scholarly journals A New, Iterative, Synchronous-Response Algorithm for Analyzing the Morton Effect

2011 ◽  
Author(s):  
Dara W. Childs ◽  
Rohit Saha
Keyword(s):  
Temperature Distribution ◽  
Circular Orbit ◽  
Elliptic Orbit ◽  
Steady Increase ◽  
Thermally Induced ◽  
Temperature Distributions ◽  
Morton Effect ◽  
Shaft Angle ◽  
The Impact ◽  
Lubricant Viscosity

Morton Effect problems involve the steady increase in rotor synchronous-response amplitudes due to differential heating across a fluid-film bearing that is in turn induced by synchronous response. The present work presents a new computational algorithm for analyzing Morton Effect. Previous studies on the Morton Effect were based on Eigen or Nyquist analysis for stability studies and predicted an onset speed of instability. The algorithm starts with a steady state elliptical orbit produced by the initial imbalance distribution, which is decomposed into a forward-precessing circular orbit and a backwards-precessing circular orbit. A separate (and numerically intensive) calculation based on the Reynolds equation plus the energy equation gives predictions for the temperature distributions induced by these separate orbits for a range of orbit radius-to-clearance ratios. Temperature distributions for the forward and backward orbits are calculated and added to produce the net temperature distribution due to the initial elliptic orbit. The temperature distribution is assumed to vary linearly across the bearing and produces a bent-shaft angle across the bearing following an analytical result due to Dimoragonas. This bent shaft angle produces a synchronous rotor excitation in the form of equal and opposite moments acting at the bearing’s ends. For a rotor with an overhung section, the bend also produces a thermally induced imbalance. The response due to the initial mechanical imbalance, the bent-shaft excitation, and the thermally-induced imbalance are added to produce a new elliptic orbit, and the process is repeated until a converged orbit is produced. For the work reported, no formal stability analysis is carried out on the converged orbit. The algorithm predicts synchronous response for the speed range of concern plus the speed where the response amplitudes becomes divergent by approaching the clearance. Predictions are presented for one examples from the published literature, and elevated vibration levels are predicted well before the motion diverges. Synchronous-response amplitudes due to Morton Effect can be orders of magnitude greater than the response due only to mechanical imbalance, particularly near rotor critical speeds. For the example considered, bent-shaft-moment excitation produces significantly higher response levels than the mechanical imbalance induced by thermal bow. The impact of changes for (1) bearing length to diameter ratio, (2) reduced lubricant viscosity, (3) bearing radius-to-clearance ratio and (4) overhung mass magnitude are investigated. Reducing lubricant viscosity and/or the overhung mass are predicted to be the best remedies for Morton Effect problems.

scholarly journals A New, Iterative, Synchronous-Response Algorithm for Analyzing the Morton Effect

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Dara W. Childs ◽  
Rohit Saha
Keyword(s):  
Temperature Distribution ◽  
Circular Orbit ◽  
Elliptic Orbit ◽  
Steady Increase ◽  
Thermally Induced ◽  
Temperature Distributions ◽  
Morton Effect ◽  
Shaft Angle ◽  
The Impact ◽  
Lubricant Viscosity

Morton Effect problems involve the steady increase in rotor synchronous-response amplitudes due to differential heating across a fluid-film bearing that is induced by synchronous response. The present work presents a new computational algorithm for analyzing the Morton Effect. Previous approaches were based on Eigen or Nyquist analyses for stability studies and predicted an onset speed of instability. The present algorithm starts with a steady state elliptical orbit produced by the initial imbalance distribution, which is decomposed into a forward-precessing circular orbit and a backwards-precessing circular orbit. A separate (and numerically intensive) calculation based on the Reynolds equation plus the energy equation gives predictions for the temperature distributions induced by these separate orbits for a range of orbit radius-to-clearance ratios. Temperature distributions for the forward and backward orbits are calculated and added to produce the net temperature distribution due to the initial elliptic orbit. The temperature distribution is assumed to vary linearly across the bearing and produces a bent-shaft angle across the bearing following an analytical result due to Dimoragonas. This bent-shaft angle produces a synchronous rotor excitation in the form of equal and opposite moments acting at the bearing’s ends. For a rotor with an overhung section, the bend also produces a thermally induced imbalance. The response is due to: (1) the initial mechanical imbalance, (2) the bent-shaft excitation, and (3) the thermally-induced imbalance are added to produce a new elliptic orbit, and the process is repeated until a converged orbit is produced. For the work reported, no formal stability analysis is carried out on the converged orbit. The algorithm predicts synchronous response across the rotor’s speed range plus the speed where the response amplitudes becomes divergent by approaching the clearance. Predictions are presented for one example from the published literature, and elevated vibration levels are predicted well before the motion diverges. Synchronous-response amplitudes due to Morton Effect can be orders of magnitude greater than the response due only to mechanical imbalance, particularly near rotor critical speeds. For the example considered, bent-shaft-moment excitation produces significantly higher response levels than the mechanical imbalance induced by thermal bow. The impact of changes in: (1) bearing length-to-diameter ratio, (2) reduced lubricant viscosity, (3) bearing radius-to-clearance ratio and (4) overhung mass magnitude are investigated. Reducing lubricant viscosity and/or reducing the overhung mass are predicted to be the best remedies for Morton Effect problems.

scholarly journals Temperature distribution and Hadley circulation in an axisymmetric model

2014 ◽  
Vol 1 (2) ◽  
pp. 1621-1655
Author(s):  
N. Tartaglione
Keyword(s):  
Temperature Distribution ◽  
Energy Input ◽  
Meridional Circulation ◽  
Hadley Circulation ◽  
Time Dependent ◽  
Lapse Rate ◽  
Jet Stream ◽  
Axisymmetric Model ◽  
Temperature Distributions ◽  
The Impact

Abstract. The impact of the temperature distribution on the Hadley circulation simulated by an axisymmetric model is studied. The temperature distributions that drive the model are modulated here by two parameters, n and k, the former controlling the horizontal broadness and the latter defining change in the vertical lapse rate. In the present study, the changes of the temperature distribution mimic changes of the energy input of the atmospheric system leaving as an invariant the equator-poles difference. Both equinoctial and time-dependent Hadley circulations are simulated and results compared. The results give evidence that concentrated temperature distributions enhance the meridional circulation and jet wind speed intensities even with a lower energy input. The meridional circulation and the subtropical jet stream widths are controlled by the broadness of horizontal temperature rather than the vertical lapse rate k, which is important only when the temperature distribution is concentrated at the equator. The jet stream position does not show any dependence with n and k, except when the temperature distribution is very wide and in such a case the jet is located at the mid-latitude. Using n = 2 and k = 1 we have the formulation of the potential temperature adopted in classical literature. A comparison with other works is performed and our results show that the model running in different configurations (equinoctial, solstitial and time-dependent) yields results similar to one another.

The association between femoral neck shaft angle and degenerative disease of the hip in a cadaveric model

2021 ◽  
pp. 112070002110130
Author(s):  
Leigh-Anne Tu ◽  
Douglas S Weinberg ◽  
Raymond W Liu
Keyword(s):  
Femoral Head ◽  
Femoral Neck ◽  
Hip Osteoarthritis ◽  
Volume Ratio ◽  
Femoral Head Coverage ◽  
Neck Shaft Angle ◽  
Hip Arthritis ◽  
Femoral Version ◽  
Shaft Angle ◽  
The Impact

Background: While the influences of acetabular dysplasia and overcoverage on hip arthritis have been studied, the impact of femoral neck-shaft angle on hip arthritis is much more poorly understood. The purpose of this study is to determine if a relationship exists between neck shaft angle and the development of osteoarthritis, a better understanding of which would be useful to surgeons planning osteotomies about the hip. Methods: 533 cadaveric femora and acetabulae (1066 total) from the Hamann-Todd Osteological Collection (Cleveland, OH) were acquired. We measured true neck shaft angle using an AP photograph with the femoral neck parallel to the table. Femoral head volume to acetabular volume ratio, representing femoral head coverage, as well as femoral version were utilised. Correlation between neck shaft angle, femoral version, femoral head coverage and osteoarthritis were evaluated with multiple regression analysis. Results: The mean age and standard deviation was 56 ± 10 years. There were 64 females (12%) and 469 males. There were 380 Caucasians (71%) and 153 African-Americans. Mean femoral version was 11° ± 12° and mean true neck shaft angle was 127.7° ± 5.9° There was a strong correlation between age and arthritis (standardised beta 0.488, p < 0.001). There was a significant correlation between increasing true neck shaft angle and decreasing hip arthritis (standardised beta -0.024, p = 0.038). In the femoral head overcoverage subset, increasing true neck shaft angle was still significantly associated with decreasing hip arthritis (standardised beta −0.088, p = 0.018), although this relationship was not significant with femoral head undercoverage subset. Conclusions: With sufficient acetabular coverage, a relative increase in femoral neck shaft angle within the physiologic range is associated with decreased hip osteoarthritis. Clinical relevance: An understanding of the relationship between femoral neck shaft angle and hip osteoarthritis could be useful for surgeons planning pelvic or proximal femur osteotomies in children.

scholarly journals Influence of CFRC Insulating Plates on Spark Plasma Sintering Process

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 393
Author(s):  
Alexander M. Laptev ◽  
Jürgen Hennicke ◽  
Robert Ihl
Keyword(s):  
Temperature Distribution ◽  
Spark Plasma Sintering ◽  
Energy Demand ◽  
Composite Powders ◽  
Fem Method ◽  
Plasma Sintering ◽  
Axial Temperature ◽  
Spark Plasma ◽  
Power And Energy ◽  
The Impact

Spark Plasma Sintering (SPS) is a technology used for fast consolidation of metallic, ceramic, and composite powders. The upscaling of this technology requires a reduction in energy consumption and homogenization of temperature in compacts. The application of Carbon Fiber-Reinforced Carbon (CFRC) insulating plates between the sintering setup and the electrodes is frequently considered as a measure to attain these goals. However, the efficiency of such a practice remains largely unexplored so far. In the present paper, the impact of CFRC plates on required power, total sintering energy, and temperature distribution was investigated by experiments and by Finite Element Modeling (FEM). The study was performed at a temperature of 1000 °C with a graphite dummy mimicking an SPS setup. A rather moderate influence of CFRC plates on power and energy demand was found. Furthermore, the cooling stage becomes considerably longer. However, the application of CFRC plates leads to a significant reduction in the axial temperature gradient. The comparative analysis of experimental and modeling results showed the good capability of the FEM method for prediction of temperature distribution and required electric current. However, a discrepancy between measured and calculated voltage and power was found. This issue must be further investigated, considering the influence of AC harmonics in the DC field.

scholarly journals Impact of Extreme Weather on Healthcare Utilization by People with HIV in Metropolitan Miami

2021 ◽  
Vol 18 (5) ◽  
pp. 2442
Author(s):  
Daniel Samano ◽  
Shubhayu Saha ◽  
Taylor Corbin Kot ◽  
JoNell E. Potter ◽  
Lunthita M. Duthely
Keyword(s):  
Relative Risk ◽  
The United States ◽  
Extreme Weather ◽  
South Florida ◽  
Heat Index ◽  
Extreme Weather Events ◽  
Weather Data ◽  
Steady Increase ◽  
Daily Weather Data ◽  
The Impact

Extreme weather events (EWE) are expected to increase as climate change intensifies, leaving coastal regions exposed to higher risks. South Florida has the highest HIV infection rate in the United States, and disruptions in clinic utilization due to extreme weather conditions could affect adherence to treatment and increase community transmission. The objective of this study was to identify the association between EWE and HIV-clinic attendance rates at a large academic medical system serving the Miami-Dade communities. The following methods were utilized: (1) Extreme heat index (EHI) and extreme precipitation (EP) were identified using daily observations from 1990–2019 that were collected at the Miami International Airport weather station located 3.6 miles from the studied HIV clinics. Data on hurricanes, coastal storms and flooding were collected from the National Oceanic and Atmospheric Administration Storms Database (NOAA) for Miami-Dade County. (2) An all-HIV clinic registry identified scheduled daily visits during the study period (hurricane seasons from 2017–2019). (3) Daily weather data were linked to the all-HIV clinic registry, where patients’ ‘no-show’ status was the variable of interest. (4) A time-stratified, case crossover model was used to estimate the relative risk of no-show on days with a high heat index, precipitation, and/or an extreme natural event. A total of 26,444 scheduled visits were analyzed during the 383-day study period. A steady increase in the relative risk of ‘no-show’ was observed in successive categories, with a 14% increase observed on days when the heat index was extreme compared to days with a relatively low EHI, 13% on days with EP compared to days with no EP, and 10% higher on days with a reported extreme weather event compared to days without such incident. This study represents a novel approach to improving local understanding of the impacts of EWE on the HIV-population’s utilization of healthcare, particularly when the frequency and intensity of EWE is expected to increase and disproportionately affect vulnerable populations. More studies are needed to understand the impact of EWE on routine outpatient settings.

Effect of Inlet Configuration on Moderator Velocity and Temperature Distribution Inside the Calandria of a Heavy Water Reactor

2008 ◽  
Author(s):  
Abhijeet Mohan Vaidya ◽  
Naresh Kumar Maheshwari ◽  
Pallippattu Krishnan Vijayan ◽  
Dilip Saha ◽  
Ratan Kumar Sinha
Keyword(s):  
Temperature Distribution ◽  
Impact Velocity ◽  
Heavy Water ◽  
Computational Study ◽  
Water Reactor ◽  
Heavy Water Reactor ◽  
The Impact

Computational study of the moderator flow in calandria vessel of a heavy water reactor is carried out for three different inlet nozzle configurations. For the computations, PHOENICS CFD code is used. The flow and temperature distribution for all the configurations are determined. The impact of moderator inlet jets on adjacent calandria tubes is studied. Based on these studies, it is found that the inlet nozzles can be designed in such a way that it can keep the impact velocity on calandria tubes within limit while keeping maximum moderator temperature well below its boiling limit.

scholarly journals The impact of donor policies in Europe: a steady increase, but not everywhere

2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Remco Coppen ◽  
Roland D Friele ◽  
Sjef KM Gevers ◽  
Geke A Blok ◽  
Jouke van der Zee
Keyword(s):  
Steady Increase ◽  
The Impact ◽  
Donor Policies

scholarly journals Impact of sewage water irrigation on agricultural soil

2021 ◽  
pp. 141-148
Keyword(s):  
Industrial Development ◽  
Municipal Wastewater ◽  
Microbial Biomass Carbon ◽  
Biological Properties ◽  
Sewage Water ◽  
Viable Count ◽  
Steady Increase ◽  
Available Nitrogen ◽  
The Impact ◽  
Flooded Field

The rapidly increasing population growth and the steady increase in water requirements for agricultural and industrial development have placed severe stress on the water resources available and the long term use of sewage water for irrigation highly affects soil properties. In this study soil samples were collected from a cauliflower field prior and after sewage water irrigation, and the impact of sewage water irrigation on physical, chemical, and biological properties of soil was compared. For this, tested were pH, Electrical Conductivity (EC), Organic Carbon, available Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Zinc, Iron, Copper, Manganese, and microbial activity. Soil microbial biomass carbon, basal soil respiration, total viable count of bacteria, coliform population, Pseudomonas species, and Azotobacter significantly increased after sewage water irrigation as compared to prior to irrigation. Nevertheless, the bulk density and Rhizobium species of the soil flooded with sewage water was decreased relative to the same characteristics prior to irrigation. Cauliflower yield was significantly increased when sewage water flooded field as compared to the tube well water flooded field (i.e., water delivered via an iron pipe). Escherichia coli contamination was greater in sewage water and groundwater that can pose health risks for the nearby communities, to farmers and consumer of farm products. Hence, the efficient use of sewage and municipal wastewater successfully increase water resource for irrigation and may help in expanding agricultural production. But excessive use of sewage water may also affect the soil flora and fertility.

scholarly journals Thermal Comfort Modeling of a Church Heated with Static Heaters

2019 ◽  
Vol 9 (1) ◽  
pp. 121-124
Author(s):  
Florin-Emilian Turcanu ◽  
Ana Diana Ancas ◽  
Mihai Profire ◽  
Marina Verdes ◽  
Marius Costel Balan
Keyword(s):  
Temperature Distribution ◽  
Thermal Comfort ◽  
Heating System ◽  
Xviii Century ◽  
Static Heating ◽  
The Impact ◽  
The Church

Abstract This paper evaluates a static heating system from a church. They are presented in almost every church. Temperature distribution in the church is done in 2d plane. The simulation is presented on a particular example, the Dormition of the Mother of God Church from Jassy, Romania. The heating system had been simulated in FLUENT and the consequences over the interior climate in the church are showed. An important issue is the impact of this system over the artwork, the church being rise in XVIII century.

The Transient Temperature Distribution in a Slab Subject to Thermal Radiation

1965 ◽  
Vol 87 (1) ◽  
pp. 117-130 ◽  
Author(s):  
R. D. Zerkle ◽  
J. Edward Sunderland
Keyword(s):  
Temperature Distribution ◽  
Thermal Radiation ◽  
Radiant Heat ◽  
Analog Computer ◽  
Graphical Form ◽  
Transient Temperature ◽  
Transient Temperature Distribution ◽  
Temperature Distributions ◽  
Approximate Analytical Solutions ◽  
Wide Range

The transient, one-dimensional temperature distribution is determined for a slab, insulated on one face, and subjected to thermal radiation at the other face. The slab is initially at a uniform temperature and is assumed to be homogeneous, isotropic, and opaque; the physical properties are assumed to be independent of temperature. Transient temperature distributions for both heating and cooling situations are obtained by means of a thermal-electrical analog computer. A diode limiter circuit is used to simulate the nonlinear radiant heat flux. The transient temperature distributions are presented in a dimensionless, graphical form for a wide range of variables. Approximate analytical solutions are also given which complement and extend the solution charts over ranges of parameters not covered in the charts.

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