arXiv subjects

Baolin Tian

Publications and source records attributed to Baolin Tian.

6 recordsLinked to original sources

arXiv2026

High-order gas-kinetic scheme for numerical simulations of wind turbine with nacelle and tower using ALM and IBM

For the first time, the actuator line model (ALM) and the immersed boundary method (IBM) are integrated into the high-order gas-kinetic scheme (GKS) to simulate the wind turbine with the nacelle and tower. The high-order GKS is extended to the simulation of three-dimensional weakly compressible isothermal flows within a well-developed two-stage fourth-order framework. For the wind turbine, the rotor blades are represented by a group of actuator points in ALM, and the nacelle and tower are represented by a group of Lagrangian points in IBM. Both ALM and IBM are integrated through an external body force added in the momentum equation within the high-order GKS. The high-order GKS is implemented on Graphics Processing Units (GPU) to achieve the parallel computing capabilities for the large-scale simulation of turbulent wakes. Turbulent channel flow and turbulent circular cylinder flow are firstly simulated to validate the numerical accuracy of weakly compressible high-order GKS. The NREL 5 MW reference wind turbine is simulated using ALM without the nacelle and tower. Furthermore, the NTNU Blind Test 1 wind turbine is simulated with nacelle and tower using IBM. The current method yields the periodic power and thrust coefficients of the rotor blade due to the blade-tower interactions, while the steady coefficients are obtained when the tower is omitted. Compared to the turbine wakes without the tower, the interaction between tower vortex and tip vortex causes an earlier transition. The high-order GKS with ALM and IBM also well predicts the asymmetric mean flows of turbine wake, including the time-averaged streamwise velocity and turbulent kinetic energy, which are in good agreement with NTNU experimental data. The multiple-GPU enabled high-order GKS integrated with ALM and IBM offers an accurate and efficient approach for realistic wind turbine simulations.

physics.flu-dyn↗

arXiv2025

Formation of external particle jets on a spherical particle bed subjected to strong explosive loading

We report the mechanism for the formation of external particle jets on a spherical particle bed subjected to strong explosive loading, revealing a critical dependence on particle size. Under strong explosive loading, the formation of external particle jets is primarily driven by a drag-coupled mechanism. We conducted Eulerian-Lagrangian simulations, with up to $2048^3$ effective cells and $1.8$ million tracked parcels on an adaptive mesh, for both small- and large-particle cases. Pronounced jets are observed only with small particles, alongside accelerated bed thickening. By defining characteristic inner and outer radii, the particle bed thickness evolution is quantified, showing an initial linear growth followed by a nonlinear deceleration. Particle dynamics analysis indicates that drag force dominates particle motion and jet formation during the nonlinear stage. The initial angular non-uniformity of the particle bed induces a non-uniform gas radial velocity. Through drag coupling, this flow asymmetry generates a radial velocity difference in small particles, thereby promoting pronounced jet formation, whereas large particles resist this drag-induced effect. The greater drag-induced deceleration on smaller particles leads to an increased velocity difference across the particle bed, explaining the accelerated thickening. A characteristic radius model that integrates the Gurney model for the linear stage with a drag-dominated deceleration model for the nonlinear stage is established and shows good agreement with numerical results across different particle sizes.

physics.flu-dyn↗

arXiv2025

A high-fidelity and efficient framework for point-particle direct numerical simulation based on multi-block overset grids

In this work, we present a high-fidelity and efficient point-particle direct numerical simulation framework based on a multi-block overset curvilinear grid system, enabling large-scale Lagrangian particle tracking in complex geometries with high-order accuracy and low computational cost. To handle the multi-domain topological challenges inherent in such configurations, we develop an efficient particle storage and redistribution framework leveraging overset grid techniques. In particular, two optimization strategies have been proposed for particle redistribution: one is an innovative inter-block mapping within overlapping zones, and the other is a fast search-locate algorithm based on particle velocity. Together, these approaches significantly reduce the particle tracking overhead, especially for particles passing through interfaces between overlapping grid blocks. Moreover, the accuracy and robustness of the present framework are rigorously validated through various cases, including massless particle trajectories, one- and two-way coupled simulations. Specifically, we demonstrate the framework's applicability to the direct numerical simulation of particle-laden flow in a linear compressor cascade at engine-relevant conditions, showcasing its capability to resolve complex particle dynamics in turbomachinery configurations with low computational costs.

physics.flu-dyn↗

arXiv2021

On the supremum of the steepness parameter in self-adjusting steepness based schemes

Self-adjusting steepness (SAS)-based schemes preserve various structures in the compressible flows. These schemes provide a range of desired behaviors depending on the steepness-adjustable limiters with the steepness measured by a steepness parameter. These properties include either high-order properties with exact steepness parameter values that are theoretically determined or having anti-diffusive/compression properties with a larger steepness parameter. Nevertheless, the supremum of the steepness parameter has not been determined theoretically yet. In this study, we derive a universal method to determine the supremum using total variation diminishing (TVD) condition of Sewby. Two typical steepness-adjustable limiters are analyzed in detail including the tangent of hyperbola for interface capturing (THINC) limiter and the steepness-adjustable harmonic (SAH) limiter. We also obtain the analytical expression of the supremum of the steepness parameter which is dependent on the Courant-Friedrichs-Lewy (CFL) number. Using this solution, we then propose supremum-determined SAS schemes. These schemes are further extended to solve the compressible Euler equations. The results of typical numerical tests confirm our theoretical conclusions and show that the final schemes are capable of sharply capturing contact discontinuities and minimizing numerical oscillations.

physics.flu-dyn↗

arXiv2017

Consistent implementation of characteristic flux-split based finite difference method for compressible multi-material flows

In order to prevent velocity, pressure, and temperature spikes at material discontinuities occurring when the interface-capturing schemes inconsistently simulate compressible multi-material flows(when the specific heats ratio is variable),various non-conservative or quasi-conservative numerical models have been proposed. However, designing a consistent numerical algorithm, especially using the high-order characteristic flux-split based finite-difference method (CFS-FDM) is still an open question. In this study, a systematical analysis of previous algorithms of the consistent implementing the high-order CFS-FDM for such flows is performed, and the reasons of special treatments in these algorithms are revealed. Based on this analysis, a new general numerical methodology that successfully avoids any special treatments as those required in previously reported algorithms, is derived. In this new algorithm, we rewrite the non-conservative term as a conservative term with a source term containing velocity divergence. By consistently treating the advection velocity in the conservative term and velocity divergence in the source term by imposing a new additional criterion, specifically, that a multi-fluid algorithm should have the ability of maintaining a pure single-fluid, we finally derive a new general algorithm that does not need any special treatment, and is very convenient to implement. The results of some benchmark tests show that the final algorithm not only maintains the velocity, pressure, and temperature equlibria, but is also suitable for problems regarding the interaction of interfaces and strong shock and rarefaction waves.

physics.comp-ph↗

arXiv2017

A Third-Order Moving Mesh Cell-Centered Scheme for One-Dimensional Elastic-Plastic Flows

A third-order moving mesh cell-centered scheme without the remapping of physical variables is developed for the numerical solution of one-dimensional elastic-plastic flows with the Mie-Gr\"{u}neisen equation of state, the Wilkins constitutive model, and the von Mises yielding criterion. The scheme combines the Lagrangian method with the MMPDE moving mesh method and adaptively moves the mesh to better resolve shock and other types of waves while preventing the mesh from crossing and tangling. It can be viewed as a direct arbitrarily Lagrangian-Eulerian method but can also be degenerated to a purely Lagrangian scheme. It treats the relative velocity of the fluid with respect to the mesh as constant in time between time steps, which allows high-order approximation of free boundaries. A time dependent scaling is used in the monitor function to avoid possible sudden movement of the mesh points due to the creation or diminishing of shock and rarefaction waves or the steepening of those waves. A two-rarefaction Riemann solver with elastic waves is employed to compute the Godunov values of the density, pressure, velocity, and deviatoric stress at cell interfaces. Numerical results are presented for three examples. The third-order convergence of the scheme and its ability to concentrate mesh points around shock and elastic rarefaction waves are demonstrated. The obtained numerical results are in good agreement with those in literature. The new scheme is also shown to be more accurate in resolving shock and rarefaction waves than an existing third-order cell-centered Lagrangian scheme.

math.NA↗