scholarly journals Helmholtz’s decomposition for compressible flows and its application to computational aeroacoustics

2020 ◽  
Vol 1 (6) ◽  
Author(s):  
Stefan Schoder ◽  
Klaus Roppert ◽  
Manfred Kaltenbacher
Keyword(s):  
Flow Velocity ◽  
Compressible Flows ◽  
Base Flow ◽  
Computational Aeroacoustics ◽  
Helmholtz Decomposition ◽  
The Finite Element Method ◽  
Main Challenge ◽  
Source Data ◽  
Flow Domain ◽  
Definition Of

Abstract The Helmholtz decomposition, a fundamental theorem in vector analysis, separates a given vector field into an irrotational (longitudinal, compressible) and a solenoidal (transverse, vortical) part. The main challenge of this decomposition is the restricted and finite flow domain without vanishing flow velocity at the boundaries. To achieve a unique and $$L_2$$ L 2 -orthogonal decomposition, we enforce the correct boundary conditions and provide its physical interpretation. Based on this formulation for bounded domains, the flow velocity is decomposed. Combining the results with Goldstein’s aeroacoustic theory, we model the non-radiating base flow by the transverse part. Thereby, this approach allows a precise physical definition of the acoustic source terms for computational aeroacoustics via the non-radiating base flow. In a final simulation example, Helmholtz’s decomposition of compressible flow data using the finite element method is applied to an overflowed rectangular cavity at Mach 0.8. The results show a reasonable agreement with the source data and illustrate the distinct parts of the Helmholtz decomposition.

scholarly journals Interpersonal nurse-patient relationship with a young schizophrenic pregnant woman

2016 ◽  
Vol 10 (2) ◽  
pp. 136-148
Author(s):  
Renata Marques de Oliveira ◽  
Antonia Regina Ferreira Furegato
Keyword(s):  
Thematic Analysis ◽  
Psychiatric Treatment ◽  
Interpersonal Relationship ◽  
Psychiatric History ◽  
Patient Relationship ◽  
Therapeutic Interaction ◽  
Main Challenge ◽  
Schizophrenic Woman ◽  
Definition Of ◽  
Insight Into

The objective of this study was to investigate elements of the personal and psychiatric history, as well as the challenges related to motherhood, of a young schizophrenic female, through person-centered therapeutic interaction. The investigation had an exploratory scope, undertaken in a teaching hospital and data were collected during nondirective interaction on the part of the nurse with a young schizophrenic woman who had been treated in the institution for 10 years. Thematic analysis of the content was undertaken, with emphasis on the nuclei of meaning, identification of the themes and definition of the categories. The patient, called L. in this study, was 30 years old, had a two-year-old child and was three months pregnant when data were collected. Her trajectory was characterized by doubts, fears and uncertainties. The episodes of hospitalization, the coexistence with other patients, and the medications promoted insight into the symptoms, and acceptance of the diagnosis. The main challenge was experiencing pregnancy and the puerperium concomitantly with the psychiatric treatment. The interpersonal relationship established evidenced that, the young woman felling understood and that her needs were attended, overcame several difficulties she had reported and felt fulfilled and integrated into her social environment.

Definition of the Temperature and Heat Flux in Micromilling of Hardened Steel Using the Finite Element Method

2014 ◽  
Vol 39 (10) ◽  
pp. 7229-7239 ◽  
Author(s):  
Sergio Luiz Moni Ribeiro Filho ◽  
Marcelo Oliveira Gomes ◽  
Carlos Henrique Lauro ◽  
Lincoln Cardoso Brandão
Keyword(s):  
Finite Element Method ◽  
Heat Flux ◽  
Finite Element ◽  
Hardened Steel ◽  
The Finite Element Method ◽  
Definition Of ◽  
Element Method

scholarly journals A spatial connectivity approach to landscapes of conflict: Julius Caesar and the assault to Puig Ciutat (NE Iberian Peninsula)

2021 ◽  
Author(s):  
Xavier Rubio-Campillo ◽  
Eduard Ble ◽  
Àngels Pujol ◽  
Roger Sala ◽  
Robert Tamba
Keyword(s):  
Iberian Peninsula ◽  
Vital Role ◽  
Statistical Hypothesis ◽  
Julius Caesar ◽  
Mobility Patterns ◽  
Least Cost Path ◽  
Statistical Hypothesis Testing ◽  
Main Challenge ◽  
Definition Of ◽  
Ne Iberian Peninsula

Landscape plays a vital role in the development of military campaigns through the definition of geostrategic landmarks that structure the control of the territory, the imposition of constraints to the movement of armies, and the identification of positions that facilitate defensive tactics against aggressors. These factors are linked to the study of past spatial mobility which is typically performed using Least-Cost Path analysis (LCP). LCP identifies the optimal route that connects any two given points based on minimizing the accumulated cost based on a friction surface map, thus allowing archaeologists to identify the most efficient pathways across a territory. The main challenge of LCP analysis for archaeological regions is that optimal pathways are not well suited to define general mobility patterns within highly uncertain scenarios. Connectivity modelling based on Circuit Theory (CT) is an alternative approach to the study of mobility. CT does not generate a single path like LCP does; it captures the connectivity of an entire region identifying not only optimal paths, but also bottlenecks, dead-ends and any other spatial feature that may impact movement.We present here a framework to study landscapes of conflict using connectivity modelling; the framework combines CT, visibility analysis and statistical hypothesis testing to understand the reasons behind the assault and destruction of Puig Ciutat (NE Iberian Peninsula) during Julius Caesar's civil war. Results suggest that the site exerted decisive control over a highly connected area linking two possible logistical bases (Emporion and Massalia) to the armies fighting at Ilerda (49 BC).

scholarly journals INFORMATIZATION OF CONSTRUCTION MANAGEMENT AS A BASIS FOR PREVENTING MAN-MADE ACCIDENTS

2021 ◽  
Vol 4 (4) ◽  
pp. 11-31
Author(s):  
S. Koryagina
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
The Finite Element Method ◽  
Calculation Results ◽  
Definition Of ◽  
Deep Pits ◽  
Geotechnical Problems ◽  
Seismic Impacts ◽  
Base Structure ◽  
Element Method

the article presents the principles and algorithms of the finite element method in solving geotechnical prob-lems taking into account seismic impacts for determining the stress-strain state of structures and slope stabil-ity, implemented in the Midas GTS NX software package. GTS NX allows you to perform calculations of various types of geotechnical problems and solve complex geotechnical problems in a single software envi-ronment. GTS NX covers the entire range of engineering and geotechnical projects, including calculations of the "base-structure" system, deep pits with various mounting options, tunnels of complex shape, consolida-tion and filtration calculations, as well as calculations for dynamic actions and stability calculations. At the same time, all types of calculations in GTS NX can be performed both in 2D and in 3D. The author does not claim to be the author of the finite element method, but he cannot do without pointing out the basic equa-tions, as this affects the definition of the boundaries of use, the formulation of algorithms for constructing calculation schemes and the analysis of calculation results.

Effects of Fuel Staging on the Hydrodynamic Stability of Multinozzle Swirl Flows

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Saarthak Gupta ◽  
Kiran Manoharan ◽  
Santosh Hemchandra
Keyword(s):  
Heat Release ◽  
Flow Velocity ◽  
Hydrodynamic Stability ◽  
Flow Model ◽  
Base Flow ◽  
Computational Domain ◽  
Fuel Staging ◽  
Flow Oscillations ◽  
The Impact ◽  
Oscillation Characteristics

Abstract Hydrodynamic instability in lean premixed gas turbine combustors can cause coherent flow velocity oscillations. These can in turn drive heat release oscillations that when favorably coupled with combustor acoustic modes can result in combustion instability. The aim of this paper is to understand the impact of fuel staging on the characteristics of hydrodynamic modes in multinozzle combustors. We extend our recent numerical study on the hydrodynamic stability characteristics of a multinozzle combustor having three nozzles in a straight line with uniform fuel–air ratio in each nozzle, to the nonuniform fuel–air ratio case. As before, we construct the base flow model for this study by superposing contributions from individual nozzles, determined using a base flow model for a nominally axisymmetric single nozzle, at every point in the computational domain. The impact of fuel staging is captured by changing the burnt to unburnt gas density ratio parameter in the individual contribution from each nozzle. We investigate the characteristics of the most locally absolutely unstable mode for two cases. The first one is when the middle nozzle is made fuel rich when compared to the side nozzles and the second is when the side nozzles are made fuel rich relative to the middle nozzle. The impact of nonuniform fuel/air ratio on the local absolutely unstable temporal eigenvalues is seen to be small. However, significant changes in the spatial structure of the flow oscillations associated with the hydrodynamic eigenmodes are observed. In the first case, the flow oscillations with a different locally azimuthal nature on the middle nozzle when compared to the side nozzles emerge as the middle nozzle is made richer. In the second case, the oscillations on the two side nozzles are suppressed leaving the middle nozzle in a state that closely matches that of a single unconfined nozzle with the same nominal base flow velocity field. These types of internozzle variations in flow oscillation characteristics can explain the emergence of nonuniformity in heat release oscillation characteristics between individual nozzles in multinozzle combustors.

scholarly journals A comparison of mechanistic signaling pathway activity analysis methods

2018 ◽  
Vol 20 (5) ◽  
pp. 1655-1668 ◽  
Author(s):  
Alicia Amadoz ◽  
Marta R Hidalgo ◽  
Cankut Çubuk ◽  
José Carbonell-Caballero ◽  
Joaquín Dopazo
Keyword(s):  
Cell Activity ◽  
New Paradigm ◽  
Pathway Activity ◽  
Pathway Enrichment ◽  
New Methods ◽  
Mechanistic Pathway ◽  
Main Challenge ◽  
Definition Of ◽  
Cell Functionality ◽  
Modular Nature

Abstract Understanding the aspects of cell functionality that account for disease mechanisms or drug modes of action is a main challenge for precision medicine. Classical gene-based approaches ignore the modular nature of most human traits, whereas conventional pathway enrichment approaches produce only illustrative results of limited practical utility. Recently, a family of new methods has emerged that change the focus from the whole pathways to the definition of elementary subpathways within them that have any mechanistic significance and to the study of their activities. Thus, mechanistic pathway activity (MPA) methods constitute a new paradigm that allows recoding poorly informative genomic measurements into cell activity quantitative values and relate them to phenotypes. Here we provide a review on the MPA methods available and explain their contribution to systems medicine approaches for addressing challenges in the diagnostic and treatment of complex diseases.

Absolute/Convective Instability Transition in a Backward Facing Step Combustor: Fundamental Mechanism and Influence of Density Gradient

2014 ◽  
Author(s):  
Kiran Manoharan ◽  
Santosh Hemchandra
Keyword(s):  
Stability Analysis ◽  
Flow Field ◽  
Flow Velocity ◽  
Convective Instability ◽  
Flow Instability ◽  
Hydrodynamic Instability ◽  
Combustion Instability ◽  
Base Flow ◽  
Flow Density ◽  
Backward Facing Step

Hydrodynamic instabilities of the flow field in lean premixed gas turbine combustors can generate velocity perturbations that wrinkle and distort the flame sheet over length scales that are smaller than the flame length. The resultant heat release oscillations can then potentially result in combustion instability. Thus, it is essential to understand the hydrodynamic instability characteristics of the combustor flow field in order to understand its overall influence on combustion instability characteristics. To this end, this paper elucidates the role of fluctuating vorticity production from a linear hydrodynamic stability analysis as the key mechanism promoting absolute/convective instability transitions in shear layers occurring in the flow behind a backward facing step. These results are obtained within the framework of an inviscid, incompressible, local temporal and spatio-temporal stability analysis. Vorticity fluctuations in this limit result from interaction between two competing mechanisms — (1) production from interaction between velocity perturbations and the base flow vorticity gradient and (2) baroclinic torque in the presence of base flow density gradients. This interaction has a significant effect on hydrodynamic instability characteristics when the base flow density and velocity gradients are co-located. Regions in the space of parameters characterizing the base flow velocity profile, i.e. shear layer thickness and ratio of forward to reverse flow velocity, corresponding to convective and absolute instability are identified. The implications of the present results on prior observations of flow instability in other flows such as heated jets and bluff-body stabilized flames is discussed.

The effect of base flow variation on flow stability

2003 ◽  
Vol 476 ◽  
pp. 293-302 ◽  
Author(s):  
ALESSANDRO BOTTARO ◽  
PETER CORBETT ◽  
PAOLO LUCHINI
Keyword(s):  
Hydrodynamic Stability ◽  
Base Flow ◽  
Plane Couette Flow ◽  
Worst Case ◽  
Unconditionally Stable ◽  
Variational Techniques ◽  
Parallel Flows ◽  
The Stability ◽  
Definition Of ◽  
The Ideal

The Orr–Sommerfeld operator's eigenvalues determine the stability of exponentially growing disturbances in parallel and quasi-parallel flows. This work assesses the sensitivity of these eigenvalues to modifications of the base flow, which need not be infinitesimally small. Such base flow variations may represent differences between the laboratory flow and its ideal, theoretical counterpart. The worst case, i.e. the change in base flow with the most destabilizing effect on the eigenvalues, is found using variational techniques for the plane Couette flow. Relatively small changes in the base flow are shown to be destabilizing, although the ideal flow is unconditionally stable according to linear theory. These observations inspire a velocity-based definition of pseudospectra in the hydrodynamic stability context.

A Study of the Effects of Baffles on Rotating Compressible Flows

1989 ◽  
Vol 56 (3) ◽  
pp. 710-712
Author(s):  
Max D. Gunzburger ◽  
Houston G. Wood ◽  
Rosser L. Wayland
Keyword(s):  
Fluid Dynamics ◽  
Mathematical Model ◽  
Compressible Flows ◽  
Numerical Examples ◽  
Thermal Boundary Conditions ◽  
Gas Centrifuge ◽  
Mass Injection ◽  
Flow Domain ◽  
The Mathematical Model ◽  
Element Algorithm

Onsager’s pancake equation for the fluid dynamics of a gas centrifuge is modified for the case of centrifuges with baffles which render the flow domain doubly connected. A finite element algorithm is used for solving the mathematical model and to compute numerical examples for flow fields induced by thermal boundary conditions and by mass injection and extraction.

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