Applied Mechanics and Materials Vols. 130-134

Abstract: This paper studied the Magneto hydrodynamic (MHD) flow and heat transfer of an electrically conducting non-Newtonian fluid over a rotating disk in the presence of a uniform magnetic field. The steady, laminar and axial-symmetric flow is driven solely by the rotating disk, and the incompressible fluid obeys the inelastic Ostwald de-Waele power-law model. The governing differential equations were reduced to a set of ordinary differential equations by utilizing the generalized Karman similarity transformation. The nonlinear two-point boundary value problem is solved by multi-shooting method. Numerical results show that the magnetic parameter and the power-law index have significant effects on the swirling flow and heat transfer.

Abstract: This investigation deals with the study on the processes involved in the phenomenon about turbulence modification in dilute gas-particle turbulent flows. The proposed model, along with other selected turbulence modification models from the literature, is used to simulate a particle-laden vertical pipe flow. The simulation results show that the new model provides improved predictions of the experimental data.

Abstract: Based on the urgent needs for high transmission speed and high reliability of wireless MWD, the OQPSK modulation of the drilling fluid continuous wave signal is proposed in this article. The Principle of delay orthogonal modulation and coherent demodulation of OQPSK are studied, and the changes in the phase vector of the inputted bit sequence are analyzed; according to the principle of continuous wave generation, the phase adjustment mechanism of rotary value are analyzed and the relationship between the signal waveform, as well as the rotational speed when adjusting the phase, is studied; the information transmission rate, band efficiency and bit error rate of the OQPSK and QDPSK continuous wave communication systems are comparatively analyzed and simulated. The results show that OQPSK eliminates the phase transition of π, which belongs to constant envelope modulation, is suitable for the transmission under low SNR drilling fluid channel, meanwhile simplifies the phase adjustment and reduces generator design. QDPSK can simplify the computational complexity of phase adjustment, and reduces the design difficulty of the continuous-wave generator’s control circuit. The rotary valve forms of "slow down - speed up" and " speed up - slow down " are suitable for π / 2 and 3π / 2 phase jump respectively; the motor control modes which combine closed loop position and closed loop velocity can achieve phase stable signal and reduce the dynamic torque of the motor; in the same carrier frequency and SNR, the information rate and bandwidth efficiency of both OQPSK’s and QDPSK’s are twice as those of the two-phase shift keying system’s, and they can improve the wireless transmission performance of MWD system.

Abstract: This paper is concerned with a mathematical model for numerical simulation of 2D flow accompanied with a hydraulic jump. The governing water equations are solved by the Mac Cormack’s predictor-corrector technique. The mathematical model is used to numerically predict 2D hydraulic jump in a rectangular open channel. The comparison and the analysis show that the proposed method is accurate, reliable and effective in simulation of hydraulic jump flows.

Abstract: This paper was concerned with a vertical two-dimensional (2D) flow model with free surface. The water governing equations were discretized with finite difference method. The function of volume method was employed to track the moving free surface. The model was used to predict the characteristics of dam-break flow in a 2D vertical plane. The surface profile and time averaged velocity were calculated, which shows the proposed model can be capable of capturing sharp water and gas interface configuration as time elapses.

Abstract: In this paper, we use two-phase mixture model and the Realizable k-ε turbulence model to numerically simulate the advection secondary flow in a sedimentation tank. The PISO algorithm is used to decouple velocity and pressure. The comparisons between the measured and computed data are in good agreement, which indicates that the model can fully simulate the flow field in a sedimentation tank.

Abstract: Dynamic atomization processes of non-Newtonian liquid were investigated by the method of numerical simulation. The full transient process of the primary instability, deformation, and fragmentation of free surface were simulated numerically by solving the Navier-Stokes equations using an algorithm based on the finite volume method. The tracking of the free surface was achieved using the volume of fluid (VOF) technique and the geometric reconstruction was based on the technique of Piecewise-Linear Interface Construction (PLIC). The continuum surface force (CSF) method was used to model surface tension. In this paper, atomization characteristics of non-Newtonian liquid were analyzed detailedly. The distribution of dimensionless potential length against time was obtained, and the dimensionless wavelength of primary waves was investigated.

Abstract: The feasibility of applying C⁴D technique to void fraction measurement of gas-liquid two-phase flow is investigated in this paper. As a preliminary research, void fraction measurement under stratified flow is studied. Conductance of two-phase fluid are obtained by a new C⁴D sensor, and then used to measure the void fraction in 15mm i.d. pipe. An empirical correlation between void fraction and normalized conductance is developed. Thus, the void fraction can be determined by this empirical correlation with the obtained conductance. The experiment results show that applying C⁴D technique to the void fraction measurement of gas-liquid two-phase flow is feasible. The measurement results of void fraction are satisfactory, and the maximum absolute error of void fraction is less than 0.03.

Abstract: A CFD method was adopted to study the transient flow and spray characteristics of multiple nozzle holes port fuel injector. The flow field inside a port fuel injector was numerically analyzed, the predicted dynamic flow rate was compared with experimental data and the cavitations levels and location at different inject pressure were captured. Using Huh-Gosman breakup model, the atomization processes at the nozzle exit were predicted with initial droplet size distribution at primary break-up region refer to the experiment date. The liquid penetration and vapor distributions versus time from start of injection were also calculated.

Abstract: This paper presents a performance analysis of a solid-liquid hydrocyclone using Ansys-CFX software. Based on the simulation, the influence of particle volume fraction of feed flow, mean diameter of particles and viscosity of liquid phase on the two-phase flow and separating performance has been investigated for optimizing design.