Steady-state Pressure Profile Research Articles

A numerical model to simulate the transient frictional viscoelastic sliding contact

Sliding motion has always been one of the major concerns when it comes to the analysis of viscoelastic contact problems. A new model simulating the transient sliding contact of smooth viscoelastic surfaces is developed in this paper. By taking the dry contact friction and the coupling between shear tractions and normal pressure into account, the effect of the early partial slip period, which is often neglected in the study of viscoelastic sliding contact problems, is investigated numerically. Compared with solutions based on the frictionless assumption, the steady-state pressure profile is found to be slightly different under the effect of the partial slip regime, including a lower peak pressure and the shift of the contacting region in the direction opposite to the sliding motion. Furthermore, the time required for the viscoelastic contact to reach its steady state is delayed owing to the partial slip period preceding the global sliding motion.

Analysis of the steady-state pressure profile of a double-layered porous journal bearing under turbulent regimes

This theoretical investigation presented the steady-state pressure profile analysis of a hydrostatic double-layered porous journal bearing dealing with the Newtonian lubricant, including the effect of turbulence. Based on Beavers–Joseph's criterion for slip flow, the modified Reynolds equation applicable to finite porous journal bearings lubricated with Newtonian fluids has been derived. The governing equations for flow in the coarse and fine layers of porous medium and the modified Reynolds equation are solved simultaneously using the finite difference method satisfying appropriate boundary conditions. The effect of various design parameters (namely Reynolds number, slenderness ratio, eccentricity ratio, permeability factor, bearing number, and bearing feeding parameter) on the steady-state pressure profile of bearing is presented for both slip and no-slip conditions under laminar and turbulent flow.

Steady-State Hydraulic Analysis of High-Rise Building Wastewater Drainage Networks: Modelling Basis

A model is presented which allows steady-state pressure profiles in high-rise wastewater drainage networks to be related to intake air flowrates and discharge water flowrates. This model is developed using data taken from academic literature, and is based on experimental observations which suggest that a vertical annular downflow develops over distance such that the pressure gradient in the wet stack may be expressed as the sum of junction components and developed flow components. The model is used to analyse a simplified ‘medium rise’ primary vented system of height 40 m, hosting two inflow junctions, crossvents and Air Admittance Valves (AAVs). The model illustrates how the air supply configuration affects the airflow rates within the stack and the vents, and how the configuration affects the steady-state hydraulic pressure profile. The model offers the possibility of an alternative approach to the design of high-rise wastewater drainage networks, compared to existing design codes. These codes generally do not explain the role that the air admitted into the network has upon its performance.

Numerical analysis of pulsatile flows in a slot-die manifold

We analyze the effects of inlet periodic pulsatile flows on the flow inside a slot-die manifold for different locations of the inlet feed port. This type of flow rate disturbance can be caused by a coating liquid pumping mechanism that may lead to coating thickness nonuniformity. In this study, we analyze the transient behavior of the three-dimensional flows inside the slot-die manifold using parallel finite element computations. For a small magnitude of inlet flow rate disturbance with a given frequency, the local flow rate per unit width and the velocity profile at the feed slot exit become periodic. Therefore, the amplification factor can be used to quantify the effect of the inlet pulsatile flows. We found that the flow inside the feed slot, which is the confined channel with a high aspect ratio, dominates the dynamics of the outlet flow. However, the overall trend of the amplification factor along the cross-web direction resembles the steady-state pressure profile inside the cavity, and hence the steady-state profile of the outlet flow rate per unit width, which is strongly affected by the choice of the inlet port location.

Pressure-driven flow of lignocellulosic biomass: A compressible Bingham fluid

Experimental data for the pressure-driven flow of concentrated lignocellulosic biomass (corn stover) in a circular pipe are presented. A positive curvature was observed in the pressure profile at steady state, both when the biomass was flowing, and for several minutes after the flow had stopped. After the flow into the pipe was stopped, biomass continued to be expelled for at least five minutes, suggesting that the material is compressible. Occasionally, the pressure and outlet flow rate exhibited rapid, transient fluctuations. The fluctuations would cease when dryer-than-average heterogeneities exited the pipe. A mathematical model is developed to treat the biomass as a compressible Bingham fluid with a density-dependent yield stress. This model quantitatively reproduces steady-state pressure profiles for both flowing and nonflowing states, and captures the transition between the two states after the inlet flow rate is set to zero. Our model cannot predict the rapid pressure fluctuations that appear to be associated with heterogeneities in composition.

Local transport barrier formation and relaxation in reverse-shear plasmas on the Tokamak Fusion Test Reactor

The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E×B and Shafranov shift effects was performed by varying the E×B shear through changes in the toroidal velocity with nearly steady-state pressure profiles. Transport and fluctuation levels increase only when E×B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balance injection.

Two-dimensional steady-state pressure structure in a coronal loop

By expressing the magnetic field and fluid velocity in terms of two Chandrasekhar-Kendall functions (n = 0, m = 0; n = 1, m = 0) we investigated the steady-state pressure profile inside a solar coronal loop. For constant density loops, we found a two-dimensional (radial and axial) structure of pressure. This work is the modified version of the work of Krishan (1985). At the base of the loop, the pressure is found to increase steeply outwards along the radius, whereas at the apex it decreases slowly. The radial variation of pressure is found to be minimum around L/5, where L is the length of the loop measured from one foot to another one. But Krishan (1985) found that the rate of increase of pressure at the base was nearly equal to the rate of decrease of pressure at the apex, and the pressure was found nearly constant at L/4. For axial variation, we found that along the loop axis the pressure increases from the base up to z = 3L/8 and then decreases up to the apex, whereas at the surface, the pressure decreases from the base up to the apex. Krishan (1985), however, found the axial variation to be linear.

Correcting Surface Pressures To Reflect Downhole Pressure Changes Measured With a Fluid-Filled Capillary Tube

Introduction One method of monitoring the downhole pressure during a well test, when the fluid in a well is two phase and when the high temperature and salinity of phase and when the high temperature and salinity of the fluid eliminates the use of a pressure transducer downhole, is with a fluid-filled capillary tube attached to a pressure transducer at the wellhead. The system originally was designed to measure the pressure profile in a well under steady-state pressure profile in a well under steady-state conditions. When the downhole pressure is not a function of time, the wellhead pressure in the capillary tube is related to the downhole pressure only by the static head of the fluid in the tube. However, when the instrument is used to measure pressure transients, the fluid transmission line will pressure transients, the fluid transmission line will distort and delay the downhole pressure signal. To use the system under these conditions, one must either correct the measured pressures for the effect of the instrument or design the system so that the error in the recorded signal will be negligible. Modeling Signal Propagation Equations were developed previously for modeling of a pressure signal through a fluid transmission line. It was assumed that the temperature of the tubing was at the temperature of the surrounding fluid. When the fluid used is a liquid, it was found that the propagation of the signal is controlled by a propagation of the signal is controlled by a diffusion-like equation: (1) with a diffusion coefficient of r i/8 mu c f. The second term on the right side is the pressure pulse generated by a temperature change in time. When a gas is used, compressibility effects become more important, and a wave-like equation with damping results: (2) when d = rho c f dp + rho Beta dT and delta rho/delta rho t = - delta(rho u)/delta x. The second term on the right side is the damping term.The equations were checked by a simple experiment for the isothermal case. Capillary tubing 8,000 ft (2438 m) in length with an inner radius of 0.054 in. (0.137 cm) was filled with 10-cs silicone oil to test Eq. 1 and then with nitrogen to test Eq. 2. At one end, the tubing was connected to a nitrogen-filled bottle at 2,000 psi (13.7 MPa). At this end, a Sperry-Sun Model PN283354 pressure monitor was connected to the capillary tubing by a tee to measure static pressures. At the second end, the tubing was closed off and connected directly to the Hewlett-Packard Model 2811A quartz pressure gauge. The fluid in the tubing was allowed to equilibrate at some initial pressure. Then a valve was opened between the tubing and nitrogen-filled bottle to increase the pressure by Delta p at this end. The pressure change with pressure by Delta p at this end. The pressure change with time was recorded at the second end. The tubing was at room temperature, so it was assumed that during the test delta T/delta t =0. Fig. 1 shows the comparison between the experiment and the numerical solution of Eq. 1 and 2. A step change k input at one end of the tubing, and then measured and calculated pressures at the second end are compared. Note that pressures at the second end are compared. Note that there is excellent agreement.Conclusions about the system design can be made from the above equations. The maximum tubing diameter possible should be used as the diffusion coefficient in Eq. 2 depends on r i. JPT P. 2020