The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Terry L. Herdman - One of the best experts on this subject based on the ideXlab platform.
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Parameter Estimation of a Thermal Fluid System
2018 Annual American Control Conference (ACC), 2018Co-Authors: John A. Burns, Eugene M. Cliff, Terry L. HerdmanAbstract:In this paper we consider the problems of parameter estimation for a counter flow heat exchanger. The problem is complicated when convection dominates the heat transfer so that the diffusion coefficient is small compared to the convection coefficient. We employ the full flux physics model, which means the model is defined by convection-diffusion equations and the parabolic equations are viewed as a perturbation of the zero diffusion model. We show that by proper formulation of the boundary conditions and employing combined finite element-finite volume schemes one can estimate the small diffusion term. Moreover, by employing constrained optimization one can obtain physically meaningful results. We compare constrained and unconstrained nonlinear least squares approaches. Numerical results are presented to illustrate the ideas and some open questions are discussed.
Vikas Mahto - One of the best experts on this subject based on the ideXlab platform.
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Formulation of a water based drilling Fluid System with synthesized graft copolymer for troublesome shale formations
Journal of Natural Gas Science and Engineering, 2017Co-Authors: Rajat Jain, Vikas MahtoAbstract:Abstract Shale formations consisting of reactive clay mineral of smectite group like montmorillonite may lead to severe wellbore instability problems with conventional water based drilling Fluids. This may be due to their high magnitude of rock-Fluid interaction inside the wellbore. Problems like hole enlargement, pipe sticking, high toque and drag etc. may escalate drilling cost and time. The present study deals with the applicability of synthesized polyacrylamide/dially dimethyl ammonium chloride-grafted-gum acacia copolymer in formulation of novel water based drilling mud System (WBDMS) for troublesome shale formations. The mechanism behind the synthesis was free radical polymerization. The structural information and morphological properties of copolymer were determined by Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM). Further, its effect on filtration and rheology of developed mud System was analyzed thoroughly as per API standard procedures. Further, effectiveness of graft copolymer on the shale stabilization was investigated using shale dispersion and slake durability tests. The reactivity of core sample with the developed drilling Fluid System was analyzed using core flooding experimental setup. The experimental investigations showed that synthesized graft copolymer has significant effect on rheological parameters and filtration characteristics of the System due to its synergistic effects in the developed System. Also, its shale stabilization property was superior to the commercially used shale stabilizer (partially hydrolyzed polyacrylamide polymer). It was evident from the high values of shale recovery and slake durability index. This was achieved due to the presence of cationic ions and formation of a protective coating on shale cuttings. It has also resulted in the low magnitude of rock-Fluid interaction. The developed drilling Fluid System exhibited low reactivity with the core sample during core flow studies. Thus, the synthesized graft copolymer can be utilized as an additive in the formulation of water based mud System customized for reactive shale formations.
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Rheological investigations of water based drilling Fluid System developed using synthesized nanocomposite
Korea-Australia Rheology Journal, 2016Co-Authors: Rajat Jain, Triveni K. Mahto, Vikas MahtoAbstract: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.
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Development of Inhibitive Water-based Drilling Fluid System for Shale Formation
2015Co-Authors: Rajat Jain, Tinku Saikia, Vikas MahtoAbstract:The drilling of troublesome shale formations leads to severe wellbore instability problems due to swelling and dispersion of the shale cuttings in the welllbore. Hence, the formulation of inhibitive water-based drilling Fluid System with enhanced rheological properties and filtration characteristics is a critical issue for these complex shale formations. This research article consists of a favourable drilling Fluid System developed using potassium chloride (KCL), partially hydrolyzed polyacrylamide (PHPA), ethylene glycol and xanthan gum polymer. The rheological properties and filtration characteristics were measured as per API recommended standard procedures for field testing of drilling Fluids. The developed System has low plastic viscosity, good gel strength, high consistency index, and moderate apparent viscosity for the optimum performance of the drilling Fluid System while dealing with shale formations. The developed drilling Fluid formulations exhibited low Fluid loss volume during the filtration studies. This System has high inhibition property which controls the hydration and dispersion of the shale cuttings inside the wellbore. Hence, developed inhibitive water-based drilling Fluid System may be suitable for the drilling of sensitive shale formations. Keywords: drilling Fluid, rheological properties, filtration characteristics, inhibition
Gregory R. Mitchell - One of the best experts on this subject based on the ideXlab platform.
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Shipboard Fluid System Diagnostic Indicators Using Non-Intrusive Load Monitoring
Naval Engineers Journal, 2007Co-Authors: Gregory R. Mitchell, James Paris, Steven B. LeebAbstract:Field studies have demonstrated that it is possible to evaluate the state of many shipboard Systems by analyzing the electrical power that is drawn by electromechanical actuators. This paper demonstrates how a device known as a non-intrusive load monitor (NILM) uses only electrical power data to detect several critical faults in shipboard Fluid Systems. Using the example of reverse-osmosis units installed aboard the US Coast Guard's Medium Endurance Cutters, it is shown that the NILM can provide ship's force with a highly reliable real-time System monitoring capability.
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Shipboard Fluid System diagnostics using non-intrusive load monitoring
2007Co-Authors: Gregory R. MitchellAbstract:Thesis (Nav. E. and S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
Johannes Lankeit - One of the best experts on this subject based on the ideXlab platform.
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long term behaviour in a chemotaxis Fluid System with logistic source
Mathematical Models and Methods in Applied Sciences, 2016Co-Authors: Johannes LankeitAbstract:We consider the coupled chemotaxis Navier–Stokes model with logistic source terms: nt + u ⋅∇n = Δn − χ∇⋅ (n∇c) + κn − μn2, ct + u ⋅∇c = Δc − nc, ut + (u ⋅∇)u = Δu + ∇P + n∇Φ + f,∇⋅ u = 0 in a bounded, smooth domain Ω ⊂ ℝ3 under homogeneous Neumann boundary conditions for n and c and homogeneous Dirichlet boundary conditions for u and with given functions f ∈ L∞(Ω × (0,∞)) satisfying certain decay conditions and Φ ∈ C1+β(Ω) for some β ∈ (0, 1). We construct weak solutions and prove that after some waiting time they become smooth and finally converge to the semi-trivial steady state (κ μ, 0, 0).
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long term behaviour in a chemotaxis Fluid System with logistic source
arXiv: Analysis of PDEs, 2016Co-Authors: Johannes LankeitAbstract:We consider the coupled chemotaxis Navier-Stokes model with logistic source terms \[ n_t + u\cdot \nabla n = \Delta n - \chi \nabla \cdot (n \nabla c) + \kappa n - \mu n^2\] \[ c_t + u\cdot \nabla c = \Delta c - nc\] \[ u_t + (u\cdot \nabla)u = \Delta u +\nabla P + n\nabla \Phi + f, \quad\qquad \nabla \cdot u=0 \] in a bounded, smooth domain $\Omega\subset \mathbb{R}^3$ under homogeneous Neumann boundary conditions for $n$ and $c$ and homogeneous Dirichlet boundary conditions for $u$ and with given functions $f\in L^\infty(\Omega\times(0,\infty))$ satisfying certain decay conditions and $\Phi\in C^{1+\beta}(\bar\Omega)$ for some $\beta\in(0,1)$. We construct weak solutions and prove that after some waiting time they become smooth and finally converge to the semi-trivial steady state $(\frac{\kappa}{\mu},0,0)$. Keywords: chemotaxis, Navier-Stokes, logistic source, boundedness, large-time behaviour
John A. Burns - One of the best experts on this subject based on the ideXlab platform.
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Parameter Estimation of a Thermal Fluid System
2018 Annual American Control Conference (ACC), 2018Co-Authors: John A. Burns, Eugene M. Cliff, Terry L. HerdmanAbstract:In this paper we consider the problems of parameter estimation for a counter flow heat exchanger. The problem is complicated when convection dominates the heat transfer so that the diffusion coefficient is small compared to the convection coefficient. We employ the full flux physics model, which means the model is defined by convection-diffusion equations and the parabolic equations are viewed as a perturbation of the zero diffusion model. We show that by proper formulation of the boundary conditions and employing combined finite element-finite volume schemes one can estimate the small diffusion term. Moreover, by employing constrained optimization one can obtain physically meaningful results. We compare constrained and unconstrained nonlinear least squares approaches. Numerical results are presented to illustrate the ideas and some open questions are discussed.
