Issue34

J. He et alii, Frattura ed Integrità Strutturale, 34 (2015) 564-573; DOI: 10.3221/IGF-ESIS.34.62 568 identically defined as 1 atm. The input volumetric flow rate is assigned as 30 L/s, which is conforming to the actual flow rate of a fluidic amplifier in hydraulic hammers with external diameter of 203 mm. The hydraulic diameter of the jet nozzle in a fluidic amplifier is 14.8mm, besides the hydraulic diameter of slagging nozzles and output nozzles are 26.5 mm and 39 mm, respectively. The parameters of boundary condition in a fluidic amplifier are shown as Tab. 2. Flow rates (L/s) 18 Inlet Velocity (m/s) 68.9 Inlet hydraulic diameter 14.8 Inlet Reynolds number 651405 Outlet Reynolds number 1777204 Inlet turbulence intensity 3% Inlet turbulence intensity 2.65% Inlet area (mm 2 ) 435 Table 2 : The parameters of boundary condition in a fluidic amplifier. Solver Settings The fluid in a fluidic amplifier is turbulent flow due to the high velocity and pressure in hydraulic hammers, hence the numerical solution was finished in software Fluent. All of the models are solved by second order upwind discretization method, which is suitable for turbulent kinetic energy and dissipation rate in numerical simulations. As for the drilling muds in directional drilling, the solid content are strictly controlled in drilling operation, thus the solid content of drilling muds is less than 10%. With regard to the drilling muds used in Victory Oilfield in China, the average density of drilling muds is 1.2 g/m 3 , and the viscosity of drilling muds is 8 mPa.s. Moreover, the density of solid particles in drilling muds is 2.3 g/m 3 , and average grain size of solid particles is 45  m. Thus the erosion property of drilling muds on a fluidic amplifier can be obtained with various material models and boundary conditions in Fluent with the same solver settings. Figure 3 : The velocity contours of a fluidic amplifier in hydraulic hammers [L/s] while the particle size of drilling muds is 45  m.