Papers by Keyword: Cavitation Number

Abstract: This paper presents a method for optimized cavitation of 3-blade type ship propeller. Cavitation flow is investigated around ship propellers experimentally. Testing of two different types of new model propellers and local type propellers are performed in this study. A 3-blades, skew angle 20 degree, developed area 50 and 35, so called model A (B3-20-50), and model B (B3-20-35) respectively, and finally a local type propeller popular used among local fisherman are compared. The results are presented in characteristic curves are related pictures. Finally, the results ate discussed, Model A and B is investigated based on existing experimental results. In addition, model C is a comparison validation to non-optimum for used to shallow-fishery and tailing Thai boat. A practical method was achieved by combining a vortex lattice lifting method and lifting surface method. The optimum circulation distribution yielding the maximum lift-to-torque ratio was computed for given thrust and chord lengths along the radius of the propeller by dividing the blade into a number of panels extending from hub to tip. The radial distribution of bound circulation could be computed by a set of vortex elements that have constant strengths. The cavitation phenomenon is appear to monograph of model A and B the better model C (local type), such as, the cavitation prediction on a hydrofoil is carried out in both steady and unsteady states. The results show good agreement in comparison with available experimental data. Furthermore, the propeller cavitation breakdown is well reproduced in the proceeding. The overall values suggest that the present approach is a practicable tool for predicting probable cavitation on propellers during design processes.

Abstract: Hydrodynamic cavitation is expected to apply to the decomposition of chemicals and the disinfection in wastewater. In this study, the effects of upstream pressure, hole diameter and shape of orifice plate on the reaction rate of I₃^- formation were investigated. The reaction rate increases with increasing upstream pressure of orifice plate. The reaction rates have maximum values, when hole diameters of orifice plate are 2.7 mm at the upstream pressure of 0.9 MPa gauge and 3.0 mm at 0.7 MPa gauge. The reaction rate increases in the order of triangle < square < hexagon < circle shaped hole of orifice plate at the same hole area.

Abstract: Based on the multiphase model of FLUENT 6.3,a underwater projectile cavitation model is established for a new designed underwater projectile which have a disc cavitator.Then the cavitation number influence on cavitation form is concerned and contrast with the empirical formula of cavitation form.The conclusion is：with the increase of cavitation number,the drag coefficient will increase non-linear;the cavitation slenderness radio is greater,the drag coefficient is smaller. Supercavitation phenomenon is that when a object moves in water and it’s speed increases constantly, according to Bernoulli's equation, this will make the hydrostatic pressure that it bears drop. And when the pressure down to the vaporization pressure of water at that temperature, the surface moisture of the object will change into steam, form bubbles and wrap it. Due to the density of water and steam has magnitude deviation, the viscous resistance acting on the underwater moving object will reduce greatly, that can make the performance of underwater weapon enhance markedly. In the military applications, there are represented by Russia, the torpedo of “snowstorm” used the ventilation supercavitation theory and, represented by USA, the “20mm Supercavitation projectile” used the nature supercavitation theory. Facing the daily intelligentized contrail guided torpedo and mine, the small caliber supercavitation projectile technology has provided a new method for the short-range defense of surface vessel. As the nature supercavition projectile is a kind of uncontrolled, unpowered underwater weapon, the formation and stability of cavitation are more significative for performing the properties of projectile. The paper has done same simulate calculation for a new designed subcaliber supercavitation projectile, focused on the cavitation morphology and drag reduction ability under several different projectile velocity circumstance. This research can provide same basis for reasonable structure design of new projectiles.

Abstract: Design a practical and effective hydrodynamic cavitation experimental apparatus, the establishment of cavitation radical scavenging method, the use of methylene blue to study the relationship of the hydroxyl radical production and cavitation cavitation intensity, the study of the various factors of cavitation radical production, and to explore optimal cavitation strengthen the conditions. Hydrodynamic cavitation kill algae has some effect, there will be varying degrees of decline in the concentration of algae. The hydrodynamic cavitation algae suppression and damaging effects.

Abstract: Based on the principle of hydraulics,an effective equipment of hydrodynamic cavitation is designed and built in this paper.The orifice plates with various geometry size were used as hydrodynamic cavitation generator to study the relation ship between many factor,such as,inlet pressure,discharge,flow speed in orifice,and the cavitation number.Analysis of water flow cavitation status for the experimental unit,this device can produce cavitation phenomenon.The methylene blue and spectrophotometer method can capture the free radicals generated successfully.This is an effective way to measuring the free radicals quantitatively in cavitation,moreover it is easy to fulfill.The intensity of cavitation increases with reduction in the cavitation number.By analyzing the influence of cavitation number on concentrations of •OH.It would be strength of hydrodynamic cavitation.The effect of operating parameters,such as inlet press,low speed in orifice and optimum the structure of hydrodynamic cavitation,best condition of the hydrodynamic cavitation is the inlet press、flow speed in orifice 14 m/s、 0.07.

Abstract: Hydraulic characteristics of orifice plates with multiple triangular holes in hydrodynamic cavitation reactor were experimentally investigated by use of three dimensional particle image velocimetry (PIV), high speed photography, electronic multi-pressure scanivalve and pressure data acquisition system, and numerically simulated by CFD software Flow 3D in this paper. Effects of number, arrangement and ratio of holes on hydraulic characteristics of the orifice plates were considered. Effects of arrangement and ratio of holes and flow velocity ahead of plate on cavitation number and velocity profile were compared. Distribution of turbulent kinetic energy and similarity of velocity profile were analyzed. And characteristics of cavitating flow downstream of the orifice plate were photographically observed by high speed camera. Also, a comparison with flow characteristics of orifice plate with hybrid holes (circle, square and triangle) was made.

Abstract: The cavitation regions of cylindrical and semi-cylindrical protrusions were experimentally investigated in non-circulating water tunnel. The cavitation numbers and structures of protrusions were compared under different velocities and aeration conditions, the common cavitation characteristics of protrusions were developed.