Precision flat surfaces finished by hand-scraping are extensively used in the sliding parts of precision positioning systems or the surface plates of precision measuring instruments.These hand-scraped surfaces are emp...Precision flat surfaces finished by hand-scraping are extensively used in the sliding parts of precision positioning systems or the surface plates of precision measuring instruments.These hand-scraped surfaces are employed to improve the flatness of the machined surfaces and the motion accuracy of the instruments.The numerous depressions of micrometer-scale depth on a scraped surface are thought to prevent wringing and improve the lubrication properties by forming oil pockets.Form measurement of the micrometer-scale features of a hand-scraped surface is one of the reasonable methods for investigating its effect on the motion accuracy of the positioning systems or the lubrication properties of the sliding parts.Because a hand-scraped surface is a rough surface composed of micrometric complex features,it is difficult to conduct precision measurement of the three-dimensional surface form using conventional measurement instruments,such as vertical-incident interferometers or stylus-type profilometers.In this study,an oblique-incident interferometer based on Abramson interferometry is introduced to measure the form of a rough surface produced by hand-scraping.Because this technique can detect high-intensity reflected light on a rough surface,it allows the measurement of the form of the hand-scraped surface in noncontact condition.In order to shorten the measurement time,the form calculation based on a five-step phase shifting method was introduced.展开更多
The reflection of oblique incident waves from breakwaters with a partially-perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigenfunction expansion method is applied to e...The reflection of oblique incident waves from breakwaters with a partially-perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigenfunction expansion method is applied to expand velocity potentials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with experimental data. The effect of porosity, the relative chamber width, the relative water depth in the wave absorbing chamber and the water depth in front of the structure are discussed.展开更多
Wave forces induced by the interaction between the oblique incident wave and the breakwater with a partially perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigen-functi...Wave forces induced by the interaction between the oblique incident wave and the breakwater with a partially perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigen-function expansion method is applied to expanding velocity potentials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with other theories and a good agreement can be found between them. Experimental data have been compared with the present theoretical results. The effect of the traverse wall on wave forces has been discussed in detail. On the basis of the linear wave theory, it is shown that in the range Of engineering practice, the incident angle of wave has small influence on wave forces on the unit length of perforated caisson.展开更多
The interaction of oblique incident waves with infinite number of perforated caissons is investigated. The fluid domain is divided into infinite sub-domains by the caissons, and eigen-function expansion is applied to ...The interaction of oblique incident waves with infinite number of perforated caissons is investigated. The fluid domain is divided into infinite sub-domains by the caissons, and eigen-function expansion is applied to expand velocity potentials in each domain. A phase relation is introduced for wave oscillation in each caisson, and the structure geometry is considered in constructing the models of reflection waves. The reflected waves with the present analysis include all of the waves traveling in different directions when incident wave period is short. Numerical examinations show that velocities at the inner and outer sides of the front walls of caissons ase close to each other, and reflection coefficients satisfy the energy conservation relation very well when porous effect parameter is infinite. Numerical results show that the reflection coefficients of oblique incident waves are smaller for shorter caissons at low frequency, and decrease with the increase of wave incident angle.展开更多
基金This research is supported by the JSPS,JapanJapan Society for the Promotion of Science,Japan KAKENHI Grant Number JP 20K04195 and research grant of the Mitutoyo Association for Science and Technology Grant Number R1901.
文摘Precision flat surfaces finished by hand-scraping are extensively used in the sliding parts of precision positioning systems or the surface plates of precision measuring instruments.These hand-scraped surfaces are employed to improve the flatness of the machined surfaces and the motion accuracy of the instruments.The numerous depressions of micrometer-scale depth on a scraped surface are thought to prevent wringing and improve the lubrication properties by forming oil pockets.Form measurement of the micrometer-scale features of a hand-scraped surface is one of the reasonable methods for investigating its effect on the motion accuracy of the positioning systems or the lubrication properties of the sliding parts.Because a hand-scraped surface is a rough surface composed of micrometric complex features,it is difficult to conduct precision measurement of the three-dimensional surface form using conventional measurement instruments,such as vertical-incident interferometers or stylus-type profilometers.In this study,an oblique-incident interferometer based on Abramson interferometry is introduced to measure the form of a rough surface produced by hand-scraping.Because this technique can detect high-intensity reflected light on a rough surface,it allows the measurement of the form of the hand-scraped surface in noncontact condition.In order to shorten the measurement time,the form calculation based on a five-step phase shifting method was introduced.
基金by Joint Fund of the National Natural Science Foundation of China the Hong Kong Science Research Bureau (49910161985)+1 种基金the National Natural Science Foundation of China (50025924,50179004)the Research Fund for the Development of harbor engineeri
文摘The reflection of oblique incident waves from breakwaters with a partially-perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigenfunction expansion method is applied to expand velocity potentials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with experimental data. The effect of porosity, the relative chamber width, the relative water depth in the wave absorbing chamber and the water depth in front of the structure are discussed.
基金This project was supported by the Research Fund for the Development of Harbor Engineering Design Specification,the Ministry of Communications of Chinathe Program for Changjiang Scholars and Innovation Research Team in University of China under contract No.IRT0420the Fok Ying Tung Education Foundation of China under contract No.81068.
文摘Wave forces induced by the interaction between the oblique incident wave and the breakwater with a partially perforated front wall is investigated. The fluid domain is divided into two sub-domains and the eigen-function expansion method is applied to expanding velocity potentials in each domain. In the eigen-expansion of the velocity potential, evanescent waves are included. Numerical results of the present model are compared with other theories and a good agreement can be found between them. Experimental data have been compared with the present theoretical results. The effect of the traverse wall on wave forces has been discussed in detail. On the basis of the linear wave theory, it is shown that in the range Of engineering practice, the incident angle of wave has small influence on wave forces on the unit length of perforated caisson.
文摘The interaction of oblique incident waves with infinite number of perforated caissons is investigated. The fluid domain is divided into infinite sub-domains by the caissons, and eigen-function expansion is applied to expand velocity potentials in each domain. A phase relation is introduced for wave oscillation in each caisson, and the structure geometry is considered in constructing the models of reflection waves. The reflected waves with the present analysis include all of the waves traveling in different directions when incident wave period is short. Numerical examinations show that velocities at the inner and outer sides of the front walls of caissons ase close to each other, and reflection coefficients satisfy the energy conservation relation very well when porous effect parameter is infinite. Numerical results show that the reflection coefficients of oblique incident waves are smaller for shorter caissons at low frequency, and decrease with the increase of wave incident angle.
