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Grawitacja widziana z Obserwatorium Astronomicznego Uniwersytetu Jagiellońskiego

Sokołowski Leszek M., Szybka Sebastian

Postępy Fizyki

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2023

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T. 74, z. 3

27--30

PL

W artykule omawiamy badania dotyczące zjawisk grawitacyjnych, które są prowadzone w Zakładzie Astrofizyki Relatywistycznej i Kosmologii, w Obserwatorium Astronomicznym Uniwersytetu Jagiellońskiego.

EN

In this article, we discuss research on gravitational phenomena being conducted at the Department of Relativistic Astrophysics and Cosmology in the Astronomical Observatory of the Jagiellonian University.

2

Formation, propagation and detection of gravitational waves

Shaliq Mohamed Armoon, Prasanna R. Sharath

Journal of Mechanical and Energy Engineering

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2020

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Vol. 4, No 2

189--196

EN

Gravitational Waves are a new form of energy that is too sensitive to measure. The study of Gravitational Waves paves a unique way to approach the new era of universal science. It is quite interesting to note that experimental proof of the early theory of Einstein is successfully proven after many years. The manuscript depicts the concepts of Gravitational Waves, propagation of Gravitational Waves, its effect on objects on Earth and various factors that affect the measurements along with their method of approach to detect Gravitational Waves. Detecting Gravitational Waves is a tedious process and it requires a very highly sensitive experimental setup to carry out the detection as well as on considering the current trend of technology it is observed that detection faces massive limitations. Detection of Gravitational Waves opens up a new way for understanding supermassive binary systems such as neutron stars and black holes and also for studying on Early universe history.

3

Fale grawitacyjne w grawitacji Newtona oraz propozycja testu laserowego interferometru fali grawitacyjnej (LIGO)

Szostek R., Góralski P., Szostek K.

Problemy Nauk Stosowanych

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2017

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T. 7

133--154

PL

Wstęp i cel: W artykule wykazane zostało, że z prawa ciążenia Newtona wynika istnienie fal grawitacyjnych. Materiał i metody: Matematyczne wyprowadzenie oraz numeryczna symulacja. Wyniki: W artykule pokazane zostały różnice pomiędzy przebiegiem fal grawitacyjnych wynikających z grawitacji Newtona oraz przebiegiem fal grawitacyjnych wynikających z Ogólnej Teorii Względności, których pomiar został ogłoszony przez zespół LIGO (Laser Interferometer Gravitational- Wave Observatory). W artykule zaproponowana została metoda testowania interferometru laserowego do pomiaru fali grawitacyjnej używanego w obserwatorium LIGO. Wniosek: Fale grawitacyjne wynikające z prawa ciążenia Newtona mają inny przebieg niż fale grawitacyjne wynikające z Ogólnej Teorii Względności. Według obu teorii fale grawitacyjne są cyklicznymi zmianami natężenia pola grawitacyjnego. Do uwiarygodnienia wyników ogłoszonych przez zespół LIGO konieczne jest strojenie tego urządzenia. Dopiero wtedy będzie wiadomo, co w rzeczywistości mierzy LIGO. Zjawisko koincydencji poważnie podważa wiarygodność pomiarów ogłoszonych przez zespół LIGO.

EN

Introduction and aim: The article shows that the gravitational waves result from Newton’s gravitational law. Material and methods: Mathematical derivation and numerical simulation. Results: The article presents the differences between the course of gravitational waves resulting from Newton’s gravity and the course of gravitational waves resulting from the General Theory of Relativity, the measurement of which was announced by the LIGO team (Laser Interferometer Gravitational-Wave Observatory). The article proposed a method for testing a laser interferometer for measuring the gravitational wave used in the LIGO Observatory. Conclusion: The gravitational waves resulting from Newton’s gravitational law have a different course than the gravitational waves resulting from the General Theory of Relativity. According to both theories, gravitational waves are cyclical changes in the intensity of the gravitational field. To authenticate the results announced by the LIGO team, it is necessary to adjustment this device. Only then will it be known what LIGO actually measures. The co-integration phenomenon seriously undermines the credibility of the measurements announced by the LIGO team.

4

Scattering of interface wave by bottom undulations in the presence of thin submerged vertical wall with a gap

Dolai P.

International Journal of Applied Mechanics and Engineering

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2016

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Vol. 21, no. 2

303--322

EN

In this paper, the problem of interface wave scattering by bottom undulations in the presence of a thin submerged vertical wall with a gap is investigated. The thin vertical wall with a gap is submerged in a lower fluid of finite depth with bottom undulations and the upper fluid is of infinite height separated by a common interface. In the method of solution, we use a simplified perturbation analysis and suitable applications of Green’s integral theorem in the two fluid regions produce first-order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom undulations and solution of the scattering problem involving a submerged vertical wall present in the lower fluid of uniform finite depth. For sinusoidal bottom undulations, the first-order transmission coefficient vanishes identically. The corresponding first-order reflection coefficient is computed numerically by solving the zero-order reflection coefficient and a suitable application of multi-term Galerkin approximations. The numerical results of the zero-order and first-order reflection coefficients are depicted graphically against the wave number in a number of figures. An oscillatory nature is observed of first-order reflection coefficient due to multiple interactions of the incident wave with bottom undulations, the edges of the submerged wall and the interface. The first-order reflection coefficient has a peak value for some particular value of the ratio of the incident wavelength and the bottom wavelength. The presence of the upper fluid has some significant effect on the reflection coefficients.

5

The effect of randomness on the stability of capillary gravity waves in the presence of air flowing over water

Majumder D. P., Dhar A. K.

International Journal of Applied Mechanics and Engineering

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2015

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Vol. 20, no. 4

835--855

EN

A nonlinear spectral transport equation for the narrow band Gaussian random surface wave trains is derived from a fourth order nonlinear evolution equation, which is a good starting point for the study of nonlinear water waves. The effect of randomness on the stability of deep water capillary gravity waves in the presence of air flowing over water is investigated. The stability is then considered for an initial homogenous wave spectrum having a simple normal form to small oblique long wave length perturbations for a range of spectral widths. An expression for the growth rate of instability is obtained; in which a higher order contribution comes from the fourth order term in the evolution equation, which is responsible for wave induced mean flow. This higher order contribution produces a decrease in the growth rate. The growth rate of instability is found to decrease with the increase of spectral width and the instability disappears if the spectral width increases beyond a certain critical value, which is not influenced by the fourth order term in the evolution equation.

6

Evolution of a random field of surface gravity waves in a two fluid domain

Senapati S., Debsarma S., Das K. P.

International Journal of Applied Mechanics and Engineering

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2012

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Vol. 17, no. 2

481-493

EN

A spectral transport equation is derived here that governs the evolution of a random field of surface gravity waves in a two layer fluid model. This equation is used to study the stability of an initially homogeneous Lorentz spectrum under long wave length perturbations. It is observed that the effect of randomness is to reduce the growth rate of instability. An increase in the thickness of the upper fluid results in an increase in the extent of instability. It is also found that the extent of instability becomes less for a smaller density difference of the two fluids.

7

Stability of small but finite amplitude interfacial capillary gravity waves for perturbations in two horizontal directions

Majumder D. P., Dhar A. K.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 2

425-434

EN

By exact numerical computation Yuen (1984) obtained regions of type-I instability for waves propagating at the interface of two superposed fluids of infinite thickness in which the upper fluid has a constant streaming velocity. In the present paper it is shown that the long wavelength part of these instability regions can be obtained analytically from a fourth order nonlinear evolution equation for small but finite amplitude interfacial capillary gravity waves in the presence of air flowing over water.

8

Fourth-order evolution equations for a surface gravity wave packet in a two layer fluid

Senapati S., Debsarma S., Das K. P.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 4

1215-1225

EN

Fourth order nonlinear evolution equations are derived for a three dimensional surface gravity wave packet in the presence of long wave length an interfacial wave in a two layer fluid domain in which the lower fluid depth is infinite. For derivation of evolution equations, the multiple-scale method is used. Using these evolution equations, stability of uniform stokes wavetrain is investigated for different values of density ratio of the two fluids and for different values of the depth of the lighter fluid.

9

Stability analysis from fourth order evolution equation for deep water capillary-gravity waves in the presence of air flowing over water

Majumder D. P., Dhar A. K.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 2

433-442

EN

Fourth order nonlinear evolution equations, which are a good starting point for the study of nonlinear water waves as first pointed out by Dysthe (1979) and later elaborated by Janssen (1983), are derived for deep water capillary-gravity waves in the presence of air flowing over water. Stability analysis is then made for a uniform Stokes capillary gravity wave train. Graphs are plotted for the maximum growth rate of instability, the frequency at marginal stability and the frequency separation for fastest growing side-band component as a function of wave steepness. Significant deviations are noticed from the results obtained from the third-order evolution equation, which is the nonlinear Schrödinger equation.

10

Fourth order nonlinear evolution equation for capillary gravity waves in deep water in the presence of a thin thermocline including the effect of wind

Debsarma S., Das K. P.

International Journal of Applied Mechanics and Engineering

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2003

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Vol. 8, no 2

177-193

EN

A fourth order non-linear evolution equation is derived for a capillary-gravity wave packet in deep water in the presence of a thin thermocline including the effect of wind and viscous dissipation in water. In deriving this equation it has been assumed that the wind induced basic current in water is exponential and the effect of shear in air flow and viscous dissipation in water is accounted for by including a term in the evolution equation. The nonlinear evolution equation is used to study the stability of a uniform capillary-gravity wave train. Expressions for the maximum growth rate of instability and wave number at marginal stability are obtained. From results shown graphically it is found that the inclusion of wind effect increases the growth rate of instability irrespective of the presence of a thin thermocline. For waves with a small wave number, a thin thermocline has a stabilizing influence both in the presence and in the absence of wind input and the maximum growth rate of instability decreases with the increase of thermocline depth. But for waves with a large wave number a thin thermocline has no influence.

11

Hydrodynamics of offshore structures under waves and current: fundamental theory, formulation of the problem and a case study

Mendes A. C.

Vibrations in Physical Systems

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2002

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Vol. 20

34--57

EN

This lecture is devoted firstly to a statement of the physical properties of gravity waves that is followed by a review on Linear Theory of waves of small amplitude, together with the related basic equations. This material includes the calculation of water pressure and water-particle kinematics, and the establishment of mass, momentum and energy balances. On a second stage it will be given a comprehensive material concerning the methodologies applied to calculate the wave forces. In the present case we will be involved with the Morison model and the corresponding hydrodynamic coefficients, when predicting the wave forces exerted upon tubular structures. Finally, a case study will be presented, relating both theoretical and experimental results obtained with a physical model of an offshore jacket platform.

12

Simulations of Gravity Wave Induced Turbulence Using 512 Pe Cray T3e

Prusa J. M., Smolarkiewicz P. K., Wyszogrodzki A. A.

International Journal of Applied Mathematics and Computer Science

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2001

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Vol. 11, no 4

883-897

EN

A 3D nonhydrostatic, Navier-Stokes solver has been employed to simulate gravity wave induced turbulence at mesopause altitudes. This paper extends our earlier 2D study reported in the literature to three spatial dimensions while maintaining fine resolution required to capture essential physics of the wave breaking. The calculations were performed on the 512 processor Cray T3E machine at the National Energy Research Scientific Computing Center (NERSC) in Berkeley. The physical results of this study clearly demonstrate advantages of highly parallel technologies. We briefly outline the physical outcome of the study, as well as compare the relative model performance across several machines using both MPI and Shmem communication software.