Propagation of long waves due to atmospheric disturbances on a rotating sea

1956 ◽  
Vol 233 (1195) ◽  
pp. 556-569 ◽  
Keyword(s):  
Steady State ◽  
Long Waves ◽  
Pressure Gradients ◽  
Constant Amplitude ◽  
Rotating System ◽  
Dispersive Waves ◽  
Atmospheric Disturbances ◽  
The Waves ◽  
Steady State Amplitude ◽  
Maximum Group

Long waves in shallow water in a non-rotating system are not dispersive but in a rotating system they are. This paper investigates the generation and propagation of these dispersive waves in an infinite sea. The mode of generation is by air-pressure gradients or wind stresses applied to the surface. Bottom friction is neglected. The surface elevation due to a stationary force of constant amplitude suddenly applied and maintained at t = 0 over one-half of an infinite sea is shown to approach, through a series of oscillations approximating more or less to an inertia period, a steady-state amplitude decreasing with distance from the generating area, The longitudinal and transverse velocities are also given. The time elapsed from the initial disturbance at a point to the first maximum of elevation decreases with the distance of the point from the edge of the generating area. A generating area whose edge moves forward with the maximum group velocity of the waves is shown to lead to an elevation of ever-increasing height. The effect of a barrier placed at right angles to the direction of propagation is also briefly considered.

On the generation of Kelvin-type waves by atmospheric disturbances

1970 ◽  
Vol 42 (4) ◽  
pp. 657-670 ◽  
Author(s):  
Richard E. Thomson
Keyword(s):  
Frequency Shift ◽  
Water Waves ◽  
Kelvin Waves ◽  
Wind Component ◽  
Constant Depth ◽  
Shallow Water Waves ◽  
Pressure System ◽  
Dispersive Waves ◽  
Atmospheric Disturbances ◽  
The Waves

This paper considers the surface response of a semi-infinite, uniformly rotating, constant depth, homogeneous ocean to a variable atmospheric force. For a general wind and pressure system it is shown that forced Kelvin-type waves can be generated and that only the longshore wind component and the pressure can generate them. In particular a semi-infinite wind and moving pressure pattern are shown to generate Kelvin waves that travel away from the force discontinuities at the speed of shallow-water waves. The waves in the latter case exhibit a frequency shift typical of non-dispersive waves from a moving source. Some numerical values for the amplitudes of the Kelvin waves are also given.

The flow of a micropolar liquid layer down an inclined plane

1968 ◽  
Vol 64 (2) ◽  
pp. 513-526 ◽  
Author(s):  
A. J. Willson
Keyword(s):  
Thin Films ◽  
Steady State ◽  
Liquid Layer ◽  
Stability Criterion ◽  
Long Waves ◽  
Inclined Plane ◽  
The Stability ◽  
Micropolar Liquid

AbstractConsideration is given to the flow of a micropolar liquid down an inclined plane. The steady state is analysed and Yih's technique is employed in an investigation of the stability of this flow with respect to long waves. Detailed calculations are given for thin films and it is shown that the micropolar properties of the liquid play an important role in the stability criterion.

Free and Forced Longitudinal Vibrations of a Cantilevered Bar With a Crack

1992 ◽  
Vol 114 (2) ◽  
pp. 171-177 ◽  
Author(s):  
K. R. Collins ◽  
R. H. Plaut ◽  
J. Wauer
Keyword(s):  
Steady State ◽  
Natural Frequency ◽  
Transverse Crack ◽  
Breathing Crack ◽  
Longitudinal Vibrations ◽  
Harmonic Force ◽  
Frequency Spectra ◽  
Crack Location ◽  
Fundamental Natural Frequency ◽  
Steady State Amplitude

Longitudinal vibrations of a cantilevered bar with a transverse crack are investigated. For undamped, unforced vibrations, frequency spectra are computed and the effects of the crack location and compliance on the fundamental natural frequency are determined. For vibrations caused by a distributed, longitudinal, harmonic force, the steady-state amplitude of motion of the free end is plotted as a function of the forcing frequency, crack location, and crack compliance, and frequency spectra are also obtained. Results for a breathing crack are compared to those for a crack which remains open and those for an uncracked bar.

Plasma cavity formation caused by ion acoustic waves and nonlinear modulation of trapped waves

1999 ◽  
Vol 61 (3) ◽  
pp. 489-505
Author(s):  
T. HONZAWA ◽  
S. WATANABE ◽  
Y. SAITOU
Keyword(s):  
Acoustic Waves ◽  
Early Stage ◽  
Cavity Formation ◽  
Pressure Gradients ◽  
Trapped Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic ◽  
Nonlinear Modulation ◽  
Ion Waves ◽  
The Waves

Externally amplitude-modulated ion acoustic waves with high frequencies of 200–320 kHz are experimentally shown to form plasma cavities and to be trapped in them at an early stage. Thereafter, the trapped waves are observed to suffer nonlinear modulation and create new lower-frequency waves with average frequencies as low as 20–40 kHz within the cavities. As a result, the externally excited high-frequency ion acoustic waves are found to be nonlinearly converted into lower-frequency ion waves in the cavities. Finally, the pressure gradients of the waves effective in cavity formation and nonlinear modulation of the trapped waves are discussed.

Coupled fields in inhomogeneous warm plasmas with static pressure gradients. I

1972 ◽  
Vol 72 (2) ◽  
pp. 285-297
Author(s):  
R. Burman
Keyword(s):  
Pressure Gradient ◽  
Acoustic Waves ◽  
Wave Equations ◽  
Static Pressure ◽  
Pressure Gradients ◽  
Coupling Region ◽  
Electron Plasmas ◽  
Coupled Wave Equations ◽  
Electron Acoustic ◽  
The Waves

Abstract.This paper deals with small amplitude waves in inhomogeneous warm electron plasmas. The waves are coupled electromagnetic and electron-acoustic waves, and are described by Maxwell's equations together with single-fluid hydrodynamical equations. Here, previous work is generalized by including the effect of a static pressure gradient. Coupled wave equations are obtained and specialized to the case of a planar stratified plasma. Then, as a preliminary to a treatment of wave coupling, the behaviour of the solutions of the uncoupled wave equations in a coupling region is investigated. The static pressure gradient complicates the behaviour of the uncoupled field components; singularities occur at two points which coalesce as the static pressure gradient is allowed to tend to zero.

Image Fluctuations in LED Electromechanical 3D–Display

2018 ◽  
Vol 17 (02) ◽  
pp. 1850022
Author(s):  
Alexey V. Klyuev ◽  
Arkady V. Yakimov
Keyword(s):  
Steady State ◽  
Rotation Angle ◽  
Light Emitting Diode ◽  
3D Display ◽  
Constant Amplitude ◽  
Harmonic Oscillations ◽  
Light Emitting ◽  
Small Increment ◽  
The Stability ◽  
Periodic Changes

Fluctuations in parameters of light-emitting diode (LED) electromechanical 3D–display are investigated. It is shown, that there are two types of fluctuations in the rotating 3D–display. The first one is caused by a small increment in the rotation angle, which has a tendency to the increase. That occurs in the form of the “drift” without periodic changes of the angle. The second one is the change in small linear increments of the angle, which occurs as undamped harmonic oscillations with constant amplitude. This shows the stability of the investigated steady state because there is no tendency to increase the amplitude of the considered parameter regime. In conclusion we give some recommendations how to improve synchronization of the system.

Spin-Off Maneuvers of Flexible Satellite Using PD Based Constant-Amplitude Inputs

2013 ◽  
Vol 465-466 ◽  
pp. 337-344
Author(s):  
Parman Setyamartana ◽  
Radzuan B. Razali ◽  
Azman Zainuddin
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Steady State ◽  
Input Shaping ◽  
Structural Flexibility ◽  
Main Body ◽  
Solar Panels ◽  
The Finite Element Method ◽  
Constant Amplitude ◽  
The Earth

Spin-off maneuver of a flexible satellite using constant-amplitude thrusters is studied in this paper. The satellite consists of a rigid main body and two symmetrical solar panels. The panels are having structural flexibility and their motions are discretized following the finite element method. Under constant-amplitude thrusts, steady-state attitude angle oscillations may occur in large amplitude after the maneuvers. Since in operation the satellite should point to certain area on the earth precisely, these oscillations of course are not acceptable. To reduce the oscillations, proportional derivative (PD) based constant-amplitude input shaping logic is proposed to determine time locations of thruster switching. Then, under such inputs, spin-downs of the satellite are simulated numerically. Results of simulations indicate that the precise orientation of the satellite can be achieved.

Analysis of the swimming of long and narrow animals

1952 ◽  
Vol 214 (1117) ◽  
pp. 158-183 ◽  
Keyword(s):  
Reynolds Number ◽  
Wave Length ◽  
Constant Speed ◽  
Forward Speed ◽  
Constant Amplitude ◽  
Flexible Cylinder ◽  
Cylinder Diameter ◽  
Wide Range ◽  
The Waves ◽  
Marine Worms

The swimming of long animals like snakes, eels and marine worms is idealized by considering the equilibrium of a flexible cylinder immersed in water when waves of bending of constant amplitude travel down it at constant speed. The force of each element of the cylinder is assumed to be the same as that which would act on a corresponding element of a long straight cylinder moving at the same speed and inclination to the direction of motion. Relevant aerodynamic data for smooth cylinders are first generalized to make them applicable over a wide range of speed and cylinder diameter. The formulae so obtained are applied to the idealized animal and a connexion established between B / λ , V / U and R 1 . Here B and λ are the amplitude and wave-length, V the velocity attained when the wave is propagated with velocity U , R 1 is the Reynolds number Udρ / μ , where d is the diameter of the cylinder, ρ and μ are the density and viscosity of water. The results of calculation are compared with James Gray’s photographs of a swimming snake and a leech. The amplitude of the waves which produce the greatest forward speed for a given output of energy is calculated and found, in the case of the snake, to be very close to that revealed by photographs. Similar calculations using force formulae applicable to rough cylinders yield results which differ from those for smooth ones in that when the roughness is sufficiently great and has a certain directional character propulsion can be achieved by a wave of bending which is propagated forward instead of backward. Gray’s photographs of a marine worm show that this remarkable method of propulsion does in fact occur in the animal world.

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