arXiv subjects

Mingbo Sun

Publications and source records attributed to Mingbo Sun.

4 recordsLinked to original sources

arXiv2026

An Oscillation-Free Real Fluid Quasi-Conservative Finite Volume Method for Transcritical and Phase-Change Flows

A new Real Fluid Quasi-Conservative (RFQC) finite volume method is developed to address the numerical simulation of real fluids involving shock waves in transcritical and phase-change flows. To eliminate the spurious pressure oscillations inherent in fully conservative schemes, we extend the classic quasi-conservative method, originally designed for two-phase flows, to real fluids governed by arbitrary equations of state (EoS). The RFQC method locally linearizes the real fluid EoS at each grid point and time step, constructing and evolving the frozen Gr\"uneisen coefficient $\Gamma$ and the linearization remainder $E_0$ via two advection equations. At the end of each time step, the evolved $\Gamma$ and $E_0$ are utilized to reconstruct the oscillation-free pressure field, followed by a thermodynamic re-projection applied to the conserved variables. Theoretical analysis demonstrates that, in smooth regions, the energy conservation error introduced by the RFQC method is a second-order small term dominated by the time-step. In discontinuous regions, this error is determined by the entropy increase rate, thereby maintaining consistency with the inherent truncation error of shock-capturing methods. A series of numerical tests verifies that the method can robustly simulate complex flow processes with only minor energy conservation errors, including transcritical flows, phase transitions, and shock-interface interactions. The RFQC method is proven to be both accurate and robust in capturing shock waves and phase transitions.

physics.comp-ph↗

arXiv2026

Flash evaporation Riemann Problem: Formulation and its Exact Solution

Flash evaporation, a liquid-to-gas phase transition phenomenon in real fluids, is prevalent in aerospace propulsion systems. To elucidate the physical mechanisms of such complex flows and provide theoretical benchmarks for Computational Fluid Dynamics simulations, this paper formalizes the Flash evaporation Riemann problem (FeRP) characterized by the expansion branch crossing the saturation line, within the framework of Homogeneous Equilibrium and Vapor-Liquid Equilibrium assumptions. An exact solution framework that analytically resolves all thermodynamic derivatives of equilibrium two-phase fluids is established for arbitrary two-parameter equations of state. By evaluating the Landau fundamental derivative, the non-classical wave structures arising in the FeRP are analyzed, for which a stable iterative solution strategy incorporating the Chapman-Jouguet condition as an outer constraint is proposed. Furthermore, an exact solution for the FeRP based on Wood's mechanical equilibrium speed of sound is developed, enabling a comprehensive evaluation of its thermodynamic implications. Results indicate that Wood's model alters the definition of the two-phase mixture entropy in the Euler equations, introducing an isentropic path characterized by a "density lag" effect and non-physical entropy decrease. Comparative analysis of the FeRP under typical scramjet fuel injection conditions reveals that, although Wood's model captures the general trend of the Riemann solution curve, it significantly underestimates intermediate pressure, velocity, and the extent of vaporization relative to the complete equilibrium model.

physics.flu-dyn↗

arXiv2019

Lattice Boltzmann simulations of the pool boiling curves above horizontal heaters with homogenous and heterogeneous wettability

A hybrid thermal lattice Boltzmann phase-change model was performed to simulate the pool boiling above a smooth horizontal heater. The effects of homogenous and heterogeneous wettability on entire boiling curves from the onset of nucleate boiling (ONB) to fully developed film boiling were investigated comprehensively. Results show that concerning the homogeneous and hydrophilic heater, increasing the wall wettability results in a high critical heat flux (CHF) and yields a rightward and upward shift of the boiling curve. It is also found that decreasing the wettability promotes the occurrence of ONB at a lower overheat, but it also makes the boiling process move into a film boiling regime with a lower degree of wall superheat. Regarding the homogeneous and hydrophobic heater, there are quite lower CHF and shorter transition boiling regime, whereas the CHF point and film boiling occur at a lower wall superheat. For the heterogeneous and hydrophilic heater, increasing the difference of wettability yields a leftward shift of the boiling curve. Furthermore, the effects of surface wettability and the width between two hydrophilic-hydrophobic mixed surface on boiling curves were studied, which indicated that decreasing the wettability of the hydrophobic surface produces an upward shift of boiling curve and decreasing the width generates a leftward and upward shift of the nucleate boiling pattern. Moreover, the enhancement of boiling heat transfer in terms of hydrophilic-hydrophobic mixed surfaces was also quantitively verified.

physics.flu-dyn↗

arXiv2019

Hybrid phase-change lattice Boltzmann simulation of the bubble nucleation and different boiling regimes of conjugate boiling heat transfer

Pool boiling characteristics in two computational domains with and without considering conjugate heat transfer (CHT) were numerically simulated by an improved hybrid pseudopotential phase-change lattice Boltzmann method (LBM). The effects of constant temperature boundary condition (BC) with nucleate spots and fluctuant temperature on the boiling process were investigated in detail. It was found that for the computational domain without CHT, the treatment of constant temperature BC with nucleate spots is quite easier to produce film boiling than the temperature BC with small fluctuation. However, the results would be the opposite for the case with CHT. The entire boiling curve from the onset of nucleate boiling to fully developed film boiling was presented using the computational domain considering CHT and constant temperature BC with nucleate spots. The simulated critical heat flux showed an excellent agreement with the existing analytical solutions. Hence, the current hybrid phase-change LBM was quantitatively verified. The highly fluctuant heat flux occurred in the CHF and transition boiling as well as the transverse movement of the bubbles had been observed. Furthermore, the thermal responses inside the heater and heat transfer mechanism in different boiling patterns were also comprehensively studied.

physics.flu-dyn↗