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Accurate estimation of the pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during wellbore drilling operation. The aim of this study is to simulate non-Newtonian (power law and Herschel-Bulkly) foam flow in underbalanced drilling condition through wellbore annulus using finite volume method. The effect of various operational parameters on pressure loss such as fluid rheology, foam fluid velocity, foam quality, drillpipe rotation and wellbore eccentricity, have been considered. Simulation results were compared with the previously published experimental data. The agreement was close with a relative error less than 5%. The results of numerical method are closer to experimental data for Herschel Bulkly model for foam fluid. Also, the results of numerical method, showed that pressure drop increases with increasing the foam fluid velocity and quality and it decreases with increasing eccentricity, but drillpipe rotation don’t have noticeable effect on pressure drop.

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Surface roughness of steam turbine blades is increased during operation. This point has harmful effect on the performance of steam turbines. In this paper effects of surface roughness on performance of a steam turbine stage in two-phase flow conditions are investigated for different outlet pressures. To do so a numerical code has been developed to simulate two-phase non-equilibrium flow in 2D steam turbine geometry. An AUSM-van Leer hybrid scheme is used to calculate inviscid fluxes, the SST turbulence model for turbulence viscosity and Wilcox roughness model for implementation of roughness on the surface of turbine blade. To validate the present in-house code the experimental results of Bakhtar has been used. According to the results of the paper, effect of surface roughness variation on the performance loss in subsonic stages is more than that in supersonic outflows. For example, in subsonic outflow case (Pb= 24.25 kPa) when the roughness height increases from 5µm to 800 µm, the value of efficiency decreases by 15%. However, for supersonic outflow case (Pb= 14.55 kPa) the value of efficiency decreases by 10% for this roughness increase.

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The pressure-time method is a flow rate measurement technique generally employed in hydropower plants to evaluate the efficiency of hydraulic turbines. The 1D numerical simulation incorporating the finite volume method is employed to evaluate the method. The results are compared with the experimental data. The flow is simulated inside a straight pipe with Reynolds number Re=6.76×〖10〗^6. The flow rate reduction curve is employed for the simulation of the deceleration part of the flow, before valve closure, in the pressure-time method. The effective parameters on the flow rate calculation including the friction losses and the definition of the final time of the valve closure are studied in detail. The increase in the accuracy of the flow rate calculation is a function of the increase in the accuracy of the friction loss calculations. The effect of several friction factors proposed for the evaluation of the unsteady flow is studied on the accuracy of the flow rate calculation. The Pezzinga friction factor shows the least error in the flow rate calculation. The available methods to find out the final time of integration still show a large error. A new method is proposed for the flow rate estimation without any need to have the exact time of the valve closure with an acceptable accuracy.