Numerical experiments on free surface water motion with bores

2005 ◽  
pp. 304-312 ◽  
Author(s):  
Maurizio Pandolfi
Keyword(s):  
Free Surface ◽  
Surface Water ◽  
Numerical Experiments ◽  
Water Motion

scholarly journals Experimental study of immersion ratio and shaft inclination angle in the performance of a surface-piercing propeller

2019 ◽  
Vol 10 (1) ◽  
pp. 153-167
Author(s):  
Seyyed Mostafa Seyyedi ◽  
Rouzbeh Shafaghat ◽  
Mohioddin Siavoshian
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Surface Water ◽  
Inclination Angle ◽  
Superior Performance ◽  
Design Parameters ◽  
Water Tunnel ◽  
Hydrodynamic Coefficients ◽  
Thrust And Torque ◽  
Surface Piercing Propeller

Abstract. Surface-piercing propellers have been widely used in light and high-speed vessels because of their superior performance. Experimental study of these propellers is one of the most reliable and accurate ways which can provide details about the performance and effect of different design parameters on the performance of the surface-piercing propellers. In this research, a five-blade surface-piercing propeller was tested in the free surface water tunnel of Babol Noshirvani University of Technology in order to expand the available experimental data and database for future engineering designs. The effects of immersion ratio and shaft inclination angle on the propeller's efficiency and hydrodynamic coefficients were examined. A free surface water tunnel and a calibrated dynamometer with the measurability of the thrust forces and the torque of a propeller were used for this purpose. Comparing the obtained results with the existing semi-experimental equations shows that the equations presented in various geometric conditions are not accurate enough, and developing the existing database is necessary. The details of the obtained results showed that the hydrodynamic coefficients of the thrust and torque increased by increasing the immersion ratio, but the coefficient of hydrodynamic thrust and efficiency reduced. The results also indicated that the coefficient of torque increased by increasing the shaft inclination angle. The highest efficiency of the propeller was achieved in the range of 40 %–50 % immersion ratios at all angles of shaft inclination. For all immersion ratios, the maximum and minimum efficiencies were obtained at 0 and 15 shaft inclination angles, respectively. The best efficiency of the propeller was at 50 % immersion ratio and zero shaft inclination angle.

Методика практического восстановления параметров формы поверхностных двухмерных дефектов с учетом нелинейных свойств ферромагнетика

2021 ◽  
pp. 46-55
Author(s):  
А.В. Никитин ◽  
А.В. Михайлов ◽  
А.С. Петров ◽  
С.Э. Попов
Keyword(s):  
Magnetic Field ◽  
Free Surface ◽  
Numerical Experiments ◽  
Input Data ◽  
Metal Plate ◽  
Two Dimensional ◽  
Nonlinear Properties ◽  
Data Errors ◽  
The Magnetic Field

A technique for determining the depth and opening of a surface two-dimensional defect in a ferromagnet is presented, that is resistant to input data errors. Defects and magnetic transducers are located on opposite sides of the metal plate. The nonlinear properties of the ferromagnet are taken into account. The components of the magnetic field in the metal were reconstructed from the measured components of the magnetic field above the defect-free surface of the metal. As a result of numerical experiments, the limits of applicability of the method were obtained. The results of the technique have been verified experimentally.

NUMERICAL EXPERIMENTS AND EXPERIMENTS OF REFLECTIONS FOR INCLINED CRACKS ON A FREE SURFACE

1989 ◽  
pp. 239-241
Author(s):  
M. UCHIDA ◽  
T. MIYAJIMA ◽  
K. HARUMI ◽  
S. OGURA
Keyword(s):  
Free Surface ◽  
Numerical Experiments ◽  
Inclined Cracks

Bistable Flow Patterns in a Free Surface Water Channel

1989 ◽  
Vol 111 (4) ◽  
pp. 408-413
Author(s):  
E. W. Adams ◽  
A. I. Stamou
Keyword(s):  
Free Surface ◽  
Surface Water ◽  
Stable State ◽  
Flow Patterns ◽  
Shear Layers ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Free Shear Layers ◽  
Side Flow ◽  
Bistable Flow

A series of experiments is reported on a free surface water tunnel with a slot inlet centered at mid-depth in which the flow exhibited equally probable bistable flow patterns. The two flow fields are strongly asymmetric even when the geometry is symmetric and consists of a long stall on one side of the inlet and a short stall on the opposite side. Flow visualization and laser-Doppler velocimetry were performed to examine the flow structure of both stable states in detail. Results showed that the mean flow and turbulence structure of the two bistable states are largely mirror images of each other within the separation zone. The effect of the wall on the flow is minor, only very close to the wall/free surface did the difference in wall constraints cause the two flow patterns to diverge. After reattachment both flows relax to free-surface channel flow. It is shown that the bistable flow pattern results from the interaction of the free shear layers and that only strong disturbances in the free shear layers can cause the flow in one stable state to switch to the other stable state. Bistable flow exists for geometries with asymmetry up to 10 percent for the expansion ratio studied.

Sign in / Sign up

Export Citation Format

Share Document