A vehicle-mounted three-dimensional underwater particle image velocimetry（PIV） device is used in a towing tank to measure the velocity distribution of the inlet duct of a waterjet ship model in a self-propulsion tes...A vehicle-mounted three-dimensional underwater particle image velocimetry（PIV） device is used in a towing tank to measure the velocity distribution of the inlet duct of a waterjet ship model in a self-propulsion test. The following points are shown through a comparison of the influences of the stationary and free states of the ship model on the measured results：（1） during the test, the ship attitude will change, specifically, the ship model will heave and trim,（2） the degree of freedom disturbs the processing of the pixel images enough to distort the subsequent image processing,（3） the stationary state of the ship model is the optimal mode for measuring the velocity distribution using the PIV device, and（4） if the changes must be considered, the man-made heaving and trimming may be pre-applied, and be made a corrected stationary mode. In addition, the momentum effect coefficient and the energy effect coefficient are calculated in a non-uniform inflowing state, and the related factors affecting the two coefficients are analyzed. The test results show that the pumping action of the waterjet creates a transverse vector in the cross-sectional speed, which increases the non-uniformity of the inflow. These results could help to establish the design requirements for a waterjet-propelled ship type.展开更多
We show that a Lipschitz domain can be expanded solely near a part of its boundary, assuming that the part is enclosed by a piecewise C1 curve. The expanded domain as well as the extended part are both Lipschitz. We a...We show that a Lipschitz domain can be expanded solely near a part of its boundary, assuming that the part is enclosed by a piecewise C1 curve. The expanded domain as well as the extended part are both Lipschitz. We apply this result to prove a regular decomposition of standard wector Sobolev spaces with vanishing traces only on part of the boundary. Another application in the construction of low-regularity projectors into finite element spaces with partial boundary conditions is also indicated.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51379043,51209048 and 51409063)
文摘A vehicle-mounted three-dimensional underwater particle image velocimetry（PIV） device is used in a towing tank to measure the velocity distribution of the inlet duct of a waterjet ship model in a self-propulsion test. The following points are shown through a comparison of the influences of the stationary and free states of the ship model on the measured results：（1） during the test, the ship attitude will change, specifically, the ship model will heave and trim,（2） the degree of freedom disturbs the processing of the pixel images enough to distort the subsequent image processing,（3） the stationary state of the ship model is the optimal mode for measuring the velocity distribution using the PIV device, and（4） if the changes must be considered, the man-made heaving and trimming may be pre-applied, and be made a corrected stationary mode. In addition, the momentum effect coefficient and the energy effect coefficient are calculated in a non-uniform inflowing state, and the related factors affecting the two coefficients are analyzed. The test results show that the pumping action of the waterjet creates a transverse vector in the cross-sectional speed, which increases the non-uniformity of the inflow. These results could help to establish the design requirements for a waterjet-propelled ship type.
文摘We show that a Lipschitz domain can be expanded solely near a part of its boundary, assuming that the part is enclosed by a piecewise C1 curve. The expanded domain as well as the extended part are both Lipschitz. We apply this result to prove a regular decomposition of standard wector Sobolev spaces with vanishing traces only on part of the boundary. Another application in the construction of low-regularity projectors into finite element spaces with partial boundary conditions is also indicated.
