Dynamic Boundary Treatment Research Articles

Numerical analysis of 3-D inner flow field for ladder-shaped multiple propellant rocket motor

In order to study the characteristics of ladder-shaped multiple propellant rocket motor, it was conducted that the numerical simulation of the full 3-D inner flow field for ladder-shaped multiple propellant rocket motor working process using FLUENT calculation software. The secondary development was carried out through UDF interface programming, and the changing rules of the added mass in propellant burning surface and dynamic boundary with the burning rate were set, so that the dynamic process of propellant combustion is accurately simulated. The numerical simulation results demonstrated the spatial distribution information of parameters, such as pressure and flow rate at each moment in the inner flow field, and the pressure-time curves of three monitoring points in front, center and rear of the combustion chamber. Then, several key characteristic moments were selected for specific analysis, and the pressure-time curve of the monitoring point was compared with the experimental data to show that the calculated results were basically accurate. The pressure, flow rate and the pressure difference between the internal and external surfaces of the propellant in the rocket motor inner flow field were analyzed. At present, the dynamic boundary treatment method that the burning rate of the propellant varies regularly with the surface pressure has not been applied in the 3-D calculation model. The research results of this paper can provide reference for the numerical simulation of similar structure of solid rocket motors.

Numerical simulation of column charge explosive in rock masses with particle flow code

The detonation of a column charge and the damage process in a rock mass are simulated in this study by the particle flow code method. The expansion loading method and the dynamic boundary treatment method are established according to the discrete element mechanism. Mechanical parameters are calibrated on the basis of the Starfield superposition principle and the dynamic compensation method. Dynamic stiffness and microscopic parameters are used for numerical simulations. Numerical test results are consistent with lab experimental test results. The velocity attenuation law is compared with that of theoretical results, and the blasting crater action index is compared with that of field test results, to verify the rationality of the numerical explosion model of the column charge. The mechanism of the rock breaking process under column charge explosion is analyzed. Stress wave propagation, detonation wave propagation, and crack extension are investigated. The stress wave gradient law is obtained, and the effects of blasting rock breaking, crack extension, and explosion effect outside the blasting crater area are determined with different initiation modes. The research method can explain the blasting stress wave propagation law and describe the dynamical failure process in rock masses. This study can provide a reliable numerical analysis method for follow-up blasting research and offer practical guidance on engineering blasting.

An improved SPH model for multiphase flows with large density ratios

SummaryThis paper presents a new smoothed particle hydrodynamics (SPH) model for simulating multiphase fluid flows with large density ratios. The new SPH model consists of an improved discretization scheme, an enhanced multiphase interface treatment algorithm, and a coupled dynamic boundary treatment technique. The presented SPH discretization scheme is developed from Taylor series analysis with kernel normalization and kernel gradient correction and is then used to discretize the Navier‐Stokes equation to obtain improved SPH equations of motion for multiphase fluid flows. The multiphase interface treatment algorithm involves treating neighboring particles from different phases as virtual particles with specially updated density to maintain pressure consistency and a repulsive interface force between neighboring interface particles into the pressure gradient to keep sharp interface. The coupled dynamic boundary treatment technique includes a soft repulsive force between approaching fluid and solid particles while the information of virtual particles are approximated using the improved SPH discretization scheme. The presented SPH model is applied to 3 typical multiphase flow problems including dam breaking, Rayleigh‐Taylor instability, and air bubble rising in water. It is demonstrated that inherent multiphase flow physics can be well captured while the dynamic evolution of the complex multiphase interfaces is sharp with consistent pressure across the interfaces.