Hydraulics boundary conditions

Hydraulical boundary conditions, initial conditions and property calibration... 

On the whole, flow is moving from within the massif towards the laboratory tunnel (from west to east). Before excavation of the FEBEX tunnel, the equipotentials were roughly parallel to the wall of this main tunnel. A zero pressure has been assumed in the laboratory tunnel. To the north and south, the model is constrained by two major shear zones S1-1-S2, as specified in Section 2.2. Figure 3 displays the hydraulic boundary conditions adopted, in a plane view. The head and gradient adopted were deduced both from measurements conducted within the boreholes intersecting our... 

To determine all the tensor terms with 3DEC, 3 sets of (hydraulic) boundary conditions have to be defined (figure 2),... 

Transient mechanical and hydraulic boundary conditions calculated at the ice/bedrock interface... 

Influence of boundary condition Two kinds of hydraulic boundary conditions are tested. The first one supposes an impermeable tunnel wall, the second a prescribed relative humidity (HR). Figure 8 shows that the assumption is very influent close to the wall (first 15 cm). The mechanical consequence of this low saturation level is an important increase of suction so that plasticity never occurs. In conclusion, imposed HR is not suitable for elastoplastic model using Bishop s effective stresses. Thus, no flow condition has been adopted. 

When using CFX-10, the solid and fluid are treated as a unitary computational domain. The interface between the solid and fluid is automatically connected by equal temperature magnitudes and heat flux values thus, only the boundaries for the unit cell are needed. Specifically, for the hydraulic boundary conditions, a uniform velocity is applied at the channel inlet ... 

Voortman describes a model for the hydraulic boundary conditions, where the JPDF (joint probability density function) of hydraulic conditions nearshore is written as a function of properties of the wind held, geometry of the North Sea basin, astronomic tide, and nearshore bathymetry. A description of the boundary conditions on the basis of parametric models found on physical concepts is favored in the thesis over pure statistic methods. 

Here, p is the density k is the thermal conductivity /xf is the fluid dynamic viscosity p is the pressure T is the temperature u is the velocity vector Cp is the specific heat capacity, and O is the viscous dissipation the subscripts f and s represent fluid and solid, respectively. For nanofluids, the corresponding effective thermal conductivities and effective fluid dynamic viscosities will be introduced. When using CFX-10, the solid and fluid are treated as a unitary computational domain. The interface between the solid and fluid is automatically connected by equal temperature magnitudes and heat flux values thus, only the boundaries for the unit cell are needed. Specifically, for the hydraulic boundary conditions, a uniform velocity is applied at the channel inlet ... 

The actual effect of such different hydraulic boundary conditions in the stage of chemicals addition, i.e., more or less successful chemicals mixing, is shown by the data described in Fig. 4 (after [4]). Here, the coagulation efficiency is described for two different chemicals dosing systems. The difference between the two systems is a solely geometrical one, as the schematic indicates. 

Hydraulic fill material is normally used for the next lifts although it could be optional to use less permeable material as well if this is locally available. It has to be realised that recently deposited hydrauhc fill remains saturated for a period of time. Such a hydraulic boundary condition needs to be considered in the analysis of the slope stability. 

The validation of the accuracy of the calculated power limit values resulting from the application of the reference codes suite is to be accomplished through having a third party, LANL, calculate power limits for the same thermal hydraulics boundary conditions. LANL will use the same safety criteria and a different set of codes/models, which has substantive differences from those adopted by WSRC. If reasonable agreement between calculations is achieved, the independent effort will establish a basis for confidence in the results. If there is significant disagreement, then both sets of codes will require an introspective review/evaluation to understand the differences and arrive at a consensus on the preferred technical approach. 

The hydraulic oil must provide adequate lubrication in the diverse operating conditions associated with the components of the various systems. It must function over an extended temperature range and sometimes under boundary conditions. It will be expected to provide a long, trouble-free service life its chemical stability must therefore be high. Its wear-resisting properties must be capable of handling the high loads in hydraulic pumps. Additionally, the oil must protect metal surfaces from corrosion and it must both resist emulsification and rapidly release entrained air that, on circulation, would produce foam. 

Wu and Cheng (2003) measured the friction factor of laminar flow of de-ionized water in smooth silicon micro-channels of trapezoidal cross-section with hydraulic diameters in the range of 25.9 to 291.0 pm. The experimental data were found to be in agreement within 11% with an existing theoretical solution for an incompressible, fully developed, laminar flow in trapezoidal channels under the no-slip boundary condition. It is confirmed that Navier-Stokes equations are still valid for the laminar flow of de-ionized water in smooth micro-channels having hydraulic diameter as small as 25.9 pm. For smooth channels with larger hydraulic diameters of 103.4-103.4-291.0pm, transition from laminar to turbulent flow occurred at Re = 1,500-2,000. 

One particular characteristic of conduction heat transfer in micro-channel heat sinks is the strong three-dimensional character of the phenomenon. The smaller the hydraulic diameter, the more important the coupling between wall and bulk fluid temperatures, because the heat transfer coefficient becomes high. Even though the thermal wall boundary conditions at the inlet and outlet of the solid wall are adiabatic, for small Reynolds numbers the heat flux can become strongly non-uniform most of the flux is transferred to the fluid at the entrance of the micro-channel. Maranzana et al. (2004) analyzed this type of problem and proposed the model of channel flow heat transfer between parallel plates. The geometry shown in Fig. 4.15 corresponds to a flow between parallel plates, the uniform heat flux is imposed on the upper face of block 1 the lower face of block 0 and the side faces of both blocks... 

The boundary conditions to be satisfied are that the lateral pressure difference between subchannels should be zero at the channel inlet and exit. Having passed once along the channel, this implies that iteration over the channel length may be necessary by using improved guesses of flow division between subchannels at the inlet. In practice, only one pass may be necessary, particularly for hydraulic model, in which lateral momentum transfer is neglected or only notionally included. Rowe (1969) has shown that for a single-pass solution to be stable and acceptable,... 

In order to facilitate the modeling as well as the physical interpretation of the pressure transmission - chemical potential test, the loading is decomposed into two fundamental modes corresponding to a hydraulic and a chemical perturbation. The upstream boundary conditions at 2 0 for each of the loading... 

The parameter , which enters into the downstream boundary conditions, can actually be interpreted as = T/,/71,., where T), - L2/D is the hydraulic diffusion time scale. When 1, there exists an intermediate asymptotic behavior corresponding to the zero-flux solution at z = L. When ( -C 1, the solution is essentially the membrane solution. 

Effect of wall thermal boundary condition oh the Nusselt number for hilly developed flow in a rectangular duct (Nusselt number based on hydraulic diameter)... 

Porosity and hydraulic conductivity are both properties of the porous medium. Hydraulic heads, and the hydraulic head gradient, may be determined by solving the equations of flow, with appropriate initial and boundary conditions [2]. 

At the aquifer scale, the most important contribution of age tracers is probably reduction in the nonuniqueness of numerical models. Lack of uniqueness stems, among other things, from inadequate knowledge of the distribution of hydraulic properties within groundwater systems and from poor constraints on boundary conditions (Konikow and Bredehoeft, 1992 Maloszewski and Zuber, 1993). Commonly, groundwater flow... 

In Section III.B, theoretical and empirical mass transfer and heat transfer relations arc discussed. The theoretical relations pertain to laminar flow, because for that flow regime the governing equations can be relatively easily solved numerically. The empirical relations pertain to turbulent flow in smooth rod assemblies. In this section the implications of the nonstandard boundary conditions in a BSR are also discussed. In Section III.C, the validity of the presented relations will be illustrated using experimental data obtained for turbulent flow in a lab-scale BSR with hydraulically rough strings of beads. 

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