Comparative study of high-pressure fluid flow in densely packed granules using a 3D CFD model in a continuous medium and a simplified 2D DEM-CFD approach

An isothermal compressible single-phase fluid flow through a non-homogeneous granular body composed of densely packed overlapping spheres imitating rock under high pressure was numerically studied using two different approaches. The first approach called the full 3D CFD model used the finite volume method (FVM) to solve the Reynolds-averaged Navier–Stokes equations using Reynolds stress model (BSL) in the continuous domain between the granulates. The model was verified, based on experimental and numerical results from the literature. The second approach was a simplified coupled DEM-CFD model based on a fluid flow network. The main aim of the work was to develop a validation procedure for simplified coupled DEM-CFD models due to the lack of experimental data for fluid flow characteristics in densely packed granules under extremely high-pressure conditions. First, a series of numerical simulations were performed for the fluid domain with the full 3D CFD model. The results of those simulations were next used to validate the 2D numerical results of the simplified coupled DEM-CFD model with respect to velocities, pressures, densities and flow rates. Almost the same pressure and density distributions and mass flow rates were obtained in both approaches. However, the fluid velocity was different due to the different fluid volumes in both fluid domains. The current simulation results constitute a reliable benchmark for validating other coupled 2D/3D DEM-CFD models that use a fluid flow network approach. Graphic abstract

The Movement Characteristics of Coal Granular Body in Excavating Rescue Channel in the Collapsed Body

The collapsed body formed after the underground power disaster is broken into loose body. The mechanical characteristics of the collapsed body are quite different from those of the homogeneous rock mass, and the rescue tunnel is affected by its moving characteristics. In this study, the lateral pressure coefficient of the collapsed body and the angle of the slip surface were deduced. The numerical experiment based on CDEM slump excavation was performed. The accumulation state of the collapsed body and the active lateral pressure coefficient and the angle of the slip surface are obtained. The characteristics of the force of the accumulation body which naturally collapsed were studied. Particle size, excavation position, excavation shape, volume, and the influence of natural repose angle on the occurrence mode and particle movement were obtained; the velocity field and slip surface of the lower left and middle lower parts during excavation and the variation of the natural repose angle were analyzed.

Laboratory testing of granular kinetic theory for intense bed load transport

Collisional interactions in a sheared granular body are typical for intense bed load transport and they significantly affect behavior of flow carrying bed load grains. Collisional mechanisms are poorly understood and modelling approaches seldom accurately describe reality. One of the used approaches is the kinetic theory of granular flows. It offers constitutive relations for local shear-induced collision-based granular quantities - normal stress, shear stress and fluctuation energy - and relates them with local grain concentration and velocity. Depth distributions of the local granular quantities produced by these constitutive relations have not been sufficiently verified by experiment for the condition of intense bed load transport in open channels and pressurized pipes. In this paper, results from a tilting-flume facility including measured velocity distribution and deduced concentration distribution (approximated as linear profiles) are used to calculate distributions of the collision-based quantities by the constitutive relations and hence to test the ability of the kinetic-theory constitutive relations to predict conditions observed in these collision-dominated flows. This test indicates that the constitutive relations can be successfully applied to model the local collisional transport of solids at positions where the local concentration is not lower than approximately 0.18 and not higher than approximately 0.47.

Geometric dimensions of mixed fodder portion at transportation by a chain-disk conveyor

Chain- disc conveyors are widely used in the organization of the distribution of fodder for livestock farms of different types due to the simplicity of design and high reliability conveyors of this type. The portion of mixed fodder, transported by chain- disc transporter, is characterized by the following geometric parameters: the length of the l1and l2sections, the angle forming the bulk of the slope, the radius R of the cylindrical part of the piece is equal to the radius of the conveyor fodder line. In accordance with the kinds of the transported forms of the bulk of the body, the mode of the chain- disk conveyor can be divided into three types: an unloaded conveyor, loaded conveyor, overloaded conveyor. The volume of fodder portions may be expressed as a function of the length of the cylindrical portion l1. When fodder’s driving on a gently sloping portions of conveyor sections, this function will have a different appearance under different loading modes. With the change in the angle of the conveyor, the character depending on the length of the cylindrical portion is not changed, only change the boundaries of reality functions for different boot modes. At the angle of inclination of the conveyor х = 400, the total angle of the slope forming the bulk φ+х = 900, i.e., the forming plane flatness becomes perpendicular to the axis of the conveyor, and a granular body takes the form of a cylinder. With such tilted of transporter, body particulate volume is a linear function of its length, and the conveyor operates in the linear regime only boot.

Penile actinomycosis clinically diagnosed as an epidermal cyst: a case report

A 27-year-old man presented at our hospital with a 1.5cm, spherical, soft and movable subcutaneous mass at the mid portion of the ventral aspect of the penile shaft. The possibility of an epidermal cyst was considered and a simple resection was performed. Histologically, the lesion was a unilocular cyst without an epithelial lining, containing eosinophilic necrotic material and a few dispersed scalloped sheets of actinomycotic granules. The centre of the largest granular body demonstrated many fragments of foreign substance. The patient was treated successfully with combined antibiotic therapy.

A new species of Goniurosaurus from Cat Ba Island, Hai Phong, northern Vietnam (Squamata: Eublepharidae)

A new species of the gekkonid genus Goniurosaurus is described from Cat Ba Island, Hai Phong, northern Vietnam. G. catbaensis sp. n. is, by its gracile body and limbs, the thin, posteriorly protracted nuchal loop, the three (or four) thin immaculate dorsal body bands between limb insertions, without dark spotting and with dark, narrow border surrounding the body bands, the lack of postrostral (internasal) scales, the presence of a greatly enlarged row of supraorbital tubercles, the outer surface of the upper eyelid being composed of granular scales of about the same size of those on top of head and with a longish row of 6–9 enlarged tubercles, granular body scales, with 8–11 granular scales surrounding the dorsal tubercles, deep axillary pockets, claws being sheathed by four scales, and 16–21 precloacal pores. The new taxon is known only from Cat Ba Island and is the eleventh Goniurosaurus species known and the fourth known species from Vietnam. We provide first data on its natural history and a key to the currently recognized Goniurosaurus species.

Groundwater Control in Complex Ground Conditions

Two fifteen metre diameter ten metre deep underground tanks were constructed immediately alongside each other by sinking bolted segmental caissons and casting the secondary lining in situ. Preliminary site investigation indicated difficult ground conditions with a high risk of base failure for excavation in the dry. Wet construction of the base slab would avoid base instability but not the problem of hydrostatic uplift of the partially completed structures.Further investigation revealed a complex sequence of interbedded sands, silts and clays of alluvial and glacial origins. The granular horizons comprised a small number of thicker continuous bands, one occurring immediately below the proposed formation levels for the tank floor slabs, and several thinner irregular bands grading laterally into silts and clays.Piezometers in the more critical granular horizons indicated artesian and sub-artesian groundwater levels. Temporarily disconnecting at ground level the piezometer showing artesian conditions and measuring the resulting water flow indicated a granular body of restricted size or limited recharge. The absence of any effect on other piezometers offered confirmation of isolated granular bodies.Despite obvious difficulties in predicting the effectiveness of a groundwater lowering installation the significant advantages of constructing in the dry over wet construction mitigated in favour of dewatering. Sixteen deep pumped wells were installed around the circumference of the tanks to form a figure of eight pattern for the wells. To reduce the risk of a base failure due to artesian groundwater in any lobes of granular material encroaching within the plan excavation but not intersected by the pumped wells, four internal relief wells per tank were installed.Successful construction was achieved, although a minor interruption to the pumping clearly demonstrated the prudence of the internal relief well installation.The paper comments on some aspects of BS 5930 in relation to the construction described.