Carbonate rocks host several large water and hydrocarbon reservoirs worldwide, some of them highly heterogeneous involving complex pore systems. Pre-salt reservoirs in the Santos Basin off the south-east coast of Brazil, are an example of such rocks, with much attention focused on proper characterization of their petrophysical and multiphase flow properties. Since it is very difficult to obtain rock samples (coquinas) from these very deep reservoirs, analogues from north-eastern Brazil are often used because of very similar geological age and petrophysical properties. We used a coquina plug from an outcrop in a quarry in northeast Brazil to perform a comprehensive set of analyses. They included Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), and micro-computed tomography (μCT) image acquisition using a series of pixel sizes, as well as direct permeability/ porosity measurements. Some of the experimental data were collected from the plug itself, and some from a small sample of the rock slab, including thin sections. Results included the carbonate rock composition and the pore system at different scales, thus allowing us to reconstruct and model the porosity and absolute permeability of the coquina using 3D digital imaging and numerical simulations with pore network models (PNMs). The experimental and numerical data provided critical information about the well-connected pore network of the coquina, thereby facilitating improved predictions of fluid flow through the sample, with as ultimate objective to improve hydrocarbon recovery procedures.
The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery.
In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.
Concentration and particle size distribution has been experimentally measured in a 2D rectangular duct under near iso-kinetic conditions for multi-sized particulate slurry. Measurements have been made at different flow velocities for various efflux concentrations in the range of 10 to 50 % by weight. It is observed that the concentration profile is highly skewed towards the bottom of the duct, which reduces with increase in efflux concentration and velocity. Similar phenomenon is observed in the distribution of individual particle size fractions with the effect being more pronounced for the coarser particles. and Rozdělení koncentrace a velikosti částic bylo měřeno ve 2D pravoúhlém kanále při proudění disperze různě velkých částic za téměř iso-kinetických podmínek. Experimenty byly provedeny při různých rychlostech s dopravními koncentracemi v rozsahu 10 až 50 hmotnostních procent. Bylo zjištěno, že koncentrační profil je výrazně zešikmený ke dnu kanálu, což se však zmenšuje s růstem koncentrace a rychlosti. Podobný jev byl pozorován u distribuce částic jednotlivých velikostních frakcí. Jev se projevuje tím výrazněji, čím větší jsou částice.
Sand-water slurry was investigated on an experimental pipe loop of inner diameter D = 100 mm with the horizontal, inclined, and vertical smooth pipe sections. A narrow particle size distribution silica sand of mean diameter 0.87 mm was used. The experimental investigation focused on the effects of pipe inclination, overall slurry concentration, and mean velocity on concentration distribution and deposition limit velocity. The measured concentration profiles showed different degrees of stratification for the positive and negative pipe inclinations. The degree of stratification depended on the pipe inclination and on overall slurry concentration and velocity. The ascending flow was less stratified than the corresponding descending flow, the difference increasing from horizontal flow up to an inclination angle of about +30°. The deposition limit velocity was sensitive to the pipe inclination, reaching higher values in the ascending than in the horizontal pipe. The maximum deposition limit value was reached for an inclination angle of about +25°, and the limit remained practically constant in value, about 1.25 times higher than that in the horizontal pipe. Conversely, in the descending pipe, the deposition limit decreased significantly with the negative slopes and tended to be zero for an inclination angle of about −30°, where no stationary bed was observed.
In his book (2021) Trueman attempts to provide a solution to the problem of the concept horse, which according to Frege’s published writings is an object, not a concept. In the course of doing so Trueman rejects Wright’s response (1998) according to which some objects are also concepts, for example, the concept horse, so the categories are not exclusive. Trueman’s argument for exclusivity (Chapter 4) is the heart of the book, and as he says, it is his response to holders of differing views, like Wright. I think that there is a gap in Trueman’s argument which needs to be filled if Wright is to be considered refuted.
Since the beginning of hydrological research hydrologists have developed models that reflect their perception about how the catchments work and make use of the available information in the most efficient way. In this paper we develop hydrologic models based on field-mapped runoff generation mechanisms as identified by a geologist. For four different catchments in Austria, we identify four different lumped model structures and constrain their parameters based on the field-mapped information. In order to understand the usefulness of geologic information, we test their capability to predict river discharge in different cases: (i) without calibration and (ii) using the standard split-sample calibration/ validation procedure. All models are compared against each other. Results show that, when no calibration is involved, using the right model structure for the catchment of interest is valuable. A-priori information on model parameters does not always improve the results but allows for more realistic model parameters. When all parameters are calibrated to the discharge data, the different model structures do not matter, i.e., the differences can largely be compensated by the choice of parameters. When parameters are constrained based on field-mapped runoff generation mechanisms, the results are not better but more consistent between different calibration periods. Models selected by runoff generation mechanisms are expected to be more robust and more suitable for extrapolation to conditions outside the calibration range than models that are purely based on parameter calibration to runoff data.
Conclusions of theoretical reasoning are assertions—or at least speech acts belonging to the class of assertives, such as hypotheses, predictions or estimates. What, however, are the conclusions of practical reasoning? Employing the concepts of speech act theory, in this paper I investigate which speech acts we perform when we’re done with an instance of a practical argument and present its result in a linguistic form. To this end, I first offer a detailed scheme of practical argument suitable for an external pragmatic account (rather than an internal cognitive account). Resorting to actual examples, I then identify a class of action-inducing speech acts as characteristic conclusions of practical argument. I argue that these speech acts—promises, orders, pieces of advice, proposals, and others—differ chiefly depending on the agent of the action induced (me, us, you, them) and their illocutionary strength.