On How the Generation of Lift Can Be Explained in a Closed Form Based on the Fundamental Conservation Equations

2020 ◽  
Author(s):  
Philipp Epple ◽  
Holger Babinsky ◽  
Michael Steppert ◽  
Manuel Fritsche
Keyword(s):  
Fluid Mechanics ◽  
Closed Form ◽  
Fundamental Problem ◽  
System Of Equations ◽  
Bernoulli Equation ◽  
Conservation Equations ◽  
Research Institutes ◽  
Conservation Principles ◽  
Newton’S Laws ◽  
The One

Abstract The generation of lift is a fundamental problem in aerodynamics and in general in fluid mechanics. The explanations on how lift is generated are often very incomplete or even not correct. Perhaps the most popular explanation of lift is the one with the Bernoulli equation and with the longer path over an airfoil as compared to the path below the airfoil, assuming the flow arrives at the same time at the trailing edge on both paths. This is an intuitive assumption, but no equation is derived from this assumption. In some explanations the Bernoulli equation is also complemented with Newton’s laws of motion. In other explanations Newton’s law is said to be the only explanation. Other explanations mention the Venturi suction effect to explain the generation of lift. In books of aerodynamics and on the homepage of well-known research institutes the explanations are, although better and partially correct, still very often incomplete. In this contribution the generation of lift is explained in a scientific way based on the conservation principles of mass, momentum and energy and how they have to be applied to close the system of equations in order to explain the generation of lift. The most common incomplete or incorrect explanations of lift are also analysed and it is explained why they are incomplete or wrong. In this work the generation of lift is explained based on the conservation equations. It is shown how and when they apply to the problem of lift generation and how the system of equations has to be closed.

On a Closed-Form Solution of Prandtl's System of Equations

2013 ◽  
Vol 40 (2) ◽  
pp. 106-114
Author(s):  
J. Venetis ◽  
Aimilios (Preferred name Emilios) Sideridis
Keyword(s):  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
System Of Equations

scholarly journals AN INDUSTRY QUESTION: THE ULTIMATE AND ONE-YEAR RESERVING UNCERTAINTY FOR DIFFERENT NON-LIFE RESERVING METHODOLOGIES

2014 ◽  
Vol 44 (3) ◽  
pp. 495-499 ◽  
Author(s):  
Eric Dal Moro ◽  
Joseph Lo
Keyword(s):  
Closed Form ◽  
Internal Models ◽  
Cape Cod ◽  
Best Estimate ◽  
To Come ◽  
Chain Ladder ◽  
One Year ◽  
The One ◽  
Best Estimates

AbstractIn the industry, generally, reserving actuaries use a mix of reserving methods to derive their best estimates. On the basis of the best estimate, Solvency 2 requires the use of a one-year volatility of the reserves. When internal models are used, such one-year volatility has to be provided by the reserving actuaries. Due to the lack of closed-form formulas for the one-year volatility of Bornhuetter-Ferguson, Cape-Cod and Benktander-Hovinen, reserving actuaries have limited possibilities to estimate such volatility apart from scaling from tractable models, which are based on other reserving methods. However, such scaling is technically difficult to justify cleanly and awkward to interact with. The challenge described in this editorial is therefore to come up with similar models like those of Mack or Merz-Wüthrich for the chain ladder, but applicable to Bornhuetter-Ferguson, mix Chain-Ladder and Bornhuetter-Ferguson, potentially Cape-Cod and Benktander-Hovinen — and their mixtures.

Wavelets in the Solution of Nongray Radiative Heat Transfer Equation

1998 ◽  
Vol 120 (1) ◽  
pp. 133-139 ◽  
Author(s):  
Y. Bayazitoglu ◽  
B. Y. Wang
Keyword(s):  
Transfer Equation ◽  
Solution Method ◽  
Radiative Heat ◽  
Radiative Transfer Equation ◽  
Basis Functions ◽  
Wavelet Basis ◽  
System Of Equations ◽  
Heat Transfer Equation ◽  
One Dimensional ◽  
The One

The wavelet basis functions are introduced into the radiative transfer equation in the frequency domain. The intensity of radiation is expanded in terms of Daubechies’ wrapped-around wavelet functions. It is shown that the wavelet basis approach to modeling nongrayness can be incorporated into any solution method for the equation of transfer. In this paper the resulting system of equations is solved for the one-dimensional radiative equilibrium problem using the P-N approximation.

scholarly journals A Neural Network-Based Approach for Approximating Arbitrary Roots of Polynomials

Mathematics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 317
Author(s):  
Diogo Freitas ◽  
Luiz Guerreiro Lopes ◽  
Fernando Morgado-Dias
Keyword(s):  
Iterative Methods ◽  
Fundamental Problem ◽  
Iterative Algorithms ◽  
Rounding Errors ◽  
Suggested Approach ◽  
Simultaneous Iterative Methods ◽  
Complex Roots ◽  
Roots Of Polynomials ◽  
Comparative Results ◽  
The One

Finding arbitrary roots of polynomials is a fundamental problem in various areas of science and engineering. A myriad of methods was suggested to address this problem, such as the sequential Newton’s method and the Durand–Kerner (D–K) simultaneous iterative method. The sequential iterative methods, on the one hand, need to use a deflation procedure in order to compute approximations to all the roots of a given polynomial, which can produce inaccurate results due to the accumulation of rounding errors. On the other hand, the simultaneous iterative methods require good initial guesses to converge. However, Artificial Neural Networks (ANNs) are widely known by their capacity to find complex mappings between the dependent and independent variables. In view of this, this paper aims to determine, based on comparative results, whether ANNs can be used to compute approximations to the real and complex roots of a given polynomial, as an alternative to simultaneous iterative algorithms like the D–K method. Although the results are very encouraging and demonstrate the viability and potentiality of the suggested approach, the ANNs were not able to surpass the accuracy of the D–K method. The results indicated, however, that the use of the approximations computed by the ANNs as the initial guesses for the D–K method can be beneficial to the accuracy of this method.

scholarly journals RELIGION IN THOUGHT MURTADHA MUTHAHHARI

Tsaqofah ◽  
2020 ◽  
Vol 18 (02) ◽  
pp. 99
Author(s):  
Didin Komarudin Komarudin
Keyword(s):  
Content Analysis ◽  
Fundamental Problem ◽  
Religious Practice ◽  
Sociological Analysis ◽  
Religion And Science ◽  
Daily Lives ◽  
The One ◽  
And Behavior ◽  
The Relationship ◽  
Religious Actors

This writing is based on the background that religious formalism is increasingly becoming a fundamental problem. This is marked by the patterns and behavior of people who claim to be religious but there is no concrete implementation in their daily lives. This research was conducted to determine the concept of religion as a fitrah for humans as well as how religious beliefs are to the level of the relationship between religion and science according to Murtadha Motahhari. This research is a qualitative study that uses a sociological analysis approach, while the data in this study come from content analysis collected from various sources. , the level of religious belief, until people know God, the criticisms of Murtadha muthahhari which are an integral part of the life of the above figures to practice true religious values. Religion as human nature gives birth to the belief that religion is the only way to fulfill all needs, so that religion is not only a label or social formality but is able to become a guide in life and life. All religions teach goodness and peace, and no religion teaches violence. But sometimes there is violence in the name of religion because of a lack of understanding or a distortion of the source of religion itself. So that religion is sometimes used, and it seems that religion and religious practice are the opposite. So what is blamed on the concept of religion itself is actually the one who is wrong for religious actors.

scholarly journals Studying and evaluating the performance of pedestrian crossing facilities in Babil governorate

2019 ◽  
Vol 28 (3) ◽  
pp. 417-431
Author(s):  
Ali Dakhil ◽  
Dheyaa Alobaidi ◽  
Saba Shaheed
Keyword(s):  
Fundamental Problem ◽  
Health Department ◽  
Positive Effects ◽  
Pedestrian Bridges ◽  
Traffic Volumes ◽  
Interview Survey ◽  
The One ◽  
Questionnaire Method ◽  
Pedestrian Crossing ◽  
In Transit

Walking is one of the oldest means of mobility. It is an indispensable necessity to reach destinations despite the fact that walking or walking is one of everyday activities of man, which have positive effects on health, and activity on the one hand; vehicles cannot reach destinations only required by often walking from the other. The main problem address by the research is the random passage of the sieve and uncontrolled when it is most designs for the city’s road network have not addressed. This fundamental problem as well as the lack of a city to the safe facilities to cross the pedestrian. Therefore, this paper is a trial to study and analyze the current reality of crossing the sap then find solutions and treatments that reduce or limit the overlap between different traffic events and events crossing the pedestrian. Field data on the syllabic traffic volumes collected in all areas of the study (peak hour volume) and the photographic technique method. The study chose four areas to study the sap (60th Street, 40th Street, Al-Hussein, intersection circle at Babel Health Department), which are residential, commercial and educational zones, representing diversity in land use and scheme sidewalk and the design of the city of Hilla. The study attempted to show the state of lateral walks. The study also used the questionnaire method (interview survey) to determine the suitability of pedestrian bridges in transit and land transit. The study concluded that the area of Al-Hussein represents the highest traffic volumes of the sieve in addition to the lack of it the sidewalks in terms of absorption and quality and abuses. As well as the reluctance to use pedestrian bridges in transit in the area of 60th Street through high ground transit time, which necessitates the establishment of dual-step (fixed and mobile) – legislation and education through all means.

scholarly journals Mathematical modeling and numerical investigation of density wave instability of supercritical natural circulation loop

2021 ◽  
Vol 321 ◽  
pp. 04004
Author(s):  
Santosh Kumar Rai ◽  
Neha Ahlawat ◽  
Pardeep Kumar ◽  
Vinay Panwar
Keyword(s):  
Energy Conservation ◽  
Natural Circulation ◽  
Density Wave ◽  
Circulation Loop ◽  
Wave Instability ◽  
Conservation Equations ◽  
One Dimensional ◽  
Natural Circulation Loop ◽  
The One ◽  
Riser Height

In present paper, a mathematical model based on the one dimensional nonlinear mass, momentum and energy conservation equations has been developed to study the density wave instability (DWI) in horizontal heater and horizontal cooler supercritical water natural circulation loop (HHHC-SCWNCL). The one dimensional nonlinear mass, momentum and energy conservation equations are discretized by using finite difference method (FDM). The numerical model is validated with the benchmark results (NOLSTA model). Numerical simulations are performed to find the threshold stability zone (TSZ) and draw the stability map for natural circulation loop. Further, effect of change in diameter and riser height on the density wave instability of SCWNCL has been investigated.

scholarly journals Asymptotic and transient behaviour for a nonlocal problem arising in population genetics

2018 ◽  
Vol 31 (1) ◽  
pp. 84-110
Author(s):  
J.-B. BURIE ◽  
R. DJIDJOU-DEMASSE ◽  
A. DUCROT
Keyword(s):  
Asymptotic Behaviour ◽  
Large Time ◽  
Nonlocal Problem ◽  
Genetic Adaptation ◽  
System Of Equations ◽  
Pathogen Population ◽  
Transient Behaviour ◽  
Selection Processes ◽  
The One ◽  
Mutation And Selection

This work is devoted to the study of an integro-differential system of equations modelling the genetic adaptation of a pathogen by taking into account both mutation and selection processes. First, we study the asymptotic behaviour of the system and prove that it eventually converges to a stationary state. Next, we more closely investigate the behaviour of the system in the presence of multiple EAs. Under suitable assumptions and based on a small mutation variance asymptotic, we describe the existence of a long transient regime during which the pathogen population remains far from its asymptotic behaviour and highly concentrated around some phenotypic value that is different from the one described by its asymptotic behaviour. In that setting, the time needed for the system to reach its large time configuration is very long and multiple evolutionary attractors may act as a barrier of evolution that can be very long to bypass.

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