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391.
A method for velocity estimation of sedimenting three-dimensional (3D) red blood cell (RBC) aggregates by means of an image processing technique is proposed. Successive images of RBC suspension near the wall of a container reveal rouleaux formation, sedimentation of 3D RBC aggregates and formation of the deposit of the cells. Plots of the position versus time for the 3D RBC aggregates were extracted by a processing of successive images of the suspension. The plots exhibit a quasi-linear structures in noisy background. With the use of the Hough transform the detection of the slope of the structures was performed and the velocity of the aggregates was estimated. To show the potential of the method spatio-temporal dependence of the aggregate velocity is presented for RBCs in plasma, RBCs in Dextran and for hardened cells at haematocrit 5%. 相似文献
392.
密度不同的颗粒在流体中的沉降特性 总被引:1,自引:0,他引:1
采用格子Boltzmann方法(LBM)对雷诺数范围为5≤Re≤12的双颗粒沉降进行了直接数值模拟研究,主要关注颗粒之间的密度差异k对其周期性振动的影响。根据雷诺数颗粒沉降特性可以分成三个阶段,即当Re较小时,颗粒的振动幅度随k的增大而减小,当Re较大时则正好相反,介于两者之间存在一个临界雷诺数,在此雷诺数附近,颗粒的沉降同时具有以上两种特征。同时还研究了两个颗粒的稳定沉降结构以及重颗粒摆脱轻颗粒的条件。 相似文献
393.
Alicja Ustrzycka Natalia Piotrowska Alicja Bonk Janusz Filipiak Wojciech Tylmann 《Isotopes in environmental and health studies》2018,54(3):225-243
An isotopic monitoring was undertaken in 2012–2014 at Lake ?abińskie (Mazurian Lakeland, NE Poland). The aim was to identify the factors and processes controlling an isotopic composition of the lake water and to explore the mechanism responsible for recording the climatic signal in stable isotope composition of deposited carbonates. δ18O and δ2H in the precipitation, lake water column, inflows and outflow, δ18O and δ13C in the carbonate fraction of sediments trapped in the water column were recorded with monthly resolution. A relationship between δ18O and δ2H in local precipitation was used to estimate the local meteoric water line. The dataset obtained for the water enabled to identify the modification of the water’s isotopic composition due to evaporation, connected with seasonal lake water stratification and mixing patterns. Statistically significant correlation coefficients suggest that the δ18O of the carbonate fraction in the sediment traps depends on the δ18O of rainfall water and on air temperature. The fractionation coefficient α shows that in summer months the carbonate precipitation process is closest to equilibrium. As expected for an exorheic lake, no significant correlation was observed between δ18O and δ13C in precipitated carbonate. 相似文献
394.
395.
《Particuology》2023
An efficient immersed boundary-lattice Boltzmann method (IB-LBM) is proposed for fully resolved simulations of suspended solid particles in viscoelastic flows. Stress LBM based on Giesekus and Oldroyd-B constitutive equation are used to model the viscoelastic stress tensor. A boundary thickening-based direct forcing IB method is adopted to solve the particle–fluid interactions with high accuracy for non-slip boundary conditions. A universal law is proposed to determine the diffusivity constant in a viscoelastic LBM model to balance the numerical accuracy and stability over a wide range of computational parameters. An asynchronous calculation strategy is adopted to further improve the computing efficiency. The method was firstly applicated to the simulation of sedimentation of a single particle and a pair of particles after good validations in cases of the flow past a fixed cylinder and particle migration in a Couette flow against FEM and FVM methods. The determination of the asynchronous calculation strategy and the effect of viscoelastic stress distribution on the settling behaviors of one and two particles are revealed. Subsequently, 504 particles settling in a closed cavity was simulated and the phenomenon that the viscoelastic stress stabilizing the Rayleigh–Taylor instabilities was observed. At last, simulations of a dense flow involving 11001 particles, the largest number of particles to date, were performed to investigate the instability behavior induced by elastic effect under hydrodynamic interactions in a viscoelastic fluid. The elasticity-induced ordering of the particle structures and fluid bubble structures in this dense flow is revealed for the first time. These simulations demonstrate the capability and prospects of the present method for aid in understanding the complex behaviors of viscoelastic particle suspensions. 相似文献