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2019年 第40卷 第3期    刊出日期：2019-03-01

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论文

Wall-modeling for large-eddy simulation of flows around an axisymmetric body using the diffuse-interface immersed boundary method

Beiji SHI, Xiaolei YANG, Guodong JIN, Guowei HE, Shizhao WANG

2019, 40(3):  305-320.  doi:10.1007/s10483-019-2425-6

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A novel method is proposed to combine the wall-modeled large-eddy simulation (LES) with the diffuse-interface direct-forcing immersed boundary (IB) method. The new developments in this method include:(i) the momentum equation is integrated along the wall-normal direction to link the tangential component of the effective body force for the IB method to the wall shear stress predicted by the wall model; (ii) a set of Lagrangian points near the wall are introduced to compute the normal component of the effective body force for the IB method by reconstructing the normal component of the velocity. This novel method will be a classical direct-forcing IB method if the grid is fine enough to resolve the flow near the wall. The method is used to simulate the flows around the DARPA SUBOFF model. The results obtained are well comparable to the measured experimental data and wall-resolved LES results.



Transport diffuse interface model for simulation of solid-fluid interaction

Li LI, Qian CHEN, Baolin TIAN

2019, 40(3):  321-330.  doi:10.1007/s10483-019-2443-9

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For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0=0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves, such as shear waves in fluids, are introduced by the artificial treatment. In this paper, a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.

Effects of the Reynolds number on the mean skin friction decomposition in turbulent channel flows

Yitong FAN, Cheng CHENG, Weipeng LI

2019, 40(3):  331-342.  doi:10.1007/s10483-019-2442-8

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As the Reynolds number increases, the skin friction has been identified as the dominant drag in many practical applications. In the present paper, the effects of the Reynolds number on the mean skin friction decomposition in turbulent channel flows up to Re_τ=5 200 are investigated based on two different methods, i.e., the FukagataIwamoto-Kasagi (FIK) identity (FUKAGATA, K., IWAMOTO, K., and KASAGI, N. Contribution of Reynolds stress distribution to the skin friction in wall-bounded flows. Physics of Fluids, 14(11), L73-L76 (2002)) and the Renard-Deck (RD) identity (DECK, S., RENARD, N., LARAUFIE, R., and WEISS, P. É. Large-scale contribution to mean wall shear stress in high-Reynolds-number flat-plate boundary layers up to Re_θ=13 650. Journal of Fluid Mechanics, 743, 202-248 (2014)). The direct numerical simulation (DNS) data provided by Lee and Moser (LEE, M. and MOSER, R. D. Direct numerical simulation of turbulent channel flow up to Re_τ ≈ 5 200. Journal of Fluid Mechanics, 774, 395-415 (2015)) are used. For these two skin friction decomposition methods, their decomposed constituents are discussed and compared for different Reynolds numbers. The integrands of the decomposed constituents are locally analyzed across the boundary layer to assess the actions associated with the inhomogeneity and multi-scale nature of turbulent motion. The scaling of the decomposed constituents and their integrands are presented. In addition, the boundary layer is divided into three sub-regions to evaluate the contributive proportion of each sub-region with an increase in the Reynolds number.

Transversal effects of high order numerical schemes for compressible fluid flows

Xin LEI, Jiequan LI

2019, 40(3):  343-354.  doi:10.1007/s10483-019-2444-6

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Finite volume schemes for the two-dimensional (2D) wave system are taken to demonstrate the role of the genuine dimensionality of Lax-Wendroff flow solvers for compressible fluid flows. When the finite volume schemes are applied, the transversal variation relative to the computational cell interfaces is neglected, and only the normal numerical flux is used, thanks to the Gauss-Green formula. In order to offset such defects, the Lax-Wendroff flow solvers or the generalized Riemann problem (GRP) solvers are adopted by substituting the time evolution of flows into the spatial variation. The numerical results show that even with the same convergence rate, the error by the GRP2D solver is almost one ninth of that by the multistage Runge-Kutta (RK) method.

A unified gas-kinetic scheme for multiscale and multicomponent flow transport

Tianbai XIAO, Kun XU, Qingdong CAI

2019, 40(3):  355-372.  doi:10.1007/s10483-019-2446-9

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Compressible flows exhibit a diverse set of behaviors, where individual particle transports and their collective dynamics play different roles at different scales. At the same time, the atmosphere is composed of different components that require additional degrees of freedom for representation in computational fluid dynamics. It is challenging to construct an accurate and efficient numerical algorithm to faithfully represent multiscale flow physics across different regimes. In this paper, a unified gas-kinetic scheme (UGKS) is developed to study non-equilibrium multicomponent gaseous flows. Based on the Boltzmann kinetic equation, an analytical space-time evolving solution is used to construct the discretized equations of gas dynamics directly according to cell size and scales of time steps, i.e., the so-called direct modeling method. With the variation in the ratio of the numerical time step to the local particle collision time (or the cell size to the local particle mean free path), the UGKS automatically recovers all scale-dependent flows over the given domain and provides a continuous spectrum of the gas dynamics. The performance of the proposed unified scheme is fully validated through numerical experiments. The UGKS can be a valuable tool to study multiscale and multicomponent flow physics.

Unsteadiness control of laminar junction flows on pressure fluctuations

Jianhua LIU, Shucheng ZHAI, E. KUDASHEV, Fangwen HONG, Kai YAN

2019, 40(3):  373-380.  doi:10.1007/s10483-019-2447-6

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Smoke-wire flow visualization is conducted carefully in a laminar junction to explore the physical behavior of laminar junction flows. The two-dimensional (2D) velocity fields in the 30° plane of a laminar junction flow are acquired by a time-resolved particle image velocimetry (PIV) system at a frame rate of 1 kHz, based on which the unsteady fluctuating pressure fields can be calculated by the multi-path integration method proposed in the literature (GAND, F., DECK, S., BRUNET,V., and SAGAUT, P. Flow dynamics past a simplified wing body junction. Physics of Fluids, 22(11), 115111 (2010)). A novel control strategy is utilized to attenuate the unsteadiness of the horseshoe vortices of the laminar junction flow, and the consequent effect on pressure fields is analyzed.

Relationship between wall shear stresses and streamwise vortices in turbulent flows over wavy boundaries

Lihao WANG, Weixi HUANG, Chunxiao XU, Lian SHEN, Zhaoshun ZHANG

2019, 40(3):  381-396.  doi:10.1007/s10483-019-2448-8

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The relationship between wall shear stresses and near-wall streamwise vortices is investigated via a direct numerical simulation (DNS) of turbulent flows over a wavy boundary with traveling-wave motion. The results indicate that the wall shear stresses are still closely related to the near-wall streamwise vortices in the presence of a wave. The wave age and wave phase significantly affect the distribution of a two-point correlation coefficient between the wall shear stresses and streamwise vorticity. For the slow wave case of c/U_m=0.14, the correlation is attenuated above the leeward side while the distribution of correlation function is more elongated and also exhibits a larger vertical extent above the crest. With respect to the fast wave case of c/U_m=1.4, the distribution of the correlation function is recovered in a manner similar to that in the flat-wall case. In this case, the maximum correlation coefficient exhibits only slight differences at different wave phases while the vertical distribution of the correlation function depends on the wave phase.

Numerical simulations of gas-particle flow behavior created by low-level rotary-winged aircraft flight over particle bed

Xiaoxue JIANG, Yingqiao XU, Chuang WANG, Linzhi MENG, Huilin LU

2019, 40(3):  397-406.  doi:10.1007/s10483-019-2449-9

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The aerodynamics of gas-particle suspensions is simulated as an Euler-Euler two-fluid model in a revolving rotor over a particle bed. The interactions of collisions between the blade and particles and particle-particle interactions are modeled using the kinetic theory of granular flow (KTGF). The gas turbulence induced by the rotation of the rotor is modeled using the k_g-ε_g model. The flow field of a revolving rotor is simulated using the multiple reference frame (MRF) method. The distributions of velocities, volume fractions, and gas pressure are predicted while the aircraft hovers at different altitudes. The gas pressure decreases from the hub to the tip of the blade, and it is higher at the pressure side than that at the suction side of the rotor. The turbulent kinetic energy of the gas increases toward the blade tip. The volume fraction of particles decreases as the hovering altitude increases. The simulated pressure coefficient is compared with that in experimental measurements.

Linear stability theory with the equivalent spanwise wavenumber correction in 3D boundary layers

Runjie SONG, Shaolong ZHANG, Jianxin LIU

2019, 40(3):  407-420.  doi:10.1007/s10483-019-2450-6

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The prediction on small disturbance propagation in complex three-dimensional (3D) boundary layers is of great significance in transition prediction methodology, especially in the aircraft design. In this paper, the linear stability theory (LST) with the equivalent spanwise wavenumber correction (ESWC) is proposed in order to accurately predict the linear evolution of a disturbance in a kind of boundary layer flow with a vital variation in the spanwise direction. The LST with the ESWC takes not only the scale of the mean flow with the significant variation but also the wavenumber evolution of the disturbance itself. Compared with the conventional LST, the results obtained by the new method are in excellent agreement with those of the numerical simulations. The LST with the ESWC is an effective method on the prediction of the disturbance evolution in 3D boundary layers, which improves the prediction of the LST in the applications to complex 3D boundary layers greatly.