favored with respect to the Chevallier-Polarsky-Linder (CPL) parametrization.
NASA Astrophysics Data System (ADS)
Jovanović, A. P.; Stankov, M. N.; Marković, V. Lj.; Stamenković, S. N.
2013-12-01
In this letter the validity of the fluid model used to simulate the electrical breakdown in air at low pressure is discussed. The new method for the determination of the ionization source term for the mixed gases is proposed. Paschen's curve obtained by the fluid model is compared to the available experimental data. The electron and ions density profiles calculated by the fluid model are presented. Based on Ohm's law, the current and voltage waveforms are calculated and compared to the ones measured by the oscilloscope in the synthetic-air filled tube with stainless-steel electrodes. It is shown that the one-dimensional fluid model can be used for modeling the electrical breakdown at pd values higher than Paschen's minimum and to determine stationary values of electron and ions densities.
Particle-particle interactions in electrorheological fluids based on surface conducting particles
NASA Astrophysics Data System (ADS)
Gonon, P.; Foulc, J.-N.; Atten, P.; Boissy, C.
1999-12-01
We develop a simple, analytical conduction model for the case of electrorheological fluids based on surface conducting particles. By modeling two contacting spheres in a dielectric liquid by a distributed impedances network we derive analytical expressions for the potential and current at the spheres surface, and for the electric field and the current in the liquid phase. The knowledge of the electric field in the dielectric liquid allows us to calculate the interparticle interaction force as a function of the applied voltage. The theoretical interaction force is compared with experimental results obtained on insulating spheres coated with a thin conducting polyaniline film. We find a good agreement between the theory and experiment. The materials properties which govern the response of the system are outlined. In this regard, the product of the liquid conductivity by the sheet resistance of the surface coating appears as a key parameter. Some applications of this model for the practical design of electrorheological fluids are given.
He, W.; Anderson, R.N.
1998-08-25
A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management. 20 figs.
He, Wei; Anderson, Roger N.
1998-01-01
A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management.
Fluid mechanical model of the acoustic impedance of small orifices
NASA Technical Reports Server (NTRS)
Hersh, A. S.; Rogers, T.
1975-01-01
A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice impedance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values (in both water and air) of orifice impedance is excellent. The model shows that (1) the acoustic flow in the immediate neighborhood of the orifice can be modelled as a locally spherical flow, (2) within this near field, the flow is, to a first approximation, unsteady and incompressible, and (3) at very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the orifice neighborhood.-
Fluid mechanical model of the acoustic impedance of small orifices
NASA Technical Reports Server (NTRS)
Hersh, A. S.; Rogers, T.
1976-01-01
A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice resistance and reactance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values is excellent. The model shows the following: (1) The acoustic flow in immediate neighborhood of the orifice can be modeled as a locally spherical flow. Within this near field, the flow is, to a first approximation, unsteady and incompressible. (2) At very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the neighborhood of the orifice. (3) For large values of the incident acoustic pressure, the impedance is dominated by nonlinear jet-like effects. (4) For low values of the pressure, the resistance and reactance are roughly equal.
Midline (Central) Fluid Percussion Model of Traumatic Brain Injury.
Rowe, Rachel K; Griffiths, Daniel R; Lifshitz, Jonathan
2016-01-01
Research models of traumatic brain injury (TBI) hold significant validity towards the human condition, with each model replicating a subset of clinical features and symptoms. After 30 years of characterization and implementation, fluid percussion injury (FPI) is firmly recognized as a clinically relevant model of TBI, encompassing concussion through severe injury. The midline variation of FPI may best represent mild and diffuse clinical brain injury, because of the acute behavioral deficits, the late onset of subtle behavioral morbidities, and the absence of gross histopathology. This chapter outlines the procedures for midline (diffuse) FPI in adult male rats and mice. With these procedures, it becomes possible to generate brain-injured laboratory animals for studies of injury-induced pathophysiology and behavioral deficits, for which rational therapeutic interventions can be implemented. PMID:27604721
Modeling of supercritical fluid extraction from herbaceous matrices
Reverchon, E.; Donsi, G.; Osseo, L.S. . Dipt. di Ingegneria Chimica e Alimentare)
1993-11-01
Experimental results of supercritical fluid extraction from various herbaceous matrices are presented. In optimal extraction conditions, the use of a fractional separation technique allows a nearly complete separation of the extract in cuticular waxes and essential oil. The modeling of these results is proposed starting from the description of the mass transfer from a single spherical particle. The simultaneous extraction of two pseudocompounds is assumed to simulate the two compound families obtained by fractionation. The model is then extended to simulate the whole extractor. The yields of essential oil and cuticular waxes obtained from rosemary, basil, and marjoram leaves are fairly simulated by the model. Intraparticle mass transfer resulted as the controlling stage in supercritical extraction of essential oils.
Physics based simulation of seismicity induced in the vicinity of a high-pressure fluid injection
NASA Astrophysics Data System (ADS)
McCloskey, J.; NicBhloscaidh, M.; Murphy, S.; O'Brien, G. S.; Bean, C. J.
2013-12-01
High-pressure fluid injection into subsurface is known, in some cases, to induce earthquakes in the surrounding volume. The increasing importance of ';fracking' as a potential source of hydrocarbons has made the seismic hazard from this effect an important issue the adjudication of planning applications and it is likely that poor understanding of the process will be used as justification of refusal of planning in Ireland and the UK. Here we attempt to understand some of the physical controls on the size and frequency of induced earthquakes using a physics-based simulation of the process and examine resulting earthquake catalogues The driver for seismicity in our simulations is identical to that used in the paper by Murphy et al. in this session. Fluid injection is simulated using pore fluid movement throughout a permeable layer from a high-pressure point source using a lattice Boltzmann scheme. Diffusivities and frictional parameters can be defined independently at individual nodes/cells allowing us to reproduce 3-D geological structures. Active faults in the model follow a fractal size distribution and exhibit characteristic event size, resulting in a power-law frequency-size distribution. The fluid injection is not hydraulically connected to the fault (i.e. fluid does not come into physical contact with the fault); however stress perturbations from the injection drive the seismicity model. The duration and pressure-time function of the fluid injection can be adjusted to model any given injection scenario and the rate of induced seismicity is controlled by the local structures and ambient stress field as well as by the stress perturbations resulting from the fluid injection. Results from the rate and state fault models of Murphy et al. are incorporated to include the effect of fault strengthening in seismically quite areas. Initial results show similarities with observed induced seismic catalogues. Seismicity is only induced where the active faults have not been
Dynamic coupling between fluid flow and vein growth in fractures: a 3D numerical model
NASA Astrophysics Data System (ADS)
Schwarz, J.-O.; Enzmann, F.
2012-04-01
Fluid flow is one of the main mass transport mechanisms in the Earth's crust and abundant mineral vein networks are important indicators for fluid flow and fluid rock interaction. These systems are dynamic and part of the so called RTM processes (reaction-transport-mechanics). Understanding of mineral vein systems requires coupling of these processes. Here we present a conceptional model for dynamic vein growth of syntaxial, posttectonic veins generated by advective fluid flow and show first results of a numerical model for this scenario. Vein generation requires three processes to occur: (i) fracture generation by mechanical stress e.g. hydro-fracturing, (ii) flow of a supersaturated fluid on that fracture and (iii) crystallization of phase(s) on or in the fracture. 3D synthetic fractures are generated with the SynFrac code (Ogilvie, et al. 2006). Subsequently solutions of the Navier-Stokes equation for this fracture are computed by a computational fluid dynamics code called GeoDict (Wiegmann 2007). Transport (advective and diffusive) of chemical species to growth sites in the fracture and vein growth are computed by a self-written MATLAB script. The numerical model discretizes the wall rock and fracture geometry by volumetric pixels (voxels). Based on this representation, the model computes the three basic functions for vein generation: (a) nucleation, (b) fluid flow with transport of chemical species and (c) growth. The following conditions were chosen for these three modules. Nucleation is heterogeneous and occurs instantaneously at the wall rock/fracture interface. Advective and diffusive flow of a supersaturated fluid and related transport of chemical species occurs according to the computed fluid flow field by GeoDict. Concentration of chemical species at the inflow is constant, representing external fluid buffering. Changes/decrease in the concentration of chemical species occurs only due to vein growth. Growth of nuclei is limited either by transport of
NASA Astrophysics Data System (ADS)
Facci, Andrea L.; Porfiri, Maurizio
2012-12-01
In this paper, we investigate finite amplitude polychromatic flexural vibration of a thin beam oscillating in a quiescent viscous fluid. We consider a cantilever beam with rectangular cross section undergoing periodic base excitation in the form of a triangular wave. Experiments are performed on centimeter-size beams in water to elucidate the effect of the amplitude and the frequency of the base excitation on the fluid structure interaction. The fundamental frequency of the excitation is selected to induce structural resonance and the shape of the cantilevers is parametrically varied to explore different flow regimes. Experimental results demonstrate the presence of a frequency-dependent nonlinear hydrodynamic damping which tends to enhance higher frequency harmonics as compared to the fundamental harmonic. Such filtering effect produced by the encompassing fluid increases with both the frequency and amplitude of the base excitation. Experimental results are interpreted through available theoretical models, based on the notion of the complex hydrodynamic function, and pertinent computational fluid dynamics findings.
Mapping fluid distribution in a pinch-out reservoir model: A physical modeling study
NASA Astrophysics Data System (ADS)
Assis, Carlos A. M.; Ceia, Marco A. R.; Misságia, Roseane M.; Lupinacci, Wagner M.
2014-10-01
This work shows the results obtained from seismic physical modeling experiments that image the non-homogeneous, two-phase distribution of immiscible fluids inside a cavity in a pinch-out model. The main goal of this study was to verify how the seismic sections can be used to observe the fluid distribution in this type of reservoir. A high-resolution deconvolution method was applied to improve the image resolution and depth migration correctly positioned the events. Instantaneous attributes were used to assist data interpretation. The results provided an image of the oil-water interface and revealed a complex fluid compartmentalization pattern that was confirmed by numerical modeling simulations. The results of this study should improve the understanding of mapping fluid distributions from seismic sections in pinch-out reservoirs.
A Multi-neutral-fluid model of comet 67P/Churyumov-Gerasimenko
NASA Astrophysics Data System (ADS)
Shou, Y.; Combi, M. R.; Gombosi, T. I.; Jia, X.; Toth, G.; Hansen, K. C.; Tenishev, V.; Fougere, N.
2014-12-01
As comet 67P/Churyumov-Gerasimenko, the Rosetta mission target, is approaching perihelion, the OSIRIS instrument observed the nucleus' very unique dumbbell-like shape recently. It arouses an interesting question as to what the coma will look like with the combination of the irregular shape and the rotation of the nucleus, as a result of solar radiation. A physics-based three dimensional coma model is highly desirable to study this topic. One candidate is Direct Simulation Monte Carlo (DSMC) method, and it has been successfully applied to such problems. However, since the comet may be considerably active closer to perihelion and the gas near the nucleus is dense, the time step in DSMC model has to be tiny to accommodate the small mean free path and the high collision frequency, which can make time-variable DSMC modeling computationally expensive. In this work, we develop a multi-neutral-fluid model based on BATS-R-US in the University of Michigan's SWMF (Space Weather Modeling Framework), which can serve as a useful alternative to DSMC methods to compute the inner coma. This model treats cometary heavy neutrals, hydrogen atoms and dusts of different particle sizes as separate fluids. In the model, we include different momentum and energy transfer coefficients for different fluids, heating from chemical reactions and frictions between gas and dust. With other necessary physics considered, it is able to give us a more physical picture than one fluid model. The preliminary results are presented and discussed. This work has been partially supported by NASA Planetary Atmospheres program grant NNX14AG84G and US Rosetta contracts JPL #1266313 and JPL #1266314.
Benchmarking computational fluid dynamics models for lava flow simulation
NASA Astrophysics Data System (ADS)
Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi
2016-04-01
Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, and COMSOL. Using the new benchmark scenarios defined in Cordonnier et al. (Geol Soc SP, 2015) as a guide, we model viscous, cooling, and solidifying flows over horizontal and sloping surfaces, topographic obstacles, and digital elevation models of natural topography. We compare model results to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We can apply these models to reconstruct past lava flows in Hawai'i and Saudi Arabia using parameters assembled from morphology, textural analysis, and eruption observations as natural test cases. Our study highlights the strengths and weaknesses of each code, including accuracy and computational costs, and provides insights regarding code selection.
Carbon dioxide-based supercritical fluids as IC manufacturing solvents
Rubin, J.B.; Davenhall, L.B.; Taylor, C.M.V.; Sivils, L.D.; Pierce, T.; Tiefert, K.
1999-05-11
The production of integrated circuits (IC's) involves a number of discrete steps which utilize hazardous or regulated solvents and generate large waste streams. ES&H considerations associated with these chemicals have prompted a search for alternative, more environmentally benign solvent systems. An emerging technology for conventional solvent replacement is the use of supercritical fluids based on carbon dioxide (CO{sub 2}). Research work, conducted at Los Alamos in conjunction with the Hewlett-Packard Company, has lead to the development of a CO{sub 2}-based supercritical fluid treatment system for the stripping of hard-baked photoresists. This treatment system, known as Supercritical CO{sub 2} Resist Remover, or CORR, uses a two-component solvent composed of a nonhazardous, non-regulated compound, dissolved in supercritical CO{sub 2}. The solvent/treatment system has been successfully tested on metallized Si wafers coated with negative and positive photoresist, the latter both before and after ion-implantation. A description of the experimental data will be presented. Based on the initial laboratory results, the project has progressed to the design and construction of prototype, single-wafer photoresist-stripping equipment. The integrated system involves a closed-loop, recirculating cycle which continuously cleans and regenerates the CO{sub 2}, recycles the dissolved solvent, and separates and concentrates the spent resist. The status of the current design and implementation strategy of a treatment system to existing IC fabrication facilities will be discussed. Additional remarks will be made on the use of a SCORR-type system for the cleaning of wafers prior to processing.
NASA Astrophysics Data System (ADS)
Song, Yongjia; Hu, Hengshan; Rudnicki, John W.
2016-07-01
Grain-scale local fluid flow is an important loss mechanism for attenuating waves in cracked fluid-saturated poroelastic rocks. In this study, a dynamic elastic modulus model is developed to quantify local flow effect on wave attenuation and velocity dispersion in porous isotropic rocks. The Eshelby transform technique, inclusion-based effective medium model (the Mori-Tanaka scheme), fluid dynamics and mass conservation principle are combined to analyze pore-fluid pressure relaxation and its influences on overall elastic properties. The derivation gives fully analytic, frequency-dependent effective bulk and shear moduli of a fluid-saturated porous rock. It is shown that the derived bulk and shear moduli rigorously satisfy the Biot-Gassmann relationship of poroelasticity in the low-frequency limit, while they are consistent with isolated-pore effective medium theory in the high-frequency limit. In particular, a simplified model is proposed to quantify the squirt-flow dispersion for frequencies lower than stiff-pore relaxation frequency. The main advantage of the proposed model over previous models is its ability to predict the dispersion due to squirt flow between pores and cracks with distributed aspect ratio instead of flow in a simply conceptual double-porosity structure. Independent input parameters include pore aspect ratio distribution, fluid bulk modulus and viscosity, and bulk and shear moduli of the solid grain. Physical assumptions made in this model include (1) pores are inter-connected and (2) crack thickness is smaller than the viscous skin depth. This study is restricted to linear elastic, well-consolidated granular rocks.
Fluid flow induced calcium response in osteoblasts: mathematical modeling.
Su, J H; Xu, F; Lu, X L; Lu, T J
2011-07-28
Fluid flow in the bone lacuno-canalicular network can induce dynamic fluctuation of intracellular calcium concentration ([Ca(2+)](i)) in osteoblasts, which plays an important role in bone remodeling. There has been limited progress in the mathematical modeling of this process probably due to its complexity, which is controlled by various factors such as Ca(2+) channels and extracellular messengers. In this study we developed a mathematical model to describe [Ca(2+)](i) response induced by fluid shear stress (SS) by integrating the major factors involved and analyzed the effects of different experimental setups (e.g. [Ca(2+)](i) baseline, pretreatment with ATP). In this model we considered the ATP release process and the activities of multiple ion channels and purinergic receptors. The model was further verified quantitatively by comparing the simulation results with experimental data reported in literature. The results showed that: (i) extracellular ATP concentration has more significant effect on [Ca(2+)](i) baseline (73% increase in [Ca(2+)](i) with extracellular ATP concentration varying between 0 and 10 μM), as compared to that induced by SS (25% variation in [Ca(2+)](i) with SS varying from 0 to 3.5 Pa); (ii) Pretreatment with ATP-medium results in different [Ca(2+)](i) response as compared to the control group (ATP-free medium) under SS; (iii) Relative [Ca(2+)](i) fluctuation over baseline is more reliable to show the [Ca(2+)](i) response process than the absolute [Ca(2+)](i) response peak. The developed model may improve the experimental design and facilitate our understanding of the mechanotransduction process in osteoblasts. PMID:21665208
Two-fluid model for two-phase flow
NASA Astrophysics Data System (ADS)
Ishii, M.
1987-06-01
The two-fluid model formulation is discussed in detail. The emphasis of the paper is on the three-dimensional formulation and the closure issues. The origin of the interfacial and turbulent transfer terms in the averaged formulation is explained and their original mathematical forms are examined. The interfacial transfer of mass, momentum, and energy is proportional to the interfacial area and driving force. This is not a postulate but a result of the careful examination of the mathematical form of the exact interfacial terms. These two effects are considered separately. Since all the interfacial transfer terms involve the interfacial area concentration, the accurate modeling of the local interfacial area concentration is the first step to be taken for a development of a reliable two-fluid model closure relations. The interfacial momentum interaction has been studied in terms of the standard-drag, lift, virtual mass, and Basset forces. Available analytical and semi-empirical correlations and closure relations are reviewed and existing shortcomings are pointed out. The other major area of importance is the modeling of turbulent transfer in two-phase flow. The two-phase flow turbulence problem is coupled with the phase separation problem even in a steady-state fully developed flow. Thus the two-phase turbulence cannot be understood without understanding the interfacial drag and lift forces accurately. There are some indications that the mixing length type model may not be sufficient to describe the three-dimensional turbulent and flow structures. Although it is a very difficult challenge, the two-phase flow turbulence should be investigated both experimentally and analytically with long time-scale research.
Over the past thirty years, scientists at the Environmental Protection Agency's (EPA) Fluid Modeling Facility (FMF) have conducted laboratory studies of fluid flow and pollutant dispersion within three distinct experimental chambers: a meteorological wind tunnel, a water-channel ...
Function of Hexagenia (Mayfly) Burrows: Fluid Model Suggests Bacterial Gardening
NASA Astrophysics Data System (ADS)
Traynham, B.; Furbish, D.; Miller, M.; White, D.
2006-12-01
Lake and stream bottoms experience an array of physical, chemical, and biological processes that create spatial variations both in the fluid column and in the sediment that provide a physical template for distinct niches. Burrowing insects are major ecological engineers of communities where they structure large areas of the benthic habitat through bioturbation and other activities including respiration, feeding, and defecation. The burrowing mayfly Hexagenia, when present in high densities, has a large impact on food-web dynamics and provides essential ecosystem services within the fluid column and benthic substrate, including sediment mixing, nutrient cycling, and ultimately, energy flow through the freshwater food web. It has long been recognized that particular benthic species are important in linking detrital energy resources to higher trophic levels and for determining how organic matter is processed in freshwater ecosystems; however, the unique contributions made by individual benthic species is largely absent from the literature. Here we present a model that describes the structure and function of a Hexagenia burrow. If testing supports this hypothesis, the model suggests that when high food concentration is available to Hexagenia, there exists a favorable tube length for harvesting bacteria that grow on the burrow walls. The burrow microhabitat created by Hexagenia serves as a case-study in understanding the influence of benthic burrowers on both energy flow through freshwater food webs and nutrient cycling.
Experiments and Modeling of G-Jitter Fluid Mechanics
NASA Technical Reports Server (NTRS)
Leslie, F. W.; Ramachandran, N.; Whitaker, Ann F. (Technical Monitor)
2002-01-01
While there is a general understanding of the acceleration environment onboard an orbiting spacecraft, past research efforts in the modeling and analysis area have still not produced a general theory that predicts the effects of multi-spectral periodic accelerations on a general class of experiments nor have they produced scaling laws that a prospective experimenter can use to assess how an experiment might be affected by this acceleration environment. Furthermore, there are no actual flight experimental data that correlates heat or mass transport with measurements of the periodic acceleration environment. The present investigation approaches this problem with carefully conducted terrestrial experiments and rigorous numerical modeling for better understanding the effect of residual gravity and gentler on experiments. The approach is to use magnetic fluids that respond to an imposed magnetic field gradient in much the same way as fluid density responds to a gravitational field. By utilizing a programmable power source in conjunction with an electromagnet, both static and dynamic body forces can be simulated in lab experiments. The paper provides an overview of the technique and includes recent results from the experiments.
NASA Astrophysics Data System (ADS)
Jain, Rajat; Mahto, Triveni K.; Mahto, Vikas
2016-02-01
In the present study, polyacrylamide grafted xanthan gum/multiwalled carbon nanotubes (PA-g-XG/MWCNT) nanocomposite was synthesized by free radical polymerization technique using potassium persulfate as an initiator. The polyacrylamide was grafted on xanthan gum backbone in the presence of MWCNT. The synthesized nanocomposite was characterized by X-ray diffraction technique (XRD), and Fourier transform infrared spectroscopy analysis (FT-IR). The morphological characteristics of the nanocomposite were analyzed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses. Also, its temperature resistance property was observed with Thermogravimetric analysis (TGA). The effect of nanocomposite on the rheological properties of the developed drilling fluid system was analyzed with a strain controlled rheometer and Fann viscometer. Flow curves were drawn for the developed water based drilling fluid system at elevated temperatures. The experimental data were fitted to Bingham, power-law, and Herschel Bulkley flow models. It was observed that the Herschel Bulkley flow model predict the flow behavior of the developed system more accurately. Further, nanocomposite exhibited non-Newtonian shear thinning flow behavior in the developed drilling fluid system. Nanocomposite showed high temperature stability and had a significant effect on the rheological properties of the developed drilling fluid system as compared to conventionally used partially hydrolyzed polyacrylamide (PHPA) polymer.
NASA Astrophysics Data System (ADS)
Zhang, G.; Zheng, Z.
2004-12-01
Leakage of high alkaline-saline fluids, such as those stored in Hanford, a site of the U.S. Department of Energy (DOE) in Washington State, has raised attention of scientific community. These fluids have unique thermodynamic and physical properties. Chemical components in the fluids are incompletely dissociated, especially those containing divalent or polyvalent ions. A number of laboratory experiments through injecting synthetic high alkaline-saline fluids (up to 10M of sodium nitrate, pH >12) into the sediments sampled from the DOE Hanford site were conducted to study the reactive transport processes of the fluids in subsurface environments. The experimental results observed show that the composition of the high alkaline sodium nitrate fluids can be drastically changed due to fluid-rock interactions, and eventually lead to pH neutralization of the fluid in the plume front. The dominant fluid-rock interactions are cation exchanges (Na+-K+-Ca+2-Mg+2-H+), precipitation of calcium and magnesium minerals, and dissolution of silica. In order to precisely model the reactive transport of these processes, a coupling of the Pitzer's ion-interaction geochemical model and a flow and transport model would be highly needed. The extended existing reactive geochemical transport code, BIO-CORE2Dc, incorporating a comprehensive Pitzer ion-interaction model, is capable of predicting the experimental observations. In addition, the developed model was tested against two reported cases. In both cases, the measured mean ionic activity coefficients were well reproduced by our model, while the Debye-Hückel model, usually used to calculate aqueous species activities in dilute solutions, was unable to predict the experimental data. Finally, modeling study based on our laboratory column experiment was performed. Our simulation is able to capture the observed pH trends, changes in exchangeable cations such as Ca+2, Mg+2, and formation of secondary precipitation phases in the plume front.
Grid-Based Hydrodynamics in Astrophysical Fluid Flows
NASA Astrophysics Data System (ADS)
Teyssier, Romain
2015-08-01
In this review, the equations of hydrodynamics, magnetohydrodynamics, and radiation hydrodynamics are presented, together with their corresponding nonideal source terms. I overview the current landscape of modern grid-based numerical techniques with an emphasis on numerical diffusion, which plays a fundamental role in stabilizing the solution but is also the main source of errors associated with these numerical techniques. I discuss in great detail the inclusion of additional important source terms, such as cooling and gravity. I also show how to modify classic operator-splitting techniques to avoid undesirable numerical errors associated with these additional source terms, in particular in the presence of highly supersonic flows. I finally present various mesh adaptation strategies that can be used to minimize these numerical errors. To conclude, I review existing astrophysical software that is publicly available to perform simulations for such astrophysical fluids.
Personal Computer (PC) based image processing applied to fluid mechanics
NASA Technical Reports Server (NTRS)
Cho, Y.-C.; Mclachlan, B. G.
1987-01-01
A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.
Two-dimensional lattice-fluid model with waterlike anomalies.
Buzano, C; De Stefanis, E; Pelizzola, A; Pretti, M
2004-06-01
We investigate a lattice-fluid model defined on a two-dimensional triangular lattice, with the aim of reproducing qualitatively some anomalous properties of water. Model molecules are of the "Mercedes Benz" type, i.e., they possess a D3 (equilateral triangle) symmetry, with three bonding arms. Bond formation depends both on orientation and local density. We work out phase diagrams, response functions, and stability limits for the liquid phase, making use of a generalized first order approximation on a triangle cluster, whose accuracy is verified, in some cases, by Monte Carlo simulations. The phase diagram displays one ordered (solid) phase which is less dense than the liquid one. At fixed pressure the liquid phase response functions show the typical anomalous behavior observed in liquid water, while, in the supercooled region, a reentrant spinodal is observed. PMID:15244571
Two-dimensional lattice-fluid model with waterlike anomalies
NASA Astrophysics Data System (ADS)
Buzano, C.; de Stefanis, E.; Pelizzola, A.; Pretti, M.
2004-06-01
We investigate a lattice-fluid model defined on a two-dimensional triangular lattice, with the aim of reproducing qualitatively some anomalous properties of water. Model molecules are of the “Mercedes Benz” type, i.e., they possess a D3 (equilateral triangle) symmetry, with three bonding arms. Bond formation depends both on orientation and local density. We work out phase diagrams, response functions, and stability limits for the liquid phase, making use of a generalized first order approximation on a triangle cluster, whose accuracy is verified, in some cases, by Monte Carlo simulations. The phase diagram displays one ordered (solid) phase which is less dense than the liquid one. At fixed pressure the liquid phase response functions show the typical anomalous behavior observed in liquid water, while, in the supercooled region, a reentrant spinodal is observed.
Industrial processing of complex fluids: Formulation and modeling
Scovel, J.C.; Bleasdale, S.; Forest, G.M.; Bechtel, S.
1997-08-01
The production of many important commercial materials involves the evolution of a complex fluid through a cooling phase into a hardened product. Textile fibers, high-strength fibers(KEVLAR, VECTRAN), plastics, chopped-fiber compounds, and fiber optical cable are such materials. Industry desires to replace experiments with on-line, real time models of these processes. Solutions to the problems are not just a matter of technology transfer, but require a fundamental description and simulation of the processes. Goals of the project are to develop models that can be used to optimize macroscopic properties of the solid product, to identify sources of undesirable defects, and to seek boundary-temperature and flow-and-material controls to optimize desired properties.
Singular Limits of Voigt Models in Fluid Dynamics
NASA Astrophysics Data System (ADS)
Coti Zelati, Michele; Gal, Ciprian G.
2015-06-01
We investigate the long-term behavior, as a certain regularization parameter vanishes, of the three-dimensional Navier-Stokes-Voigt model of a viscoelastic incompressible fluid. We prove the existence of global and exponential attractors of optimal regularity. We then derive explicit upper bounds for the dimension of these attractors in terms of the three-dimensional Grashof number and the regularization parameter. Finally, we also prove convergence of the (strong) global attractor of the 3D Navier-Stokes-Voigt model to the (weak) global attractor of the 3D Navier-Stokes equation. Our analysis improves and extends recent results obtained by Kalantarov and Titi (Chin Ann Math Ser B 30:697-714, 2009).
REVIEW ARTICLE: Network models of fluid, hexatic and polymerized membranes
NASA Astrophysics Data System (ADS)
Gompper, G.; Kroll, D. M.
1997-10-01
The thermal behaviour of membranes - surfaces of nearly vanishing tension - depends strongly on their internal state, which can be either fluid, crystalline (or polymerized), or hexatic. Thermal fluctuations have a dramatic effect on the conformation and elastic properties of membranes. We describe in this review both the continuum models of membranes which are used for theoretical analyses as well as the network models employed in simulations. The fruitful interaction between these two approaches, which has lead to recent progress in this field, is emphasized. We summarize the essential results of recent research on fluctuating membranes; in particular, the effects of bending rigidity, self-avoidance, attractive interactions, disorder, topological defects and external compression forces are discussed in detail.
[Present status and trend of heart fluid mechanics research based on medical image analysis].
Gan, Jianhong; Yin, Lixue; Xie, Shenghua; Li, Wenhua; Lu, Jing; Luo, Anguo
2014-06-01
With introduction of current main methods for heart fluid mechanics researches, we studied the characteristics and weakness for three primary analysis methods based on magnetic resonance imaging, color Doppler ultrasound and grayscale ultrasound image, respectively. It is pointed out that particle image velocity (PIV), speckle tracking and block match have the same nature, and three algorithms all adopt block correlation. The further analysis shows that, with the development of information technology and sensor, the research for cardiac function and fluid mechanics will focus on energy transfer process of heart fluid, characteristics of Chamber wall related to blood fluid and Fluid-structure interaction in the future heart fluid mechanics fields. PMID:25219260
Two-fluid model of a Bose-Einstein condensate in the cavity optomechanical regime
NASA Astrophysics Data System (ADS)
Goldbaum, Dan; Zhang, Keye; Meystre, Pierre
2010-03-01
We analyze an atomic Bose-Einstein condensate trapped in a high-Q optical cavity driven by a feeble optical field. The dynamics of the resulting collective density excitation of the condensate are formally analogous to the central model system of cavity optomechanics: a radiation pressure driven mechanical oscillator [Brennecke et al., Science 322, 235 (2008)]. However, although BEC-based optomechanical systems have several desirable properties, one must also take into account the effect of atom-atom interactions. We treat these interactions via a two-fluid model that retains the intuitive appeal of the non-interacting two-mode description. We find that the Bogoliubov excitation spectrum of this system comprises a gapped upper branch and a lower branch that can include an unstable excitation mode. [4pt] D. S. Goldbaum, K. Zhang and P. Meystre, Two-fluid model of a Bose-Einstein condensate in the cavity optomechanical regime, arXiv:0911.3234.
Methods of use for sensor based fluid detection devices
NASA Technical Reports Server (NTRS)
Lewis, Nathan S. (Inventor)
2001-01-01
Methods of use and devices for detecting analyte in fluid. A system for detecting an analyte in a fluid is described comprising a substrate having a sensor comprising a first organic material and a second organic material where the sensor has a response to permeation by an analyte. A detector is operatively associated with the sensor. Further, a fluid delivery appliance is operatively associated with the sensor. The sensor device has information storage and processing equipment, which is operably connected with the device. This device compares a response from the detector with a stored ideal response to detect the presence of analyte. An integrated system for detecting an analyte in a fluid is also described where the sensing device, detector, information storage and processing device, and fluid delivery device are incorporated in a substrate. Methods for use for the above system are also described where the first organic material and a second organic material are sensed and the analyte is detected with a detector operatively associated with the sensor. The method provides for a device, which delivers fluid to the sensor and measures the response of the sensor with the detector. Further, the response is compared to a stored ideal response for the analyte to determine the presence of the analyte. In different embodiments, the fluid measured may be a gaseous fluid, a liquid, or a fluid extracted from a solid. Methods of fluid delivery for each embodiment are accordingly provided.
Methods for simulation-based analysis of fluid-structure interaction.
Barone, Matthew Franklin; Payne, Jeffrey L.
2005-10-01
Methods for analysis of fluid-structure interaction using high fidelity simulations are critically reviewed. First, a literature review of modern numerical techniques for simulation of aeroelastic phenomena is presented. The review focuses on methods contained within the arbitrary Lagrangian-Eulerian (ALE) framework for coupling computational fluid dynamics codes to computational structural mechanics codes. The review treats mesh movement algorithms, the role of the geometric conservation law, time advancement schemes, wetted surface interface strategies, and some representative applications. The complexity and computational expense of coupled Navier-Stokes/structural dynamics simulations points to the need for reduced order modeling to facilitate parametric analysis. The proper orthogonal decomposition (POD)/Galerkin projection approach for building a reduced order model (ROM) is presented, along with ideas for extension of the methodology to allow construction of ROMs based on data generated from ALE simulations.
Modeling the Chemical Composition of the Fluid that Formed the ALH84001 Carbonates
NASA Astrophysics Data System (ADS)
Niles, P. B.; Leshin, L.
2005-12-01
The character of aqueous systems on Mars can provide us with important information regarding the history of water and the possibilities for the presence of life on Mars. Evidence of these aqueous systems has been preserved in carbonates found in the martian meteorite ALH84001 whose crystallization age of 4.5 Ga indicates that it has experienced almost all of Mars' history. In addition, the 3.9 Ga age of the carbonates places their formation at a critical time that has been argued to have been `warm and wet' by many studies. The carbonates in the ALH84001 meteorite provide the best opportunity, among all of the martian meteorites, to understand the details of an ancient aqueous system on Mars. Their unique chemical, isotopic and mineralogical composition provides the opportunity to make conclusive statements about the geological conditions in which they formed including the temperature, association with the atmosphere, chemistry of the fluids, and the presence or absence of life. This study uses an empirical model to understand the attributes of the formation fluid based on the unique chemical compositions of the carbonates. This requires the assumption that the ALH84001 carbonate globules formed from a single fluid whose chemical composition changed due to the precipitation of carbonates more calcium rich than the overall fluid composition. The model consists of a simple stepwise stoichiometric calculation of the precipitation of the ALH84001 carbonates from a hypothetical solution. From extensive measurements of the chemical composition of the globules and their abundance in the rock, one can calculate the total amount of magnesium, calcium, and iron removed from the formation fluid as the carbonates precipitated. The unique zoned nature of the ALH84001 carbonates provides a real constraint on the possible fluid compositions consistent with their precipitation. Our results indicate that the fluid that formed the ALH84001 carbonates had an Mg/Ca ratio that was
Modelling Fault Zone Evolution: Implications for fluid flow.
NASA Astrophysics Data System (ADS)
Moir, H.; Lunn, R. J.; Shipton, Z. K.
2009-04-01
Flow simulation models are of major interest to many industries including hydrocarbon, nuclear waste, sequestering of carbon dioxide and mining. One of the major uncertainties in these models is in predicting the permeability of faults, principally in the detailed structure of the fault zone. Studying the detailed structure of a fault zone is difficult because of the inaccessible nature of sub-surface faults and also because of their highly complex nature; fault zones show a high degree of spatial and temporal heterogeneity i.e. the properties of the fault change as you move along the fault, they also change with time. It is well understood that faults influence fluid flow characteristics. They may act as a conduit or a barrier or even as both by blocking flow across the fault while promoting flow along it. Controls on fault hydraulic properties include cementation, stress field orientation, fault zone components and fault zone geometry. Within brittle rocks, such as granite, fracture networks are limited but provide the dominant pathway for flow within this rock type. Research at the EU's Soultz-sous-Forệt Hot Dry Rock test site [Evans et al., 2005] showed that 95% of flow into the borehole was associated with a single fault zone at 3490m depth, and that 10 open fractures account for the majority of flow within the zone. These data underline the critical role of faults in deep flow systems and the importance of achieving a predictive understanding of fault hydraulic properties. To improve estimates of fault zone permeability, it is important to understand the underlying hydro-mechanical processes of fault zone formation. In this research, we explore the spatial and temporal evolution of fault zones in brittle rock through development and application of a 2D hydro-mechanical finite element model, MOPEDZ. The authors have previously presented numerical simulations of the development of fault linkage structures from two or three pre-existing joints, the results of
Rastgoo, Abbas; Ahmadian, Mohammad Taghi
2013-01-01
Summary The paper presents the effects of fluid flow on the static and dynamic properties of carbon nanotubes that convey a viscous fluid. The mathematical model is based on the modified couple stress theory. The effects of various fluid parameters and boundary conditions on the pull-in voltages are investigated in detail. The applicability of the proposed system as nanovalves or nanosensors in nanoscale fluidic systems is elaborated. The results confirm that the nanoscale system studied in this paper can be properly applied for these purposes. PMID:24367746
Vaughan, T J; Mullen, C A; Verbruggen, S W; McNamara, L M
2015-08-01
Load-induced fluid flow acts as an important biophysical signal for bone cell mechanotransduction in vivo, where the mechanical environment is thought to be monitored by integrin and primary cilia mechanoreceptors on the cell body. However, precisely how integrin- and primary cilia-based mechanosensors interact with the surrounding fluid flow stimulus and ultimately contribute to the biochemical response of bone cells within either the in vitro or in vivo environment remains poorly understood. In this study, we developed fluid-structure interaction models to characterise the deformation of integrin- and primary cilia-based mechanosensors in bone cells under fluid flow stimulation. Under in vitro fluid flow stimulation, these models predicted that integrin attachments on the cell-substrate interface were highly stimulated ε(eq) > 200,000 με, while the presence of a primary cilium on the cell also resulted in significant strain amplifications, arising at the ciliary base. As such, these mechanosensors likely play a role in mediating bone mechanotransduction in vitro. Under in vivo fluid flow stimulation, integrin attachments along the canalicular wall were highly stimulated and likely play a role in mediating cellular responses in vivo. The role of the primary cilium as a flow sensor in vivo depended upon its configuration within the lacunar cavity. Specifically, our results showed that a short free-standing primary cilium could not effectively fulfil a flow sensing role in vivo. However, a primary cilium that discretely attaches the lacunar wall can be highly stimulated, due to hydrodynamic pressure in the lacunocanalicular system and, as such, could play a role in mediating bone mechanotransduction in vivo. PMID:25399300
AIR INGRESS ANALYSIS: PART 2 – COMPUTATIONAL FLUID DYNAMIC MODELS
Chang H. Oh; Eung S. Kim; Richard Schultz; Hans Gougar; David Petti; Hyung S. Kang
2011-01-01
The Idaho National Laboratory (INL), under the auspices of the U.S. Department of Energy, is performing research and development that focuses on key phenomena important during potential scenarios that may occur in very high temperature reactors (VHTRs). Phenomena Identification and Ranking Studies to date have ranked an air ingress event, following on the heels of a VHTR depressurization, as important with regard to core safety. Consequently, the development of advanced air ingress-related models and verification and validation data are a very high priority. Following a loss of coolant and system depressurization incident, air will enter the core of the High Temperature Gas Cooled Reactor through the break, possibly causing oxidation of the in-the core and reflector graphite structure. Simple core and plant models indicate that, under certain circumstances, the oxidation may proceed at an elevated rate with additional heat generated from the oxidation reaction itself. Under postulated conditions of fluid flow and temperature, excessive degradation of the lower plenum graphite can lead to a loss of structural support. Excessive oxidation of core graphite can also lead to the release of fission products into the confinement, which could be detrimental to a reactor safety. Computational fluid dynamic model developed in this study will improve our understanding of this phenomenon. This paper presents two-dimensional and three-dimensional CFD results for the quantitative assessment of the air ingress phenomena. A portion of results of the density-driven stratified flow in the inlet pipe will be compared with results of the experimental results.
Supersonic diode pumped alkali lasers: Computational fluid dynamics modeling
NASA Astrophysics Data System (ADS)
Rosenwaks, Salman; Yacoby, Eyal; Waichman, Karol; Sadot, Oren; Barmashenko, Boris D.
2015-10-01
We report on recent progress on our three-dimensional computational fluid dynamics (3D CFD) modeling of supersonic diode pumped alkali lasers (DPALs), taking into account fluid dynamics and kinetic processes in the lasing medium. For a supersonic Cs DPAL with laser section geometry and resonator parameters similar to those of the 1-kW flowing-gas subsonic Cs DPAL [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] the maximum achievable output power, ~ 7 kW, is 25% higher than that achievable in the subsonic case. Comparison between semi-analytical and 3D CFD models for Cs shows that the latter predicts much higher maximum achievable output power than the former. Optimization of the laser parameters using 3D CFD modeling shows that very high power and optical-to-optical efficiency, 35 kW and 82%, respectively, can be achieved in a Cs supersonic device pumped by a collimated cylindrical (0.5 cm diameter) beam. Application of end- or transverse-pumping by collimated rectangular (large cross section ~ 2 - 4 cm2) beam makes it possible to obtain even higher output power, > 250 kW, for ~ 350 kW pumping power. The main processes limiting the power of Cs supersonic DPAL are saturation of the D2 transition and large ~ 40% losses of alkali atoms due to ionization, whereas the influence of gas heating is negligibly small. For supersonic K DPAL both gas heating and ionization effects are shown to be unimportant and the maximum achievable power, ~ 40 kW and 350 kW, for pumping by ~ 100 kW cylindrical and ~ 700 kW rectangular beam, respectively, are higher than those achievable in the Cs supersonic laser. The power achieved in the supersonic K DPAL is two times higher than for the subsonic version with the same resonator and K density at the gas inlet, the maximum optical-to-optical efficiency being 82%.
Preparation and Characterization of Water-Based Nano-fluids for Nuclear Applications
Williams, W.C.; Forrest, E.; Hu, L.W.; Buongiorno, J.
2006-07-01
As part of an effort to evaluate water-based nano-fluids for nuclear applications, preparation and characterization has been performed for nano-fluids being considered for MIT's nano-fluid heat transfer experiments. Three methods of generating these nano-fluids are available: creating them from chemical precipitation, purchasing the nano-particles in powder form and mixing them with the base fluid, and direct purchase of prepared nano-fluids. Characterization of nano-fluids includes colloidal stability, size distribution, concentration, and elemental composition. Quality control of the nano-fluids to be used for heat transfer testing is crucial; an exact knowledge of the fluid constituents is essential to uncovering mechanisms responsible for heat transport enhancement. Testing indicates that nano-fluids created by mixing a liquid with nano-particles in powder form are often not stable, although some degree of stabilization is obtainable with pH control and/or surfactant addition. Some commercially available prepared nano-fluids have been found to contain unacceptable levels of impurities and/or include a different weight percent of nano-particles compared to vendor specifications. Tools utilized to characterize and qualify nano-fluids for this study include neutron activation analysis (NAA), inductively-coupled plasma spectroscopy (ICP), transmission electron microscopy (TEM) imaging, thermogravimetric analysis (TGA) and dynamic light scattering (DLS). Preparation procedures and characterization results for selected nano-fluids will be discussed in detail. (authors)
NASA Astrophysics Data System (ADS)
Yang, Juan-Cheng; Li, Feng-Chen; Cai, Wei-Hua; Zhang, Hong-Na; Yu, Bo
2015-08-01
Our previous experimental studies have confirmed that viscoelastic-fluid-based nanofluid (VFBN) prepared by suspending nanoparticles in a viscoelastic base fluid (VBF, behaves drag reduction at turbulent flow state) can reduce turbulent flow resistance as compared with water and enhance heat transfer as compared with VBF. Direct numerical simulation (DNS) is performed in this study to explore the mechanisms of heat transfer enhancement (HTE) and flow drag reduction (DR) for the VFBN turbulent flow. The Giesekus model is used as the constitutive equation for VFBN. Our previously proposed thermal dispersion model is adopted to take into account the thermal dispersion effects of nanoparticles in the VFBN turbulent flow. The DNS results show similar behaviors for flow resistance and heat transfer to those obtained in our previous experiments. Detailed analyses are conducted for the turbulent velocity, temperature, and conformation fields obtained by DNSs for different fluid cases, and for the friction factor with viscous, turbulent, and elastic contributions and heat transfer rate with conductive, turbulent and thermal dispersion contributions of nanoparticles, respectively. The mechanisms of HTE and DR of VFBN turbulent flows are then discussed. Based on analogy theory, the ratios of Chilton-Colburn factor to friction factor for different fluid flow cases are investigated, which from another aspect show the significant enhancement in heat transfer performance for some cases of water-based nanofluid and VFBN turbulent flows. Project supported by the National Natural Science Foundation of China (Grant No. 51276046), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20112302110020), the China Postdoctoral Science Foundation (Grant No. 2014M561037), and the President Fund of University of Chinese Academy of Sciences, China (Grant No. Y3510213N00).
Working fluid selection for space-based two-phase heat transport systems
NASA Technical Reports Server (NTRS)
Mclinden, Mark O.
1988-01-01
The working fluid for externally-mounted, space-based two-phase heat transport systems is considered. A sequence of screening criteria involving freezing and critical point temperatures and latent heat of vaporization and vapor density are applied to a data base of 860 fluids. The thermal performance of the 52 fluids which pass this preliminary screening are then ranked according to their impact on the weight of a reference system. Upon considering other nonthermal criteria (flammability, toxicity, and chemical stability) a final set of 10 preferred fluids is obtained. The effects of variations in system parameters is investigated for these 10 fluids by means of a factorial design.
Morin, Kristen T; Lenz, Michelle S; Labat, Caroline A; Tranquillo, Robert T
2015-05-01
Knowledge is limited about fluid flow in tissues containing engineered microvessels, which can be substantially different in topology than native capillary networks. A need exists for a computational model that allows for flow through tissues dense in nonpercolating and possibly nonperfusable microvessels to be efficiently evaluated. A finite difference (FD) model based on Poiseuille flow through a distribution of straight tubes acting as point sources and sinks, and Darcy flow through the interstitium, was developed to describe fluid flow through a tissue containing engineered microvessels. Accuracy of the FD model was assessed by comparison to a finite element (FE) model for the case of a single tube. Because the case of interest is a tissue with microvessels aligned with the flow, accuracy was also assessed in depth for a corresponding 2D FD model. The potential utility of the 2D FD model was then explored by correlating metrics of flow through the model tissue to microvessel morphometric properties. The results indicate that the model can predict the density of perfused microvessels based on parameters that can be easily measured. PMID:25424905
Spatial and Temporal Low-Dimensional Models for Fluid Flow
NASA Technical Reports Server (NTRS)
Kalb, Virginia
2008-01-01
A document discusses work that obtains a low-dimensional model that captures both temporal and spatial flow by constructing spatial and temporal four-mode models for two classic flow problems. The models are based on the proper orthogonal decomposition at two reference Reynolds numbers. Model predictions are made at an intermediate Reynolds number and compared with direct numerical simulation results at the new Reynolds number.
Luo, Qizhi; Li, Wei; Zou, Xin; Dang, Yongming; Wu, Jun
2015-01-01
Acute burn injuries are among the most devastating forms of trauma and lead to significant morbidity and mortality. Appropriate fluid resuscitation after severe burn, specifically during the first 48 hours following injury, is considered as the single most important therapeutic intervention in burn treatment. Although many formulas have been developed to estimate the required fluid amount in severe burn patients, many lines of evidence showed that patients still receive far more fluid than formulas recommend. Overresuscitation, which is known as “fluid creep,” has emerged as one of the most important problems during the initial period of burn care. If fluid titration can be personalized and automated during the resuscitation phase, more efficient burn care and outcome will be anticipated. In the present study, a dynamic urine output based infusion rate prediction model was developed and validated during the initial 48 hours in severe thermal burn adult patients. The experimental results demonstrated that the developed dynamic fluid resuscitation model might significantly reduce the total fluid volume by accurately predicting hourly urine output and has the potential to aid fluid administration in severe burn patients. PMID:26090415
NASA Astrophysics Data System (ADS)
Rajabzadeh Oghaz, Hamidreza; Damiano, Robert; Meng, Hui
2015-11-01
Intracranial aneurysms (IAs) are pathological outpouchings of cerebral vessels, the progression of which are mediated by complex interactions between the blood flow and vasculature. Image-based computational fluid dynamics (CFD) has been used for decades to investigate IA hemodynamics. However, the commonly adopted simplifying assumptions in CFD (e.g. rigid wall) compromise the simulation accuracy and mask the complex physics involved in IA progression and eventual rupture. Several groups have considered the wall compliance by using fluid-structure interaction (FSI) modeling. However, FSI simulation is highly sensitive to numerical assumptions (e.g. linear-elastic wall material, Newtonian fluid, initial vessel configuration, and constant pressure outlet), the effects of which are poorly understood. In this study, a comprehensive investigation of the sensitivity of FSI simulations in patient-specific IAs is investigated using a multi-stage approach with a varying level of complexity. We start with simulations incorporating several common simplifications: rigid wall, Newtonian fluid, and constant pressure at the outlets, and then we stepwise remove these simplifications until the most comprehensive FSI simulations. Hemodynamic parameters such as wall shear stress and oscillatory shear index are assessed and compared at each stage to better understand the sensitivity of in FSI simulations for IA to model assumptions. Supported by the National Institutes of Health (1R01 NS 091075-01).
Comparison of perturbations in fluid and scalar field models of dark energy
Jassal, H. K.
2009-06-15
We compare perturbations in a fluid model of dark energy with those in a scalar field. As compared to the {lambda}CDM model, large scale matter power spectrum is suppressed in fluid model as well as in a generic quintessence dark energy model. To check the efficacy of fluid description of dark energy in emulating a scalar field, we consider a potential which gives the same background evolution as a fluid with a constant equation of state. We show that for sub-Hubble scales, a fluid model effectively emulates a scalar field model. At larger scales, where dark energy perturbations may play a significant role, the fluid analogy breaks down and the evolution of matter density contrast depends on individual scalar field models.
Barker, Andrew T. Cai Xiaochuan
2010-02-01
We introduce and study numerically a scalable parallel finite element solver for the simulation of blood flow in compliant arteries. The incompressible Navier-Stokes equations are used to model the fluid and coupled to an incompressible linear elastic model for the blood vessel walls. Our method features an unstructured dynamic mesh capable of modeling complicated geometries, an arbitrary Lagrangian-Eulerian framework that allows for large displacements of the moving fluid domain, monolithic coupling between the fluid and structure equations, and fully implicit time discretization. Simulations based on blood vessel geometries derived from patient-specific clinical data are performed on large supercomputers using scalable Newton-Krylov algorithms preconditioned with an overlapping restricted additive Schwarz method that preconditions the entire fluid-structure system together. The algorithm is shown to be robust and scalable for a variety of physical parameters, scaling to hundreds of processors and millions of unknowns.
COTHERM: Modelling fluid-rock interactions in Icelandic geothermal systems
NASA Astrophysics Data System (ADS)
Thien, Bruno; Kosakowski, Georg; Kulik, Dmitrii
2014-05-01
Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced geothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. We model the mineralogical and porosity evolution of Icelandic geothermal systems with 1D and 2D reactive transport models. These geothermal systems are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. The shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. We investigate two contrasting geothermal systems: Krafla, for which the water recharge consists of meteoritic water; and Reykjanes, for which the water recharge mainly consists of seawater. The initial rock composition is a fresh basalt. We use the GEM-Selektor geochemical modeling package [1] for calculation of kinetically controlled mineral equilibria between the rock and the ingression water. We consider basalt minerals dissolution kinetics according to Palandri & Kharaka [2]. Reactive surface areas are assumed to be geometric surface areas, and are corrected using a spherical-particle surface/mass relationship. For secondary minerals, we consider the partial equilibrium assuming that the primary mineral dissolution is slow, and the secondary mineral precipitation is fast. Comparison of our modeling results with the mineralogical assemblages observed in the
Critique of fluid theory of magnetospheric phenomena. [kinetic theory vs two fluid models
NASA Technical Reports Server (NTRS)
Heikkila, W. J.
1973-01-01
Discussion of the limitations and shortcomings of the fluid theory of magnetospheric phenomena. Following a brief qualitative review of the various theoretical approaches and of their interrelation, some of the limitations of the fluid theory with respect to magnetospheric problems are outlined, and the subsequent fallacies are exposed. The idea of frozen field convection and the concept of field line annihilation or merging are criticized. In conclusion, a plea is made for a more balanced approach to magnetospheric problems.
Gamma-ray free-electron lasers: Quantum fluid model
NASA Astrophysics Data System (ADS)
Silva, H. M.; Serbeto, A.; Galvão, R. M. O.; Mendonça, J. T.; Monteiro, L. F.
2014-12-01
A quantum fluid model is used to describe the interaction of a nondegenerate cold relativistic electron beam with an intense optical wiggler taking into account the beam space-charge potential and photon recoil effect. A nonlinear set of coupled equations is obtained and solved numerically. The numerical results indicate that intense γ-ray free-electron laser emission, with intensities approaching the Schwinger limit, can be driven by the strong nonlinear space-charge wave, for feasible values of the electron beam parameters. However, the achievement of this regime of extreme intensities depends rather critically on the choice of the detuning and of the signal initial phase at the entrance of the interaction region.
Modeling golf ball fluid mechanics - challenges and opportunities
NASA Astrophysics Data System (ADS)
Squires, Kyle
2009-11-01
Numerical simulation presents a powerful tool for understanding the fundamental fluid mechanics that influence golf ball aerodynamics, as well as providing an approach for ultimately analyzing and designing golf balls for manufacture. Robust and accurate simulation strategies are central to providing a means to screen designs prior to costly prototyping and field measurement. Results from a hierarchy of simulation strategies applied to the flow around golf balls will be presented, ranging from Reynolds-averaged Navier-Stokes (RANS) computations to Direct Numerical Simulation (DNS). RANS methods, while leading to computationally efficient approaches, are challenged to represent using ad hoc turbulence models the subtle effects induced by surface dimpling. DNS on the other hand, offers a first-principles approach that enables detailed examination of mechanisms though carries a significant computational cost. Predictions from both techniques are contrasted; opportunities for advancing each technique are identified.
A one-domain approach for modeling and simulation of free fluid over a porous medium
NASA Astrophysics Data System (ADS)
Chen, Huangxin; Wang, Xiao-Ping
2014-02-01
We propose a one-domain approach based on the Brinkman model for the modeling and simulation of the transport phenomenon between free fluid and a porous medium. A thin transition layer is introduced between the free fluid region and the porous media region, across which the porosity and permeability undergo a rapid but continuous change. We study the behavior of the solution to the one-domain model analytically and numerically. Using the method of matched asymptotic expansion, we recover the Beavers-Joseph-Saffman (BJS) interface condition as the thickness of the transition layer goes to zero. We also calculate the error estimates between the leading order solution of the one-domain model and the standard Darcy-Stokes model of two-domain model with BJS condition. Numerical methods are developed for both the one-domain model and the two-domain model. Numerical results are presented to support the analytical results, thereby justifying the one-domain model as a good approximation to the two domain Stokes-Darcy model.
Model for hydromagnetic convection in a magnetized fluid.
Macek, Wiesław M; Strumik, Marek
2010-08-01
We consider convection in a horizontally magnetized viscous fluid layer in the gravitational field heated from below with a vertical temperature gradient. Following Rayleigh-Bénard scenario and using a general magnetohydrodynamic approach, we obtain a simple set of four ordinary differential equations. In addition to the usual three-dimensional Lorenz model a new variable describes the profile of the induced magnetic field. We show that nonperiodic oscillations are influenced by anisotropic magnetic forces resulting not only in an additional viscosity but also substantially modifying nonlinear forcing of the system. On the other hand, this can stabilize convective motion of the flow. However, for certain values of the model parameters we have identified a deterministic intermittent behavior of the system resulting from bifurcation. In this way, we have identified here a basic mechanism of intermittent release of energy bursts, which is frequently observed in space and laboratory plasmas. Hence, we propose this model as a useful tool for the analysis of intermittent behavior of various environments, including convection in planets and stars. Therefore, we hope that our simple but still a more general nonlinear model could shed light on the nature of hydromagnetic convection. PMID:20866943
NASA Astrophysics Data System (ADS)
Wang, L. X.; Kamath, H.
2006-12-01
A dynamical mathematical model is proposed to model the hysteretic behaviour of magnetorheological fluids and dampers using phase-transition theory. To construct the model involving hysteresis, the magnetorheological fluids are assumed to be switchable between different phases upon the application of a shear strain rate, with one solid-like phase and two fluid-like phases. The Landau theory for phase transition is employed to model the dynamics of the phase transition in the fluids. The proposed model is able to capture hysteresis loops, and is rate dependent (frequency dependent). A comparison between predicted and experimental behaviour of the damper is presented, and perfect agreement is obtained.
Controllable magneto-rheological fluid-based dampers for drilling
Raymond, David W.; Elsayed, Mostafa Ahmed
2006-05-02
A damping apparatus and method for a drillstring comprising a bit comprising providing to the drillstring a damping mechanism comprising magnetorheological fluid and generating an electromagnetic field affecting the magnetorheological fluid in response to changing ambient conditions encountered by the bit.
Covariant Analysis of Newtonian Multi-Fluid Models for Neutron Stars I:
NASA Astrophysics Data System (ADS)
Carter, Brandon; Chamel, Nicolas
This is the first of a series of articles showing how 4 dimensionally covariant analytical procedures developed in the context of General Relativity can be usefully adapted for application in a purely Newtonian framework where they provide physical insights (e.g. concerning helicity currents) that are not so easy to obtain by the traditional approach based on a 3+1 spacetime decomposition. After an introductory presentation of the relevant Milne spacetime structure and the associated Cartan connection, the essential principles are illustrated by application to the variational formulation of simple barotropic perfect fluid models. This variational treatment is then extended to conservative multiconstituent self-gravitating fluid models of the more general kind that is needed for treating the effects of superfluidity in neutron stars.
Microtomography and pore-scale modeling of two-phase Fluid Distribution
Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.
2010-10-19
Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.
Evaluation of generic types of drilling fluid using a risk-based analytic hierarchy process.
Sadiq, Rehan; Husain, Tahir; Veitch, Brian; Bose, Neil
2003-12-01
The composition of drilling muds is based on a mixture of clays and additives in a base fluid. There are three generic categories of base fluid--water, oil, and synthetic. Water-based fluids (WBFs) are relatively environmentally benign, but drilling performance is better with oil-based fluids (OBFs). The oil and gas industry developed synthetic-based fluids (SBFs), such as vegetable esters, olefins, ethers, and others, which provide drilling performance comparable to OBFs, but with lower environmental and occupational health effects. The primary objective of this paper is to present a methodology to guide decision-making in the selection and evaluation of three generic types of drilling fluids using a risk-based analytic hierarchy process (AHP). In this paper a comparison of drilling fluids is made considering various activities involved in the life cycle of drilling fluids. This paper evaluates OBFs, WBFs, and SBFs based on four major impacts--operations, resources, economics, and liabilities. Four major activities--drilling, discharging offshore, loading and transporting, and disposing onshore--cause the operational impacts. Each activity involves risks related to occupational injuries (safety), general public health, environmental impact, and energy use. A multicriteria analysis strategy was used for the selection and evaluation of drilling fluids using a risk-based AHP. A four-level hierarchical structure is developed to determine the final relative scores, and the SBFs are found to be the best option. PMID:15160901
Numeric modeling approximation of the fluid dynamics in an optical fiber trap
NASA Astrophysics Data System (ADS)
Hernández Zavala, J. E.; Cerecedo Nuñez, H. H.; Vigueras Zuñiga, M. O.; Padilla Sosa, P.
2014-09-01
This document presents a first approach to study the behavior of a static fluid radiated by infrared light (980nm,100mW) transmitted by a single-mode optical fiber, for this simulation temperature and radiation pressure are calculated based on the intensity delivered by a laser diode. The Computing Fluid Dynamics (CFD) results were based on a mesh Tet/Hybrid, TGrid for a Silica micro-particle and a mesh Hex/Wedge, Cooper for the beam. The results show that as the particle moves along the axis, temperature and pressure decreases, having the points of mayor temperature and pressure around the axis. The conclusion of this work is that it is possible to simulate the interactions between the beam, the micro-particle and the surrounding medium in terms of temperature, velocity and pressure using the energy and viscous model.
NASA Astrophysics Data System (ADS)
Huang, Weifeng; Liao, Chuanjun; Liu, Xiangfeng; Suo, Shuangfu; Liu, Ying; Wang, Yuming
2014-09-01
Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants. More accurate models on the operating mechanism of the seals are needed to help improve their performance. The thermal fluid-solid interaction (TFSI) mechanism of the hydrostatic seal is investigated in this study. Numerical models of the flow field and seal assembly are developed. Based on the mechanism for the continuity condition of the physical quantities at the fluid-solid interface, an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method. Dynamic mesh technology is adopted to adapt to the changing boundary shape. Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure. The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data. Using the TFSI model, the behavior of the seal is presented, including mechanical and thermal deformation, and the temperature field. The influences of the rotating speed and differential pressure of the sealing device on the temperature field, which occur widely in the actual use of the seal, are studied. This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals, and the model is validated by full-sized experiments.
A fully dynamic magneto-rheological fluid damper model
NASA Astrophysics Data System (ADS)
Jiang, Z.; Christenson, R. E.
2012-06-01
Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.
NASA Astrophysics Data System (ADS)
Seward, R. J.; Reed, M. H.; Fridriksson, T.
2013-12-01
Single phase geothermal fluids sampled at depth (Hardardottir et al. 2007) from the Reykjanes geothermal system in Iceland show large differences in dissolved copper, zinc, and iron concentrations when compared with fluid sampled from the same well at the surface. Equilibrium modeling of the samples taken at depth indicate that the fluid was supersaturated in sulfide minerals even at moderately acidic pH values, suggesting that the deep samples, as collected, are out of equilibrium. One possibility for this discrepancy is that the down-well mechanical sampler trapped suspended particles of sulfide minerals that were treated as part of the dissolved constituents of the fluid when it was analyzed, thus inflating the concentrations of Cu, Zn and Fe. In addition to possible entrained solids, techniques used to take in-situ fluid samples at depth in these wells do not provide a complete picture of dissolved species within the fluid because gases are lost when samples are brought to the surface. This precludes meaningful pH measurements and therefore requires chemical modeling of surface samples to understand the state of fluids at depth. In this study geothermal fluids are modeled from surface sample analyses and compared with results from models of fluids collected at depth in the same geothermal wells by calculating a full chemical speciation of geothermal fluids as they boil with decreasing pressure and temperature using programs SOLVEQ-xpt and CHIM-xpt. One of the wells examined for this study was well RN-12. In-situ down-well samples were collected at 1500m, within the single phase region as indicated by pre-sampling pressure and temperature logging in the well which showed that boiling starts at 1300m, and 295 degrees C. Fluid and gas samples which were collected at the well head are recomputed as a single phase fluid to be compared with the down-well sampler. These surface fluids reached a maximum temperature of 300 to 320 degrees C, determined by computing the
NASA Astrophysics Data System (ADS)
Wang, Jie; Zhao, Shougen; Wu, Dafang; Jing, Xingjian
2016-01-01
Micro-vibration isolation is a hot topic in spacecraft vibration control, and fluid based vibration isolators alternatively provide a good and reliable solution to this challenging issue. In this paper, a novel fluid based micro-vibration isolator (FBMVI) is investigated. According to its inherent working principle and deformation pattern, the generation mechanisms of the damping and stiffness characteristics are derived, which are nonlinear functions of the environmental temperature. Then a lumped parameter model which is expressed by the physical design parameters (PDPs) is constructed, and the corresponding performance objective indices (POIs) are also obtained by applying the equivalence of mechanical impedance. Based on the finite element analysis of the internal damping component, a single variable method is further adopted to carry out the parametric study, and the influences of each PDP on the POIs are analyzed in details. Finally, experiments are conducted to identify the variation of fluid bulk modulus with the outside environmental temperature, and to validate the performance of the isolator under different temperature environments. The tested results show great consistence compared with the predicted tendencies of the parametric study. The results of this study can provide a very useful insight into and/or an important guidance for the design and application of this type of FBMVIs in engineering practice.
Modelling reacting localized air pollution using Computational Fluid Dynamics (CFD)
NASA Astrophysics Data System (ADS)
Karim, A. A.; Nolan, P. F.
2011-02-01
A Computational Fluid Dynamics (CFD) approach is used to model reacting NO 2 dispersion of vehicle pollutants released from a dual carriageway in Maidstone, UK. The simulations are carried out over the course of one full day during January, 2008. The developed CFD model utilizes a modified k- ɛ turbulence model and Arrhenius reaction kinetics with source terms for the reactions which include a photo-stationary set with peroxy radicals. An approach is taken whereby the reactions are solved specific to the rush hour period corresponding to the availability of certain hydrocarbons released from the vehicles. The results of the simulation are compared with field measurements taken at the site which is made up of several, different sized buildings on varying terrain in Maidstone UK. The predictions and field measurements are considered over a 12 h period with averaged hourly results. It was found that the reactive pollutant approach greatly improves the predictions as compared to the experiments. Furthermore the effect of peroxy radicals during rush hour periods is found to be a major disturbance to the photo-stationary set and its inclusion improved the predictions further.
Modeling strain and pore pressure associated with fluid extraction: The Pathfinder Ranch experiment
NASA Astrophysics Data System (ADS)
Barbour, Andrew J.; Wyatt, Frank K.
2014-06-01
Strainmeters can be subject to hydrologic effects from pumping of nearby water wells, depending on the state of the local rock. Strain signals associated with hydrology are generally not used and regarded as troublesome because they are much larger than most tectonic signals (e.g., tides or slow slip episodes in Cascadia), but here we show that fluid extraction leads to detectable strain and pore pressure signals, which we use to constrain valuable material properties of the rock, namely the hydraulic diffusivity and elastic shear modulus. We collected multiple years of pump activity at two active water wells near a pair of Plate Boundary Observatory borehole strainmeters in southern California. These data demonstrate clearly the connection between fluid extraction and deformation: the onset of transient strains and pore pressures is strongly correlated with both the onset of fluid extraction, and the sizes of the transient signals are strongly correlated with cumulative extraction volumes. These data also suggest that the instruments are a possible tool for remote monitoring of fluid injection and withdrawal. Based on poroelastic modeling, we find estimates of hydraulic diffusivity (0.061 m2s-1 to 0.126 m2s-1) which are consistent with data for fractured igneous rock, and estimates of shear modulus (39.7 MPa to 101 MPa) which are comparable to data for shallow granodiorite—expected to be weak from weathering, and other sources of damage (e.g., faulting). We infer that crustal rock in this region is drained at shallow depths by pervasive, hydraulically conductive fractures: as a result of changes in applied stress, fluid flow will occur rather than a sustained change in pore fluid pressure.
Excess-entropy-based anomalies for a waterlike fluid.
Errington, Jeffrey R; Truskett, Thomas M; Mittal, Jeetain
2006-12-28
Many thermodynamic and dynamic properties of water display unusual behavior at low enough temperatures. In a recent study, Yan et al. [Phys. Rev. Lett. 95, 130604 (2005)] identified a spherically symmetric two-scale potential that displays many of the same anomalous properties as water. More specifically, for select parametrizations of the potential, one finds that the regions where isothermal compression anomalously (i) decreases the fluid's structural order, (ii) increases its translational self-diffusivity, and (iii) increases its entropy form nested domes in the temperature-density plane. These property relationships are similar to those found for more realistic models of water. In this work, the authors provide evidence that suggests that the anomalous regions specified above can all be linked through knowledge of the excess entropy. Specifically, the authors show how entropy scaling relationships developed by Rosenfeld [Phys. Rev. A 15, 2545 (1977)] can be used to describe the region of diffusivity anomalies and to predict the state conditions for which anomalous viscosity and thermal conductivity behavior might be found. PMID:17199350
Four fluid model and numerical simulations of magnetic structures in the heliosheath
NASA Astrophysics Data System (ADS)
Avinash, K.; Cox, S. M.; Shaikh, D.; Zank, G. P.
2007-12-01
A magnetic hole/hump is a stable structure with small scale minima/maxima of the mean magnetic field in the centre. Such structure has been observed in inter-planetary magnetic field, planetary magneto sheath, cometary's plasma, and very recently in the heliosheath, as revealed by Voyager I observations. Recently, we have proposed a realistic three fluid model that comprises of three fluids in the model are electrons, heliosheath ions, and neutrals. Stationary, time independent solutions of this model consisting of holes, humps, trains of holes and humps etc. were found to be consistent with Voyager observations e.g. a few tens of ion gyro-radii width, large magnetic maxima/minima, oblique angles of propagation and well approximated by Gaussians. In the first part of the present work, we extend the three fluid model to a four fluid model consisting of electrons, pick up ions (PUI), solar wind ions (SWI), and neutrals. The PUIs are generated by neutrals via charge exchange with SWI. The kinetic pressure of PUI is nearly three to four times the pressure of SWI. Hence these are more suited to mediate small scale structures in heliosheath like shocks, magnetic holes/humps etc. We show that the constant energy exchange between these two fluid drives them non adiabatic. The modified adiabatic index, is calculated by solving the corresponding enthalpy equation. The PUI are found to be isothermal ( = 1) while SWI have 1.25. In the four fluid model, these effects are captured by including a modified equation of state for PUIs and SWIs. The phase space of time independent solutions in terms of the Mach numbers of PUI and SWI is constructed to delineate the parameter space which allows structure formation. In the second part of the present work, we examine the stability of our time independent solution by evolving them via a full set of modified Hall-MHD equations. The evolutions are examined using two codes e.g. a pseudo spectral code and a code based on finite difference
NASA Astrophysics Data System (ADS)
Ghanbari, Mina; Hossainpour, Siamak; Rezazadeh, Ghader
2015-11-01
This paper deals with the analysis of a novel micro-electromechanical sensor for measurement of microscale fluid physical properties. The proposed sensor is made up of a micro-beam with one end fixed and a micro-plate as a sensing element at its free end, which is immersed in a microscale fluid media. As fluids show different behavior in microscale than in macroscale, the microscale fluid media have been modeled based on micro-polar theory. So non-classical properties of fluid that are absent in macroscale flows need to be measured. In order to actuate the sensor longitudinally, an AC voltage is applied to the piezoelectric layers on the upper and lower surfaces of the micro-beam. Coupled governing partial differential equations of motion of the fluid field and longitudinal vibration of the micro-beam have been derived based on micro-polar theory. The obtained governing differential equations with time-varying boundary conditions have been simplified and transformed to an enhanced form with homogenous boundary conditions. Then, they have been discretized over the beam and fluid domain using Galerkin-based reduced-order model. The dynamic response of the sensing element for different piezoelectric actuation voltages and different exciting frequencies has been studied. It has been shown that by investigating damping and inertial effect fluid loading on response of the micro-beam, properties of a microscale fluid can be measured. At the end, effects of geometrical parameters of the sensor on the response of sensing element have been studied.
Relativistic model of anisotropic charged fluid sphere in general relativity
NASA Astrophysics Data System (ADS)
Pant, Neeraj; Pradhan, N.; Bansal, Rajeev K.
2016-01-01
In this present paper, we present a class of static, spherically symmetric charged anisotropic fluid models of super dense stars in isotropic coordinates by considering a particular type of metric potential, a specific choice of electric field intensity E and pressure anisotropy factor Δ which involve parameters K (charge) and α (anisotropy) respectively. The solutions so obtained are utilized to construct the models for super-dense stars like neutron stars and strange quark stars. Our solutions are well behaved within the following ranges of different constant parameters. In the absence of pressure anisotropy and charge present model reduces to the isotropic model Pant et al. (Astrophys. Space Sci. 330:353-359, 2010). Our solution is well behaved in all respects for all values of X lying in the range 0< X ≤ 0.18, α lying in the range 0 ≤ α ≤6.6, K lying in the range 0< K ≤ 6.6 and Schwarzschild compactness parameter "u" lying in the range 0< u ≤ 0.38. Since our solution is well behaved for a wide ranges of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We have shown that corresponding to X=0.088, α=0.6 and K=4.3 for which u=0.2054 and by assuming surface density ρb = 4.6888 × 10^{14} g/cm3 the mass and radius are found to be 1.51 M_{\\varTheta} and 10.90 km respectively. Assuming surface density ρb = 2 × 10^{14} g/cm3 the mass and radius for a neutron star candidate are found to be 2.313 M_{\\varTheta} and 16.690 km respectively. Hence we obtain masses and radii that fall in the range of what is generally expected for quark stars and neutron stars.
NASA Astrophysics Data System (ADS)
Hu, F. F.; Chen, T.; Wu, D. Z.; Wang, L. Q.
2013-12-01
The internal flow evolution of the pump was induced with impeller movement. In various conditions, the peak load on centrifugal blade under the change of rotational speed or flow rate was also changed. It would cause an error when inertia load with a safety coefficient (that was difficult to ascertain) was applied in structure design. In order to accurately analyze the impeller stress under various conditions and improve the reliability of pump, based on a mixed flow pump model, the stress distribution characteristic was analyzed under different flow rates and rotational speeds. Based on a three-dimensional calculation model including impeller, guide blade, inlet and outlet, the three-dimension incompressible turbulence flow in the centrifugal pump was simulated by using the standard k-epsilon turbulence model. Based on the sequentially coupled simulation approach, a three-dimensional finite element model of impeller was established, and the fluid-structure interaction method of the blade load transfer was discussed. The blades pressure from flow simulation, together with inertia force acting on the blade, was used as the blade loading on solid surface. The Finite Element Method (FEM) was used to calculate the stress distribution of the blade respectively under inertia load, or fluid load, or combined load. The results showed that the blade stress changed with flow rate and rotational speed. In all cases, the maximum stress on the blade appeared on the pressure side near the hub, and the maximum static stress increased with the decreasing of the flow rate and the increasing of rotational speed. There was a big difference on the static stress when inertia load, fluid load and combined loads was applied respectively. In order to more accurately calculate the stress distribution, the structure analysis should be conducted due to combined loads. The results could provide basis for the stress analysis and structure optimization of pump.
Patch testing with components of water-based metalworking fluids.
Geier, Johannes; Lessmann, Holger; Frosch, Peter J; Pirker, Claudia; Koch, Patrick; Aschoff, Roland; Richter, Gerhard; Becker, Detlef; Eckert, Christian; Uter, Wolfgang; Schnuch, Axel; Fuchs, Thomas
2003-08-01
Water-based metalworking fluids (MWFs) may cause both irritant and allergic contact dermatitis. Several well-known MWF allergens are available for patch testing, but considering the wide variety of possible components used in MWF, our diagnostic arsenal covers only a small part of potential allergens. We therefore selected 13 frequently used MWF components that might be sensitizers and had not yet been tested routinely. In 5 centres, 233 dermatitis patients with present or past occupational exposure to MWF were patch tested with this and other panels. Only 7 patients showed positive reactions to the study panel. Allergic reactions to the emulsifier diglycolamine [syn. 2-(2-aminoethoxy) ethanol] were seen in 5 patients, and 1 patient each reacted positively to 2-amino-2-ethyl-1,3-propanediol (AEPD) and methyldiethanolamine (MDEA). Clinical relevance of the reactions to diglycolamine was unequivocally proven by its presence in the MWF from the patients' workplace in 3 cases. Diglycolamine seems to be an important MWF allergen, independently from monoethanolamine and diethanolamine. A test concentration of 1% petrolatum (pet.) appears to be appropriate. The importance of AEPD and MDEA as MWF allergens still remains to be established. The lack of positive test reactions to the other MWF components tested may be due to their low-sensitizing potential or too low a patch test concentration being used. PMID:14641356
Effect of viscosity of base fluid on thermal conductivity of nanofluids
NASA Astrophysics Data System (ADS)
Tsai, Tsung-Han; Kuo, Long-Sheng; Chen, Ping-Hei; Yang, Chin-Ting
2008-12-01
This study aims to investigate the effect of viscosity of the base fluid on the thermal conductivity of nanofluids in which Fe3O4 nanoparticles are suspended in the base fluid composed of diesel oil and polydimethylsiloxane. Viscosity of the base fluid is varied by changing the volumetric fractions between both fluids. The measured thermal conductivity of nanofluids gradually approaches the value predicted by the Maxwell equation by increasing the viscosity. It demonstrates that the viscosity of nanofluids does affect the thermal conductivity of nanofluids, and the Brownian motion of suspended particles could be an important factor that enhances the thermal conductivity of nanofluids.
Rheologically stable, nontoxic, high-temperature, water-based drilling fluid
Elward-Berry, J.; Darby, J.B.
1997-09-01
An exceptionally stable, high-temperature, water-based drilling fluid has been developed based on a fundamental redesign of drilling fluid components and functions, while still using commercially available materials. Rheological stability was characterized by extensive Fann 50C low-shear-rate viscosity vs. temperature studies and supporting viscoelastic rheological data. The fluid has been used in offshore and land applications, at temperatures as high as 420 F and densities as high as 15.5 lbm/gal.
A numerical model for elliptical instability of the Earth's fluid outer core
NASA Astrophysics Data System (ADS)
Seyed-Mahmoud, Behnam; Henderson, Gary; Aldridge, Keith
2000-01-01
A dynamical model is proposed for the elliptical instability that has been reported by Aldridge et al. [Aldridge, K.D., Seyed-Mahmoud, B., Henderson, G.A., van Wijngaarden, W., 1997. Elliptical instability of the Earth's fluid core. Phys. Earth Planet. Inter., 103, 365-374] in connection with recent experiments on an ellipsoidal shell of rotating fluid. The frequencies and growth rates of the instability are obtained numerically by means of a Galerkin method that is based upon the normal modes of the contained fluid. A finite-element method has been employed to approximately solve the ill-posed Poincaré problem for the normal modes. The numerical results for a special case are compared with their analytical counterparts, and the agreement is to within 0.1% for shells of small ellipticity. Results are presented for other cases, including some where the boundary perturbation is allowed to rotate slowly with respect to the inertial frame. The conclusion is that such investigations are of geophysical interest, since tidal forcing might be sufficient to excite an elliptical instability of the fluid outer core of the Earth and thus contribute to the geomagnetic field.
Acoustic and Aero-Mixing Experimental Results for Fluid Shield Scale Model Nozzles
NASA Technical Reports Server (NTRS)
Salikuddin, M.; Mengle, V. G.; Shin, H. W.; Majjigi, R. K.
2005-01-01
The principle objectives of this investigation are to evaluate the acoustic and aerodynamic characteristics of fluid shield nozzle concept and to assess Far 36, Stage 3 potential for fluid shield nozzle with Flade Cycle. Acoustic data for nine scale model nozzle configurations are obtained. The effects of simulated flight and geometric and aerothermodynamic flow variables on the acoustic behavior of the fluid shield are determined. The acoustic tests are aimed at studying the effect of: (1) shield thickness, (2) wrap angle, (3) mass flow and velocity ratios between shield and core streams at constant cycle specific thrust (i.e., mixed velocity), (4) porous plug, and (5) subsonic shield. Shadowgraphs of six nozzle configurations are obtained to understand the plume flowfield features. Static pressure data on suppressor chutes in the core stream (shielded and unshielded) sides and on plug surface are acquired to determine the impact of fluid shield on base drag of the 36-chute suppressor nozzle and the thrust augmentation due to the plug, respectively.
Modeling relaxation effects on multiphase fluid transport in wells and pipelines
NASA Astrophysics Data System (ADS)
Michel Villazon, Guillermo German
The effect of relaxation in processes involving phase transition during flow of reservoir fluids in pipelines and wells is investigated and formulated. Applications concerning the steady-state flow of producing wells, waxy-oil rheology during transient cooling, and wax gelation of shut-in submarine pipes are studied by the means of numerical simulation. This is accomplished by description of the transport of reservoir fluids flowing through pipes in terms of spatially-averaged phase properties. Several homogeneous models are developed by introducing the spatially-averaged properties into the equations describing the concurrent transport of phases, referred to as multi-fluid model. Thus, the number of unknown variables is decreased from several sets of properties corresponding to each phase in the multi-fluid model to one set of properties corresponding to a single pseudo-phase in the homogenous model. First, flow of reservoir fluids in oil production wells is described by a three-phase model. Relaxation phenomenon concerning dissolved-gas separation from the oil and water phases is elaborated. Two numerical procedures are presented for simulating the gas/oil/brine flow in production pipes with heat transfer at steady state: one based on liquid holdup estimation and the other based on relaxation of gas separation. Deviation of actual fluid conditions from equilibrium is characterized by a new constitutive equation. Effect of relaxation time and holdup of liquids involving in typical field scenarios is demonstrated for reservoir fluids containing oil, water, and gas phases. It is observed that the liquid holdup phenomenon at steady-state conditions can be described as a metastable state characterized by an incomplete separation of the gas phase. Also, the gas separation from the oil and water phases constitutes two different non-equilibrium processes and, therefore, these phases should not be lumped into one liquid phase. Second, a description of the more relevant
VOLD, ERIK L.; SCANNAPIECO, TONY J.
2007-10-16
A sub-grid mix model based on a volume-of-fluids (VOF) representation is described for computational simulations of the transient mixing between reactive fluids, in which the atomically mixed components enter into the reactivity. The multi-fluid model allows each fluid species to have independent values for density, energy, pressure and temperature, as well as independent velocities and volume fractions. Fluid volume fractions are further divided into mix components to represent their 'mixedness' for more accurate prediction of reactivity. Time dependent conversion from unmixed volume fractions (denoted cf) to atomically mixed (af) fluids by diffusive processes is represented in resolved scale simulations with the volume fractions (cf, af mix). In unresolved scale simulations, the transition to atomically mixed materials begins with a conversion from unmixed material to a sub-grid volume fraction (pf). This fraction represents the unresolved small scales in the fluids, heterogeneously mixed by turbulent or multi-phase mixing processes, and this fraction then proceeds in a second step to the atomically mixed fraction by diffusion (cf, pf, af mix). Species velocities are evaluated with a species drift flux, {rho}{sub i}u{sub di} = {rho}{sub i}(u{sub i}-u), used to describe the fluid mixing sources in several closure options. A simple example of mixing fluids during 'interfacial deceleration mixing with a small amount of diffusion illustrates the generation of atomically mixed fluids in two cases, for resolved scale simulations and for unresolved scale simulations. Application to reactive mixing, including Inertial Confinement Fusion (ICF), is planned for future work.
Differential Geometry Based Multiscale Models
Wei, Guo-Wei
2010-01-01
Large chemical and biological systems such as fuel cells, ion channels, molecular motors, and viruses are of great importance to the scientific community and public health. Typically, these complex systems in conjunction with their aquatic environment pose a fabulous challenge to theoretical description, simulation, and prediction. In this work, we propose a differential geometry based multiscale paradigm to model complex macromolecular systems, and to put macroscopic and microscopic descriptions on an equal footing. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum mechanical description of the aquatic environment with the microscopic discrete atom-istic description of the macromolecule. Multiscale free energy functionals, or multiscale action functionals are constructed as a unified framework to derive the governing equations for the dynamics of different scales and different descriptions. Two types of aqueous macromolecular complexes, ones that are near equilibrium and others that are far from equilibrium, are considered in our formulations. We show that generalized Navier–Stokes equations for the fluid dynamics, generalized Poisson equations or generalized Poisson–Boltzmann equations for electrostatic interactions, and Newton's equation for the molecular dynamics can be derived by the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows. Comparison is given to classical descriptions of the fluid and electrostatic interactions without geometric flow based micro-macro interfaces. The detailed balance of forces is emphasized in the present work. We further extend the proposed multiscale paradigm to micro-macro analysis of electrohydrodynamics, electrophoresis, fuel cells, and ion channels. We derive generalized Poisson–Nernst–Planck equations that
Graphene oxide as a high-performance fluid-loss-control additive in water-based drilling fluids.
Kosynkin, Dmitry V; Ceriotti, Gabriel; Wilson, Kurt C; Lomeda, Jay R; Scorsone, Jason T; Patel, Arvind D; Friedheim, James E; Tour, James M
2012-01-01
Graphene oxide (GO) performs well as a filtration additive in water-based drilling fluids at concentrations as low as 0.2 % (w/w) by carbon content. Standard American Petroleum Institute (API) filtration tests were conducted on pH-adjusted, aqueous dispersions of GO and xanthan gum. It was found that a combination of large-flake GO and powdered GO in a 3:1 ratio performed best in the API tests, allowing an average fluid loss of 6.1 mL over 30 min and leaving a filter cake ~20 μm thick. In comparison, a standard suspension (~12 g/L) of clays and polymers used in the oil industry gave an average fluid loss of 7.2 mL and a filter cake ~280 μm thick. Scanning electron microscopy imaging revealed the extreme pliability of well-exfoliated GO, as the pressure due to filtration crumpled single GO sheets, forcing them to slide through pores with diameters much smaller than the flake's flattened size. GO solutions also exhibited greater shear thinning and higher temperature stability compared to clay-based fluid-loss additives, demonstrating potential for high-temperature well applications. PMID:22136134
A Pressure Based Multi-Fluid Algorithm for Multiphase Flow
NASA Astrophysics Data System (ADS)
Ming, P. J.; Zhang, W. P.; Lei, G. D.; Zhu, M. G.
A new finite volume-based numerical algorithm for predicting multiphase flow phenomena is presented. The method is formulated on an orthogonal coordinate system in collocated primitive variables. The SIMPLE-like algorithms are based on the prediction and correction procedure, and they are extended for all speed range. The object of the present work is to extent single phase SIMPLE algorithm to multiphase flow. The overview of the algorithm is described and relevant numerical issues are discussed extensively, including implicit process of the moment interaction with “partial elimination” (of the drag term), introduction of under-relaxation factor, formulation of momentum interpolation, and pressure correction equation. This model is based on the k-ɛ model assumed that the turbulence is dictated by the continuous phase. Thus only the transport equation for the continuous phase turbulence energy kc needed to be solved while a algebraic turbulence model is used for dispersed phase. The present author also designed a general program with FORTRAN90 program language for the new algorithm based on the household code General Transport Equation Analyzer (GTEA). The performance of the new method is assessed by solving a 3D bubbly two-phase flow in a vertical pipe. A good agreement is achieved between the numerical result and experimental data in the literature.
E-1 Dynamic Fluid-Flow Model Update: EASY/ROCETS Enhancement and Model Development Support
NASA Technical Reports Server (NTRS)
Follett, Randolph F.; Taylor, Robert P.
1998-01-01
This report documents the research conducted to update computer models for dynamic fluid flow simulation of the E-1 test stand subsystems at te NASA John C. Stennis Space Center.Work also involved significant upgrades to the capabilities of EASY/ROCKETS library through the inclusion of the NIST-12 thermodynamic property database and development of new control system modules.
ASSESSING THE IMPACT OF SYNTHETIC-BASED DRILLING FLUIDS ON BENTHIC ORGANISMS IN TEMPERATE WATERS
Efforts to enhance the efficiency of oil/gas drilling operations and to minimize hazards to marine ecosystems have resulted in the increased use of synthetic-based fluids (SBF). SBFs have performance characteristics closely related to oil-based fluids (OBF) however their lower PA...
Ubbelohde viscometer measurement of water-based Fe3O4 magnetic fluid prepared by coprecipitation
NASA Astrophysics Data System (ADS)
Gu, H.; Tang, X.; Hong, R. Y.; Feng, W. G.; Xie, H. D.; Chen, D. X.; Badami, D.
2013-12-01
Fe3O4 nanoparticles were prepared by co-precipitation and coated by sodium dodecyl benzene sulfonate (SDBS) to obtain water-based magnetic fluid. The viscosity of the magnetic fluid was measured using an Ubbelohde viscometer. The effects of magnetic particles volume fraction, surfactant mass fraction and temperature on the viscosity were studied. Experimental results showed that the magnetic fluid with low magnetic particle volume fraction behaved as a Newtonian fluid and the viscosity of the magnetic fluid increased with an increase of the suspended magnetic particles volume fraction. The experimental data was compared with the results of a theoretically derived equation. The viscosity of the magnetic fluid also increased with an increase in surfactant mass portion, while it decreased with increasing temperature. Moreover, the viscosity increased with increasing the magnetic field intensity. Increasing the temperature and the surfactant mass fraction weakened the influence of the magnetic field on the viscosity of the magnetic fluid.
NASA Astrophysics Data System (ADS)
Meakin, Paul; Tartakovsky, Alexandre M.
2009-07-01
In the subsurface, fluids play a critical role by transporting dissolved minerals, colloids, and contaminants (sometimes over long distances); by mediating dissolution and precipitation processes; and by enabling chemical transformations in solution and at mineral surfaces. Although the complex geometries of fracture apertures, fracture networks, and pore spaces may make it difficult to accurately predict fluid flow in saturated (single-phase) subsurface systems, well-developed methods are available. The simulation of multiphase fluid flow in the subsurface is much more challenging because of the large density and/or viscosity ratios found in important applications (water/air in the vadose zone; water/oil, water/gas, gas/oil, and water/oil/gas in hydrocarbon reservoirs; water/air/nonaqueous phase liquids (nonaqueous phase liquids/dense nonaqueous phase liquids) in contaminated vadose zone systems; and gas/molten rock in volcanic systems, for example). In addition, the complex behavior of fluid-fluid-solid contact lines and their impact on dynamic contact angles must also be taken into account and coupled with the fluid flow. Here we review the methods that are currently being used to simulate pore-scale multiphase fluid flow and reactive transport in fractured and porous media. After the introduction, the review begins with an overview of the fundamental physics of multiphase fluids flow followed by a more detailed discussion of the complex dynamic behavior of contact lines and contact angles, an important barrier to accurate pore-scale modeling and simulation. The main part of the review focuses on five different approaches: pore network models, lattice gas and lattice Boltzmann methods, Monte Carlo methods, particle methods (molecular dynamics, dissipative particle dynamics, and smoothed particle hydrodynamics), and traditional grid-based computational fluid dynamics coupled with interface tracking and a contact angle model. Finally, the review closes with a
A Model For Multicomponent Fluid Saturation In C-o-h-s-silicate Melt Systems
NASA Astrophysics Data System (ADS)
Moretti, R.; Papale, P.; Ottonello, G.
The dissolution behavior of volatile components in magmas is essential to model the volcanic process from the deep regions of magma generation and storage to the shal- low regions of magma eruption and emplacement. Water, carbon dioxide, and sulfur compounds are the main volatile components in nat- ural magmas, constituting in most cases more than 99% of the volcanic gases released before, during, and after eruption. We have developed a method to calculate the chem- ical equilibrium between a fluid phase in the C-O-H-S system and a silicate melt with composition defined by ten major oxides. The method is based on a previous model for the saturation of H2O-CO2 fluids [1] and on a sulfur solubility model [2] in silicate liquids. For the computation of the fugacities of components in fluids with complex composition we used the SUPERFLUID code [3]. The model allows determining the partition of H2O, CO2, and S between the silicate liquid and the coexisting fluid, and the composition of the fluid phase in terms of H2O, CO2, SO2, and H2S, as a func- tion of pressure, temperature, volatile-free liquid composition, oxygen fugacity, and total amount of each volatile component in the system. App lications are presented to several silicate liquids with rhyolitic and basaltic composition, oxygen fugacities in the range NNO +/- 2, and pressure from a few hundred MPa to atmospheric, with the simplifying assumption that no reduced or oxidized sulfur-saturated solid or liquid phases nucleate or separate from the liquid-gas system. Results show the well-known minima in sulfur saturation contents as a function of oxygen fugacity, the reciprocal effects of volatiles on their saturation contents, and the complex relationships between saturation surface of a multicomponent fluid, liquid composition, volatile abundance, P-T conditions, and oxidation state. The method represents therefore a new powerful tool for the prediction of multicomponent gas-melt equilibria in magmas. REFERENCES [1
Evaluation of Propylene Glycol-Based Fluids for Constellation Habitats and Vehicles
NASA Technical Reports Server (NTRS)
Lee, Steve
2009-01-01
Two fluid life tests have been conducted to evaluate propylene glycol-based fluids for use in Constellation habitats and vehicles. The first test was conducted from November 2008 to January 2009 to help determine the compatibility of the propylene glycol-based fluid selected for Orion at the time. When the first test uncovered problems with the fluid selection, an investigation and selection of a new fluid were conducted. A second test was started in March 2010 to evaluate the new selection. For the first test, the fluid was subjected to a thermal fluid loop that had flight-like properties, as compared to Orion. The fluid loop had similar wetted materials, temperatures, flow rates, and aluminum wetted surface area to fluid volume ratio. The test was designed to last for 10 years, the life expectancy of the lunar habitat. However, the test lasted less than two months. System filters became clogged with precipitate, rendering the fluid system inoperable. Upon examination of the precipitate, it was determined that the precipitate composition contained aluminum, which could have only come from materials in the test stand, as aluminum is not part of the original fluid composition. Also, the fluid pH was determined to have increased from 10.1, at the first test sample, to 12.2, at the completion of the test. This high of a pH is corrosive to aluminum and was certainly a contributing factor to the development of precipitate. Due to the problems encountered during this test, the fluid was rejected as a coolant candidate for Orion. A new propylene glycol-based fluid was selected by the Orion project for use in the Orion vehicle. The Orion project has conducted a series of screening tests to help verify that there will be no problems with the new fluid selection. To compliment testing performed by the Orion project team, a new life test was developed to test the new fluid. The new test bed was similar to the original test bed, but with some improvements based on experience
NASA Technical Reports Server (NTRS)
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Modeling and Algorithmic Approaches to Constitutively-Complex, Microstructured Fluids
Miller, Gregory H.; Forest, Gregory
2011-12-22
We present a new multiscale model for complex uids based on three scales: microscopic, kinetic, and continuum. We choose the microscopic level as Kramers' bead-rod model for polymers, which we describe as a system of stochastic di erential equations with an implicit constraint formulation. The associated Fokker-Planck equation is then derived, and adiabatic elimination removes the fast momentum coordinates. Approached in this way, the kinetic level reduces to a dispersive drift equation. The continuum level is modeled with a nite volume Godunov-projection algorithm. We demonstrate computation of viscoelastic stress divergence using this multiscale approach.
Mauldon, A.D.; Karasaki, K.; Martel, S.J.; Long, J.C.S.; Landsfield, M.; Mensch, A. ); Vomvoris, S. )
1993-11-01
One of the characteristics of flow and transport in fractured rock is that the flow may be largely confined to a poorly connected network of fractures. In order to represent this condition, Lawrence Berkeley Laboratory has been developing a new type of fracture hydrology model called an equivalent discontinuum model. In this model we represent the discontinuous nature of the problem through flow on a partially filled lattice. This is done through a statistical inverse technique called [open quotes]simulated annealing.[close quotes] The fracture network model is [open quotes]annealed[close quotes] by continually modifying a base model, or [open quotes]template,[close quotes] so that with each modification, the model behaves more and more like the observed system. This template is constructed using geological and geophysical data to identify the regions that possibly conduct fluid an the probable orientations of channels that conduct fluid. In order to see how the simulated annealing algorithm works, we have developed a synthetic case. In this case, the geometry of the fracture network is completely known, so that the results of annealing to steady state data can be evaluated absolutely. We also analyze field data from the Migration Experiment at the Grimsel Rock Laboratory in Switzerland. 28 refs., 14 figs., 3 tabs.
Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova
Glimm, James
2008-06-24
The three year plan for this project is to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (both Direct Numerical Simulation and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We will model 2D and 3D perturbations of planar interfaces. We will compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we will develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. We will conduct analytic studies of mix, in support of these objectives. Advanced issues, including multiple layers and reshock, will be considered.
A new approach to epithelial isotonic fluid transport: an osmosensor feedback model.
Hill, A E; Shachar-Hill, B
2006-03-01
A model for control of the transport rate and osmolarity of epithelial fluid (isotonic transport) is presented by using an analogy with the control of temperature and flow rate in a shower. The model brings recent findings and theory concerning the role of aquaporins in epithelia together with measurements of epithelial paracellular flow into a single scheme. It is not based upon osmotic equilibration across the epithelium but rather on the function of aquaporins as osmotic sensors that control the tonicity of the transported fluid by mixing cellular and paracellular flows, which may be regarded individually as hyper- and hypo-tonic fluids, to achieve near-isotonicity. The system is built on a simple feedback loop and the quasi-isotonic behavior is robust to the precise values of most parameters. Although the two flows are separate, the overall fluid transport rate is governed by the rate of salt pumping through the cell. The model explains many things: how cell pumping and paracellular flow can be coupled via control of the tight junctions; how osmolarity is controlled without depending upon the precise magnitude of membrane osmotic permeability; and why many epithelia have different aquaporins at the two membranes. The model reproduces all the salient features of epithelial fluid transport seen over many years but also indicates novel behavior that may provide a subject for future research and serve to distinguish it from other schemes such as simple osmotic equilibration. Isotonic transport is freed from constraints due to limited permeability of the membranes and the precise geometry of the system. It achieves near-isotonicity in epithelia in which partial water transport by co-transporters may be present, and shows apparent electro-osmotic effects. The model has been developed with a minimum of parameters, some of which require measurement, but the model is flexible enough for the basic idea to be extended both to complex systems of water and salt transport
A Blended Finite Element Method for Multi-Fluid Plasma Modeling
NASA Astrophysics Data System (ADS)
Sousa, Eder Marinho
In a multi-fluid plasma model electrons and ions are represented as separate fluids that interact through collisions and electromagnetic fields. The model encapsulates physics that spans a vast range of temporal and spatial scales, which renders the model stiff and consequently difficult to solve numerically. To address the large range of time scales, a blended continuous and discontinuous Galerkin method is proposed, where ions are modeled using an explicit Runge-Kutta discontinuous Galerkin method while the electrons and electromagnetic fields are modeled using an implicit continuous Galerkin method. This approach is able to capture large-gradient ion physics like shock formation, while resolving high-frequency electron dynamics in a computationally efficient manner. The convergence properties of the method are analyzed and the method is tested on an electromagnetic shock problem. The numerical method produces results comparable with current state-of-the-art finite volume and discontinuous Galerkin methods, while decreasing the computational time for cases where realistic ion-to-electron mass ratios are used, and realistic speed-of-light to thermal speed ratios are needed. The method is used to study Inertial Confinement Fusion (ICF) fuel species separation where multi-fluid effects are relevant, and the high pressure gradient experienced by the ions causes them to shock, separate, and generate large electric fields. In addition, it is shown that single-fluid plasma codes can overestimate the neutron yield in ICF. For validation purposes, simulation results are compared with experimental data. A meaningful comparison requires the quantification of uncertainties in simulations. The uncertainties in the method are quantified using the multi-level Monte Carlo (MMC) method. The method reduces the computational cost over the standard Monte Carlo method by using multiple levels of discretization to calculate the statistical information of a given model. The MMC method
Visualization of Two-Fluid-Phase Flow Dynamics Using Micro-models
NASA Astrophysics Data System (ADS)
Dye, A. L.; McClure, J. E.; Gray, W. G.; Pyrak-Nolte, L. J.; Miller, C. T.
2015-12-01
Microfluidic approaches provide an opportunity to observe phase distributions, interfaces, common curves, and curvatures at high spatial and temporal resolutions in two-fluid-phase porous medium systems. Such observations provide an opportunity to visualize mechanisms, determine closure relations needed for existing and evolving models, and provide a means to validate theoretical predictions. We use a 500-micron cell with a circular solid phase to study two-fluid-phase displacement, including a dense pattern of drainage, imbibition, and scanning curves at very high spatial and temporal distribution. Viscous fingering, Haines jumps, and snap-off processes are visualized. A lattice Boltzmann method (LBM) is used to model the experimental data and shows excellent agreement for equilibrium states and certain aspects of the dynamics. Pressure dynamics, displacement processes, and interface curvature change time scales are shown. The fluid pressure, saturation, curvature, and interfacial area data is used to demonstrate that a unique, non-hysteretic closure relation exists. Further, the data is compared to mechanistic predictions based upon the thermodynamically constrained averaging theory (TCAT), validating key aspects of the theory.
Numerical simulation of cavitating flow of liquid helium in a pipe using multi-fluid model
NASA Astrophysics Data System (ADS)
Ishimoto, J.; Oike, M.; Kamijo, K.
2002-05-01
The two-dimensional characteristics of the cavitating flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the turbulent cavitating flow of liquid helium passing through the orifice is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic cavitating flow are predicted.
Modelling of fluid-structure interaction with multiphase viscous flows using an immersed-body method
NASA Astrophysics Data System (ADS)
Yang, P.; Xiang, J.; Fang, F.; Pavlidis, D.; Latham, J.-P.; Pain, C. C.
2016-09-01
An immersed-body method is developed here to model fluid-structure interaction for multiphase viscous flows. It does this by coupling a finite element multiphase fluid model and a combined finite-discrete element solid model. A coupling term containing the fluid stresses is introduced within a thin shell mesh surrounding the solid surface. The thin shell mesh acts as a numerical delta function in order to help apply the solid-fluid boundary conditions. When used with an advanced interface capturing method, the immersed-body method has the capability to solve problems with fluid-solid interfaces in the presence of multiphase fluid-fluid interfaces. Importantly, the solid-fluid coupling terms are treated implicitly to enable larger time steps to be used. This two-way coupling method has been validated by three numerical test cases: a free falling cylinder in a fluid at rest, elastic membrane and a collapsing column of water moving an initially stationary solid square. A fourth simulation example is of a water-air interface with a floating solid square being moved around by complex hydrodynamic flows including wave breaking. The results show that the immersed-body method is an effective approach for two-way solid-fluid coupling in multiphase viscous flows.
Preparation and properties of low boiling point of alcohol and acetone-based magnetic fluid
NASA Astrophysics Data System (ADS)
Fujita, T.; Miyazaki, T.; Nishiyama, H.; Jeyadevan, B.
1999-07-01
Ultra-fine magnetic particles are difficult to be dispersed in low boiling point solvents such as alcohol (C 1-C 4) and acetone. In this paper, we report the preparation methods of several alcohol and acetone-based magnetic fluids. The stability of magnetic fluid depended on the HLB (hydrophile-lipophile balance) of the solvent and alkyl chain lengths of organic layers. The fluid was most stable only when the HLB value of surfactant and the solvents are similar.
NASA Astrophysics Data System (ADS)
Huda, Nazmul; Naser, Jamal; Brooks, Geoffrey; Reuter, Markus A.; Matusewicz, Robert W.
2012-02-01
Slag fuming is a reductive treatment process for molten zinciferous slags for extracting zinc in the form of metal vapor by injecting or adding a reductant source such as pulverized coal or lump coal and natural gas. A computational fluid dynamic (CFD) model was developed to study the zinc slag fuming process from imperial smelting furnace (ISF) slag in a top-submerged lance furnace and to investigate the details of fluid flow, reaction kinetics, and heat transfer in the furnace. The model integrates combustion phenomena and chemical reactions with the heat, mass, and momentum interfacial interaction between the phases present in the system. A commercial CFD package AVL Fire 2009.2 (AVL, Graz, Austria) coupled with a number of user-defined subroutines in FORTRAN programming language were used to develop the model. The model is based on three-dimensional (3-D) Eulerian multiphase flow approach, and it predicts the velocity and temperature field of the molten slag bath, generated turbulence, and vortex and plume shape at the lance tip. The model also predicts the mass fractions of slag and gaseous components inside the furnace. The model predicted that the percent of ZnO in the slag bath decreases linearly with time and is consistent broadly with the experimental data. The zinc fuming rate from the slag bath predicted by the model was validated through macrostep validation process against the experimental study of Waladan et al. The model results predicted that the rate of ZnO reduction is controlled by the mass transfer of ZnO from the bulk slag to slag-gas interface and rate of gas-carbon reaction for the specified simulation time studied. Although the model is based on zinc slag fuming, the basic approach could be expanded or applied for the CFD analysis of analogous systems.
Statistical properties of three-dimensional two-fluid plasma model
Qaisrani, M. Hasnain; Xia, ZhenWei; Zou, Dandan
2015-09-15
The nonlinear dynamics of incompressible non-dissipative two-fluid plasma model is investigated through classical Gibbs ensemble methods. Liouville's theorem of phase space for each wave number is proved, and the absolute equilibrium spectra for Galerkin truncated two-fluid model are calculated. In two-fluid theory, the equilibrium is built on the conservation of three quadratic invariants: the total energy and the self-helicities for ions and electrons fluid, respectively. The implications of statistic equilibrium spectra with arbitrary ratios of conserved invariants are discussed.
Immersed boundary-finite element model of fluid-structure interaction in the aortic root
NASA Astrophysics Data System (ADS)
Flamini, Vittoria; DeAnda, Abe; Griffith, Boyce E.
2016-04-01
It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe a fluid-structure interaction model of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employs a version of Peskin's immersed boundary (IB) method with a finite element description of the structural elasticity. As in earlier work, we use a fiber-based model of the valve leaflets, but this study extends earlier IB models of the aortic root by employing an incompressible hyperelastic model of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backward displacement method that determines the unloaded configuration of the root model. Our model yields realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations indicate that although the detailed leaflet and root kinematics show some grid sensitivity, our IB model of the aortic root nonetheless produces essentially grid-converged flow rates and pressures at practical grid spacings for the high Reynolds number flows of the aortic root. These results thereby clarify minimum grid resolutions required by such models when used as stand-alone models of the aortic valve as well as when used to provide models of the outflow valves in models of left-ventricular fluid dynamics.
The impact of fluid topology on residual saturations - A pore-network model study
NASA Astrophysics Data System (ADS)
Doster, F.; Kallel, W.; van Dijke, R.
2014-12-01
In two-phase flow in porous media only fractions of the resident fluid are mobilised during a displacement process and, in general, a significant amount of the resident fluid remains permanently trapped. Depending on the application, entrapment is desirable (geological carbon storage), or it should be obviated (enhanced oil recovery, contaminant remediation). Despite its utmost importance for these applications, predictions of trapped fluid saturations for macroscopic systems, in particular under changing displacement conditions, remain challenging. The models that aim to represent trapping phenomena are typically empirical and require tracking of the history of the state variables. This exacerbates the experimental verification and the design of sophisticated displacement technologies that enhance or impede trapping. Recently, experiments [1] have suggested that a macroscopic normalized Euler number, quantifying the topology of fluid distributions, could serve as a parameter to predict residual saturations based on state variables. In these experiments the entrapment of fluids was visualised through 3D micro CT imaging. However, the experiments are notoriously time consuming and therefore only allow for a sparse sampling of the parameter space. Pore-network models represent porous media through an equivalent network structure of pores and throats. Under quasi-static capillary dominated conditions displacement processes can be modeled through simple invasion percolation rules. Hence, in contrast to experiments, pore-network models are fast and therefore allow full sampling of the parameter space. Here, we use pore-network modeling [2] to critically investigate the knowledge gained through observing and tracking the normalized Euler number. More specifically, we identify conditions under which (a) systems with the same saturations but different normalized Euler numbers lead to different residual saturations and (b) systems with the same saturations and the same
Appplication of a general fluid mechanics program to NTP system modeling
NASA Astrophysics Data System (ADS)
Lee, Stacey K.
1993-01-01
An effort is currently underway at NASA and the Department of Energy (DOE) to develop an accurate model for predicting nuclear thermal propulsion (NTP) system performance. The objective of the effort is to develop several levels of computer programs which vary in detail and complexity according to user's needs. The current focus is on the Level 1 steady-state, parametric system model. This system model will combine a general fluid mechanics program, SAFSIM, with the ability to analyze turbines, pumps, nozzles, and reactor physics. SAFSIM (System Analysis Flow SIMulator) is a FORTRAN computer program that simulates integrated performance of systems involving fluid mechanics, heat transfer, and reactor dynamics. SAFSIM has the versatility to allow simulation of almost any system, including a nuclear reactor system. The focus of this paper is the validation of SAFSIM's capabilities as a base computational engine for a nuclear thermal propulsion system model. Validation is being accomplished by modeling of a nuclear engine test using SAFSIM and comparing the results to known experimental data. For this study, the NRX/EST test was chosen; it was the first of the tests to demonstrate the integration of all system components (including the turbopump) and it utilized the hot bleed cycle. This paper present a comparison of analytical results with experimental system performance in terms of state points, mass flow rates, wall temperatures, and specific impulse. In addition, the methodology used in the validation efforts will be discussed.
Viscoelastic behaviour of human blood and polyacrylamide model fluids for heart valve testing
NASA Astrophysics Data System (ADS)
Lerche, Dietmar; Vlastos, Georgios; Koch, Brigitte; Pohl, Manfred; Affeld, Klaus
1993-06-01
New heart valves and other cardiovascular assist systems have to be tested for hydrodynamic performance. In place of human blood simple model fluids like glycerol solutions are employed often due to ethical and practical reasons. But blood exhibits complex non-Newtonian and viscoelastic behaviour. Rheological blood properties are reviewed based on literature and own experimental results. Furthermore we studied polymer solutions with respect to blood-like flow behaviour. Rheology was assessed by means of the low shear rotational viscometer (LS 40, Mettler-Toledo, Switzerland) under stationary and dynamic shear conditions (variation of frequency and angular displacement).
Efficient tunable generic model for self-assembling fluid bilayer membranes
NASA Astrophysics Data System (ADS)
Deserno, Markus
2005-03-01
We present a new model for the simulation of generic lipid bilayers in the mesoscopic regime (between a few nanometers and many tens of nanometers), which is very robust, versatile, and extremely efficient, since it avoids the need for an embedding solvent. Based entirely on simple pair potentials, it features a wide region of unassisted self assembly into fluid bilayers without the need for careful parameter tuning. The resulting membranes display the correct continuum elastic behavior with bending constants in the experimentally relevant range. It can be readily used to study events like bilayer fusion, bilayer melting, lipid mixtures, rafts, and protein-bilayer interactions.
This paper discusses the status and application of Computational Fluid Dynamics (CFD) models to address challenges for modeling human exposures to air pollutants around urban building microenvironments. There are challenges for more detailed understanding of air pollutant sour...
Kim, Jihoon; Um, Evan; Moridis, George
2014-12-01
We investigate fracture propagation induced by hydraulic fracturing with water injection, using numerical simulation. For rigorous, full 3D modeling, we employ a numerical method that can model failure resulting from tensile and shear stresses, dynamic nonlinear permeability, leak-off in all directions, and thermo-poro-mechanical effects with the double porosity approach. Our numerical results indicate that fracture propagation is not the same as propagation of the water front, because fracturing is governed by geomechanics, whereas water saturation is determined by fluid flow. At early times, the water saturation front is almost identical to the fracture tip, suggesting that the fracture is mostly filled with injected water. However, at late times, advance of the water front is retarded compared to fracture propagation, yielding a significant gap between the water front and the fracture top, which is filled with reservoir gas. We also find considerable leak-off of water to the reservoir. The inconsistency between the fracture volume and the volume of injected water cannot properly calculate the fracture length, when it is estimated based on the simple assumption that the fracture is fully saturated with injected water. As an example of flow-geomechanical responses, we identify pressure fluctuation under constant water injection, because hydraulic fracturing is itself a set of many failure processes, in which pressure consistently drops when failure occurs, but fluctuation decreases as the fracture length grows. We also study application of electromagnetic (EM) geophysical methods, because these methods are highly sensitive to changes in porosity and pore-fluid properties due to water injection into gas reservoirs. Employing a 3D finite-element EM geophysical simulator, we evaluate the sensitivity of the crosswell EM method for monitoring fluid movements in shaly reservoirs. For this sensitivity evaluation, reservoir models are generated through the coupled flow
ERIC Educational Resources Information Center
Besson, Ugo; Viennot, Laurence
2004-01-01
This article examines the didactic suitability of introducing models at an intermediate (i.e. mesoscopic) scale in teaching certain subjects, at an early stage. The design and evaluation of two short sequences based on this rationale will be outlined: one bears on propulsion by solid friction, the other on fluid statics in the presence of gravity.…
NASA Astrophysics Data System (ADS)
El-Wahed, Ali K.; Stanway, Roger; Sproston, John L.
2002-06-01
It is now widely accepted that smart fluids in the so-called squeeze-flow mode have many potential applications in vibration damping and isolation. In squeeze-flow the fluid is subjected to forces imposed by oscillating electrodes (or poles) which alternatively subject the fluid to tensile and compressive loading. Consequently displacement levels are limited to a few millimeters but large force levels are available. Modeling of smart fluid squeeze-flow devices is a complex process, primarily since the fluid is liable to be subjected to simultaneous changes in the inter-electrode gap and the strength of the applied electric (or magnetic) field. Consequently the authors have developed a comprehensive test facility dedicated to the study of smart fluids in dynamic squeeze-flow operation. In the present paper, the authors will describe a new approach to modeling smart fluids in squeeze-flow. The analysis relates specifically to an electrorheological fluid modeled using a bi- viscous shear stress/shear strain characteristics. By assuming that the electrically stressed fluid has a yield stress which is dependent on the strain direction, it will be shown how the model is able to account for observed experimental behavior.
Beyond the Fluid Approximation: Improved Modeling of the Intracluster Plasma
NASA Astrophysics Data System (ADS)
O'Shea, Brian
Cosmological simulations of galaxy clusters typically treat the intracluster medium as a simple magnetized fluid - an approximation that is now understood to be simplistic at best due to the physical characteristics of this hot, diffuse, and weakly magnetized plasma. The properties of the intracluster medium at or near the resolution limits of cosmological simulations - including its viscosity, conductivity, and turbulent dissipation of energy - rely strongly on the properties of the plasma at smaller scales. In addition, observations of the intracluster medium display features relating to bubbles from active galactic nuclei, as well as shocks and cold fronts relating to cluster mergers, that are not typically reproduced in cosmological simulations. It is clear that a closer examination of our treatment of diffuse, ionized intergalactic plasmas in cosmological simulations is required in order to be able to meaningfully interpret current and future observations of galaxy clusters. We propose to advance our understanding of the plasma physical processes that are relevant in the intracluster medium using a combination of cosmological magnetohydrodynamical (MHD) simulations and targeted, parametrized simulations using non-ideal MHD, hybrid gyrokinetic + MHD, and particle-in-cell electrodynamics calculations. This proposal aims to create a unified, multiscale model of the intracluster medium, tying together plasma microinstabilities at the parsec and sub-parsec scale to the behavior and observable properties of galaxy clusters at the multi-kiloparsec and megaparsec scales. Using this coupling, we will be able to constrain our theoretical models using X-ray, Sunyaev-Zel'dovich, and radio observations of the intracluster medium. More broadly, this project addresses the clear need to closely examine our treatment of diffuse, ionized plasmas in cosmological simulations, in order to be able to meaningfully make predictions for, and interpret data from, large astronomical
Kimijima, Tomohiko; Edanaga, Mitsutaka; Yamakage, Michiaki
2016-06-01
The objective of this study was to compare fluid leakage across endotracheal tube cuffs using a three-dimensional (3D)-printed human tracheal model that anatomically simulates the human trachea. We made two models based on computed tomography data of the neck and chest. Using a Mallinckrodt Hi-Lo™ (HL), ThinCuff(®) (TC), and Mallinckrodt TaperGuard™ (TG), we sequentially measured the amount of fluid leakage across each endotracheal tube cuff after applying saline or viscous liquid above the cuff. The TG allowed significantly less leakage than the HL and TC with both saline and the viscous liquid. Our study, using a 3D-printed tracheal model, indicated that a conical-shaped endotracheal tube cuff significantly reduces fluid leakage across the cuff compared with conventional cylindrical-shaped cuffs made of polyurethane or polyvinylchloride, contrary to the results of a previous study using a solid cylindrical structure. PMID:26816263
A knowledge-based approach to automated flow-field zoning for computational fluid dynamics
NASA Technical Reports Server (NTRS)
Vogel, Alison Andrews
1989-01-01
An automated three-dimensional zonal grid generation capability for computational fluid dynamics is shown through the development of a demonstration computer program capable of automatically zoning the flow field of representative two-dimensional (2-D) aerodynamic configurations. The applicability of a knowledge-based programming approach to the domain of flow-field zoning is examined. Several aspects of flow-field zoning make the application of knowledge-based techniques challenging: the need for perceptual information, the role of individual bias in the design and evaluation of zonings, and the fact that the zoning process is modeled as a constructive, design-type task (for which there are relatively few examples of successful knowledge-based systems in any domain). Engineering solutions to the problems arising from these aspects are developed, and a demonstration system is implemented which can design, generate, and output flow-field zonings for representative 2-D aerodynamic configurations.
Sanford, Ward E.; Pearson, S.C.P.; Kiyosugi, K.; Lehto, H.L.; Saballos, J.A.; Connor, C.B.
2012-01-01
We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (~250 m), relatively impermeable normal faults dipping at ~60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE-SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3-4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 x 10-5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.
SDEM modelling of deformation associated with a listric fault system and associated fluid flow
NASA Astrophysics Data System (ADS)
Rasmussen, Marie L.; Clausen, Ole R.; Egholm, David L.; Andresen, Katrine J.
2016-04-01
zones of high chimney probability coincide with the modelled vertical deformation zones. It cannot be excluded that the vertical deformation zones which have been inferred from the numerical modelling are responsible for or highly influence the high chimney probabilities observed in the chimney cube and thus that the interpretation of chimneys (and vertical fluid migration) is incorrect. However, since the chimney cube is also based on seed picks from areas without deformation, we suggest that the vertical deformation zones contributed to vertical fluid flow from the deeper succession into the shallow gas compartments. Thus the modelling demonstrates the capability of resolving sub-seismic deformation zones which appear to be critical for the facilitation of vertical fluid migration in the study area. Similar vertical deformation zones may therefore constitute the fluid migration routes in areas where such are only inferred but not imaged by the seismic data.
NASA Astrophysics Data System (ADS)
Horsten, N.; Dekeyser, W.; Samaey, G.; Baelmans, M.
2016-01-01
We derive fluid neutral approximations for a simplified 1D edge plasma model, suitable to study the neutral behavior close to the target of a nuclear fusion divertor, and compare its solutions to the solution of the corresponding kinetic Boltzmann equation. The plasma is considered as a fixed background extracted from a detached 2D simulation. We show that the Maxwellian equilibrium distribution is already obtained very close to the target, justifying the use of a fluid approximation. We compare three fluid neutral models: (i) a diffusion model; (ii) a pressure-diffusion model (i.e., a combination of a continuity and momentum equation) assuming equal neutral and ion temperatures; and (iii) the pressure-diffusion model coupled to a neutral energy equation taking into account temperature differences between neutrals and ions. Partial reflection of neutrals reaching the boundaries is included in both the kinetic and fluid models. We propose two methods to obtain an incident neutral flux boundary condition for the fluid models: one based on a diffusion approximation and the other assuming a truncated Chapman-Enskog distribution. The pressure-diffusion model predicts the plasma sources very well. The diffusion boundary condition gives slightly better results overall. Although including an energy equation still improves the results, the assumption of equal ion and neutral temperature already gives a very good approximation.