Purpose The paper targets on providing new experimental data for validation of the well-established mathematical models within the framework of the lattice Boltzmann method (LBM), which are applied to problems of casting processes in complex mould cavities. Design/methodology/approach An experimental campaign aiming at the free-surface flow within a system of narrow channels is designed and executed under well-controlled laboratory conditions. An in-house lattice Boltzmann solver is implemented. Its algorithm is described in detail and its performance is tested thoroughly using both the newly recorded experimental data and well-known analytical benchmark tests. Findings The benchmark tests prove the ability of the implemented algorithm to provide a reliable solution when the surface tension effects become dominant. The convergence of the implemented method is assessed. The two new experimentally studied problems are resolved well by simulations using a coarse computational grid. Originality/value A detailed set of original experimental data for validation of computational schemes for simulations of free-surface gravity-driven flow within a system of narrow channels is presented.

PURPOSE OF THE STUDY Vertically unstable transforaminal sacral fractures can be stabilized with several types of transiliac internal fixators (TIFI): the classical one (TIFI-C), the supraacetabular one (TIFI-A) and by dual application of TIFI (DTIFI). MATERIAL AND METHODS Pelvic models made of solid foam (Sawbones 1301) were used in the study. Mechanical loading tests were performed in order to assess the stiffness of the studied pelvic structures. The stiffness of the intact model was approximated as the slope of load/displacement curve. Then vertically unstable right-sided linear transforaminal fracture was created and subsequently fixed by TIFI-C, TIFI-A and DTIFI (each fixator for a separate model). The fixation techniques were compared based on the ratio between the stiffness of the treated and of the intact pelvis. Motion of the posterior pelvic structures and their deformations were measured using a photogrammetric system with four synchronous cameras. Loads applied at the base of sacrum and sacral base displacements were recorded by the testing device and used to assess the stiffness of the model structure. A dedicated load cell and a monoaxial extensometer were utilised. Every measurement was repeated at least 10 times. Obtained data were analysed by one way ANOVA test with post hoc comparison by Tukey HSD test. RESULTS Mean stiffness ratio (±1SD) of pelvic structure was 0.638 ± 0.005 for TIFI-C, 0.722 ± 0.014 for TIFI-A and 0.720 ± 0.008 for DTIFI. Dual transiliac internal fixation and supraacetabular fixation were superior to the classical one (p < 0.0001), but DTIFI and TIFI-A stiffness ratios were statistically equivalent (p = 0.9112). CONCLUSIONS Results of the mechanical analysis using pelvic models indicate that for linear vertical transforaminal sacral fracture without comminuted zone, an application of either TIFI-A or DTIFI provides significantly higher stiffness of the lateral pelvic segment than application of TIFI-C. Key words: transforaminal sacral fracture, transiliac internal fixator, dual TIFI, stability, biomechanics, digital image correlation.

An experimental investigation of casting processes performed under well controlled laboratory conditions is presented. Casting molds made of transparent material allow for analysis of flow patterns by means of standard optical measurement methods. The tests are carried out for selected highly-viscous Newtonian fluids at room temperature. The physical properties of the test fluids (i.e. viscosity, surface tension and density) are identified. As a result, an extensive set of experimental data is provided.

Objective The aim of this study was to evaluate whether a previously identified modification of Viennese method of perineal protection remains most effective for reduction of perineal tension in cases with substantially smaller or larger fetal heads. Methods A previously designed finite element model was used to compare perineal tension of different modifications of the Viennese method of perineal protection to "hands-off" technique for three different sizes of the fetal head. Quantity and extent of tension throughout the perineal body during vaginal delivery at the time when the suboccipito-bregmatic circumference passes between the fourchette and the lower margin of the pubis was determined. Results The order of effectiveness of different modifications of manual perineal protection was similar for all three sizes of fetal head. The reduction of perineal tension was most significant in delivery simulations with larger heads. The final position of fingers 2cm anteriorly from the fourchette (y = +2) consistently remains most effective in reducing the tension. The extent of finger movement along the anterior-posterior (y-axis) contributes to the effectiveness of manual perineal protection. Conclusion Appropriately performed Viennese manual perineal protection seems to reduce the perineal tension regardless of the fetal head size, and thus the method seems to be applicable to reduce risk of perineal trauma for all parturients.

Comparison of the modifications of the Viennese method of manual perineal protection (VMPP) and hands-off delivery techniques by applying basic principles of mechanics with assessments of tensions within perineal structures using a novel biomechanical model of the perineum. Evaluation of the role of the precise placements of the accoucheur’s posterior (dominant) thumb and index finger in perineal tissue tension when performing a modified Viennese method of MPP.

The Finite Volume Particle Method (FVPM) is a meshless method based on a definition of interparticle area which is closely analogous to cell face area in the classical finite volume method. In previous work, the interparticle area has been computed by numerical integration, which is a source of error and is extremely expensive. We show that if the particle weight or kernel function is defined as a discontinuous top-hat function, the particle interaction vectors may be evaluated exactly and efficiently. The new formulation reduces overall computational time by a factor between 6.4 and 8.2. In numerical experiments on a viscous flow with an analytical solution, the method converges under all conditions. Significantly, in contrast with standard FVPM and SPH, error depends on particle size but not on particle overlap (as long as the computational domain is completely covered by particles). The new method is shown to be superior to standard FVPM for shock tube flow and inviscid steady transonic flow. In benchmarking on a viscous multiphase flow application, FVPM with exact interparticle area is shown to be competitive with a mesh-based volume-of-fluid solver in terms of computational time required to resolve the structure of an interface.

INTRODUCTION AND HYPOTHESIS:We compared hands-on manual perineal protection (MPP) and hands-off delivery techniques using the basic principles of mechanics and assessed the tension of perineal structures using a novel biomechanical model of the perineum. We also measured the effect of the thumb and index finger of the accoucheur's dominant-posterior hand on perineal tissue tension when a modified Viennese method of MPP is performed.METHODS:Hands-off and two variations of hands-on manual perineal protection during vaginal delivery were simulated using a biomechanical model, with the main outcome measure being strain/tension throughout the perineal body during vaginal delivery.RESULTS:Stress distribution with the hands-on model shows that when using MPP, the value of highest stress was decreased by 39 % (model B) and by 30 % (model C) compared with the hands-off model A. On the cross section there is a significant decrease in areas of equal tension throughout the perineal body in both hands-on models. Simulation of the modified Viennese MPP significantly reduces the maximum tension on the inner surface of the perineum measured at intervals of 2 mm from the posterior fourchette.CONCLUSIONS:In a biomechanical assessment with a finite element model of vaginal delivery, appropriate application of the thumb and index finger of the accoucheur's dominant-posterior hand to the surface of the perineum during the second stage of delivery significantly reduces tissue tension throughout the entire thickness of the perineum; thus, this intervention might help reduce obstetric perineal trauma.

In this paper are presented comparisons of SPH variants on academic test cases classically used to validate numerical fluid dynamics software. These comparisons are extracted from NextMuSE FP7 project activities which will be published more extensively in the near future. One of the goals of this project was to better understand the SPH method and to leave the path to its establishment within CFD methods. An important work load was thus dedicated to benchmark SPH variants on selected test cases.A number of results and conclusions of this comparative study are presented in this paper. The studied variants are: standard weekly-compressible SPH, delta-SPH, Riemann-SPH, incompressible SPH, and FVPM. The majority of the test cases also present a reference solution, either experimental or computed using a mesh-based solver. Test cases include: wave propagation, flow past a cylinder, jet impact, floating body, bubble rise, dam break on obstacle, floating body dynamics, etc. Conclusions may help SPH practitioners to choose one variant or another and shall give detailed understanding necessary to derive further improvements of the method.

OBJECTIVE:To analyze deformation of the perineum during normal vaginal delivery in order to identify clinical steps that might be beneficial when executing manual perineal protection. METHODS:The present prospective study at Charles University Hospital, Pilsen, Czech Republic, enrolled 10 primiparous women at term undergoing non-instrumental vaginal delivery assisted by the same obstetrician between September 2009 and September 2010. A modified hands-poised technique performed concurrently with stereophotogrammetry was used to analyze and quantify perineal deformation and strain at the final stage of delivery. RESULTS:The highest tissue strain (mean, 177%; 95% confidence interval [CI], 106.3-248.5) was in a transverse direction and occurred at the level of the fourchette (i.e. 1cm was transversely stretched and deformed to 2.77 cm during the final stage of vaginal delivery). This strain was more than 4 times higher than the maximum anteroposterior strain (mean, 43%; 95% CI, 28.6-57.4). CONCLUSION:On the basis of these stereophotogrammetry data, a technique of perineal protection executed by fingers of the posterior (right) hand can be proposed. Further experimental and clinical studies are needed to evaluate whether this technique might assist in reducing obstetric perineal trauma.

Bileaflet mechanical heart valves (MHVs) are one of the most widely used aortic valve replacements. Despite experimental advances in understanding MHV fluid dynamics, computational modelling has had little, if any, impact on MHV design to date. This is in part a result of the difficulty of modelling MHV flow by conventional (mesh-based) methods, which become cumbersome when modelling a flow domain which changes geometrically and topologically as the MHV leaflets move. These problems may be avoided by novel but maturing mesh-free particle methods. In the following, MHV flow is simulated by means of the mesh-free finite volume particle method (FVPM).

We describe the development of a highly interactive approach to simulation of engineering multi-mechanics problems, using the smoothed particle hydrodynamics mesh-free method as the computational engine, for applications including ship survival, medical devices and Pelton turbines.

Objective: To assess the relevance of the suture angle when evaluating mediolateral episiotomy, and the safety of the accepted lower limit of 40 degrees for the incision angle. Method: The angles formed by the incision and suture lines with the midline were measured, and any perineal tear noted, in 50 consecutive women undergoing their first vaginal delivery. Results: The angles were significantly different (40 degrees and 22.5 degrees, respectively; P < 0.001). The only variable significantly Linked to the difference was the timing of the episiotomy. Conclusion: The suture angle cannot currently be used to assess the adequacy of the incision angle; moreover, an incision angle of 40 degrees is probably too acute to prevent potential sphincter damage. (c) 2008 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

Fundamentals of two different numerical approaches to the fluid flow modelling are presented. The smoothed particle hydrodynamics (SPH) is a meshless approach, while the finite volume (FV) method is defined on a grid. Within SPH, the computational grid is replaced by a finite set of interpolating points. The fluid flow is described by Euler equations and dissipative effects are treated by artificial viscosity terms. Within the cell-centred FV method, the computational domain is discretised with a structured grid and the fluid flow is defined by a non-linear conservative system of the Navier–Stokes equations. The artificial dissipation and the algebraic turbulence model are applied. Implemented SPH and FV codes are tested on a two-dimensional flow of Newtonian fluid through a rigid channel.