Quasi-direct Numerical Simulation Research Articles

Experimental and numerical investigation on the effect of surface roughness on the drag coefficient of a spherical particle

The drag coefficient (CD) for particles has a significant effect on the gas–solid fluidization characteristics. However, it is unclear whether the particle surface roughness (Rap) can notably affect CD at relatively low particle Reynolds numbers (Rep). Herein, the CD for several single near-spherical particles with different Rap and density were determined using high-speed videography in conjunction with the image analysis method. In addition, a quasi-direct numerical simulation (q-DNS) method was applied to further resolve the flow field surrounding the particle. Both experimental and simulation results suggest that within a low Rep range (<500), there is no evident difference in CD. However, if the Rep exceeds 500, CD gradually decreases with the increase in Rap. Since the separation point of the particle boundary layer moves downstream, the rough sphere experiences lower pressure in the wake vortex region. This study provides a valuable conclusion: the Rap is a non-negligible factor in studying hydrodynamic behaviors of two-phase flow, especially at high fluidization velocity.

A novel configuration capable of enhancing flame acceleration and detonation

This study proposes a novel design concept that leverages the geometric effects of channels with varying diameters and bends to boost flame acceleration and detonation in microchannels. A quasi-direct numerical simulation with detailed chemical kinetics is used to evaluate the processes of flame acceleration and detonation. A comparative study on the impact of equidistant spiral and converging spiral shapes of detonation channels on flame acceleration is conducted and discussed. The results indicate that in the low-speed and high-speed stages of flame propagation, Fermat's spiral channel exhibits a more significant promoting effect on flame acceleration compared to the Archimedes spiral channel. Fermat's spiral channel has significant advantages in terms of combustion efficiency and can save about 30% of fuel during the detonation process. This study helps to further reduce the scale of the detonation system.

LES of turbulent partially-premixed flames using reaction–diffusion manifold-reduced chemistry with a consistent gradient estimate determined “on the fly”

This paper devises and applies a method for determining consistent, system-adapted reaction–diffusion manifolds (REDIM) for turbulent partially-premixed combustion. The method is an extension of a previous technique which was limited to laminar flames. It adapts a REDIM to the scalar gradients present in a given reacting flow by an iterative procedure, in which gradients from REDIM-reduced simulations are used to create a new and improved REDIM. An application of the method is demonstrated using large eddy simulations (LES) of a turbulent partially-premixed methane/air flame as the “gradient estimate generating” flame simulation. Compared to the previous laminar flame studies, the turbulent flame features less sharp gradient-scalar correlations because of the strong scattering of data. Methods for capturing the scatter in scalar-gradient correlations are applied, allowing us to assess the influence of the scatter on the resulting REDIM. Also, the fact that turbulent flame simulations often involve spatial filtering operations which tend to reduce the magnitude of the gradients is taken into account by comparing the REDIM output to quasi-direct numerical simulation (qDNS) data. It is found that the gradients devised from the filtered simulations are by a factor of 2–3 below those of the more fully resolved qDNS. Nevertheless, the REDIM devised from the LES predicts the states of the qDNS with good accuracy. Overall, observations show that the method can produce realistic reduced models also for systems with complex interactions of chemical reaction, molecular transport and flow, like partially-premixed turbulent flames.

Evaluation of Synthetic Jet Flow Control Technique for Modulating Turbulent Jet Noise

The use of a synthetic jet as the flow control technique to modulate a turbulent incompressible round jet was explored and assessed by numerical simulations. The flow response was characterised in terms of turbulent statistics and acoustic response in the far-field. A quasi-Direct Numerical Simulation (qDNS) strategy was used to predict the turbulent effects. The Ffowcs-Williams and Hawkings (FWH) acoustic analogy was employed to compute the far-field acoustic response. An amplification effect of the instabilities induced by the control jet was observed for some of the parameters explored. It was observed that the control technique allows controlling the axial distribution of the production and dissipation of turbulent kinetic energy, but with respect to the acoustic aspects, the appearance of a greater number of noise sources was observed, which in the far-field, resulted in an increase from 1 to 20 dB of the equivalent noise for the different operating parameters of the control technique studied.

Numerical and experimental investigation of the flame kernel growth in a methane/air mixture near the lean flammability limit

Lean combustion has the potential to improve the thermal efficiency of spark-ignition engines, but it faces the significant challenge of increased cycle-to-cycle variation due to low mixture reactivity and unstable flame dynamics. Computational fluid dynamics (CFD) employing predictive models can guide engine design and optimize operating strategies for lean combustion. However, ignition and combustion models have rarely been validated at fuel-lean conditions, and a fundamental understanding of the early flame kernel growth process is also lacking for a successful sub-model development. The present study develops a numerical simulation framework used to investigate early flame kernel growth in methane/air mixtures. A nanosecond-pulsed discharge (NPD) approach is employed to effectively decouple the flame kernel growth from the electrical discharge due to their difference in timescales, and equivalence ratios near the experimentally measured lean flammability limit (LFL) are selected to focus on challenging mixture conditions. Three numerical investigations, such as the choice of turbulence modeling, grid size, and grid control strategies, are examined to match both LFL and flame kernel structure measured from experiments. It is demonstrated that a quasi-direct numerical simulation (QDNS) with a fixed grid embedding of 10 µm can predict the LFL as ϕCFD=0.61 and match the displacement speed of the kernel's boundary marked in schlieren images. To predict the LFL and flame kernel shape, a fine grid (Δ≤12.5 µm) is needed to capture the consumption of formaldehyde (CH2O) in kernel's reaction branches attached to the anode, and adaptive mesh refinement is replaced with the fixed embedding due to loss of simulation accuracy. Also, it is found that a large-eddy simulation (LES) using the Dynamic Structure model is not suitable for the NPD-induced flame kernel simulation because artificial sub-grid turbulent kinetic energy induced by shock dynamics alters the flow velocity calculation, resulting in divergence of LES from QDNS. Lastly, the simulation well matches the experimental data for the flame kernel evolution in three mixture conditions (ϕ = 0.7, 0.61, 0.55), showing toroidal flame kernel expansion and flame kernel growth/extinction.

A dual-mesh hybrid Reynolds-averaged Navier-Stokes/Large eddy simulation study of the buoyant flow between coaxial cylinders

This study is concerned with the investigation of the suitability of the dual-mesh method for the buoyancy driven flow inside a cylindrical annulus with one internal cylinder. This flow situation can occur, for instance, in gas cooled nuclear reactors and is characterized by complex features, including a buoyant plume and a negatively buoyant wall-jet. The buoyancy forces in this flow are generated by the temperature difference between the inner and outer cylinders. The dual-mesh approach is a hybrid RANS-LES method in which an unsteady Reynolds-averaged Navier-Stokes (RANS) simulation and a coarse Large eddy simulation (i.e. an LES that is under-resolved near walls) are run simultaneously on two different grids. In this approach, a criterion is used to determine the locations at which each simulation is expected to perform better than the other. Consequently, at every location the less accurate simulation is forced and corrected towards the more accurate one. This correction is done using source terms that are included in the equations of the flow and thermal fields of the two simultaneous simulations. It is observed that the buoyancy-extended lengthscale resolution criterion behaves satisfactorily in defining the regions where the LES is corrected towards the RANS and vice versa. Moreover, both quantitative and qualitative analyses of the results are conducted using quasi direct numerical simulation results from the literature. It is shown that the dual-mesh method has the potential to yield results that are better than the results of the pure RANS and the pure coarse LES simulations.

A quasi-direct numerical simulation solver for compressible reacting flows

A new quasi-direct numerical simulation (q-DNS) solver named combustionFoam, capable of simulating reacting flows at arbitrary Mach number with a detailed chemical reaction mechanism, has been developed. This solver is implemented based on reactingFoam-solver from OpenFOAM-v7. The main improvements are a mixture-averaged formula transport model and ability to simulate reacting flows at arbitrary Mach number. The transport model is implemented by developing an data exchange interface to couple OpenFOAM® with Cantera. To damped nonphysical oscillations near shocks, a hybrid KT/KNP approach derived by Kraposhin et al. [18] is adopted. This solver was validated by two test cases: (1) a low speed steady two dimensional non-premixed counterflow diffusion flame; (2) a supersonic transient one dimensional detonation waves. Comparisons of the results with data from other solvers and literatures are carried out and good agreements are obtained.

Towards validated prediction with RANS CFD of flow and heat transport in a wire-wrap fuel assembly

Liquid metal fast reactors (LMFRs) are foreseen to play an important role in the future of nuclear energy, thanks to their increased fuel utilization and safety features profiting from the optimal heat transfer performance of the metallic coolants. Accurate thermal-hydraulic analysis of their fuel assemblies, typically employed with wire-wraps as spacers, is recognized as a crucial scientific and engineering contribution to support the deployment of such technology. This challenges the modeling and simulation community.To this aspect, various reference databases (both experimental and numerical) for different wire-wrapped fuel assembly configurations have been created recently and are being used for validation of engineering simulation approaches based on Reynolds Averaged Navier Stokes (RANS) modelling. These databases include:•7-pin rod bundle: A detailed experiment with Particle Image Velocimetry (PIV) is performed. In order to allow accurate measurements of the flow topology, a matched-index-of-refraction technique was used employing water as working fluid.•19-pin bundle: A series of experiments is performed covering a wide range of Reynolds and Peclet numbers as well as thermal powers. The experiments use liquid lead-bismuth eutectic as working fluid. The measurements include pressure drop and local temperatures.•61-pin rod bundle: This large eddy simulation including conjugate heat transfer from the pin cladding to the coolant allows to bridge the gap from small bundles (less than 37 pins) to large bundles (more than 37 pins). In literature, a fundamental different behavior has been observed for small bundles compared to large bundles.•127-pin bundle: Isothermal experiments using lead-bismuth eutectic characterizing pressure drop are performed on a full scale fuel assembly representative for the MYRRHA reactor.•Infinite pin bundle: This reference quasi-direct numerical simulation profits from periodicity in all directions. It provides a detailed view into the flow field and in addition reveals details of the heat transfer from the rod bundle into the flow.Reference databases aim to serve the nuclear scientific community to validate engineering simulation approaches. The paper will introduce these reference databases, and how they have been used to validate RANS based turbulence modelling approaches within a mainly European context.

Quasi-direct numerical simulation of forced convection over a backward-facing step: Effect of Prandtl number

Quasi direct numerical simulations (quasi-DNS) of forced heat convection over a backward-facing step are performed to study the turbulent heat transfer of low Prandtl number fluids in complex flow regimes. Reynolds number based on step height and inlet bulk velocity equals 4805. The expansion wall is heating by uniform dimensionless heat flux density. Effects of Prandtl number (Pr = 0.01, 0.025, 0.1, 1.0) on mean temperatures, heat transfer coefficients, heat fluxes, turbulent Prandtl numbers and instantaneous velocity and temperature fluctuations, are compared with each other. For low Prandtl numbers, diffusion effect is prominent, thermal boundary layer is much thicker, Nusselt number is smaller and Stanton number is larger. The maximum heat transfer location moves upstream of the reattachment point for larger Prandtl numbers while it is at the reattachment point for low Prandtl numbers. Wall-normal heat flux decomposition shows the turbulent part is comparable to the molecular one in the recirculation zone even for low Prandtl numbers. Turbulent Prandtl number profiles are irregular in the recirculation zone but in the recovering zone they increase first and then decrease. Their peak values decrease as Prandtl number increases. Near-wall instantaneous fields for streamwise velocity and temperature fluctuations show that the streak structures disappear in the recirculation zone but exist in the recovering zone. These highly-resolved data with heat transfer could serve for the validation and improvement of turbulence heat transfer models for low Prandtl media in future.

A quantification method for numerical dissipation in quasi-DNS and under-resolved DNS, and effects of numerical dissipation in quasi-DNS and under-resolved DNS of turbulent channel flows

LES for industrial applications with complex geometries is mostly characterised by: a) a finite volume CFD method using a non-staggered arrangement of the flow variables and second order accurate spatial and temporal discretisation schemes, b) an implicit top-hat filter, where the filter length is equal to the local computational cell size, and c) eddy-viscosity type LES models. LES based on these three main characteristics is indicated as industrial LES in this paper.It becomes increasingly clear that the numerical dissipation in CFD codes typically used in industrial applications with complex geometries may inhibit the predictive capabilities of explicit LES. Therefore, there is a need to quantify the numerical dissipation rate in such CFD codes. In this paper, we quantify the numerical dissipation rate in physical space based on an analysis of the transport equation for the mean turbulent kinetic energy. Using this method, we quantify the numerical dissipation rate in a quasi-Direct Numerical Simulation (DNS) and in under-resolved DNS of, as a basic demonstration case, fully-developed turbulent channel flow. With quasi-DNS, we indicate a DNS performed using a second order accurate finite volume method typically used in industrial applications. Furthermore, we determine and explain the trends in the performance of industrial LES for fully-developed turbulent channel flow for four different Reynolds numbers for three different LES mesh resolutions. The presented explanation of the mechanisms behind the observed trends is based on an analysis of the turbulent kinetic energy budgets.The presented quantitative analyses demonstrate that the numerical errors in the industrial LES computations of the considered turbulent channel flows result in a net numerical dissipation rate which is larger than the subgrid-scale dissipation rate.No new computational methods are presented in this paper. Instead, the main new elements in this paper are our detailed quantification method for the numerical dissipation rate, the application of this method to a quasi-DNS and under-resolved DNS of fully-developed turbulent channel flow, and the explanation of the effects of the numerical dissipation on the observed trends in the performance of industrial LES for fully-developed turbulent channel flows.

DNS and LES of 3-D wall-bounded turbulence using Smoothed Particle Hydrodynamics

Smoothed Particle Hydrodynamics (SPH) has been used in the simulation of fluid flows for several years. Recently, SPH saw its range of applications extended to the simulation of real-world engineering applications which often concern the simulation of turbulent three-dimensional flows. However, there is a significant lack in the investigation of such turbulent flows even for simplified applications. Most three-dimensional SPH simulations that analyze properties of a turbulent flow examine the decay of isotropic turbulence, where no solid walls influence the flow. In the present paper several three-dimensional turbulent channel flows are simulated using the SPH method to address this gap in literature. The first set of simulations investigates a quasi direct numerical simulation (DNS) of a channel with reduced size. This enables evaluation of SPH as a pure Navier–Stokes solver by avoiding the introduction of turbulence models. The results show the correct reproduction of the turbulent statistics except for some fluctuations in the near wall region. The second set of simulations attempts a large eddy simulation (LES) of a standard size channel. It is shown that the present SPH formulation fails to reproduce the correct turbulent statistics and the cause for this failure is analyzed with the aide of the Taylor–Green vortex flow and attributed to incorrect reproduction of velocity–pressure interactions by the collocated and large stencil SPH discretisation.

Numerical simulation of nuclear pebble bed configurations

High Temperature Reactors (HTRs) are being considered all over the world. An HTR uses helium gas as a coolant, while the moderator function is taken up by graphite. The fuel is embedded in the graphite moderator. A particular inherent safety advantage of HTR designs is that the graphite can withstand very high temperatures, that the fuel inside will stay inside the graphite pebble and cannot escape to the surroundings even in the event of loss of cooling. Generally, the core can be designed using a graphite pebble bed. Some experimental and demonstration reactors have been operated using a pebble bed design. The test reactors have shown safe and efficient operation, however questions have been raised about possible occurrence of local hot spots in the pebble bed which may affect the pebble integrity. Analysis of the fuel integrity requires detailed evaluation of local heat transport phenomena in a pebble bed, and since such phenomena cannot easily be modelled experimentally, numerical simulations are a useful tool.As a part of a European project, named Thermal Hydraulics of Innovative Nuclear Systems (THINS), a benchmarking quasi-direct numerical simulation (q-DNS) of a well-defined pebble bed configuration has been performed. This q-DNS will serve as a reference database in order to evaluate the prediction capabilities of different turbulence modelling approaches. A wide range of numerical simulations based on different available turbulence modelling approaches are performed and compared with the reference q-DNS. This paper reports a detailed comparison of LES, Hybrid (RANS/LES) and RANS models with the reference q-DNS. These simulations are performed for a well-defined single face cubic centred pebble configuration. The obtained flow and thermal fields are extensively analyzed to understand the flow physics in such complex flow regime. Furthermore, lessons learned from these simulations are summarized in the form of guidelines for such complex flow configurations. In addition, following these guidelines, a strategy has been developed to perform large eddy simulations of a realistic limited sized random pebble bed.

Direct and large-eddy simulation of turbulent flows on composite multi-resolution grids by the lattice Boltzmann method

In order to properly address the simulation of complex (weakly compressible) turbulent flows, the lattice Boltzmann method, originally designed for uniform structured grids, needs to be extended to composite multi-domain grids displaying various levels of spatial resolution. Therefore, physical conditions must be specified to determine the mapping of statistical information (about the populations of moving particles) at the interface between two domains of different resolutions. quite simply in terms of the probability distributions of the underlying discrete-velocity Boltzmann equation. Namely, the continuity of the mass density and fluid momentum is fulfilled by imposing the continuity of the equilibrium part of these distributions, whereas the discontinuity of the rate-of-strain tensor is ensured by applying a “spatial transformation” to the collision term of the discrete-velocity Boltzmann equation. The latter condition allows us to explicitly account for the subgrid-scale modeling in the treatment of resolution changes.Test computations of a turbulent plane-channel flow have been carried out. The lattice Boltzmann scheme relies on the standard D3Q19 lattice in a cell-vertex representation, and uses the BGK approximation for the collision term. A shear-improved variant of the Smagorinsky viscosity is used to account for possible subgrid-scale dynamics. In a quasi-direct numerical simulation at Reτ=180 with two levels of grid resolution, the results are found in excellent agreement with reference data obtained by a high-resolution pseudo-spectral simulation. In a Large-Eddy Simulation (LES) at Reτ=395 with three levels of grid resolution, the results compare reasonably well with high-resolution reference data. The accuracy is improved in comparison with a standard finite-volume LES performed with the same subgrid-scale viscosity and comparable grid resolution.By combining the simplicity and physical relevance of the shear-improved Smagorinsky model and the computational efficiency of the lattice Boltzmann scheme, here extended to composite multi-resolution grids, we believe that our proposal offers a high potential for the simulation of complex turbulent flows.

Large eddy simulation of a nuclear pebble bed configuration

High Temperature Reactors (HTRs) are being considered all over the world for deployment because of their excellent safety features. A particular inherent safety advantage of HTR designs is related to the very high temperature that the fuel can sustain basically preventing the fuel from melting even in the event of loss of cooling. Generally, the core can be designed using a graphite pebble bed. Test reactors have shown safe and efficient operation, however questions have been raised about possible occurrence of local hot spots in the pebble bed which may affect the pebble integrity. A good prediction of the flow and heat transfer phenomena in the pebble bed core of an HTR is a challenge for available turbulence models, which still require to be validated for pebble bed applications. In the present study large eddy simulation (LES) of a well-defined single face cubic centered pebble bed is performed. The obtained results are extensively compared with a quasi-direct numerical simulation (q-DNS) database in order to analyze the prediction capabilities and feasibility of used LES approach for such a complex flow regime. The simulations are performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. The obtained results are found to be in good agreement with the q-DNS results.

Quasi-direct numerical simulation of a pebble bed configuration, Part-II: Temperature field analysis

Good prediction of the flow and heat transfer phenomena in the pebble bed core of a high temperature reactor (HTR) is a challenge for available turbulence models, which still require to be validated. While experimental data are generally desirable in this validation process, due to the complex geometric configuration and measurement difficulties, a very limited amount of data is currently available. On the other hand, direct numerical simulation (DNS) is considered an accurate simulation technique, which may serve as an alternative for validating turbulence models. In the framework of the present study, quasi-direct numerical simulation (q-DNS) of a single face cubic centered pebble bed is performed, which will serve as a reference for the validation of different turbulence modeling approaches in order to perform calculations for a randomly arranged pebble bed. These simulations were performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Results related to flow field (mean, RMS and covariance of velocity) have been presented in Part-I, whereas, in the present article, we focus our attention to the analysis of the temperature field. A wide range of qualitative and quantitative data for the thermal field (mean, RMS and turbulent heat flux) has been generated.

Quasi-direct numerical simulation of a pebble bed configuration. Part I: Flow (velocity) field analysis

High temperature reactors (HTR) are being considered for deployment around the world because of their excellent safety features. The fuel is embedded in a graphite moderator and can sustain very high temperatures. However, the appearance of hot spots in the pebble bed cores of HTR's may affect the integrity of the pebbles. A good prediction of the flow and heat transport in such a pebble bed core is a challenge for available turbulence models and such models need to be validated. In the present article, quasi direct numerical simulations (q-DNS) of a pebble bed configuration are reported, which may serve as a reference for the validation of different turbulence modeling approaches. Such approaches can be used in order to perform calculations for a randomly arranged pebble bed. Simulations are performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Detailed flow analyses have shown complex physics flow behavior and make this case challenging for turbulence model validation. Hence, a wide range of qualitative and quantitative data for velocity and temperature field have been extracted for this benchmark. In the present article (part I), results related to the flow field (mean, RMS and covariance of velocity) are documented and discussed in detail. Moreover, the discussion regarding the temperature field will be published in a separate article.

Optimization of a pebble bed configuration for quasi-direct numerical simulation

Abstract A high temperature reactor (HTR) is envisaged to be one of the renewed reactor designs to play a role in nuclear power generation including process heat applications. The HTR design concept exhibits excellent safety features due to the low power density and the large amount of graphite present in the core which gives a large thermal inertia in the event of an accident such as loss of coolant. However, the possible appearance of hot spots in the pebble bed cores of HTR may affect the integrity of the pebbles. This has drawn the attention of several scientists to understand this highly three-dimensional complex phenomenon. A good prediction of the flow and heat transport in such a pebble bed core is a challenge for CFD based on the available turbulence models and computational power. Such models need to be validated in order to gain trust in the simulation of these types of flow configurations. Direct numerical simulation (DNS), while imposing some restrictions in terms of flow parameters and numerical tools corresponding to the available computational resources, can serve as a reference for model development and validation. In the present article, a wide range of numerical simulations has been performed in order to optimize a pebble bed configuration for quasi-DNS which may serve as reference for validation.

Wall-Resolved LES and Zonal LES of Round Jet Impingement Heat Transfer on a Flat Plate

Numerical large-eddy simulation (NLES) is performed for a round jet impinging on a flat surface at a Reynolds number of Re = 23,000 for nozzle-to-plate spacings of H/D = 6 and 2, where H is the distance from the nozzle to the plate and D is the jet diameter. The Reynolds number has been set to match the experiments of Cooper et al. (Int J. Heat Mass Transfer, vol. 36, pp. 2675–2684, 1993). Two numerical large-eddy simulation approaches are examined. The first quasi-direct numerical simulation (DNS) approach resolves streaklike structures using fine near-wall grids; the second is the zonal approach of Tucker (Int J. Heat Fluid Flow, vol. 25, pp. 625–635, 2004), which uses the Wolfshtein k–l (Int J. Heat Mass Transfer, vol. 12, pp. 301–318, 1969) Reynolds-averaged Navier-Stokes (RANS) model near the walls and NLES elsewhere. A Hamilton-Jacobi equation is used to match the RANS region to the NLES zone. The use of a Spalart-Allmaras model leads to low levels of turbulent viscosity in the near-wall region. This is also observed when using detached-eddy (DES) when using a volume-based filter. The use of the standard DES filter based on maximum grid spacing prevents jet shear-layer transition. The k–l near-wall model maintains RANS levels of turbulent viscosity in the boundary layer. The results of both the near-wall quasi-DNS and hybrid RANS-NLES methods are generally encouraging.

A Numerical Study on Interparticle Collisions in a Microseparator/Classifier by a Macroscopic Particle Model

An effect of feed concentration on particle focusing in an arc microchannel is numerically examined. A macroscopic particle model, which does not need any drag and lift force correlations and hence can be regarded as quasi-direct numerical simulation, is employed to model interparticle collisions due to high shear rates in the microchannel. The model can take into account physical boundaries of particles in contact. In dilute conditions, all particle trajectories formed smooth inward spirals over the transverse plane. In dense flow conditions, the particle trajectories were distorted by collisions, and then the particle focusing declined. It suggests that a particle concentration, which is regarded as dilute in terms of volume concentration, can be regarded as hydraulically dense due to shear-induced particle collisions in a microchannel. It is predicted that the angle between particle-velocity vectors at successive time steps during collision is rather small. The importance of collision mechanism is discussed for the device application to various materials.

Quasi-direct numerical simulation of lift force-induced particle separation in a curved microchannel by use of a macroscopic particle model

The macroscopic particle model (MPM) based on the finite volume method is employed to validate a mechanism of lift force-induced particle separation in a curved microchannel. According to the particle velocity at each time step in the unsteady simulation, the MPM gives momentum to those fluid cells touching the particle physical boundary. The summation of the given momentum with the reversed sign is divided by the time step to obtain the hydrodynamic force acting on the particle. Namely, the existence and motion of the particle causes fluid flow around the particle, while the flow field caused by the particle determines the particle motion by means of the hydrodynamic force. Therefore, the MPM can be regarded as implementing a quasi-direct numerical simulation over the static computational cells. The lift force acting on a spherical particle in a shear flow is a purely hydrodynamic force caused by the flow field around the particle. It is expected, therefore, that the MPM could predict the lift force effect without any additional model. At first, it is shown that the MPM is capable of predicting particle migration away from the wall of a straight microchannel due to the lift force. In a curved microchannel, subsequently, the particle trajectories from representative release points predicted by the MPM are compared to those predicted by a common particle tracking method without any lift force model. The MPM predicted that the particle trajectories are confined in the outer region of the channel cross-section. On the other hand, the circulating trajectories predicted by the tracking method tend to expand due to centrifugal force caused by the Dean vortices. It is concluded, therefore, that the lift force due to the steep shear rate is a significant factor to cause particle separation in a curved microchannel.