Model flow resistance method

The inlet and outlet flows will face resistance from pipelines and valves and may be modelled using the methods of Chapters 6 and 10. The variables necessary to determine these flows are the upstream pressure, the upstream specific volume, the downstream pressure and the valve position. The internal mass flows, Wj, i =, ...,N, are calculated as the flows through each nozzle, and this procedure may be carried out iteratively at each timestep. Calculation of the overall performance of the turbine at each timestep follows the following sequence. [Pg.187]

The three-element Windkessel model approximates the pulse propagation quahty of the arterial system as a combination of an infinitely long tube, which is represented by its characteristic impedance, Z , in series with a parallel arrangement of a peripheral flow resistance, R, and a total arterial compliance, C,. Within a single cardiac cycle, these three parameters are generally assumed to be constants (Toorop et al, 1987). Recent studies have scrutinized this assumption. For example, compliance has been shown to depend on the level of arterial pressure (Bergel, 1961). Other studies have called into question the accuracy of the various methods employed to experimentally determine their values (Stergiopulos et al.. [Pg.441]

In the JCA model, the pororrs material has to be characterized by its porosity ((>, its static flow resistivity a, its tortuosity a , its viscous and thermal charaeteristie lengths A and A, its bulk density and its meehanieal properties (Young s modulus, poisson ratio and loss factor). In practice, these parameters need to be determined using direct and/or indirect techniques. A detailed description of these parameters and their determination methods can be found in the hterature [1,3, and 7]. In the current work, a Nitrogen pycnometer is used for the measurement of the porosity [7] the flow resistivity is measured following ASTM-C522 the Ultrasound technique is used to measure the tortuosity [8] and an inverse method is used to estimate the viscous and thermal characteristics lengths from the normal incidence absorption tests [7,8]. [Pg.2055]

Schneider and Klein(5) have pointed out that the early stages of cross-flow microfiltration often follow such a pattern although the growth of the cake is limited by the cross-flow of the process liquid. There are a number of ways of accounting for the control of cake growth. A useful method is to rewrite the resistance model to allow for the dynamics of polarisation in the film layer as discussed by Fane 6. Equation 8.3 is then written as ... [Pg.445]

The weight of soil carried in the surface runoff has been estimated by relating the sediment load to the rate of energy dissipation at the land surface by the rainfall and flowing water. The resistance of the soil to eroding forces has also been considered (4), and a method has been developed to estimate the net effect of erosion on radioaerosol transport. The volume of the liquid phase is estimated on a continuous basis by the Stanford watershed model, through consideration of a water budget. This feature has been retained in the HTM-1. [Pg.503]

The modelling of gas permeation has been applied by several authors in the qualitative characterisation of porous structures of ceramic membranes [132-138]. Concerning the difficult case of gas transport analysis in microporous membranes, we have to notice the extensive works of A.B. Shelekhin et al. on glass membranes [139,14] as well as those more recent of R.S.A. de Lange et al. on sol-gel derived molecular sieve membranes [137,138]. The influence of errors in measured variables on the reliability of membrane structural parameters have been discussed in [136]. The accuracy of experimental data and the mutual relation between the resistance to gas flow of the separation layer and of the support are the limitations for the application of the permeation method. The interpretation of flux data must be further considered in heterogeneous media due to the effects of pore size distribution and pore connectivity. This can be conveniently done in terms of structure factors [5]. Furthermore the adsorption of gas is often considered as negligible in simple kinetic theories. Application of flow methods should always be critically examined with this in mind. [Pg.104]

For the dynamic simulation of the SMB-SFC process a plug-flow model with axial dispersion and linear mass-transfer resistance was used. The solution of the resulting mass-balance equations was performed with a finite difference method first developed by Rouchon et al. [69] and adapted to the conditions of the SMB process by Kniep et al. [70]. The pressure drop in the columns is calculated with the Darcy equation. The equation of state from Span and Wagner [60] is used to calculate the mobile phase density. The density of the mobile phase is considered variable. [Pg.308]

During the process of dam-break evacuation, besides traffic capacity of motor vehicle, non-motor vehicle s traffic load also impacts on the travel time (or travel speed) (Wang Wei, Xu Jian, 1992), therefore, some scholars adopt half-theory and half-experience road resistance function method to calculate the travel time under the heavy mixed traffic situation (Zhang Xingxing, 2011). The major thought is as follows firstly determine the theoretical model of road resistance function based on the relationship of flow, speed and density. In such theoretical model, only consider the influence of traffic volume of motor vehicle, then correct non-motor vehicle s traffic volume, traffic lane number, traffic lane width and traffic disconnection (intersection) and calculation formula is shown below (Li Chaojie, 2007) (Wan Qing, Li Huiguo, 1995)... [Pg.135]

The most advanced material model presently available for UHMWPE is the HM. This model focuses on creating a mathematical representation of the deformation resistance and flow characteristics for conventional and highly crosslinked UHMWPE at the molecular level. The physics of the deformation mechanisms establish the framework and equations necessary to model the behavior on the macroscale. As already mentioned, to use the constitutive model for a given material requires a calibration step where material-specific parameters are determined. A variety of numerical methods may be used to determine the material-specific parameters for a constitutive theory. In the previous section we employed a numerical optimization technique to identify the material parameters for the constitutive theory. [Pg.334]

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