Discrete effects on boundary conditions of the lattice Boltzmann method for fluid flows with curved no-slip walls
PHYSICAL REVIEW E
Authors: Wang, Liang; Tao, Shi; Meng, Xuhui; Zhang, Kai; Lu, Gui
Abstract
The lattice Boltzmann method (LBM) has been formulated as a powerful numerical tool to simulate incompressible fluid flows. However, it is still a critical issue for the LBM to overcome the discrete effects on boundary conditions successfully for curved no-slip walls. In this paper, we focus on the discrete effects of curved boundary conditions within the framework of the multiple-relaxation-time (MRT) model. We analyze in detail a single-node curved boundary condition [Zhao et al., Multiscale Model. Simul. 17, 854 (2015)] for predicting the Poiseuille flow and derive the numerical slip at the boundary dependent on a free parameter as well as the distance ratio and the relaxation times. An approach by virtue of the free parameter is then proposed to eliminate the slip velocity while with uniform relaxation parameters. The theoretical analysis also indicates that for previous curved boundary schemes only with the distance ratio and the halfway bounce-back (HBB) boundary scheme, the numerical slip cannot be removed with uniform relaxation times virtually. We further carried out some simulations to validate our theoretical derivations, and the numerical results for the case of straight and curved boundaries confirm our theoretical analysis. Finally, for fluid flows with curved boundary geometries, resorting to more degrees of freedom from the boundary scheme may have more potential to eliminate the discrete effect at the boundary with uniform relaxation times.
The effect of hyoscine n- butylbromide on labor progress: A systematic review
BMC PREGNANCY AND CHILDBIRTH
Authors: Mohaghegh, Zaynab; Abedi, Parvin; Faal, Shahla; Jahanfar, Shayesteh; Surdock, Alayna; Sharifipour, Foruzan; Zahedian, Maryam
Abstract
Background The objective of this systematic review and meta-analysis was to assess the effectiveness of hyoscine n-butylbromide in labor progress. Methods The databases including PubMed, the Cochrane Library, Science-Direct, Scopus and Web of Science were searched for studies published up to December 2019. Articles that published as randomized controlled trials (RCTs), and full-text articles published in English or other languages were included and participants were primi or multigravida women who were in active phase of labor. The intervention included HBB compared to placebo (normal saline) that was used during active phase of labor. Pooled estimates were measured using the fixed or random effect model, while the overall effect was reported in a mean difference (MD). All data were analyzed using Review Manager 5.3. Results Twenty studies involving 3108 women were included in meta-analysis. Based on subgroup analysis by parity, use of HBB significantly reduced the duration of the first stage of labor in primigravida women (MD = - 57.73; 95% CI: [- 61.48, - 53.60]) and in multigravida women (MD = - 90.74; 95% CI: [- 97.24, - 84.24]). Administering HBB could reduce the second stages of labor in primigravidas and multigravidas about 6 min and 4 min respectively. Also, HBB reduced the duration of the third stage of labor in multigravidas about 3 min. APGAR score at one and 5 min after birth was not affected. The main maternal adverse effect was tachycardia and dry mouth. Labor duration in studies in which the participants were primi-and multigravida was not presented based on separate parities except for four papers, and the route of HBB administration was not the same across all studies. Conclusions Although, the effect of HBB was minimal when multigravidas and primigravidas women were considered together, the HBB was clinically effective in primigravida and multigravida women for shortening the first and the second stages of labor. Also, HBB could reduce the length of the third stage of labor in multigravidas.