Braking System Cooling Time Simulation

2003 ◽  
Author(s):  
Luiz Tobaldini Neto ◽  
Ramon Papa ◽  
Luis C. de Castro Santos
Keyword(s):  
Stokes Equations ◽  
Thermal Environment ◽  
Computational Cost ◽  
Calibration Procedure ◽  
Accurate Solution ◽  
Temperature Fields ◽  
Convection Flow ◽  
Time Interval ◽  
Braking System ◽  
The Impact

Aircraft braking pads are subject to an extremely severe thermal environment. During a typical landing the carbon brake pads can reach temperatures up to 700–800 K or even more. Between landings during the taxi and parking phase the brakes have to cool off back to their operational limits in a time interval consistent with the average operational time. In order to evaluate the impact of design modifications on the wheel mounting and fairings, without the need of extensive laboratory and flight campaigns, a CFD (Computational Fluid Dynamics) based methodology was developed. Due to the geometry complexity the need of a geometrically representative, but simplified model comes up, in order to capture the major features of the natural convection flow and temperature fields and can be used to evaluate the influence of design changes on the braking system cooling times. A calibration procedure is carried out, aiming a better representation of the transient phenomenon, using a thermal resistances setting up feature from the solver used. An example of the application of this methodology is presented. A computational grid of over 700,000 tetrahedral elements was constructed and the Navier-Stokes equations are solved using a commercial package (FLUENT). The computational cost for a time accurate solution demands the use of parallel processing in order to complete the analysis in a typical industrial environment timeframe. Comparison with both laboratory and flight data calibrate and validate the results of the computational model. This paper describes the details of the construction of the CFD model, the setting of the initial and boundary conditions and the comparison between measured and simulated parameters.

Coriolis effects on MHD newtonian flow over a rotating non-uniform surface

2020 ◽  
pp. 095440622096973
Author(s):  
Abayomi S Oke ◽  
Winifred N Mutuku ◽  
Mark Kimathi ◽  
Isaac Lare Animasaun
Keyword(s):  
Differential Equations ◽  
Lorentz Force ◽  
Coriolis Force ◽  
Stokes Equations ◽  
Physical Phenomenon ◽  
Nonlinear Partial Differential Equations ◽  
Mhd Flow ◽  
Simultaneous Increase ◽  
Convection Flow ◽  
The Impact

The roles of the simultaneous effect of Coriolis force and Lorentz force (resulting from MHD flow) in Sunspots, solar wind, and many other natural and physical phenomenon is undoubtedly significant. The impact of fluids heated by the Sun is influenced by the rotation of the earth’s surface and this necessitates the study of fluid flow over such surface as the Earth. For this reason, the significance of Coriolis force on MHD free-convection flow of Newtonian fluid over the rotating upper horizontal surface of paraboloid of revolution is explored. The relevant body forces are derived and included in the Navier-Stokes equations to obtain appropriate equations governing the flow. By nondimensionalizing the governing equations using similarity variables, the system of nonlinear partial differential equations is reduced to a system of nonlinear ordinary differential equations which is solved using Runge-Kutta-Gills method along with Shooting technique and the results are depicted graphically. It is observed that simultaneous increase in both Coriolis force and Lorentz force causes an increase in the temperature profile of the flow. It is also observed that the effect of increasing Coriolis force on the Skin Friction and heat transfer rate is counter-balanced by increasing Lorentz force.

scholarly journals Convection regimes induced by local boundary heating in a liquid–gas system

2019 ◽  
Vol 873 ◽  
pp. 441-458 ◽  
Author(s):  
Victoria B. Bekezhanova ◽  
A. S. Ovcharova
Keyword(s):  
Gas Flow ◽  
Stokes Equations ◽  
Local Heating ◽  
Fluid Motion ◽  
Lower Boundary ◽  
Conjugate Problem ◽  
Temperature Fields ◽  
Layer System ◽  
Local Boundary ◽  
The Impact

In the framework of the complete formulation of the conjugate problem, the liquid–gas flow structure arising upon local heating using thermal sources is investigated numerically. The two-layer system is confined by solid impermeable walls. The Navier–Stokes equations in the Boussinesq approximation in the ‘streamfunction–vorticity’ variables are used to describe the media motion. The dynamic conditions at the interface are formulated in terms of the tangential and normal velocities, while the temperature conditions at the external boundaries of the system take into account the presence of local heaters. The influence of the number of heaters and heating modes on the dynamics and character of the appearing convective regimes is analysed. The steady and commutated heating modes for one and two heaters arranged at the lower boundary are investigated. The heating initiates convective and thermocapillary mechanisms causing the fluid motion. Transient regimes with the successive formation of two-vortex, quadruple-vortex and two-vortex flows are observed before the stabilization of the system in the uniform heating mode. A stable thermocapillary deflection appears at the interface above the heater. The commutated mode of heating entails oscillations of the interface with a change in the deflection form and the formation of travelling vortices in the fluids. The impact of particular mechanisms on the flow patterns is analysed. The paper presents typical distributions of the velocity and temperature fields in the system and the position of the interface for the considered cases.

scholarly journals DynamFluid: Development and Validation of a New GUI-Based CFD Tool for the Analysis of Incompressible Non-Isothermal Flows

Processes ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 777
Author(s):  
Héctor Redal ◽  
Jaime Carpio ◽  
Pablo A. García-Salaberri ◽  
Marcos Vera
Keyword(s):  
Circular Cylinder ◽  
Stokes Equations ◽  
Vertical Channel ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Convection Flow ◽  
Constant Density ◽  
Flow Past ◽  
Isothermal Flows ◽  
Definition Of

A computational fluid dynamics software (DynamFluid) based on the application of the finite element method with the characteristic-based-split algorithm is presented and validated. The software is used to numerically integrate the steady and unsteady Navier–Stokes equations for both constant-density and Boussinesq non-isothermal flows. Benchmark two-dimensional computations carried out with DynamFluid show good agreement with previous results reported in the literature. Test cases used for validation include (i) the lid-driven cavity flow, (ii) mixed convection flow in a vertical channel with asymmetric wall temperatures, (iii) unsteady incompressible flow past a circular cylinder, and (iv) steady non-isothermal flow past a circular cylinder with negligible buoyancy effects. The new software is equipped with a graphical user interface that facilitates the definition of the fluid properties, the discretization of the physical domain, the definition of the boundary conditions, and the post-processing of the computed velocity, pressure and temperature fields.

scholarly journals A Model for the Thermal Behaviour of an Offshore Cable Installed in a J-Tube

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 31
Author(s):  
Jeremy Arancio ◽  
Ahmed Ould El Moctar ◽  
Minh Nguyen Tuan ◽  
Faradj Tayat ◽  
Jean-Philippe Roques
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Thermal Behaviour ◽  
Energy Production ◽  
Power Transmission ◽  
Temperature Fields ◽  
Sobol Indices ◽  
Lumped Element ◽  
Thermal Phenomena ◽  
The Impact

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube.

scholarly journals Time-to-Treatment in Oral Cancer: Causes and Implications for Survival

Cancers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1321
Author(s):  
Constanza Saka-Herrán ◽  
Enric Jané-Salas ◽  
Antoni Mari-Roig ◽  
Albert Estrugo-Devesa ◽  
José López-López
Keyword(s):  
Oral Cancer ◽  
Previous Treatment ◽  
Diagnostic Procedures ◽  
Original Data ◽  
Primary Treatment ◽  
Medical Attention ◽  
Time Interval ◽  
Pre Treatment ◽  
The Impact ◽  
Lack Of Knowledge

The purpose of this review was to identify and describe the causes that influence the time-intervals in the pathway of diagnosis and treatment of oral cancer and to assess its impact on prognosis and survival. The review was structured according to the recommendations of the Aarhus statement, considering original data from individual studies and systematic reviews that reported outcomes related to the patient, diagnostic and pre-treatment intervals. The patient interval is the major contributor to the total time-interval. Unawareness of signs and/or symptoms, denial and lack of knowledge about oral cancer are the major contributors to the process of seeking medical attention. The diagnostic interval is influenced by tumor factors, delays in referral due to higher number of consultations and previous treatment with different medicines or dental procedures and by professional factors such as experience and lack of knowledge related to the disease and diagnostic procedures. Patients with advanced stage disease, primary treatment with radiotherapy, treatment at an academic facility and transitions in care are associated with prolonged pre-treatment intervals. An emerging body of evidence supports the impact of prolonged pre-treatment and treatment intervals with poorer survival from oral cancer.

scholarly journals The Impact of Time Interval between Hepatic Resection and Liver Transplantation on Clinical Outcome in Patients with Hepatocellular Carcinoma

Cancers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 2398
Author(s):  
Matteo Serenari ◽  
Enrico Prosperi ◽  
Marc-Antoine Allard ◽  
Michele Paterno ◽  
Nicolas Golse ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Liver Transplantation ◽  
Hepatic Resection ◽  
Primary Outcome ◽  
Polynomial Regression ◽  
Secondary Outcome ◽  
Time Interval ◽  
Comprehensive Complication Index ◽  
Fractional Polynomial ◽  
The Impact

Hepatic resection (HR) for hepatocellular carcinoma (HCC) may require secondary liver transplantation (SLT). However, a previous HR is supposed to worsen post-SLT outcomes. Data of patients treated by SLT between 2000 and 2018 at two tertiary referral centers were analyzed. The primary outcome of the study was to analyze the impact of HR on post-LT complications. A Comprehensive Complication Index ≥ 29.6 was chosen as cutoff. The secondary outcome was HCC-related death by means of competing-risk regression analysis. In the study period, 140 patients were included. Patients were transplanted in a median of 23 months after HR (IQR 14–41). Among all the features analyzed regarding the prior HR, only time interval between HR and SLT (time HR-SLT) was an independent predictor of severe complications after LT (OR = 0.98, p < 0.001). According to fractional polynomial regression, the probability of severe complications increased up to 15 months after HR (43%), then slowly decreased over time (OR = 0.88, p < 0.001). There was no significant association between HCC-related death and time HR-SLT at the multivariable competing risks regression model (SHR, 1.06; 95% CI: 0.69–1.62, p = 0.796). This study showed that time HR-SLT was key in predicting complications after LT, without affecting HCC-related death.

scholarly journals Effect of the Assimilation Frequency of Radar Reflectivity on Rain Storm Prediction by Using WRF-3DVAR

2021 ◽  
Vol 13 (11) ◽  
pp. 2103
Author(s):  
Yuchen Liu ◽  
Jia Liu ◽  
Chuanzhe Li ◽  
Fuliang Yu ◽  
Wei Wang
Keyword(s):  
Data Assimilation ◽  
Northern China ◽  
Horizontal Resolution ◽  
Radar Reflectivity ◽  
Small Scale ◽  
Time Interval ◽  
Outer Domain ◽  
Storm Prediction ◽  
The Impact ◽  
Assimilation Time

An attempt was made to evaluate the impact of assimilating Doppler Weather Radar (DWR) reflectivity together with Global Telecommunication System (GTS) data in the three-dimensional variational data assimilation (3DVAR) system of the Weather Research Forecast (WRF) model on rain storm prediction in Daqinghe basin of northern China. The aim of this study was to explore the potential effects of data assimilation frequency and to evaluate the outputs from different domain resolutions in improving the meso-scale NWP rainfall products. In this study, four numerical experiments (no assimilation, 1 and 6 h assimilation time interval with DWR and GTS at 1 km horizontal resolution, 6 h assimilation time interval with radar reflectivity, and GTS data at 3 km horizontal resolution) are carried out to evaluate the impact of data assimilation on prediction of convective rain storms. The results show that the assimilation of radar reflectivity and GTS data collectively enhanced the performance of the WRF-3DVAR system over the Beijing-Tianjin-Hebei region of northern China. It is indicated by the experimental results that the rapid update assimilation has a positive impact on the prediction of the location, tendency, and development of rain storms associated with the study area. In order to explore the influence of data assimilation in the outer domain on the output of the inner domain, the rainfall outputs of 3 and 1 km resolution are compared. The results show that the data assimilation in the outer domain has a positive effect on the output of the inner domain. Since the 3DVAR system is able to analyze certain small-scale and convective-scale features through the incorporation of radar observations, hourly assimilation time interval does not always significantly improve precipitation forecasts because of the inaccurate radar reflectivity observations. Therefore, before data assimilation, the validity of assimilation data should be judged as far as possible in advance, which can not only improve the prediction accuracy, but also improve the assimilation efficiency.

scholarly journals Financing Growth through Remittances and Foreign Direct Investment: Evidences from Balkan Countries

2021 ◽  
Vol 14 (3) ◽  
pp. 117
Author(s):  
Esmeralda Jushi ◽  
Eglantina Hysa ◽  
Arjona Cela ◽  
Mirela Panait ◽  
Marian Catalin Voica
Keyword(s):  
Developing Economies ◽  
Central Banks ◽  
Sustainable Growth ◽  
Time Interval ◽  
Foreign Direct Investments ◽  
Factors Affecting ◽  
Balkan Countries ◽  
To Come ◽  
Sustainable Economic Growth ◽  
The Impact

The ultimate goal of central banks, worldwide, is to promote the foundations for sustainable economic growth. In the case of developing economies, in particular, such objective requires time, huge efforts, attention, and plenty of resources in order to be accomplished to the fullest degree. This paper thoroughly investigates key factors affecting Balkan countries’ economic development (as measured by gross domestic product (GDP) growth), focusing especially on the impact of remittances. The analysis was done over an 18-year time interval (2000–2017) and builds on 144 observations. The data figures were retrieved from the World Bank database while two dummies were created to test the impact of the last financial crisis (2008–2012). Econometric tools were employed to carry out a broad analysis on the interdependencies that exist and, in particular, to determine the role of remittance income on growth. The vector auto regressive model was estimated using EViews software, and was used to come up with relevant insights. Empirical findings suggest the following: population growth, remittances, and labor force participation are insignificant factors for sustainable growth. On the other hand, previous levels of GDP, trade, and foreign direct investments (FDIs) appear to be relevant for the predictor. This research provides up-to-date conclusions, which can be considered during the decision-making process of central banks, as well as by government policymakers.

scholarly journals Imaging Appropriateness in Pediatric Radiology during COVID-19 Pandemic: A Retrospective Comparison with No COVID-19 Period

Children ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 463
Author(s):  
Giampiero Bottari ◽  
Giandomenico Stellacci ◽  
Davide Ferorelli ◽  
Alessandro Dell’Erba ◽  
Maurizio Aricò ◽  
...  
Keyword(s):  
Bone Fractures ◽  
Sharp Decrease ◽  
Pediatric Emergency ◽  
Time Interval ◽  
Imaging Studies ◽  
Retrospective Comparison ◽  
Imaging Appropriateness ◽  
Therapeutic Protocols ◽  
The Impact ◽  
Negative Imaging

During the COVID-19 pandemic, the number of accesses to the Pediatric Emergency Department (pED) in Italy sharply decreased by 30%. The purpose of this study is to evaluate how this novel setting impacted on management of children with trauma, and the use and appropriateness of imaging studies in such patients at the pED. All imaging studies performed in patients with trauma at the pED of a tertiary children’s Hospital during the first wave of the COVID-19 pandemic (between March and May 2020) were reviewed, in comparison with a control time interval (March to May 2019). In the pre-COVID control era, 669 imaging studies documented bone fractures in 145/568 children (25.5%). In the COVID-era, 79/177 (44.6%) pediatric patients showed bone fractures on 193 imaging studies. Comparative analysis shows a 71% decrease in imaging studies, and the proportion of negative imaging studies (with no evidence of bone fractures) dropped in 2020 by 19% compared to the 2019 control era (p < 0.001). The sharp decrease of negative studies suggests that the rate of appropriateness was higher during COVID-era, suggesting some attitude toward defensive medicine in the previous control year, as a result of some degree of imaging inappropriateness. The impact of a pandemic on emergency medicine may offer a unique opportunity to revisit diagnostic and therapeutic protocols in pediatrics.

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