Supersonic-to-subsonic transition of a radiation wave observed at the LMJ

The problem of a circular cylinder array slowly oscillating in both diffraction and radiation wave fields is considered in the present work. As a result of the interaction between the wave fields and the low-frequency motion, nonlinear wave loads may be separated into the so-called wave-drift added mass and damping. They are force components proportional to the square of the wave amplitude but in phase of the acceleration and velocity of the low-frequency motion respectively. The frequency of the slow oscillation is assumed to be much smaller than the wave frequency. Perturbation expansion based on two time scales and two small parameters is performed to the order to include the effects of the acceleration of the low-frequency motion. Solutions to these higher order potentials are suggested in the present work. Wave loads including the wave drift added mass and damping are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface.

Download Full-text

The Method for Numerical Simulation of the Impact on the Infrared Radiation Seeker from the Warhead Shock Layer

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.390.464 ◽

2013 ◽

Vol 390 ◽

pp. 464-467

Author(s):

Da Lei Luo ◽

Jun Liu ◽

Yuan Wang ◽

Deng Feng Fan

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Radiation Field ◽

Shock Layer ◽

Infrared Radiation ◽

Wave Band ◽

Radiation Wave ◽

Main Mirror ◽

The Impact ◽

Calculated Model

It counts the impact on the infrared radiation seeker which in the head of the hypersonic missile. Firstly, it built the calculated model based on the shape of a missile, and compartmentalized the aerodynamics flow field grid , the infrared radiation seeker main mirror grid , the radiation field grid, and had the relation of the grids unambiguous, and got the communication of the aerodynamics flow field. Then it educed irradiance formula about the shock layer aerodynamic flow fled radiation affect to the infrared radiation seeker main mirror. The result is the infrared radiation wave band 3~5 to the main mirror, from the shock layer aerodynamic flow fled is about 120 W/m2. The distributing law of the impact is annular circumfused the center of the main mirror, the infrared radiation is the highest in the center of the main mirror, decreased by the radius of the main mirror.

Download Full-text

Toward Rapid and Well-Controlled Ambient Temperature RAFT Polymerization under UV−Vis Radiation: Effect of Radiation Wave Range

Macromolecules ◽

10.1021/ma060157x ◽

2006 ◽

Vol 39 (11) ◽

pp. 3770-3776 ◽

Cited By ~ 126

Author(s):

Lican Lu ◽

Haijia Zhang ◽

Nianfa Yang ◽

Yuanli Cai

Keyword(s):

Ambient Temperature ◽

Radiation Effect ◽

Raft Polymerization ◽

Radiation Wave ◽

Wave Range

Download Full-text

Concerning one mechanism of laser-radiation wave-absorption propagation in optical breakdown in disperse media

Journal of Soviet Laser Research ◽

10.1007/bf01120880 ◽

1984 ◽

Vol 5 (2) ◽

pp. 252-254

Author(s):

A. P. Budnik ◽

A. G. Popov

Keyword(s):

Laser Radiation ◽

Optical Breakdown ◽

Wave Absorption ◽

Radiation Wave

Download Full-text

Prediction of the Damping-Controlled Response of Offshore Structures to Random Wave Excitation

Society of Petroleum Engineers Journal ◽

10.2118/7828-pa ◽

1980 ◽

Vol 20 (01) ◽

pp. 5-14 ◽

Cited By ~ 2

Author(s):

Kim J. Vandiver

Keyword(s):

Wave Spectrum ◽

Wave Force ◽

Ocean Waves ◽

Radiation Damping ◽

Explicit Calculation ◽

Random Wave ◽

Wave Forces ◽

Linear Wave ◽

Radiation Wave ◽

Diffraction Effects

Abstract A method is presented for predicting the damping-controlled response of a structure at a known natural frequency to random wave forces. The principal advantage of the proposed method over those in current use proposed method over those in current use is that explicit calculation of wave forces is not required in the analysis. This is accomplished by application of the principle of reciprocity: that the linear wave force spectrum for a particular vibration mode is proportional to the radiation (wave-making) proportional to the radiation (wave-making) damping of that mode. Several example calculations are presented including the prediction of the heave response of a prediction of the heave response of a tension-leg platform. The directional distribution of the wave spectrum included in the analysis. Introduction This paper introduces a simple procedure for estimating the dynamic response of a structure at each of its natural frequencies to the random excitation of ocean waves. The principal advantage of the proposed method is that the explicit calculation of wave forces has been eliminated from the analysis. This is made possible by a direct applications of the reciprocity relations for ocean waves, originally established by Haskind and described by Newman, in a form that is easy to implement. Briefly stated, fore many structures it is possible to derive a simple expression for the wave force spectrum in terms of the radiation damping and the prescribed wave amplitude spectrum. In general, such a substitution is of little use because the radiation damping coefficient may be equally difficult to find. However, the substitution leads to a very useful result when the dynamically amplified response at a natural frequency is of concern. In such cases it is shown that, contrary to popular belief, the response is not inversely proportional to the total damping but is, in fact, proportional to the ratio of the radiation damping to the total damping. Therefore, in the absence of a reliable estimate of either the total damping or the ratio of the radiation component to the total, an upper bound estimate of the response still may be achieved because of the existence of this upper bound is one of the key contributions of this paper.Linear wave theory is assumed; therefore, excitation caused by drag forces is not considered. However, for many structures drag excitation is negligible except for very large wave events. In the design process extreme events are modeled deterministically process extreme events are modeled deterministically by means of a prescribed design wave and not stochastically as is done here. In many circumstances linear wave forces will dominate, and the results shown here will be applicable. Although drag-exciting forces are not included, damping resulting from hydrodynamic drag is included. Wave diffraction effects are extremely difficult to calculate. This analysis includes diffraction effects but never requires explicit evaluation of them.It has been recognized that directional spreading of the wave spectrum is an important consideration in the estimation of dynamic response. In this paper such effects are accounted for in closed-form expressions. The evaluation of the expressions requires knowledge of estimates of the variation of the modal exciting force with wave incidence angle. However, only the relative variation of the modal exciting force as a percent of that at an arbitrarily chosen reference angle is required. Evaluation of the wave force in absolute terms still is not required. SPEJ p. 5

Download Full-text