Michell Investigation of the Significant Influence on the Hydrodynamic of a Warp-Chine Pentamaran

This study attempted to investigate the hydrodynamic performance of various pentamaran configurations with a focus on the interference flow around the component hulls. A computer simulation was conducted based on Michell’s thin ship theory alongside a commercial CFD computation as a comparison. Experiments in the towing tank were performed to validate the numerical calculations, resulting in some hydrodynamic characteristics on the far-field wave pattern, wave interference, wave resistance, and total resistance. Analyses on both transversal and divergent waves were performed to assess the magnitude of wave resistance occurring due to the placement of the side hull to the main hull. Analyses on both waves were also conducted to assess the magnitude of wave resistance due to the placement of outriggers. Looking at the results, numerical calculations based on Michell’s theory were in parallel with experimental data, particularly at Fn greater than .4. Michell’s theory was observed as doing a little preferable agreement with the results of experiments than CFD. Besides, flow patterns obtained numerically from Michell’s and CFD analyses appeared as identical to photographs observed in a towing tank. This investigation identified that a configuration with aligning placement of the main to side hull on the formation of arrow tri-hull, near the Kelvin angle, would cancel the wave formed by the leading hull and can be used as a practical setting to reduce the total wave resistance.

Theory and Experiment Study on Laser Self-Mixing Interference with Multiway Feedback External Cavity

The self-mixing interference (SMI) effect with multiway feedback is analyzed in this paper. The basic theory of SMI with multiway feedback external cavity (MFEC) can be derived from the theory of interference as well as the theory of laser self-mixing interference (LSMI). Based on the external cavity structure with MFEC, a SMI model with two feedback external cavity structure is proposed. The expressions of the phase and output power in the MFEC are deduced and some simulation analyses are made. It is found that the output signal of the SMI system with two external cavity is sinusoidal or sawtooth waves, which is similar to the signal of SMI with a low frequency sinusoidal phase modulation. The density of interference signal fringes is uneven in one period and the shape of the interference wave is determined by the intensity of the external feedback. Furthermore, a SMI with two feedback external cavity experiment system is considered, and the experiment verifies the simulations.

Hybridization of Theory and Experiment in Optimizing Di-Hull Configuration With Respect to Wave Resistance

A fast method for optimizing the configuration of a di-hull system is to take advantage of the wave-cut signatures of each hull and evaluate the combined resistance of the hull system using analytical expressions that portray the interference effects of the hull-generated waves. This interference formula is available in Yeung et al. [1] and can be used in conjunction with the wave-cut signatures. The Longitudinal Wave-cut Method (LCM) is utilized to acquire the wave-making spectrum for each monohull. Then the di-hull interference wave resistance is deduced by substituting these experimentally-acquired information into analytical expressions for resistance computation. The pre-acquired wave-spectrum information can be stored and used for a combination of any component hulls, identical or not. This hybridization procedure of theory and experiments is tested and evaluated. Its merits and deficiencies are discussed.

Design and Implementation of Seismic Data Digital Filter

In order to improve the quality and precision of seismic data, taking out or suppressing interference wave consisting in the earthquake wave will be one important link in the digital processing of seismic data .The fast Fournier transformation resolves big points N into certain dot’s DFT combinations .And then breaking a large number of multiply operations to add operations and a small quality of multiply operations, thus the computation speed of the Discrete Fourier Transformation (DFT) will be enhanced greatly. The widespread uses of FFT make it to be a powerful tool in digital signal processing. The present paper will introduce the quite comprehensive narration of the principle of filter, the characteristic of fast Fournier transformation algorithm principle as well as the realization.