جستجوی مقالات مرتبط با کلیدواژه « جریان کاویتاسیونی » در نشریات گروه « مکانیک »

In this paper, cavitation and non-cavitation ows around a marine propeller, DTMB 4119, with the RANS method, the K- 03b5 turbulence model, the Singhal transfer model and the mixed model, were solved. The velocity and pressure elds around the propeller surfaces were obtained using the equations of continuity, momentum and the K-03b5 model of turbulence. The pressure coe- cient for two sections of the propeller with experimental data (Jessup 1989) in non-cavitation ow, and three sections in cavitation ow with numerical data (Sun 2008), was validated. Thrust, torque and eciency coecients were extracted for this propeller in eight simulations and compared with experimental data. The cavitation pattern was speci ed and also the position and the cavity development area were obtained. Furthermore, numerical investigations for the three important parameters, such as: advance coecient, propeller working depth and surface roughness of propeller in cavitation ow, were undertaken. An advanced coecient eect study on the propeller surfaces showed that with less advance coecient, more vapor phase value is observed. Also, cavity boundaries are extended. Between advance coef- cient values of 0.833 and 0.7, cavity volume results are less than the advance coecient values of 0.7 and 0.6. So, the cavity boundaries are signi cantly extended. By downing the propeller working depth under open water conditions (increasing hydrostatic pressure), cavity boundary movement, cavity volume variation and curve peak reduction of the vapor phase volume fraction were investigated. The cavity center was away from the leading edge and the probability of tip vortex cavitation was reduced. The sustainability of tip vortex cavitation is more than sheet cavitation, the casue of which is, rst, tip vortex cavitation, and then, sheet cavitation of the leading edge. Investigation on propeller surface roughness showed that optimal roughness height could be found. A and B models showed less cavity volume than the smooth model, while the C model showed more cavity volume. When roughness height was increased, the vapor phase volume fraction was rstly reduced, the results of A and B models being nearly the same. As a result, increasing the roughness height to a speci c value caused a decrease in the vapor phase volume fraction value, which afterwards grew.

Numerical analysis and simulation of cavitating flows due to appearance and its application in the maritime industry، water turbomachinery، hydrofoils، underwater vehicles، etc. have specific importance. For this reason in this research، the effect of blowing on hydrodynamic behavior of cavitating flows over hydrofoils has been investigated. Jameson''s finite volume method and power-law preconditioning method with single-phase cavitation model (Barotropic model) have been used to the analyzing of cavitating flow. The stabilization of solution has been achieved with help of the second and fourth-order dissipation term. Explicit four step Runge-Kutta method has been used to achieve the steady state condition. As regards the cavitation often occurs at high Reynolds number، to facilitate the simulation the inviscid flow equations are considered. For apply the blowing from hydrofoil surface، a jet has been placed on hydrofoil’s upper surface. The parameters of jet location، blowing velocity ratio، blowing angle and width of jet are investigated and simulation has been performed for two different cavitation numbers. The numerical results show that the power-law precondition increases the convergence speed significantly. Blowing reduces the cavity length، lift and pressure drag coefficients compared to no blowing case. Also the increase of blowing velocity ratio، blowing angle and width of jet، decrease the cavity length، lift and pressure drag coefficients.