Dynamic Unstructured Grids Method with Applications to Unsteady Flows Involving Moving Boundaries

2015 ◽  
Vol 757 ◽  
pp. 87-91
Author(s):  
Jun Li Wang ◽  
Dong Sheng Zhang
Keyword(s):  
Unstructured Grids ◽  
Boundary Effect ◽  
Analogy Method ◽  
Torsion Oscillation ◽  
Spring Method ◽  
Euler Solver ◽  
Long Endurance ◽  
Good Agreement ◽  
Rigid Wing

Spring analogy method for dynamic unstructured grids is studied. The stiffness of the springs in the vertex spring method is analyzed. Improvements considering squashing spring effect and boundary effect are developed to the standard method. Applications of the improved spring analogy method to dynamic grids generation show that the new method greatly improves the deforming ability and the quality of the grids. This improved unstructured dynamic mesh method, coupled with ALE Euler solver, is then applied to simulate unsteady transonic flow about harmonious oscillation of rigid wing and bend-torsion oscillation of high-aspect ratio sweepback wing of High-Altitude-Long-Endurance Unmanned Aerial Vehicles; computational results are in good agreement with those of other literatures and experiments

A finite-volume solution to the geophysical electromagnetic forward problem using unstructured grids

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. E287-E302 ◽  
Author(s):  
Hormoz Jahandari ◽  
Colin G. Farquharson
Keyword(s):  
Electric Field ◽  
Finite Volume ◽  
Unstructured Grids ◽  
Real Data ◽  
Electromagnetic Problems ◽  
Tetrahedral Elements ◽  
Finite Volume Approach ◽  
Anomalous Bodies ◽  
Good Agreement

The application of unstructured grids can improve the solution of total field electromagnetic problems because these grids allow efficient local refinement of the mesh at the locations of high field gradients. Unstructured grids also provide the flexibility required for representing arbitrary topography and subsurface interfaces. We investigated the generalization of the standard Yee’s staggered scheme to unstructured tetrahedral-Voronoï grids using a finite-volume approach. We discretized the Helmholtz equation for the electric field in the frequency domain and solved the problem to find the projection of the total electric field along the edges of the tetrahedral elements. To compute the electric and magnetic fields at the observation points, an interpolation technique was employed, which uses the edge vector interpolation functions of the tetrahedral elements. To verify the presented scheme, two examples were evaluated, which revealed the computation of the total and secondary fields due to electric and magnetic sources in half-spaces that contain anomalous bodies. The results had good agreement with those from the literature. For the second example, accuracy studies were conducted to better understand the relative importance of different refinements in the grid and also the effect of the general quality of the grid. The results revealed the utmost importance of the quality of the tetrahedral grid and refinement at the observation locations. To validate the versatility of the approach, we synthesized helicopter-borne data for a model of the Ovoid ore body at Voisey’s Bay, Labrador, Canada, which had good agreement with real data.

Simulation and Optimization of Wedge-Shaped Ultrasonic Transducers Using Finite Element Method (FEM)

2013 ◽  
Vol 281 ◽  
pp. 112-115 ◽  
Author(s):  
Dan Jin ◽  
Zhao Hui Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Effect ◽  
Ultrasonic Transducers ◽  
Fe Model ◽  
Limited Size ◽  
Simulation And Optimization ◽  
Ultrasonic Flaw ◽  
Shape And Size ◽  
Good Agreement

Wedge-shaped transducers have been widely used in industry as probes for ultrasonic flowmeters or for ultrasonic flaw detectors. But by now, few studies have focused on the influence to the performance of the wedge-shaped transducers brought by their limited size. In this paper, the effect of the shape and size of wedge-shaped substrates on the whole transducer system is discussed and the shape and size of a transducer (0.5MHz) is optimized to eliminate the influence of the boundary effect by using a 2-D Finite Element (FE) model. Lastly, wedge-shaped transducers have been manufactured for experiment which shows a good agreement with the simulation.

scholarly journals Performance of TRMM TMPA 3B42 V7 in Replicating Daily Rainfall and Regional Rainfall Regimes in the Amazon Basin (1998–2013)

2018 ◽  
Vol 10 (12) ◽  
pp. 1879 ◽  
Author(s):  
Véronique Michot ◽  
Daniel Vila ◽  
Damien Arvor ◽  
Thomas Corpetti ◽  
Josyane Ronchail ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Daily Rainfall ◽  
Rain Gauge ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Spatial Coverage ◽  
Rainfall Regimes ◽  
Trmm 3B42 ◽  
Good Agreement

Knowledge and studies on precipitation in the Amazon Basin (AB) are determinant for environmental aspects such as hydrology, ecology, as well as for social aspects like agriculture, food security, or health issues. Availability of rainfall data at high spatio-temporal resolution is thus crucial for these purposes. Remote sensing techniques provide extensive spatial coverage compared to ground-based rainfall data but it is imperative to assess the quality of the estimates. Previous studies underline at regional scale in the AB, and for some years, the efficiency of the Tropical Rainfall Measurement Mission (TRMM) 3B42 Version 7 (V7) (hereafter 3B42) daily product data, to provide a good view of the rainfall time variability which is important to understand the impacts of El Nino Southern Oscilation. Then our study aims to enhance the knowledge about the quality of this product on the entire AB and provide a useful understanding about his capacity to reproduce the annual rainfall regimes. For that purpose we compared 3B42 against 205 quality-controlled rain gauge measurements for the period from March 1998 to July 2013, with the aim to know whether 3B42 is reliable for climate studies. Analysis of quantitative (Bias, Relative RMSE) and categorical statistics (POD, FAR) for the whole period show a more accurate spatial distribution of mean daily rainfall estimations in the lowlands than in the Andean regions. In the latter, the location of a rain gauge and its exposure seem to be more relevant to explain mismatches with 3B42 rather than its elevation. In general, a good agreement is observed between rain gauge derived regimes and those from 3B42; however, performance is better in the rainy period. Finally, an original way to validate the estimations is by taking into account the interannual variability of rainfall regimes (i.e., the presence of sub-regimes): four sub-regimes in the northeast AB defined from rain gauges and 3B42 were found to be in good agreement. Furthermore, this work examined whether TRMM 3B42 V7 rainfall estimates for all the grid points in the AB, outgoing longwave radiation (OLR) and water vapor flux patterns are consistent in the northeast of AB.

A Combined Global Coarsening Method for 3D Multigrid Applications

2012 ◽  
Vol 236-237 ◽  
pp. 1049-1053
Author(s):  
Zong Zhe Li ◽  
Zheng Hua Wang ◽  
Lu Yao ◽  
Wei Cao
Keyword(s):  
Aspect Ratio ◽  
Present Method ◽  
Unstructured Grid ◽  
Unstructured Grids ◽  
Coarse Grid ◽  
3D Flow ◽  
High Quality ◽  
Coarse Grids

An automatic agglomeration methodology to generate coarse grids for 3D flow solutions on anisotropic unstructured grids has been introduced in this paper. The algorithm combines isotropic octree based coarsening and anisotropic directional agglomeration to yield a desired coarsening ratio and high quality of coarse grids, which developed for cell-centered multigrid applications. This coarsening strategy developed is presented on an unstructured grid over 3D ONERA M6 wing. It is shown that the present method provides suitable coarsening ratio and well defined aspect ratio cells at all coarse grid levels.

scholarly journals A 16-week multicenter observational study of the efficiency and safety of rheumatoid arthritis therapy with methotrexate

2018 ◽  
Vol 12 (4) ◽  
pp. 106-111
Author(s):  
R. M. Balabanova
Keyword(s):  
Rheumatoid Arthritis ◽  
Combination Therapy ◽  
Fasting Glucose ◽  
Morning Stiffness ◽  
Hypolipidemic Effect ◽  
Multicenter Observational Study ◽  
High Doses ◽  
Positive Effect ◽  
Good Agreement

Objective: to evaluate the efficiency of combination therapy with methotrexate (MTX) and hydroxychloroquine (HC) in rheumatoid arthritis (RA) in real clinical practice.Patients and methods. The investigation enrolled 430 patients with documented RA who had been followed up for 16 weeks by rheumatologists in different regions of the country. Individual schedules were filled out for the patients, by adding demographic, clinical, and laboratory parameters that made it possible to assess the activity of the disease and to estimate the level of glucose, cholesterol, and low-density lipoproteins (LDL). The results of the investigation were evaluated at the inclusion of patients in it and then at 8 and 16 weeks. Taking into account the insufficient previous effect of MTX, the treatment was enhanced by HC.Results and discussion. By the end of the investigation, the combination therapy with MTX + HC led to significant decreases in the number of swollen and tender joints, the duration of morning stiffness, the severity of pain, and the integrated DAS28 index. The therapy showed a positive effect on the levels of fasting glucose, cholesterol, and LDL. The quality of life improved in patients by Visit 3. The results obtained are in good agreement with the data by foreign and Russian investigators on the greater efficiency of combination therapy with MTX + HC than that of MTX monotherapy and on the pleiotropic (hypolipidemic and hypolipidemic) effect of HC.Conclusion. It is concluded that in Russian practice when monotherapy with MTX shows an insufficient effect or its high doses cannot be administered to enhance the efficacy of RA therapy, it is possible to use a combination of MTX + HC, especially in older patients with comorbidity (hyperglycemia and hypercholesterolemia).

scholarly journals Single-sided NMR for the measurement of the degree of cross-linking and curing

2018 ◽  
Vol 7 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Norbert Halmen ◽  
Christoph Kugler ◽  
Eduard Kraus ◽  
Benjamin Baudrit ◽  
Thomas Hochrein ◽  
...  
Keyword(s):  
Relaxation Times ◽  
Curing Kinetics ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
First Results ◽  
Non Destructive ◽  
Kinetics Of ◽  
Good Agreement

Abstract. The degree of cross-linking and curing is one of the most important values concerning the quality of cross-linked polyethylene (PE-X) and the functionality of adhesives and resin-based components. Up to now, the measurement of this property has mostly been time-consuming and usually destructive. Within the shown work the feasibility of single-sided nuclear magnetic resonance (NMR) for the non-destructive determination of the degree of cross-linking and curing as process monitoring was investigated. First results indicate the possibility of distinguishing between PE-X samples with different degrees of cross-linking. The homogeneity of the samples and the curing kinetics of adhesives can also be monitored. The measurements show good agreement with reference tests (wet chemical analysis, differential scanning calorimetry, dielectric analysis). Furthermore, the influence of sample temperature on the characteristic relaxation times can be observed.

scholarly journals Modeling the Peach Sugar Contents in Relation to Fruit Growth

1996 ◽  
Vol 121 (6) ◽  
pp. 1122-1131 ◽  
Author(s):  
Michel Génard ◽  
Michel Souty
Keyword(s):  
Growth Curve ◽  
Prunus Persica ◽  
Transfer Functions ◽  
Dry Weight ◽  
Fruit Growth ◽  
Data Sets ◽  
Weight Growth ◽  
Using Data ◽  
Good Agreement

The edible quality of peaches (Prunus persica L. Batsch) to a great extent depends on their sweetness, which is related to sugar composition. Our objective was to develop a model to predict carbon partitioning within fruit flesh and to predict the sucrose, sorbitol, glucose, and fructose contents. The model is dynamic and deterministic and was designed to be driven by the flesh dry-weight growth curve, flesh water content, and temperature data. It uses differential equations where the state of the system is defined by variables that describe how much carbon is present as each form of sugar and as other compounds (acids and structural carbohydrates). The rates of change of these amounts of carbon depend on the current values of corresponding variables and on the transfer functions between them. These functions are defined by rate constants or by functions of degree-days after full bloom. The model was calibrated and tested using data sets from treatments that covered several leaf: fruit ratios. The predictions of the model were in fairly good agreement with experimental data. A sensitivity analysis was performed to identify the most influential transfer function parameters. Carbon flows between sugar forms were analyzed. Sucrose, which was the most abundant sugar, and fructose, which is the sweetest, contributed most to fruit sweetness. Simulations were performed to study the effects of changes in fruit growth-curve parameters on sugar contents and concentrations.

scholarly journals Optimization of the Countersinking Parameters Based on the Response Surface Method

2021 ◽  
Author(s):  
Hassen Mosbah ◽  
Slimen Attyaoui ◽  
Rachid Nasri
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Sequential Quadratic Programming ◽  
Numerical Optimization ◽  
Element Model ◽  
Poor Quality ◽  
Blank Holder ◽  
Surface Method ◽  
Good Agreement

Abstract The countersinking process is affected by many factors including the tools and the workpiece parameters. Some forming phenomena such as the knife-edge affect the quality of the countersunk hole. Up to now, many kinds of research rely mainly on the experiments which lead to poor quality and difficult control of this process. In this paper, a proposed numerical optimization of the countersinking process is developed to obtain a normalized countersunk hole. This optimisation approach is based on the response surface method (RMS), design of experiments (DOE) and the sequential quadratic programming (SQP). Finite element model is performed with an elasto-plastic behaviour for simulating the process. A configuration with an imposed displacement applied to the blank holder is adopted in this study. The comparison between the results of the numerical model and the experiments showed a good agreement.

A Model and Application for Estimating Completeness of Registration

2001 ◽  
Vol 40 (02) ◽  
pp. 122-126 ◽  
Author(s):  
W.-J. Stronegger ◽  
K.-D. Wernecke ◽  
A. Berghold
Keyword(s):  
Down Syndrome ◽  
Demographic Data ◽  
Population Based ◽  
Quality Of Information ◽  
Data Set ◽  
Time Varying Parameters ◽  
Capture Recapture ◽  
Completeness Of Reporting ◽  
Good Agreement

AbstractCompleteness of population-based registration systems is recognized to be an important aspect of the quality of information in registries which has to be examined. In this paper a model is presented which was used to estimate completeness of reporting of Down syndrome data notified to the Styrian Malformation registry between 1985-92. The model introduced is based on the two-source capture-recapture method allowing for time-varying parameters. For estimation of the parameters a discrete-time filtering algorithm was developed. For the used data set, an estimate of completeness derived from this model was in good agreement with an independent estimator based on demographic data and maternal age-specific Down syndrome risks whereas the usual two-source capture-recapture method gave a higher estimate.

Heat and Mass Transfer during Drying of Clay Ceramic Materials: A Three-Dimensional Analytical Study

2017 ◽  
Vol 10 ◽  
pp. 93-106 ◽  
Author(s):  
M.K. Teixeira de Brito ◽  
D.B. Teixeira de Almeida ◽  
A.G. Barbosa de Lima ◽  
L. Almeida Rocha ◽  
E. Santana de Lima ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Analytical Study ◽  
Separation Of Variables ◽  
Three Dimensional ◽  
Ceramic Materials ◽  
Governing Equations ◽  
Convective Boundary ◽  
Good Agreement

This work aims to study heat and mass transfer in solids with parallelepiped shape with particular reference to drying process. A transient three-dimensional mathematical model based on the Fick ́s and Fourier ́s Laws was developed to predict heat and mass transport in solids considering constant physical properties and convective boundary conditions at the surface of the solid. The analytical solution of the governing equations was obtained using the method of separation of variables. The study was applied in the drying of common ceramic bricks. Predicted results of the heating and drying kinetics and the moisture and temperature distributions inside the material during the process, are compared with experimental data and good agreement was obtained. It has been found that the vertices of the solid dry and heat first. This provokes thermal and hydric stresses inside the material, which may compromise the quality of the product after drying.

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