Naval Postgraduate School

About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Nonlinear system. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.

High-order nonlinear solver for multiple roots

Abstract: A method of order four for finding multiple zeros of nonlinear functions is developed. The method is based on Jarratt's fifth-order method (for simple roots) and it requires one evaluation of the function and three evaluations of the derivative. The informational efficiency of the method is the same as previously developed schemes of lower order. For the special case of double root, we found a family of fourth-order methods requiring one less derivative. Thus this family is more efficient than all others. All these methods require the knowledge of the multiplicity.

Surf zone eddies coupled with rip current morphology

Abstract: [1] Energetic very low frequency (VLF; frequencies <0.004 Hz) surf zone eddies (SZEs) were observed on a beach composed of shore-connected shoals with quasi-periodic (∼125 m) incised rip channels at Sand City, Monterey Bay, California. Incident waves consisted of predominantly shore-normal narrow-banded swell waves. SZEs were located outside the gravity region in alongshore wave number, ky, spaced within the VLF band, and did not appear to exist in higher-frequency bands. The SZEs were significant (Urms,VLF ∼ 0.25 m/s) and constant in intensity within the surf zone (shore-connected shoals and rip channels) and rapidly decreased offshore. The alongshore and cross-shore SZE velocity variances were similar in magnitude. VLF SZE velocities were not forced by VLF surface elevations and were not well correlated with rip current flows (r2 = 0.18). There is an indication that the SZEs were related to wave forcing, with the SZEs statistically correlated with incoming sea-swell wave height (r2 = 0.49). F-ky spectral estimates illustrate a strong relationship between rip channel spacing and SZE cross-shore velocities (ky = ±0.008 m−1) and minimal SZE alongshore velocity variation (ky = 0 m−1). Data analysis suggests that the SZEs are not simply instabilities of an unstable rip current jet. A simple conceptual model suggests that SZE f-ky spectra can be explained by the entire rip current circulation cells oscillating predominantly in the cross shore and slightly in the alongshore.

Variation op longshore current across the surf zone

Abstract: The wave-induced longshore current variation across the surf zone is described for a simplified model The basic assumptions are that the conditions are steady, the bottom contours are straight and parallel but allow for an arbitrary bottom profile, the waves are adequately described by linear theory, and that spilling breakers exist across the surf zone Conservation equations of mass, momentum, and energy, separated into the steady and unsteady components, are used to describe second order-wave-induced phenomena of shoaling waves approaching at an angle to the beach An expression for the longshore current is developed, based on the alongshore component of excess momentum flux due to the presence of unsteady wave motion Wave set-down and set-up have been included in the formulation Emphasis in the analysis is placed on formulating usable predictive equations for engineering practice Comparison with experimental results from the laboratory and field show that if the assumed conditions are approximately fulfilled, the predicted results compare quite favorably.