Large eddy simulation of a lifted ethylene flame using a dynamic nonequilibrium model for subfilter scalar variance and dissipation rate

Accurate prediction of nonpremixed turbulent combustion using large eddy simulation(LES) requires detailed modeling of the mixing between fuel and oxidizer at scales finer than the LES filter resolution. In conserved scalar combustion models, the small scale mixing process is quantified by two parameters, the subfilter scalar variance and the subfilter scalar dissipation rate. The most commonly used models for these quantities assume a local equilibrium exists between production and dissipation of variance. Such an assumption has limited validity in realistic, technically relevant flow configurations. However, nonequilibrium models for variance and dissipation rate typically contain a model coefficient whose optimal value is unknown a priori for a given simulation. Furthermore, conventional dynamic procedures are not useful for estimating the value of this coefficient. In this work, an alternative dynamic procedure based on the transport equation for subfilter scalar variance is presented, along with a robust conditional averaging approach for evaluation of themodel coefficient. This dynamic nonequilibrium modeling approach is used for simulation of a turbulent lifted ethylene flame, previously studied using DNS by Yoo et al. (Proc. Comb. Inst., 2011). The predictions of the new model are compared to those of a static nonequilibrium modeling approach using an assumed model coefficient, as well as those of the equilibrium modeling approach. The equilibrium models are found to systematically underpredict both subfilter scalar variance and dissipation rate. Use of the dynamic procedure is shown to increase the accuracy of the nonequilibrium modeling approach. However, numerical errors that arise as a consequence of grid-based implicit filtering appear to degrade the accuracy of all three modeling options. Thus, while these results confirm the usefulness of the new dynamic model, they also show that the quality of subfilter model predictions depends on several factors extrinsic to the formulation of the subfilter model itself

Resistance to flow in sand channels

CER65EVR27.June, 1965.Includes bibliographical references (pages 77-81).In partial fulfillment of the requirements for the Degree of Doctor of Philosophy in Civil Engineering.A theoretical and laboratory investigation was made of resistance to flow in sand-bed channels. The objectives were to determine the type of flow and energy dissipation in sand-bed channels and develop equations and relations for predicting resistance to flow and mean velocity. The types of flow, energy dissipation and, thus resistance to flow in sand-bed channels is extremely variable because (1) the configuration of the boundary, (2) the properties of the fluid, and (3) the characteristics of the turbulence are functions of the flow, fluid, and sand characteristics and of the geometry of the channel. The boundary configurations that form in a sand bed are ripples, ripples on dunes, dunes, plane bed, antidunes or chutes-and-pools. The type of flow in a sand channel with constant discharge and average energy gradient may be steady or unsteady and uniform or nonuniform, depending on the boundary configuration. With the array of boundary configurations found in sand channels, the dissipation of energy may result from grain roughness, form roughness, acceleration of the flow, breaking waves or any combinations of them. With variable boundary configuration, type of flow and energy dissipation, it is impossible to determine a general equation to predict resistance to flow and mean velocity for all flow conditions. However, if the boundary configuration is known, specific relations and equations are developed for predicting resistance to flow. For steady uniform flow, the equations are based on integrating the Reynolds equation for turbulent flow. The coefficients in the integrated equation were determined from a study of the velocity distribution and verified using the mean flow variables. For nonuniform and (or) unsteady flow, resistance to flow is determined by applying a correction term to the equation developed for flow over a plane bed. The correction term compensates for the increase in energy dissipation resulting from form roughness, flow acceleration and breaking waves. The study of the velocity profiles for plane bed flow when there is considerable bed-material movement, determined that there is an inner and outer flow zone. In the inner zone, the slope A and intercept B in the relation u = A ln y + B are variable. The variation of the slope and intercept are functions of the size and concentration of suspended sediment in the inner zone. In the outer zone , the slope and intercept are constant

Hydraulic model studies

CER62EVR18.Series statement and numbering from publisher's list.Includes bibliographical references (page 13).Stage-discharge relations for two artificial controls were determined in a model study conducted at Colorado State University. The controls are used to measure the discharge at two gaging stations (Cibecue Ridge No. 1 and Cibecue Ridge No. 2), that form a part of an intensive hydrologic investigation of the semi-arid environment of Central Arizona. The gaging stations are located in a remote area where the runoff is infrequent and of brief duration. The model studies were conducted because it was virtually impossible to calibrate the controls in the field. In addition to determining the stage-discharge relation, modifications in the controls are proposed to improve the discharge records for the two stations. A hydraulic jump occurs in the present controls at the section where the stage is measured. The hydraulic jump keeps the controls clear of the large sediment discharge of the streams, but causes large fluctuations of the water surface in the stilling wells. The modified controls eliminate the hydraulic jump, make extensive use of the construction that presently exists, will pass the sediment discharge of the streams, and have a fairly sensitive stage-discharge relation. The recorded elevation of the water surf ace in the stilling well lags the actual elevation of the stream because the connection between the control and the stilling well is too small in relation to the size of the stilling well. The lag can be decreased by replacing the present stilling well with a tube 14 to 20 inches in diameter

Exploiting the synergy between carboplatin and ABT-737 in the treatment of ovarian carcinomas

Platinum drug-resistance in ovarian cancers is a major factor contributing to chemotherapeutic resistance of recurrent disease. Members of the Bcl-2 family such as the anti-apoptotic protein Bcl-XL have been shown to play a role in this resistance. Consequently, concurrent inhibition of Bcl-XL in combination with standard chemotherapy may improve treatment outcomes for ovarian cancer patients. Here, we develop a mathematical model to investigate the potential of combination therapy with ABT-737, a small molecule inhibitor of Bcl-XL, and carboplatin, a platinum-based drug, on a simulated tumor xenograft. The model is calibrated against in vivo\ud experimental data, wherein tumor xenografts were established in mice and treated with ABT-737 and carboplatin on a fixed periodic schedule, alone or in combination, and tumor sizes recorded regularly. We show that the validated model can be used to predict the minimum drug load that will achieve a predetermined level of tumor growth inhibition, thereby maximizing the synergy between the two drugs. Our simulations suggest that the time of infusion of each carboplatin dose is a critical parameter, with an 8-hour infusion of carboplatin administered each week combined with a daily bolus dose of ABT-737 predicted to minimize residual disease. We also investigate the potential of ABT-737 co-therapy with carboplatin to prevent or delay the onset of carboplatin-resistance under two scenarios. When resistance is acquired as a result of aberrant DNA-damage repair in cells treated with carboplatin, the model is used to identify drug delivery schedules that induce tumor remission with even low doses of combination therapy. When resistance is intrinsic, due to a pre-existing cohort of resistant cells, tumor remission is no longer feasible, but our model can be used to identify dosing strategies that extend disease-free survival periods. These results underscore the potential of our model to accelerate the development of novel therapeutics such as ABT-737, by predicting optimal treatment strategies when these drugs are given in combination with currently approved cancer medications

Economic value of sediment discharge data

April 1974.Bibliography: pages 37-38.Financially supported by the Colorado State University Experiment Station

On the direct indecomposability of infinite irreducible Coxeter groups and the Isomorphism Problem of Coxeter groups

In this paper we prove, without the finite rank assumption, that any irreducible Coxeter group of infinite order is directly indecomposable as an abstract group. The key ingredient of the proof is that we can determine, for an irreducible Coxeter group, the centralizers of the normal subgroups that are generated by involutions. As a consequence, we show that the problem of deciding whether two general Coxeter groups are isomorphic, as abstract groups, is reduced to the case of irreducible Coxeter groups, without assuming the finiteness of the number of the irreducible components or their ranks. We also give a description of the automorphism group of a general Coxeter group in terms of those of its irreducible components.Comment: 30 page

Effect of liposomally trapped antitumour drugs on a drug-resistant mouse lymphoma in vivo

A TLX-5 mouse lymphoma which was resistant to 1-β-D-arabinofuranosyl cytosine (AraC) was used in vivo to study the possibility of using liposomes as drug-delivery vehicles in order to overcome drug resistance

Resistance to flow in alluvial channels

CER61DBS79.Includes bibliographical references.From: Transactions of the American Society of Civil Engineers, 1962

Forms of bed roughness in alluvial channels

CER60DBS3.January 1960.Includes bibliographical references

Dye dilution method of discharge measurement

January 1971.CER70-71WSL-EVR47.Includes bibliographical references.Council of U.S. Universities for Soil and Water Development in Arid and Sub-humid Areas.Prepared under support of United States Agency for International Development, AID/csd-2162, Water management research in arid and sub-humid lands of the less developed countries