Three-Dimensional Numerical Simulation of Dry Spinning

Three-dimensional particle-resolved direct numerical simulation study of behaviors of a particle settling near a vertical wall

Numerical simulations of cardiac blood pump systems are integral to the optimization of device design, hydraulic performance and hemocompatibility. In wave membrane blood pumps, blood propulsion arises from the wave propagation along an oscillating immersed membrane, which generates small pockets of fluid that are pushed towards the outlet against an adverse pressure gradient. We studied the Fluid-Structure Interaction between the oscillating membrane and the blood flow via three-dimensional simulations using the Extended Finite Element Method (XFEM), an unfitted numerical technique that avoids remeshing by using a fluid fixed mesh. Our three-dimensional numerical simulations in a realistic pump geometry highlighted, for the first time in this field of application, that XFEM is a reliable strategy to handle complex industrial problems. Moreover, they showed the role of the membrane deformation in promoting a blood flow towards the outlet despite an adverse pressure gradient. We also simulated the pump system at different pressure conditions and we validated the numerical results against in-vitro experimental data.

We perform fully general relativistic simulations of rotating stellar core collapse in three spatial dimensions. The hydrodynamic equations are solved using a high-resolution shock-capturing scheme. A parametric equation of state is adopted to model collapsing stellar cores and neutron stars following Dimmelmeier et al. The early stage of the collapse is followed by an axisymmetric code. When the stellar core becomes compact enough, we start a three-dimensional simulation adding a bar-mode nonaxisymmetric density perturbation. The axisymmetric simulations are performed for a wide variety of initial conditions changing the rotational velocity profile, parameters of the equations of state, and the total mass. It is clarified that the maximum density, the maximum value of the compactness, and the maximum value of the ratio of the kinetic energy $T$ to the gravitational potential energy $W$ ($\ensuremath{\beta}\ensuremath{\equiv}T/W$) achieved during the stellar collapse and bounce depend sensitively on the velocity profile and the total mass of the initial core and equations of state. It is also found that for all the models with a high degree of differential rotation, a funnel structure is formed around the rotational axis after the formation of neutron stars. For selected models in which the maximum value of $\ensuremath{\beta}$ is larger than $\ensuremath{\sim}0.27$, three-dimensional numerical simulations are performed. It is found that the bar-mode dynamical instability sets in for the case that the following conditions are satisfied: (i) the progenitor of the stellar core collapse should be rapidly rotating with the initial value of $0.01\ensuremath{\lesssim}\ensuremath{\beta}\ensuremath{\lesssim}0.02$, (ii) the degree of differential rotation for the velocity profile of the initial condition should be sufficiently high, and (iii) a depletion factor of pressure in an early stage of collapse should be large enough to induce a significant contraction to form a compact stellar core for which an efficient spin-up can be achieved surmounting the strong centrifugal force. As a result of the onset of the bar-mode dynamical instabilities, the amplitude of gravitational waves can be by a factor of $\ensuremath{\sim}10$ larger than that in the axisymmetric collapse. It is found that a dynamical instability with the $m=1$ mode is also induced for the dynamically unstable cases against the bar mode, but the perturbation does not grow significantly and, hence, it does not contribute to an outstanding amplification of gravitational waves. No evidence for fragmentation of the protoneutron stars is found in the first few 10 msec after the bounce.

Numerical modeling of shrinkage induced cracking in cementitious materials with three-dimensional simulation and phase-field method

A set of complete two- and three-dimensional direct numerical simulations (DNS) in a differentially heated air-filled cavity of aspect ratio 4 with adiabatic horizontal walls is presented in this paper. Although the physical phenomenon is three-dimensional, owing to its prohibitive computational costs the majority of the previous DNS of turbulent and transition natural convection flows in enclosed cavities assumed a two-dimensional behaviour. The configurations selected here (Rayleigh number based on the cavity height 6.4 × 108, 2 × 109 and 1010, Pr = 0.71) are an extension to three dimensions of previous two-dimensional problems.An overview of the numerical algorithm and the methodology used to verify the code and the simulations is presented. The main features of the flow, including the time-averaged flow structure, the power spectra and probability density distributions of a set of selected monitoring points, the turbulent statistics, the global kinetic energy balances and the internal waves motion phenomenon are described and discussed.As expected, significant differences are observed between two- and three-dimensional results. For two-dimensional simulations the oscillations at the downstream part of the vertical boundary layer are clearly stronger, ejecting large eddies to the cavity core. In the three-dimensional simulations these large eddies do not persist and their energy is rapidly passed down to smaller scales of motion. It yields on a reduction of the large-scale mixing effect at the hot upper and cold lower regions and consequently the cavity core still remains almost motionless even for the highest Rayleigh number. The boundary layers remain laminar in their upstream parts up to the point where these eddies are ejected. The point where this phenomenon occurs clearly moves upstream for the three-dimensional simulations. It is also shown that, even for the three-dimensional simulations, these eddies are large enough to permanently excite an internal wave motion in the stratified core region. All these differences become more marked for the highest Rayleigh number.

The generation of radio frequency thermal plasma contains rich and complex physical field distribution. Correct understanding of these physical field distribution has a guiding role in the application of radio frequency thermal plasma in the industrial field. Radio frequency (RF) thermal plasma technology can be widely used in the industrial field. To obtain more accurate information of the plasma physical field, a three-dimensional numerical simulation was used to study the distribution of the RF thermal plasma physical field. The mathematical model of plasma was established based on three-dimensional numerical simulation. The electromagnetic field equation was set. The relationship between electric field and magnetic induction was obtained. The thermodynamic equation of the plasma physical field was obtained, and the inlet and outlet boundary conditions were set. A plasma physical field distribution simulation algorithm is designed to obtain a physical field simulation distribution result. In the simulation analysis, the voltage, current and electron temperature are simulated and analyzed respectively. The experimental results verify that when the pressure increases, the current and voltage show a certain downward trend, and when the discharge power increases, the current and voltage show a synchronous increasing trend. The electron temperatures at 100 Pa and 205 Pa are between 1.07-1.10 and 1.04-1.07, respectively. The difference between the simulated electron density and the actual electron density is less than 1 × 1019, which indicates that the method has high accuracy. The physical field distribution simulation method provides technical support for the practical application of the plasma in the radio frequency heat, and has great application value. Besides, The research results have important guiding significance for optimizing and controlling the practical application process of RF thermal plasma.

Evaluation of the diffusion coefficient of cement paste from pore size distribution using three-dimensional simulation

Three-dimensional experiment and numerical simulation of the discharge performance of sluice passageway for tidal power plant

We carried out a comparative study of electrical injection in longitudinal p-i-n and coaxial p-n core-shell nanowires by performing a three-dimensional numerical simulation. In the case of the core-shell structure, we show that both electrons and holes of high density can be efficiently injected into and confined in the structure even without an i-region. The required bias voltage and doping concentrations in the core-shell structure are smaller than those in the longitudinal p-i-n structure to achieve the same carrier injection level. Furthermore, we show that a type-I band alignment, as required in traditional p-i-n structure is not necessary in core-shell structure, allowing more flexibility in nanowire devices design. Our results thus provide a theoretical foundation and understanding that a core-shell structure is far superior to the longitudinal p-i-n structure for electrical injection nanowire lasers.

Novel three-dimensional simplified numerical simulation method of a compact precooler for hypersonic precooled air-breathing engine

A true mechanistic pavement design procedure should be able to correctly predict pavement response and the development of pavement distress (such as rutting and fatigue cracking) under various traffic and environmental conditions. A three-dimensional (3-D) numerical simulation procedure with realistic material models would be an effective tool that could be used to achieve such an objective. The results of a 3-D numerical simulation at the Louisiana Accelerated Loading Facility are presented. A 3-D finite-element procedure with moving wheel loads was developed for such analyses. Rate-dependent viscoplastic models were incorporated into the 3-D finite-element procedure. A creep model was used to predict rutting of the asphalt pavement. The results indicated that the 3-D finite-element procedure with viscoplastic models is capable of reflecting the pavement responses and predicting pavement rutting with reasonable accuracy.

Vortex-induced vibration (VIV) of an elastically mounted rigid circular cylinder in an oscillatory flow is investigated by three-dimensional direct numerical simulations (DNS). The cylinder...

Three-dimensional numerical simulation of oscillatory flow around a circular cylinder at right and oblique attacks

Based on the detailed analysis of site engineering geological and hydro-geological conditions for the proposed project Nanchang International Finance Center high-rise building, the dewatering design of this fundamental pit is proposed， in accordance with the surrounding environment as well as those pit design elements and so on. The three-dimensional numerical simulation model of groundwater for dewatering is also established. Using the three-dimensional groundwater numerical simulation software, Visual-modflow, the site is meshed into grid and the dewatering model is built under different well numbers and space. Al last, an optimal program (10 pumping wells for each pit and well equaling space) for this pit has been determined. It is also to simulate the water level vs. time during the dewatering. This does not only provide a strong basis for the optimum design of the foundation pit dewatering, but also provide a scientific basis for decision making to the underground construction.

Two- versus three-dimensional direct simulations of turbulent methane flame kernels using realistic chemistry