Number Kn Research Articles

Computational investigation of aspect ratio and inclination effects on natural convection heat transfer in nanofluid-filled rough wall cavities

Numerical analysis is performed to deduce the effect of aspect ratio (AR) and inclination of a rough-walled cavity on heat transfer, fluid flow, and entropy generation due to natural convection for Rayleigh number (Ra = 105). The cavity is filled with Al2O3-water nanofluid of 0.05 solid volume fraction. The natural convection process is caused by the temperature difference between the left hot wall and the right cold wall of the cavity. The walls are subjected to slip boundary conditions and the slip velocity is characterized by the Knudsen number (Kn = 0.5). The profile of the rough surface is generated by Weierstrass-Mandelbrot (W-M) function. Numerical simulations have been performed using Finite Element based software COMSOL Multiphysics 6.0. The AR is varied in the range of 0.5 to 4, and the inclination of the cavity is kept at 0°, 30°, and 60°. The numerical results are exhibited in terms of isotherms, streamlines, entropy generation due to heat transfer, and fluid friction irreversibilities. It is observed that the slip velocity on the walls has a strong influence on the fluid flow. Entropy generation due to fluid friction is found to increase with the rise in AR up to 2 and then it starts declining. The entropy generation due to fluid friction irreversibility at the center of the cavity is minimal, so the Bejan number is close to unity. Cavity with an inclination of 30° gives the maximum Nusselt number at any value of AR. Notably, the total entropy generation is observed to reach its maximum at α = 60° and minimum at α = 30°, offering comprehensive insights into the interplay of geometric and flow parameters within the cavity.

A normal-mode approach for high-speed rarefied plane Couette flow

Based on gas kinetic theory, a linear stability analysis method for low-speed rarefied flows was developed by Zou et al. [“A new linear stability analysis approach for microchannel flow based on the Boltzmann Bhatnagar–Gross–Krook equation,” Phys. Fluids 34, 124114 (2022) and “A novel linear stability analysis method for plane Couette flow considering rarefaction effects,” J. Fluid Mech. 963, A33 (2023)]. In the present study, we extended the method to high-speed rarefied flows using the Bhatnagar–Gross–Krook model. The Chebyshev spectral method is employed to discretize physical space, and the Gauss–Hermite and fourth-order Newton–Cotes quadrature methods are used to discretize velocity space. The fourth-order Newton–Cotes quadrature method was found to have sufficient accuracy for the stability analysis, laying the foundation for future research on hypersonic flows. The stability analysis of compressible rarefied Couette flow showed that acoustic modes are reflected between the wall and the relative sonic line, and the variation in their phase speed and growth rate with the wavenumber is not affected by the Mach number (Ma) and the Knudsen number (Kn). Increasing Kn has a stabilizing effect on both the acoustic and viscous modes, but as Ma increases, the attenuation rate of each mode's growth rate gradually decreases. In subsonic and sonic flows, the least stable viscous mode dominates in the case of small numbers. As Kn increases, the viscous mode gradually dominates over all wavenumber ranges considered in subsonic flow. In sonic flow, mode 1 is dominant in the region beyond the range of small wavenumbers. In supersonic flow, mode 2 is the least stable in the large wavenumber ranges, while mode 1 is the least stable in other wavenumber ranges. At a fixed wavenumber, as Kn increases, the decay rate of the growth rate of mode 2 is the highest. Additionally, under different Knudsen numbers, the growth rates of mode 1, mode 2, and the least stable viscous mode monotonically increase with an increase in Ma, with mode 2 showing the most significant increase.

Numerical Analysis of Rarefied Gas Flow through a System of Short Channels

The S-model kinetic equation is used to study the rarefied gas flow from a high-pressure tank to a low-pressure one through a flat membrane with a finite number of pores. The kinetic equation is solved numerically using a second-order accurate implicit conservative method implemented in the in-house code Nesvetay. For transitional and continuum flow regimes, numerical solutions of the compressible Navier–Stokes equations are obtained. The gas flow rate through the system of pores and the forces acting on the membrane bars are investigated as functions of the Knudsen number (Kn) at a pressure ratio of 2 : 1 in the tanks. The features of the flow field near the membrane and away from it are described.

Significance of Upstream Wall Conditions in Characterizing the Heat Transfer Phenomena of Rarefied Flows

Abstract Slip flows in small-scale flow networks involve simultaneous presence of multiple factors governing the flow field. In addition, conditions of upstream wall need to be clearly defined for quantifying the total heat that fluid receives from the wall. The present work addresses these aspects by analyzing the heat transfer aspects of slip flow of gaseous nitrogen through a circular pipe, undergoing either heating or cooling. The complete form of the governing equations is solved numerically while retaining property variation. The thermal field is found to exhibit two distinct asymptotic regions, with the first one representing fully developed heat transfer and the second one representing isothermal states. The fully developed Nusselt number (Nufd) is found to rise first, before dropping continuously with rise in Knudsen number (Kn). The pair of Kn and maximum Nufd is found to be dependent on Peclet number (Pe) of the system. Local Nu is found to drop to a minimum, lower than Nufd for Kn∼O(10−3) due to a significant radial advection. The presence of an adiabatic upstream wall reveals that heat may propagate up to the inlet for Kn≳0.015. An analytical solution is developed to approximate this limiting value of Kn, and it agrees well with the numerical results. The observed flow behavior leads to the categorization of flow regime into three types: (i) Kn<0.001, possessing dependence on change in Pe only, (ii) 0.001≤Kn<0.01, possessing concurrence of effects due to change in Pe and Kn, and (iii) 0.01≤Kn<0.1, possessing dependence on change in Kn only. Further, Pe is shown to represent Nubulk for the flow, where in the range 0.01≤Kn<0.1, Nutot≈Nubulk as Kn approaches 0.01 and Nutot≈Nuin as Kn approaches 0.1. A convenient approach is proposed to evaluate Nutot for any condition of the upstream wall. These outcomes indicate the necessity to clearly define the condition of the upstream wall and to evaluate the total heat transfer in small-scale heat exchangers, which may be much larger than what fluid carries downstream.

Instability onset of Rayleigh-Bénard convection for diatomic rarefied gases: Effects of molecular interaction models and flow parameters

Studies on the stability of Rayleigh-Bénard convection in rarefied gases mainly focus on monatomic gases, whereas diatomic gases are the prevailing medium in actual flows. This paper conducts a study on the Rayleigh-Bénard convection stability of diatomic rarefied gases based on the Navier-Stokes (NS) equations modified with slip boundary conditions. We aim to elaborate the effects of different molecular interaction models and flow parameters (Knudsen number Kn, Froude number Fr, Prandtl number Pr, etc.). And several interesting phenomena have been discovered: (1) Compared with monatomic gases, the instability region of diatomic gases expands towards higher Knudsen numbers and smaller Froude numbers; (2) It is generally believed that increasing rarefaction leads to flow stabilization. However, we have found that in the case of small wave numbers within the scope of our research, the rarer the gas, the higher the growth rate, which contradicts traditional cognition; (3) Competition mechanism between buoyancy and gravity in the stability of Rayleigh-Bénard convection exists; (4) When considering the variations of Prandtl number and specific heat ratio with temperature, the relative deviation of the growth rate of the most unstable mode is significant.

Velocity-slip boundary conditions and shape factor effects on MHD hybrid nanofluid flow via converging/diverging channels

The most important objective of this research-work is to investigate the impacts of velocity-slip boundary conditions and shape factor of solid nanoparticles on the hydrodynamic behavior of the nonlinear problem of MHD Jeffery–Hamel hybrid nanofluid flow where the mixture H2O-C2H6O2 (50%-50%) was utilized as a base fluid. Using appropriate velocity transformations, the basic partial differential equations arising from mathematical modeling are transformed into non-linear ordinary differential equations. Afterwards, the determined nonlinear equation was numerically solved utilizing Runge-Kutta-Fehlberg 4th–5th order approach featuring shooting technique and analytically with the help of Duan–Rach Approach (DRA). The impact of active factors like Reynolds number, channel half-angle, Hartman number, base fluids nature, hybrid nanoparticles, velocity-slip boundary conditions, shape and Geometry of solid nanoparticles on hybrid nanofluid velocity and skin friction coefficient are visualized and investigated. The minimal local skin friction is found to be obtainable with the nanoparticles of Platelet form and second-order slip model where a reduction of 70% is gained compared to the local skin friction coefficient with spherical nanoparticles when the Hartmann number is higher. Results obtained also reveal that a higher reduction of 69% in local skin friction coefficient intensity is observed for both hybrid phase Al2O3-Cu and mixture base fluid H2O-C2H6O2 with second-order slip boundary condition model when Knudsen number Kn = 0,08. A comparison was made between the results obtained from this investigation in particular cases and the results obtained via the HAM-based Mathematica package for validation. Also, the obtained analytical DRA data are compared with numerical RKF45 data and the ones represented in the literature. The comparison revealed that the results match perfectly which justifies applicability, validity, and the higher exactness of the adopted Duan-Rach approach.

Flow pattern diagram of compressible non-equilibrium gas flow around a circular cylinder

An investigation into the non-equilibrium gas flow around a circular cylinder within the Knudsen number (Kn) range of 0.001–1 and the free-stream Mach number (Ma) range of 0.01–6 is presented using the unstructured grid unified gas kinetic scheme. The primary objective is to examine the impact of Kn and Ma on flow patterns. The flow pattern diagram illustrating seven flow patterns in the Ma-Kn space is provided, including the transition boundary between bow shock-wave with laminar flow (BS+L) and bow shock-wave with vortex flow (BS+V). The relationships between Re-Kn and Ma-Re both follow the power function: y=eβxα, where α and β are constants. The study also provides a more precise critical curve of vortex shedding in subsonic inflow, the boundary of tailing shock-wave, and the boundary of vortex shedding in a transonic inflow. The flow pattern diagram indicates that the variation of flow separation with Kn is non-monotonic across the entire Ma range but is monotonic at Ma>1. In the subsonic inflow, the critical Re of flow separation (Rec) increases with Ma, while Rec initially increases and then decreases with Kn. The critical Ma at the turning point is about 0.72. In supersonic inflow, the critical Re associated with the onset of flow separation either increases or decreases with the increase in Ma or Kn. The critical Re of vortex shedding is non-monotonic with Kn. The critical Re of the trailing shock-wave decreases with both Kn and Ma. In the transonic inflow, the critical Re and critical Ma of vortex shedding decrease with Kn. As rarefaction increases, the type of flow patterns decreases. The flow pattern diagram provides a visual representation of the impact of rarefaction and compressibility effects on flow pattern transitions and assists in determining the applicable range of the drag coefficient model.

Study on aerosol thermophoretic force and thermophoresis deposition model in reactor building

During nuclear reactor severe accident, the input of external passive containment cooling system will result in significant aerosol thermophoresis deposition in reactor building, which plays important factor affecting the safety assessment of nuclear reactor. Ratio of aerosol particles radius and gas molecule mean free path (Kn number) in reactor building is not greater than 2, corresponding to the near-continuous medium zone and transition zone. Firstly the typical thermophoretic force equations for these zones are evaluated. Combined with key influencing factors analysis, the correction factor connected to Kn number is introduced to address the deviation in the prediction for the transition zone of the current equations. The modified thermophoretic force equation obviously improves the underestimation of the original equation and is then used to obtain the thermophoresis deposition coefficient. According to experimental validation, the obtained coefficient is more accurate than the model that is widely employed in analysis codes in predicting the thermophoresis deposition of aerosol particles. Finally, fluid continuity, momentum, energy and particle continuity equations are established with deduced thermophoresis deposition coefficient and solved numerically. The thermophoresis deposition model considering natural convection (CT model) is established by theoretical derivation and fitting with the numerical solutions. By introducing the effects of natural convection on temperature distribution and aerosol concentration distribution the CT model could accurately describe the aerosol thermophoresis deposition behavior under natural convection conditions for Kn number is not greater than 2, which can be applied to aerosol thermophoresis deposition prediction in reactor building.

Advanced numerical analysis of convective rarefied flows in microchannels: Studying the impact of multiple obstacle arrangements through LBM modeling

The investigation of fluid flow and forced convective heat transfer in microchannels with square barriers is the focus of this study. The positioning of obstacles was varied in three cases: at the top wall, bottom wall, and symmetrically distributed on both sides of the microchannel wall. The thermal Lattice Boltzmann Method in conjunction with the Double Distribution Function and Bhatnagar–Gross–Krook approach was used for simulation through computer code in Python. Slip velocity and temperature jump were considered in the boundary conditions for the walls of the microchannel and obstacles. The results demonstrate that the rarefaction effect, placement of barriers, and choice of square obstacles significantly impact fluid flow and heat transfer. An increase in Knudsen numbers (Kn) leads to a decrease in temperature and velocity. The presence of obstructions on both sides of the microchannel walls reduces the fluid’s velocity and cools the fluid at the microchannel’s exit. The third case, with obstacles on both sides, presents a practical approach for reducing the fluid’s temperature at the exit, resulting in the lowest level of skin friction (Cf) and a reduction in the Nusselt number (Nu). The proposed configurations can be utilized to enhance the geometry of microchannels and for cooling purposes in small-scale devices and systems with miniature mechanical and electrical components. The study’s findings suggest that the placement of obstacles at the bottom or on both sides, depending on the need for best cooling on both sides or only at the top to reduce material consumption, can achieve low temperature at the exit of a rectangular microchannel.

On application of the regularized lattice Boltzmann method for isothermal flows with non-vanishing Knudsen numbers

Despite the advances in microscale modelling capabilities, physically observed non-zero Knudsen number (Kn) effects still elude the lattice Boltzmann method (LBM). This article details various Regularized LBM (RLBM) strategies used to model microscale flows and presents a thorough analysis on their applicability for the force-driven Poiseuille flow problem. In particular, we compare the formulations of eight schemes: Projected RLBM (P-RLBM), standard and Galilean Invariant Filtered Collision RLBM, Kn-dependant P-RLBM, Recursively Regularized LBM (R-RLBM), Hybrid R-RLBM, Central-Moment RLBM, and Onsager-Regularized LBM. We demonstrate, at different Kn with discrete Maxwell’s diffuse kinetic wall boundary conditions, the numerical equivalence of the considered RLBM schemes for hard sphere molecules on the D2Q9 lattice. Thereafter, we include a Kn-dependant wall-modified mean-free-path and extend the characterization onto higher-order D2Q17, D2Q21 and Q2Q25-Zero-One-Three, Q2Q49-Zero-One-Two-Three lattices. The study indicates that RLBM schemes are Navier-Stokes solvers which fail to entirely capture all the non-equilibrium phenomenon of slip/transition regime flows.

Rarefaction effect on the aerodynamics of bristled wings in miniature insects

All previous studies on the aerodynamics of bristled wings in miniature insects are based on continuum flows. However, the diameter of the bristle is very small, and the diameter-based Knudsen number (Kn) is approximately between 0.03 and 0.11, indicating that the flow around the bristle is in the slip-flow regime and rarefaction effect will be present. To investigate how the rarefaction will affect the aerodynamic force and flow field of the bristled wing, we calculated and analyzed the flow around a model bristled wing under two conditions: the continuum flow and the slip flow. The following is shown. Within the range of Kn considered in this study (0.01 ≤ Kn ≤ 0.1), the rarefaction has a very small effect on the aerodynamic force of the bristled wing: it decreases the aerodynamic force by less than 0.5% compared with that of the continuum flow. However, the rarefaction has a significant effect on the contributions of the viscous tangential and normal stress terms to the aerodynamic force: in the continuum flow, the force contribution of the viscous tangential stress is 50.7% and that of the viscous normal stress is zero, whereas in the slip flow, e.g., at Kn = 0.08, the contribution of the viscous tangential stress is only 37.7% and that of the viscous normal stress is 12.9% instead of zero; this is because the rarefaction-induced slip velocity in the slip flow changes the normal derivative of the velocity on the bristle surface compared with that of the continuum flow. Since the rarefaction has only a slight effect on the aerodynamic force, the results on the aerodynamic force of the bristled wing obtained based on continuum flows in previous studies are very good approximations to the correct results.

INERTIAL DEPOSITION OF SUBMICRON AEROSOLS IN MODEL FIBROUS FILTERS COMPOSED OF ULTRAFINE FIBERS

The influence of the inertia of submicron particles on their deposition from a Stokes flow in model fine-fiber filters is considered at low Reynolds numbers. The fiber collection efficiencies are calculated by the limiting trajectory method for a cell model of the filter and for a row of parallel fibers oriented perpendicularly to the direction of the gas flow for the ranges of interception parameter R = 0.01–1, Stokes number Stk = 0–20, and Knudsen number Kn = 0–1. The simulation results are consistent with the experimental data.

Sub-Diffusion Two-Temperature Model and Accurate Numerical Scheme for Heat Conduction Induced by Ultrashort-Pulsed Laser Heating

In this study, we propose a new sub-diffusion two-temperature model and its accurate numerical method by introducing the Knudsen number (Kn) and two Caputo fractional derivatives (0<α,β<1) in time into the parabolic two-temperature model of the diffusive type. We prove that the obtained sub-diffusion two-temperature model is well posed. The numerical scheme is obtained based on the L1 approximation for the Caputo fractional derivatives and the second-order finite difference for the spatial derivatives. Using the discrete energy method, we prove the numerical scheme to be unconditionally stable and convergent with O(τmin{2−α,2−β}+h2), where τ,h are time and space steps, respectively. The accuracy and applicability of the present numerical scheme are tested in two examples. Results show that the numerical solutions are accurate, and the present model and its numerical scheme could be used as a tool by changing the values of the Knudsen number and fractional-order derivatives as well as the parameter in the boundary condition for analyzing the heat conduction in porous media, such as porous thin metal films exposed to ultrashort-pulsed lasers, where the energy transports in phonons and electrons may be ultraslow at different rates.

Third-order accurate 13-moment equations for non-continuum transport phenomenon

The derivation of analytical equations of non-continuum macroscopic transport phenomena is underpinned by approximate descriptions of the particle distribution function and is required due to the inability of the Navier–Stokes equations to describe flows at high Knudsen number (Kn ∼ 1). In this paper, we present a compact representation of the second-order correction to the Maxwellian distribution function and 13-moment transport equations that contain fewer terms compared to available moment-based representations. The intrinsic inviscid and isentropic assumptions of the second-order accurate distribution function are then relaxed to present a third-order accurate representation of the distribution function, using which corresponding third-order accurate moment transport equations are derived. Validation studies performed for Grad’s second problem and the force-driven plane Poiseuille flow problem at non-zero Knudsen numbers for Maxwell molecules highlight an improvement over results obtained by using the Navier–Stokes equations and Grad’s 13-moment (G13) equations. To establish the ability of the proposed equations to accurately capture the bulk behavior of the fluid, the results of Grad’s second problem have been validated against the analytical solution of the Boltzmann equation. For the planar Poiseuille flow problem, validations against the direct simulation Monte Carlo method data reveal that, in contrast to G13 equations, the proposed equations are capable of accurately capturing the Knudsen boundary layer.

Gas separation simulation based on ab initio and variable soft sphere model in ratchet-shaped microchannels

A technique for the separation of rarefied gas mixtures based on microelectromechanical systems (MEMS) has recently attracted the attention of researchers. The mechanism of gas separation is the thermally induced flow caused by inhomogeneous temperature gradients within the microchannel, which distinguishes the velocity of different gas species. In this paper, the effects of Knudsen number Kn and equilibrium temperature T0 on the flow properties of each gas species within the gas mixture, such as velocity, molar fraction, streamlines, temperature, and pressure, are investigated by the Direct simulation Monte Carlo (DSMC) method. The flow of the gas mixture is numerically simulated using a quantum scattering-based ab initio (AI) potential and compared with the results of numerical simulations based on the variable soft sphere (VSS) model. The results show that the gas velocity accelerates with increasing temperature, but decreases with increasing Knudsen number. The streamlines are very sensitive to the Knudsen number, yet they are only affected by the temperature in the transitional flow. When the conditions are the same, He flows faster than Ne and the streamlines are smoother. The gas separation factor increases with equilibrium temperature at T0<100K and decreases slightly with equilibrium temperature at T0≥100K. The gas separation efficiency is best in the transitional flow. The temperature discrepancy for the different gas species is less affected by the equilibrium temperature and Knudsen number, with the maximum discrepancy rate being only 2.727% for He and Ne. The pressure discrepancy is more affected by the equilibrium temperature and Knudsen number, with the maximum rate of discrepancy reaching 39.228% for He and Ne. At T0=10K and Kn=1, the discrepancy rates of the gas separation factor, temperature, and pressure obtained based on the AI potential and the VSS model reach maximum values of 44.802%, 4.675%, and 52.716%, respectively. Compared to the VSS model, the AI potential based on quantum scattering is applicable to a wider range of temperatures and is more accurate for both low and high temperatures. Furthermore, the AI potential is more accurate than the VSS model in the transitional flow. The results obtained from the AI potential based on quantum scattering will be more desirable when performing gas separation studies based on thermally induced flows in rarefied gases.

Numerical simulation optimization of neutral flow dynamics in low-power Hall thruster

This paper utilizes a low-power Hall thruster to investigate its flow field’s neutral flow dynamics. Specifically, under a free molecular flow with a high Knudsen number (Kn>10), we employ the flow conductance theory to investigate the interplay between the internal structural parameters of the thruster flow field and its conductance, which is directly reflected in the neutral gas distribution.Hence, first, we increase the number and diameter of the orifices in the buffer chamber so that the baffle effectively increases the flow field conductance, and thus the number density (nn) of the neutral gas in the discharge channel increases. This phenomenon reduces the ionization mean free path (λi) and thus increases the utilization rate (ηi) of the neutral gas. Then, we alter the baffle orifices distribution to an unequally spaced distribution and stagger the outlet orifices, resulting in a highly homogeneity neutral gas distribution in the circumferential direction, ultimately increasing the effective outlet area and reducing the backflow probability of the neutral gas molecules. This operation reduces the low-frequency oscillation amplitude and thus enhances the thruster’s operation stability. Finally, we explore the influence of the entire operating conditions, especially temperature and mass flow rate variations, on the universality of the simulation results. Overall, this work provides a new concept for optimizing the neutral flow field dynamics of a Hall thruster.

Self-similar analysis of gas dynamics for van der Waals gas in slipping flow after normal shock wave

A self-similar model of gas dynamics and heat transfer behind the shock wave was developed with allowance for the effects of slippage and dissipation. The model takes into account the impact of the following factors: shock wave intensity (U∞/Us), physical properties (Prandtl number Pr), thermodynamic gas properties (van der Waals numbers Waa, Wab), slippage effects (Knundsen number Kn), and dissipation (Brinkman number Br), as well as the relation of the temperatures of the flow and the wall (T0/Tw). The numerical solution was performed with the help of MATLAB software, as well as an in-house code written using the programming language C++ to verify the accuracy of calculations. The study demonstrated that for the case at hand, the Reynolds analogy holds under the influence of all mentioned factors provided that Pr = 1, except for the conditions when the effects of mechanical energy dissipation become significant. The paper presents the results of calculations of the velocity and temperature profiles, friction, and heat transfer coefficients (Nusselt numbers).

Solution of the Boltzmann Equation in the Continuum Flow Regime

A method for solving the Boltzmann equation is presented that makes it possible to calculate gas flows in the continuum flow regime described by the Navier–Stokes equations. Progress into the region of continuum flows was achieved by applying the conservative projection method for calculating the Boltzmann collision integral, which preserves the leading term of the Enskog–Chapman asymptotics. Optimization of this method that made it possible to considerably decrease the amount of computations is described. Examples of the longitudinal subsonic flow around a flat plate for the case of the Knudsen numbers Kn = (0,01 0,001 0,0001) are discussed.

On Some Theoretical Aspects of The Evaporation Process of a Droplet and Its Optimal Size When Extinguishing Fires

We are proposing a model mathematical description of droplet evaporation using the kinetic approach. We have obtained the basic equation of the theory by using the law of conserving the full power of the vapor–liquid system, which has not been done before. We have found the range of droplet sizes at which it is stable. We have given a comparison of the obtained results with the known traditional ones. We have given numerical estimates for the critical size of the fine-dispersed phase up to the value of which ordinary evaporation takes place (that is for Knudsen number Kn=lR, inequality Kn≪1 must be fulfilled, where l− is the free path of the molecule and R− is the droplet radius). We have given the optimal droplet size which is the most effective from the point of view of technical use in extinguishing flammable oil transformers.

Minireview on Lattice Boltzmann Modeling of Gas Flow and Adsorption in Shale Porous Media: Progress and Future Direction

As an important unconventional resource, shale gas reservoirs have unique characteristics different from conventional oil and gas reservoirs. The ultrasmall pore sizes in shale induce the nanopore confinement effect on shale gas flow. In addition, shale rocks are rich in organic matter, which has strong interactions with gas molecules and results in gas adsorption. The lattice Boltzmann method (LBM) for micro- and nanoscale gas flow, which is originally designed for micro-electro-mechanical systems (MEMS), has been modified to simulate gas flow and adsorption in shale rocks. This work reviews four types of lattice Boltzmann models developed recently for shale gas flow/adsorption: (1) the slip-velocity-based LBM, (2) high-order LBM, (3) diffusion-based LBM, and (4) REV-scale LBM. Among these models, the slip-velocity-based LBM is widely used for shale gas modeling, which incorporates the slip boundary condition and Knudsen number (Kn)-determined relaxation time to simulate the nanopore confinement effect. To model the gas adsorption, the fluid–solid interaction force is introduced into the model, and the magnitude of this interaction force is usually obtained from the molecular level simulations. LBMs have been regarded as an efficient numerical tool to estimate the shale gas apparent permeability, to describe the pore-scale flow behaviors, and to address the influence of gas adsorption on shale gas storage and transport. Nevertheless, some challenges exist in current applications of LBMs for shale gas flow and adsorption simulations that are discussed in this minireview as well.