IMEX peer methods for fast-wave–slow-wave problems

2017 ◽  
Vol 118 ◽  
pp. 221-237 ◽  
Author(s):  
Behnam Soleimani ◽  
Oswald Knoth ◽  
Rüdiger Weiner
Keyword(s):  
Slow Wave ◽  
Fast Wave ◽  
Wave Problems

scholarly journals Implicit–Explicit Multistep Methods for Fast-Wave–Slow-Wave Problems

2012 ◽  
Vol 140 (4) ◽  
pp. 1307-1325 ◽  
Author(s):  
Dale R. Durran ◽  
Peter N. Blossey
Keyword(s):  
Slow Wave ◽  
Multistep Methods ◽  
Linear Multistep Methods ◽  
Fast Wave ◽  
Localized Source ◽  
Adams Methods ◽  
Imex Schemes ◽  
Low Amplitude ◽  
Wave Problems ◽  
Oscillation Equation

Implicit–explicit (IMEX) linear multistep methods are examined with respect to their suitability for the integration of fast-wave–slow-wave problems in which the fast wave has relatively low amplitude and need not be accurately simulated. The widely used combination of trapezoidal implicit and leapfrog explicit differencing is compared to schemes based on Adams methods or on backward differencing. Two new families of methods are proposed that have good stability properties in fast-wave–slow-wave problems: one family is based on Adams methods and the other on backward schemes. Here the focus is primarily on four specific schemes drawn from these two families: a pair of Adams methods and a pair of backward methods that are either (i) optimized for third-order accuracy in the explicit component of the full IMEX scheme, or (ii) employ particularly good schemes for the implicit component. These new schemes are superior, in many respects, to the linear multistep IMEX schemes currently in use. The behavior of these schemes is compared theoretically in the context of the simple oscillation equation and also for the linearized equations governing stratified compressible flow. Several schemes are also tested in fully nonlinear simulations of gravity waves generated by a localized source in a shear flow.

scholarly journals Implicit–Explicit Runge–Kutta Methods for Fast–Slow Wave Problems

2013 ◽  
Vol 141 (10) ◽  
pp. 3426-3434 ◽  
Author(s):  
Jeffrey S. Whitaker ◽  
Sajal K. Kar
Keyword(s):  
Slow Wave ◽  
Time Integration ◽  
Forecast Model ◽  
Second Order ◽  
Water Model ◽  
Fast Wave ◽  
Integration Schemes ◽  
Time Integration Schemes ◽  
Runge Kutta ◽  
Wave Problems

Abstract Linear multistage (Runge–Kutta) implicit–explicit (IMEX) time integration schemes for the time integration of fast-wave–slow-wave problems for which the fast wave has low amplitude and need not be accurately simulated are investigated. The authors focus on three-stage, second-order schemes and show that a scheme recently proposed by one of them (Kar) is unstable for purely oscillatory problems. The instability is reduced if the averaging inherent in the implicit part of the scheme is decentered, sacrificing second-order accuracy. Two alternative schemes are proposed with better stability properties for purely oscillatory problems. One of these utilizes a 3-cycle Lorenz scheme for the slow-wave terms and a trapezoidal scheme for the fast-wave terms. The other is a combination of two previously proposed schemes, which is stable for purely oscillatory problems for all fast-wave frequencies when the slow-wave frequency is less than a critical value. The alternative schemes are tested using a global spectral shallow-water model and a version of the NCEP operational global forecast model. The accuracy and stability of the alternative schemes are discussed, along with their computational efficiency.

La S-adénosyl-L-homocystéine : 1. Inductrice de sommeil

1980 ◽  
Vol 58 (2) ◽  
pp. 160-166 ◽  
Author(s):  
Pierre Fonlupt ◽  
Maurice Roche ◽  
Lucien Cronenberger ◽  
Henri Pacheco
Keyword(s):  
Slow Wave ◽  
Fast Wave ◽  
Serotonin Metabolism ◽  
Sleep Patterns

S-Adenosylhomocysteine, 0.1–20 mg/kg, influences the sleep patterns of rat, cat and rabbit by increasing the slow-wave and fast-wave sleep for 6 h. The SAH effects are increased by p-chlorophenylalanine and iproniazid and unchanged by reserpine. SAH effects are correlated with modification of norepinephrine and serotonin metabolism.

A novel hybrid slow-wave/fast-wave traveling-wave amplifier

1997 ◽  
Vol 25 (5) ◽  
pp. 1150-1154 ◽  
Author(s):  
W. Lawson ◽  
A. Fernandez ◽  
T. Hutchings ◽  
G.P. Saraph
Keyword(s):  
Slow Wave ◽  
Traveling Wave ◽  
Fast Wave ◽  
Traveling Wave Amplifier

scholarly journals Edge plasma parameters affecting fast wave and slow wave intensities in scrape off layer

2020 ◽  
Author(s):  
L. Ai ◽  
L. N. Liu ◽  
C. M. Qin ◽  
X. J. Zhang ◽  
Y. P. Zhao
Keyword(s):  
Slow Wave ◽  
Edge Plasma ◽  
Fast Wave ◽  
Plasma Parameters

Plastic Waves of Combined Stresses Due to Longitudinal Impact of a Pretorqued Tube—Part 1: Experimental Results

1970 ◽  
Vol 37 (4) ◽  
pp. 1107-1112 ◽  
Author(s):  
J. Lipkin ◽  
R. J. Clifton
Keyword(s):  
Slow Wave ◽  
Longitudinal Strain ◽  
Fast Wave ◽  
Longitudinal Impact ◽  
Strain Response ◽  
Torsional Strain ◽  
Time Profiles ◽  
Combined Stresses ◽  
Fast Waves ◽  
Longitudinal Strains

Experiments are reported in which annealed aluminum tubes are subjected to a static plastic torque followed by a longitudinal compressive impact. Measurements are made of both longitudinal and shear strain-time profiles at stations along the specimen. Qualitatively, the strain response at the gages corresponds to the arrival of a fast wave for which torsional strain decreases while longitudinal strain increases followed by a slow wave for which both torsional and longitudinal strains increase. Between the slow and fast waves and following the slow wave, a strain rate of the order of 10 sec−1 is maintained.

scholarly journals Fast-wave current drive above the slow-wave density limit

1990 ◽  
Vol 64 (11) ◽  
pp. 1258-1261 ◽  
Author(s):  
D. P. Sheehan ◽  
R. McWilliams ◽  
N. S. Wolf ◽  
D. Edrich
Keyword(s):  
Slow Wave ◽  
Current Drive ◽  
Fast Wave ◽  
Density Limit

scholarly journals Fast wave current drive above the slow wave density limit

1989 ◽  
Author(s):  
R. McWilliams ◽  
D. P. Sheehan ◽  
N. S. Wolf ◽  
D. Edrich
Keyword(s):  
Slow Wave ◽  
Current Drive ◽  
Fast Wave ◽  
Density Limit
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