Fluent (United States)

Abstract Coal gasification is presented in terms of the chemistry of coal conversion and the product gas characteristics, the historical development of coal gasifiers, variations in the types and performance of coal gasifiers, the configuration of gasification systems, and the status and economics of coal gasification. In many ways, coal gasification processes have been tailored to adapt to the different types of coal feedstocks available. Gasification technology is presented from a historical perspective considering early uses of coal, the first practical demonstration and utilization of coal gasification, and the evolution of the various processes used for coal gasification. The development of the gasification industry is traced from its inception to its current status in the world economy. Each type of gasifier is considered focusing on the process innovations required to meet the changing market needs. Complete gasification systems are described including typical system configurations, required system attributes, and aspects of the industry's environmental and performance demands. The current status, economics of gasification technology, and future of gasification are also discussed.

Mixed phenotype acute leukemia (MPAL) is a leukemia whose biologic drivers are poorly understood, therapeutic strategy remains unclear, and prognosis is poor. We performed multiomic single cell (SC) profiling of 14 newly diagnosed adult MPAL patients to characterize the immunophenotypic, genetic, and transcriptional landscapes of MPAL. We show that neither genetic profile nor transcriptome reliably correlate with specific MPAL immunophenotypes. However, progressive acquisition of mutations is associated with increased expression of immunophenotypic markers of immaturity. Using SC transcriptional profiling, we find that MPAL blasts express a stem cell-like transcriptional profile distinct from other acute leukemias and indicative of high differentiation potential. Further, patients with the highest differentiation potential demonstrated inferior survival in our dataset. A gene set score, MPAL95, derived from genes highly enriched in this cohort, is applicable to bulk RNA sequencing data and was predictive of survival in an independent patient cohort, suggesting utility for clinical risk stratification.

Nationwide, the demand for electricity due to population and industrial growth is on the rise. However, climate change and air quality issues raise serious questions about the wisdom of addressing these shortages through the construction of additional fossil fueled power plants. In 1997, the President's Committee of Advisors on Science and Technology Energy Research and Development Panel determined that restoring a viable nuclear energy option was essential and that the DOE should implement a R&D effort to address principal obstacles to achieving this option. This work has addressed the need for improved thermal/fluid analysis capabilities, through the use of computational fluid dynamics, which are necessary to support the design of generation IV gas-cooled and supercritical water reactors.

Abstract We use the well established core‐annulus flow regime as a numerical benchmark to evaluate the sensitivity of gas–solids continuum models and boundary conditions to model formalisms and parameters. By using transient, 1D, grid‐independent numerical solutions, we avoid the use of speculative closure terms and show that the kinetic theory of granular flow (KTGF) is sufficient to model core‐annulus regime. That regime arises in the time‐average solution as a consequence of the fluctuating motion of regions with high solids concentration. These fluctuations are most sensitive to the gravitational acceleration (g) and granular energy dissipation terms. The fluctuation frequency is α $ \sqrt g $. The effect of fluctuations is so dominant that decreasing the restitution coefficient (KTGF parameter) actually increases the average granular temperature. The wall boundary conditions for solids momentum and granular energy equations dictate the core‐annulus flow regime. They must cause a net dissipation of granular energy at the wall for predicting that regime. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Many design concepts of high-speed tactical guided missiles use aerospikes to reduce the drag and heating on the missiles body. The accurate numerical prediction of hypersonic flows over aerospike-protected missile shapes using Computational Fluid Dynamics (CFD) can be a valuable tool in the evaluation of such co ncepts. This study presents an effective and robust numerical approach to the problem of a hypersonic flow over a missile body shielded with aerospike/aerodisc. The problem considers three-dimensional flow around aerospikeprotected missile domes at a free stream Mach number ranging from 4.5 to 6.06 and angles of attack varying from 0 to 16 deg. Steady-state nu merical simulations are carried out using the general purpose CFD code FLUENT, version 6.3. Pressure-based coupled solver formulation is chosen to obtain an accurate fast-co nverging solution. SST ω k turbulence model is employed to simulate turbulence effects. T he near-wall mesh is fine enough to resolve the viscosity-affected near-wall region all the way to the laminar sublayer, and FLUENT’s enhanced wall treatment is applied. Numerical results expressed in terms of pressure coefficient are compared with experimental data, and favorable agreement is found. Effects of aerospike on missile dome surface aeroheating are also presented.

Purpose: Computational fluid dynamics (CFD) is increasingly common in optimization of blood pump designs. Ension is leveraging CFD techniques for analysis of a novel pump-oxygenator which utilizes a hollow fiber membrane (HFM) rotor. This application is unusually demanding due to the geometric complexity of the HFM rotor over traditional pump vanes. The purpose is to identify a porous media analog of the HFM rotor to reduce the computational demands of CFD analysis. Methods: A miniature HFM rotor was developed to minimize the fluid domain and allow direct modeling of each fiber geometry in the rotor. A computational mesh was created in Gambit (∼12 million cells) and simulated in Fluent v6 (Fluent, Inc. Lebanon, NH). After completion of the direct model analysis, a periodic interstitial fluid domain of the HFM rotor was modeled and simulated at flow velocities observed in the direct model simulations allowing derivation of porous media characteristics of the HFM rotor. A new computational model of the miniaturized rotor was developed, replacing the individual fiber geometries with a porous media region. Results: Both the direct fiber and porous media models were verified with experimental data and showed good agreement. The porous media approach allowed for a reduction of the computational mesh from 12 million to 2 million cells, with very little loss in accuracy. This strategy is being used by Ension to model and optimize full-scale pump-oxygenator configurations.

Many design concepts of unmanned aerial vehicles (UAV), especially mini- and microUAVs, use oscillating and flapping wings for propulsion and control. The accurate numerical prediction of transient turbulent flows over airfoils with complex motion via CFD can be a valuable tool in the evaluation of such concepts. This study presents and compares two moving mesh methods to analyze unsteady turbulent flows over an oscillatory pitching airfoil. The problem considers two-dimensional flow around NACA64A010 airfoil at a free stream Mach number of 0.796. This flow is transonic with weak shocks developing near the mid-chord. Unsteady numerical simulation in the time domain is carried out using the general purpose CFD code FLUENT, version 6.2. The realizable e k turbulence model is employed to simulate turbulence effects. The near-wall mesh is fine enough to resolve the viscosity-affected near-wall region all the way to the laminar sublayer, and Fluent’s enhanced wall treatment is applied. The oscillatory pitching motion of the airfoil around its quarter-chord is prescribed using two separate approaches: (i) the sliding mesh model where the moving zone encompassing the airfoil oscillates in discrete steps relative to the surrounding stationary zone with both zones communicating via a non-conformal sliding interface, and (ii) the dynamic mesh model where the mesh surrounding the airfoil is deformed based on the new positions of the airfoil using the spring-based smoothing method. Both approaches reproduce numerical solutions in close agreement with each other. The lift and moment coefficients are compared with experimental data and favorable agreement is found. Other turbulence models including Spalart-Allmaras, SST ω k and F v 2 are also considered.

This letter presents the first implementation of the concurrent complementary operators method (C-COM) for mesh truncation in finite-element simulations, in general, and to waveguide structures in particular. In addition to presenting the procedure of the implementation, the strength of the C-COM is demonstrated by focusing on the absorption of spurious evanescent waves that are typically the most challenging to eliminate when truncating computational boundaries. Numerical results for both evanescent TE and TM modes in parallel-plate waveguides are provided.