scholarly journals K-ε Turbulence Model Parameter Estimates Using an Approximate Self-similar Jet-in-Crossflow Solution

2017 ◽  
Author(s):  
Lawrence J. DeChant ◽  
Jaideep Ray ◽  
Sophia Lefantzi ◽  
Julia Ling ◽  
Srinivasan Arunajatesan
Keyword(s):  
Turbulence Model ◽  
Parameter Estimates ◽  
Model Parameter ◽  
Jet In Crossflow ◽  
Self Similar

Optimized blood sampling protocols and sequential design of kinetic experiments

1981 ◽  
Vol 240 (5) ◽  
pp. R259-R265 ◽  
Author(s):  
J. J. DiStefano
Keyword(s):  
Endocrine System ◽  
Primary Objective ◽  
Blood Sampling ◽  
Optimal Designs ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Reverse T3 ◽  
Model Parameter ◽  
Maximum Accuracy ◽  
Sampling Protocols

Design of optimal blood sampling protocols for kinetic experiments is discussed and evaluated, with the aid of several examples--including an endocrine system case study. The criterion of optimality is maximum accuracy of kinetic model parameter estimates. A simple example illustrates why a sequential experiment approach is required; optimal designs depend on the true model parameter values, knowledge of which is usually a primary objective of the experiment, as well as the structure of the model and the measurement error (e.g., assay) variance. The methodology is evaluated from the results of a series of experiments designed to quantify the dynamics of distribution and metabolism of three iodothyronines, T3, T4, and reverse-T3. This analysis indicates that 1) the sequential optimal experiment approach can be effective and efficient in the laboratory, 2) it works in the presence of reasonably controlled biological variation, producing sufficiently robust sampling protocols, and 3) optimal designs can be highly efficient designs in practice, requiring for maximum accuracy a number of blood samples equal to the number of independently adjustable model parameters, no more or less.

scholarly journals The Recirculation Zone Characteristics of the Circular Transverse Jet in Crossflow

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3224
Author(s):  
Ziwan Li ◽  
Yixiang Yuan ◽  
Baoting Guo ◽  
V. L. Varsegov ◽  
Jun Yao
Keyword(s):  
Turbulence Model ◽  
Negative Pressure ◽  
Recirculation Zone ◽  
Turbulence Models ◽  
Combustion Efficiency ◽  
Width Ratio ◽  
Transverse Jet ◽  
Jet In Crossflow ◽  
Pressure Zone ◽  
Jet Trajectory

Transverse jets in crossflow are widely used in energy systems, especially as dilution air jets, fuel/air mixers, and combustion equipment, and have received extensive attention and plenty of research. However, the studies of the circular transverse jet issued from a circular gap at the circumferential direction of a tube in crossflow are very limited. This paper studies a relatively new jet: the circular transverse jet. Firstly, numerical calculations are conducted under different turbulence models but with the same boundary conditions. By comparing the numerical results of different turbulence models with the existing experimental data, the turbulence model which is most suitable for the numerical calculation of the circular transverse jet is selected. Then, this turbulence model is used to calculate and analyze the flow field structure and its characteristics. It is found that due to the aerodynamic barrier effect of the high-velocity jet, a negative pressure zone is formed behind the jet trajectory; the existence of the negative pressure zone causes the formation of a vortex structure and a recirculation zone downstream the circular transverse jet; and the length/width ratio of the recirculation zone does not change with the changes of the crossflow and the jet parameters. It means that the recirculation zone is a fixed shape for a definite device. This would be fundamental references for the studying of fuel/air mixing characteristics and combustion efficiency when the circular transverse jet is used as a fuel/air mixer and stable combustion system.

scholarly journals A Regionalised Neyman-Scott Model of Rainfall with Convective and Stratiform Cells

1997 ◽  
Vol 1 (1) ◽  
pp. 71-80 ◽  
Author(s):  
P. S. P. Cowpertwait ◽  
P. E. O'Connell
Keyword(s):  
Cluster Model ◽  
Regression Models ◽  
Parameter Estimates ◽  
Model Parameter ◽  
Lack Of Fit ◽  
Dependent Variables ◽  
The Uk ◽  
Poisson Cluster ◽  
Residual Errors ◽  
Urban Sites

Abstract. A single-site Neyman-Scott Poisson cluster model of rainfall, with convective and stratiform cells, is fitted to data for 112 sites scattered throughout the UK using harmonic variables to account for seasonality. The model is regionalised by regressing the estimates of the harmonic variables on site dependent variables (e.g. altitude) to enable rainfall to be simulated at any ungauged site in the UK. An assessment of the residual errors indicates that the regression models can be used with reasonable confidence for urban sites. Furthermore, the regional variations of the model parameter estimates are found to be in agreement with meteorological knowledge and observation. Simulated I h extreme rainfalls are found to compare favourably with observed historical values, although some lack-of-fit is evident for higher aggregation levels.

Event Location with Sparse Data: When Probabilistic Global Search is Important

2020 ◽  
Author(s):  
Stephen Arrowsmith ◽  
Junghyun Park ◽  
Il-Young Che ◽  
Brian Stump ◽  
Gil Averbuch
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Arrival Time ◽  
Real Data ◽  
Parameter Estimates ◽  
Model Parameter ◽  
Event Location ◽  
Seismic Location ◽  
Probability Density Function Pdf

Abstract Locating events with sparse observations is a challenge for which conventional seismic location techniques are not well suited. In particular, Geiger’s method and its variants do not properly capture the full uncertainty in model parameter estimates, which is characterized by the probability density function (PDF). For sparse observations, we show that this PDF can deviate significantly from the ellipsoidal form assumed in conventional methods. Furthermore, we show how combining arrival time and direction-of-arrival constraints—as can be measured by three-component polarization or array methods—can significantly improve the precision, and in some cases reduce bias, in location solutions. This article explores these issues using various types of synthetic and real data (including single-component seismic, three-component seismic, and infrasound).

scholarly journals HIV Model Parameter Estimates from Interruption Trial Data including Drug Efficacy and Reservoir Dynamics

PLoS ONE ◽  
2012 ◽  
Vol 7 (7) ◽  
pp. e40198 ◽  
Author(s):  
Rutao Luo ◽  
Michael J. Piovoso ◽  
Javier Martinez-Picado ◽  
Ryan Zurakowski
Keyword(s):  
Drug Efficacy ◽  
Trial Data ◽  
Parameter Estimates ◽  
Hiv Model ◽  
Model Parameter

Computational Study of Jet-in-Crossflow and Film Cooling Using a New Unsteady-Based Turbulence Model

2005 ◽  
Author(s):  
D. Scott Holloway ◽  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Computational Study ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Turbulence Models ◽  
Streamwise Velocity ◽  
Pressure Side ◽  
Good Test ◽  
Jet In Crossflow

This paper documents a computational investigation of the unsteady behavior of jet-in-crossflow applications. Improved prediction of fundamental physics is achieved by implementing a new unsteady, RANS-based turbulence model developed by the authors. Two test cases are examined that match experimental efforts previously documented in the open literature. One is the well-documented normal jet-in-crossflow, and the other is film cooling on the pressure side of a turbine blade. All simulations are three-dimensional, fully converged, and grid-independent. High-quality and high-density grids are constructed using multiple topologies and an unstructured, super-block approach to ensure that numerical viscosity is minimized. Computational domains include the passage, film hole, and coolant supply plenum. Results for the normal jet-in-crossflow are for a density ratio of 1 and velocity ratio of 0.5 and include streamwise velocity profiles and injected flow or “coolant” distribution. The Reynolds number based on the average jet exit velocity and jet diameter is 20,500. This represents a good test case since normal injection is known to exaggerate the key flow mechanisms seen in film-cooling applications. Results for the pressure side film-cooling case include coolant distribution and adiabatic effectiveness for a density and blowing ratio of 2. In addition to the in-house model that incorporates new unsteady physics, CFD simulations utilize standard, RANS-based turbulence models, such as the “realizable” k-ε model. The present study demonstrates the importance of unsteady physics in the prediction of jet-in-crossflow interactions and for film cooling flows that exhibit jet liftoff.

scholarly journals Aspects of Theophylline Clearance in Children

1997 ◽  
Vol 25 (5) ◽  
pp. 497-501 ◽  
Author(s):  
B. J. Anderson ◽  
N. H. G. Holford ◽  
G. A. Woollard
Keyword(s):  
Plasma Concentrations ◽  
Volume Of Distribution ◽  
Pharmacokinetic Parameters ◽  
Parameter Estimates ◽  
Power Model ◽  
Theophylline Clearance ◽  
Concentration Data ◽  
Model Parameter ◽  
Age Related ◽  
Menten Constant

Michaelis-Menten pharmacokinetic parameters for theophylline were estimated in a three-month infant following an accidental overdose of intravenous aminophylline. Fitting of time-concentration data was performed using nonlinear regression with MKMODEL. A mixed order elimination model was superior to a first order model. Parameter estimates were standardized to a 70 kg human using an allometric power model. Parameter estimates (SE) were: maximum rate of metabolism (Vmax) 71(42) mg.h–1, Michaelis-Menten constant (Km) 32.3 (33.5) mg.l–1, volume of distribution (Vd) 46.9 (2.6) l. This Michaelis-Menten constant is lower than that reported for adults and consequently non-linear elimination will occur at lower plasma concentrations in infants than in adults. Theophylline clearance has traditionally been reported as directly proportional to body weight. This per kilogram model gives an erroneous impression that clearance is greatest in early childhood and then decreases with age until adult rates are reached in late adolescence. Age-related clearance values reported in the literature were reviewed using an allometric 3/4 power model. This size model demonstrates that clearance increases in infancy and reaches adult rates in the first one to two years of life.

Respirometry-based on-line model parameter estimation at a full-scale WWTP

2002 ◽  
Vol 45 (4-5) ◽  
pp. 335-343 ◽  
Author(s):  
H. Spanjers ◽  
G.G. Patry ◽  
K.J. Keesman
Keyword(s):  
Wastewater Treatment ◽  
Parameter Estimation ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Parameter Estimates ◽  
Model Parameter ◽  
Model Parameter Estimation ◽  
On Line ◽  
Set Up

This paper describes part of a project to develop a systematic approach to knowledge extraction from on-line respirometric measurements in support of wastewater treatment plant control and operation. The paper deals with the following issues: (1) test of the implementation of an automatic set-up consisting of a continuous laboratory respirometer integrated in a mobile trailer with sampling and dosing equipment, and data-acquisition and communication system; (2) assessment of activated sludge/sewage characteristics from sludge respirograms by model parameter estimation; (3) comparison of the parameter estimates with regular plant data and information obtained from supplementary wastewater respirograms. The paper describes the equipment and some of its measuring results from a period of one week at a large-scale wastewater treatment plant. The measurements were evaluated in terms of the common activated sludge modelling practice. The automatic set-up allowed reliable measurements during at least one week. The data were used to calibrate two different version of the model, and independent parameter estimates were obtained.

scholarly journals The Effect of Schmidt Number on Turbulent Scalar Mixing in a Jet-in-Crossflow

1999 ◽  
Author(s):  
Guangbin He ◽  
Yanhu Guo ◽  
Andrew T. Hsu ◽  
A. Brankovic ◽  
S. Syed ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Momentum Flux ◽  
Schmidt Number ◽  
Stokes Equations ◽  
Scalar Fields ◽  
Spreading Rate ◽  
Navier Stokes ◽  
Appreciable Effect ◽  
Jet In Crossflow ◽  
Schmidt Numbers

The adequacy and accuracy of the constant Schmidt number assumption in predicting turbulent scalar fields in jet-in-crossflows are assessed in the present work. A round jet injected into a confined crossflow in a rectangular tunnel has been simulated using the Reynolds-Averaged Navier-Stokes equations coupled with the standard k-ε turbulence model. A semi-analytical qualitative analysis was made to guide the selection of Schmidt number values. A series of parametric studies were performed, and Schmidt numbers ranging from 0.2 to 1.5 and jet-to-crossflow momentum flux ratios from 8 to 72 were tested. The principal observation is that the Schmidt number does not have an appreciable effect on the species penetration, but it does have a significant effect on species spreading rate in jet-in-crossflows, especially for the cases where the jet-to-crossflow momentum flux ratios are relatively small. A Schmidt number of 0.2 is recommended for best agreement with data. The limitations of the standard k–ε turbulence model and the constant Schmidt number assumption are discussed.

Sign in / Sign up

Export Citation Format

Share Document