Zhenhua Wan

Zhenhua Wan
University of Science and Technology of China | USTC · Department of Modern Mechanics

PhD

About

80
Publications
10,892
Reads
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502
Citations
Introduction
Zhenhua Wan currently works at the Department of Modern Mechanics, University of Science and Technology of China. Zhenhua does research in Aeronautical Engineering and Mechanical Engineering. Their current projects are 'aerodynamic noise simulation, modelling and control', 'instabilities and turbulence in thermal and multiphase flows', and 'data-driven science in fluid mechanics'.
Additional affiliations
April 2020 - present
University of Science and Technology of China
Position
  • Professor (Associate)
Education
September 2008 - November 2013

Publications

Publications (80)
Article
Pressure fluctuations play an essential role in the transport of turbulent kinetic energy and vibrational loading. This study focuses on examining the effect of wall cooling on pressure fluctuations in compressible turbulent boundary layers by high-fidelity direct numerical simulations. Pressure fluctuations result from the vorticity mode and the a...
Article
Self-generated magnetic fields in single-mode ablative Rayleigh–Taylor instability (ARTI) relevant to the acceleration phase of inertial confinement fusion (ICF) implosions are studied via two dimensional simulations. In ARTI, [Formula: see text] T magnetic fields can be generated via the Biermann battery source without considering the Nernst effec...
Article
A high-fidelity finite difference method for simulation of viscoelastic turbulence in cylindrical coordinates has been developed. In this algorithm, the evolution equation for the polymer conformation tensor is discretized by an improved Kurganov-Tadmor (KT) scheme, while the continuity and momentum equations are discretized by a well-established s...
Article
The two-plasmon-decay instability (TPD) in the large-incidence-angle regime is studied via fluid and particle-in-cell (PIC) simulations. It is found that the TPD threshold in this regime within a narrow incidence angle range close to $60^\circ$ can be orders of magnitude lower than the normal-incidence threshold. A threshold formula is proposed for...
Article
Full-text available
Trailing-edge serrations inspired by owls are capable of reducing broadband noise. In this study, the wall-resolved large-eddy simulations (LES) are carried out on the flow over NACA-0012 airfoil with additional serrated trailing edges. The computations are conducted with the high-order flux reconstruction method on unstructured meshes. Three kinds...
Article
In the study of Rayleigh-Bénard (RB) convection, it is usually assumed that sidewalls are adiabatic. However, this is not always the case in real heat exchangers. Consequently, the flow structures and heat transfer will be inevitably affected by non-adiabatic walls. The effect of the thermal conductivity of sidewalls on RB convection is investigate...
Article
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An alternative formulation of targeted ENO scheme (AFTENO) is proposed for hyperbolic conservation laws. The new scheme combines the advantages of targeted ENO (TENO) and the alternative formulation of weighted essentially non-oscillatory scheme (AFWENO). AFTENO has more flexible characteristics than the original TENO. For instance, the former can...
Article
Full-text available
A high fidelity flow simulation for complex geometries for high Reynolds number (Re) flow is still very challenging, requiring a more powerful HPC system. However, the development of HPC with traditional CPU architecture suffers bottlenecks due to its high power consumption and technical difficulties. Heterogeneous architecture computation is raise...
Article
Full-text available
For the compressible Rayleigh-Taylor instability (RTI), density stratification is found to cause different bubble behaviors for different Atwood number (At) values. We propose a modified buoyancy-drag model that interprets the physical mechanism causing these behaviors, and analyze the acceleration behavior of a bubble at high At in detail. This wo...
Article
Self-sustained oscillation and the sound radiation of flow over an open cavity is of great importance in nature and industry. Influences of filled porous media in the cavity are investigated numerically by using a lattice Boltzmann method in two-dimensional space. It is shown that the outcomes of the porous patch depend on the location of the patch...
Article
A direct numerical simulation database of a weakly compressible turbulent channel flow with bulk Mach number 1.56 is studied in detail, including the geometrical relationships between the pressure-Hessian tensor and the vorticity/strain-rate tensor, as well as the mechanism of the pressure-Hessian tensor contributing to the evolution of invariants...
Article
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A high-order transition route from inertial to elasticity-dominated turbulence (EDT) in Taylor-Couette flows of polymeric solutions has been discovered via direct numerical simulations. This novel two-step transition route is realized by enhancing the extensional viscosity and hoop stresses of the polymeric solution via increasing the maximum chain...
Article
Based on the fully compressible Navier–Stokes equations, the linear stability of thermal convection in rapidly rotating spherical shells of various radius ratios η is studied for a wide range of Taylor number Ta, Prandtl number Pr and the number of density scale height Nρ. Besides the classical inertial mode and columnar mode, which are widely stud...
Article
Buoyancy driven turbulence with free-slip top and bottom plates in a confined box is studied via direct numerical simulations (DNS). The Rayleigh number is fixed to Ra=108 and the Prandtl number is Pr=10. The length/height aspect ratio Γy is fixed to 2, while the depth/height aspect ratio Γx varies from 0.125 to 0.3. With the variation of Γx, the h...
Article
Thermal convection in a tilted three-dimensional rectangular box has been systematically investigated by direct numerical simulation. The Rayleigh number Ra varies from 10⁷ to 10⁹, the Prandtl number Pr is set to 0.7, and the tilted angle β ranges from 0° to 90°. The effects of tilting on large-scale circulation (LSC), Nusselt number (Nu), Reynolds...
Article
Rough-surface Rayleigh-Bénard convection is investigated using direct numerical simulations in two-dimensional convection cells with aspect ratio Γ=2. Three types of fractal roughness elements, which are marked as n1, n2 and n3, are constructed based on the Koch curve and sparsely mounted on both the plates, where n denotes the level of the roughne...
Article
Full-text available
With the aid of a large eddy simulation (LES) model of a turbulent jet, we study the modeling of jet noise based on wavepackets by considering a certain degree of nonlinearity. Linear parabolized stability equations (PSEs) are utilized to solve the spatial evolution of wavepackets with the base flow obtained from the LES. The spectral proper orthog...
Article
A modified multiscale method without constitutive equation is proposed to investigate the microscopic information and macroscopic flow properties of polymeric fluid with the memory effect between parallel plates. In this method, the domain is entirely described by macro model with isolated molecular dynamics simulations applied to calculate the nec...
Article
Full-text available
We present particle-in-cell (PIC) simulations of laser plasma instabilities (LPIs) with a laser pulse duration of a few picoseconds. The simulation parameters are appropriate to the planar-target LPI experimental conditions on SG-II. In this regime, the plasmas are characterized by a long electron density scale length and a large electron density r...
Article
Full-text available
The low shear rate interfacial slip behaviors of nonentangled bead–spring polymer melts are firstly simulated using a multiscale method without constitutive relations and wall slip hypotheses. Two orders of magnitude less computation compared with pure molecular dynamics simulations offers the present multiscale method unique capability to resolve...
Article
Full-text available
In implicit large eddy simulations, a porous material was used to suppress the noise produced by a flow past an open cavity. The base case has a Mach number and Reynolds number based on the cavity depth ReD = 10^5. Strong pressure fluctuations were produced. The solid cavity floor was replaced by a porous material to suppress high-pressure oscillat...
Article
Full-text available
The near-wall structures and statistics of fluctuating pressure (p ′) in compressible turbulent channel flows (CTCF) with isothermal walls have been investigated by direct numerical simulations. Two typical cases for high bulk Mach number Ma = 3.83 and low one Ma = 1.56 are considered. A novel type of near-wall pressure structures named "alternatin...
Article
Full-text available
Rectangular supersonic jets exist widely in propulsion systems of aircrafts. When they are imperfectly expanded under certain conditions, the upstream traveling waves referred to as screech tones will be produced, which may cause structural fatigue failure. In this work, high fidelity simulations are employed to investigate the bevelled effects due...
Article
Direct numerical simulations of supersonic flows past a two-dimensional cavity with a length-to-depth ratio of 4 under different Mach numbers are performed. Firstly, as the Mach number increased from 1.1 to 2.7 with a small initial boundary layer thickness, the dominant flow mode transforms from a wake mode to the Rossiter II mode, and to the Rossi...
Preprint
Full-text available
A high fidelity flow simulation for complex geometries for high Reynolds number ($Re$) flow is still very challenging, which requires more powerful computational capability of HPC system. However, the development of HPC with traditional CPU architecture suffers bottlenecks due to its high power consumption and technical difficulties. Heterogeneous...
Preprint
Full-text available
We perform a numerical study of the heat transfer and flow structure of Rayleigh-B\'enard (RB) convection in (in most cases regular) porous media, which are comprised of circular, solid obstacles located on a square lattice. This study is focused on the role of porosity $\phi$ in the flow properties during the transition process from the traditiona...
Article
Full-text available
We perform a numerical study of the heat transfer and flow structure of Rayleigh-Bénard (RB) convection in (in most cases regular) porous media, which are comprised of circular, solid obstacles located on a square lattice. This study is focused on the role of porosity φ in the flow properties during the transition process from the traditional RB co...
Article
On non-Oberbeck–Boussinesq effects in Rayleigh–Bénard convection of air for large temperature differences - Volume 889 - Zhen-Hua Wan, Qi Wang, Ben Wang, Shu-Ning Xia, Quan Zhou, De-Jun Sun
Article
Full-text available
In Rayleigh–Bénard convection experiments, the thermal coupling between the sidewall and fluid is unavoidable. As a result, the thermal properties of the sidewall can influence the flow structure that develops. To get a better understanding of the influence of the sidewall, we performed a one-to-one comparison between experiments and direct numeric...
Article
In a turbulent jet, the numerical investigation of space-time correlations $C(r,\tau)$ at two-point and two-time of streamwise fluctuating velocities is presented along the nozzle lipline. Large-eddy simulation (LES) is performed for a Mach $0.9$ turbulent jet issuing from a round nozzle. The turbulent boundary layer is well developed at the nozzle...
Article
Full-text available
The onset of thermal convection in a rapidly rotating spherical shell is studied by linear stability analysis based on the fully compressible Navier–Stokes equations. Compressibility is quantified by the number of density scale heights N_\rho, which measures the intensity of density stratification of the motionless, polytropic base state. The nearl...
Article
Full-text available
Penetrative turbulent Rayleigh-Bénard convection which depends on the density maximum of water near 4 • C is studied using two-dimensional and three-dimensional direct numerical simulations. The working fluid is water near 4 • C with Prandtl number Pr = 11.57. The considered Rayleigh numbers Ra range from 10 7 to 10 10. The density inversion parame...
Article
The bifurcations of penetrative Rayleigh-Bénard convection in cylindrical containers are studied by the linear stability analysis (LSA) combined with the direct numerical simulation (DNS) method. The working fluid is cold water near 4°C, where the Prandtl number Pr is 11.57, and the aspect ratio (radius/height) of the cylinder ranges from 0.66 to 2...
Article
We present a study of absolute and convective instabilities in electrohydrodynamic flow subjected to a Poiseuille flow (EHD-Poiseuille). The electric field is imposed on two infinite flat plates filled with a non-conducting dielectric fluid with unipolar ion injection. Mathematically, the dispersion relation of the linearised problem is studied bas...
Article
The coupling and evolution of two-mode ablative Rayleigh-Taylor instability (ARTI) in two-dimensional geometry are studied via numerical simulations. We focus primarily on two scenarios: Coupling and bubble competition of a long and a short wavelength mode and of two short-wavelength modes. It is found that the long-wavelength modes tend to dominat...
Article
Full-text available
Thermal convection in a two-dimensional tilted cell with aspect ratio (Γ = width/height) 0.5 is studied using direct numerical simulations. The considered tilt angle β ranges from 0 deg. to 90 deg. The Prandtl number Pr dependence is first studied in the range of 0.01 ≤ Pr ≤ 100 for a fixed Rayleigh number Ra = 10^7. The Ra dependence is also inves...
Article
Full-text available
We numerically investigate non-Oberbeck-Boussinesq (NOB) effects due to large temperature differences in a two-dimensional differentially heated square cavity using low-Mach-number equations. The working fluid is air and the Prandtl number P r is 0.71 for the reference state. The considered Rayleigh numbers Ra range from 10 5 to 10 9. Various tempe...
Preprint
Full-text available
Penetrative turbulent Rayleigh-B\'enard convection which depends on the density maximum of water near $4^\circ\rm{C}$ is studied using two-dimensional (2D) and three-dimensional (3D) direct numerical simulations (DNS). The working fluid is water near $4^\circ\rm{C}$ with reference Prandtl number $Pr=11.57$. The considered Rayleigh numbers $Ra$ rang...
Article
Full-text available
The coexistence of multiple turbulent states was reported in several recent studies in different flows. We present in this work that multiple turbulent states also exist for thermal convection in two-dimensional tilted cells with large aspect ratios (\Gamma= width/height) through direct numerical simulations for the Rayleigh number Ra = 10^7 and th...
Article
Full-text available
The influence of tilt on flow reversals in two-dimensional thermal convection in rectangular cells with two typical aspect ratios, $\unicode[STIX]{x1D6E4}=\text{width/height}=1$ and 2, are investigated by means of direct numerical simulations. For $\unicode[STIX]{x1D6E4}=1$ , tilt tends to suppress flow reversals. However, it is found that flow rev...
Article
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A numerical technique of high-order piecewise parabolic method in combination of HLLD ("D" denotes Discontinuities) Riemann solver is developed for the numerical simulation of elastic-plastic flow. The introduction of the plastic effect is realized by decomposing the total deformation gradient tensor as the product of elastic and plastic deformatio...
Article
Full-text available
The influences of non-Oberbeck–Boussinesq (NOB) effects on flow instabilities and bifurcation characteristics of Rayleigh–Bénard convection are examined. The working fluid is air with reference Prandtl number $Pr=0.71$ and contained in two-dimensional rigid cavities of finite aspect ratios. The fluid flow is governed by the low-Mach-number equation...
Article
Full-text available
The adjoint-based control of noise emission for two supersonic turbulent jets with different temperature ratios is attempted by modifying the inlet perturbations. The major noise emission of supersonic jets can be modeled by the spatially developing instability waves, which are obtained by solving parabolized stability equation (PSE) based on the s...
Article
An effective boundary potential has been proposed to solve non-periodic boundary condition (NPBC) of hybrid method. The optimized hybrid method is applied to investigate the influences of the channel height and solid-liquid interaction parameters on slip characteristics of Couette flows in micro/nanochannels. By changing the channel height, we find...
Article
Full-text available
Spatial instability waves associated with low-frequency noise radiation at shallow polar angles in the chevron jet are investigated and are compared to the round counterpart. The Reynolds-averaged Navier–Stokes equations are solved to obtain the mean flow fields, which serve as the baseflow for linear stability analysis. The chevron jet has more co...
Article
Full-text available
We present the application of Harten-Lax-van Leer (HLL)-type solvers on Riemann problems in nonlinear elasticity which undergoes high-load conditions. In particular, the HLLD (“D” denotes Discontinuities) Riemann solver is proved to have better robustness and efficiency for resolving complex nonlinear wave structures compared with the HLL and HLLC...
Article
Full-text available
Thermal convection in a three-dimensional tilted rectangular cell with aspect ratio 0.5 is studied using direct numerical simulations within both Oberbeck-Boussinesq (OB) approximation and strong non-Oberbeck-Boussinesq (NOB) effects. The considered Rayleigh numbers í µí±í µí±Ž range from 10 5 to 10 7 , the working fluid is air at 300 K, and the co...
Article
Full-text available
The reduced-order model (ROM) for the two-dimensional supersonic cavity flow based on proper orthogonal decomposition (POD) and Galerkin projection is investigated. Presently, popular ROMs in cavity flows are based on an isentropic assumption, valid only for flows at low or moderate Mach numbers. A new ROM is constructed involving primitive variabl...
Article
Full-text available
A large eddy simulation (LES) is performed for two subsonic jets with a Reynolds number of Re=10^5, which have different core temperatures, i.e., the cold and hot jet. The far-field overall sound pressure levels (OASPL) and noise spectra are well validated against previous experimental results. It is found that the OASPL is raised by heating at sha...
Article
Full-text available
A direct simulation with selected inflow forcing is performed for an accurate description of the jet flow field and far-field noise. The effects of the Mach number and heating on the acoustic field are studied in detail. The beam patterns and acoustic intensities are both varied as the change of the Mach number and temperature. The decomposition of...
Article
Large eddy simulation is performed for investigating thermal effects in subsonic swirling jet. The effects on the flow development and far-field noise are discussed in detail. The results of linear stability theory shows that the growth rates of the shear layers rise as the core temperature increases, the LES results show that heating promotes the...
Article
The flow instabilities of Rayleigh-Bénard convection in a cylinder with effect of uniform internal heat source are investigated numerically. The instabilities of the static state and of axisymmetric flows are investigated by linear stability analysis. The convection threshold depends on the strength of internal heat source q and the aspect ratio of...
Article
Flow reversals in two-dimensional Rayleigh–Bénard convection led by non-Oberbeck–Boussinesq (NOB) effects due to large temperature differences are studied by direct numerical simulation. Perfect gas is chosen as the working fluid and the Prandtl number is 0.71 for the reference state. If NOB effects are included, the flow pattern $P_{11}$ with on...
Article
Full-text available
Supersonic flows past two-dimensional cavities with/without control are investigated by the direct numerical simulation (DNS). For an uncontrolled cavity, as the thickness of the boundary layer declines, transition of the dominant mode from the steady mode to the Rossiter II mode and then to the Rossiter III mode is observed due to the change of vo...
Article
A subsonic transitional jet is simulated by large eddy simulation, while the flow and acoustic properties are validated against existed experimental results. In the hydrodynamic region, the total disturbance kinetic energy declines as azimuthal wavenumber ( ) or frequency increases. In the far field, the acoustic field is dominated by the axisymmet...
Article
Full-text available
Large eddy simulation was performed for two jets, i.e. a cold jet and its heated counterpart, with the same exit Mach number. The far-field noise was predicted by Kirchhoff's integral method based on the near-field pressure fields on a controlled surface. The directivity and intensity of the far-field noise are found to be in good agreement with ex...
Article
Full-text available
Thermal effects on the sound generation by vortex pairing are investigated in axisymmetric subsonic jets. Direct numerical simu- lation of compressible Navier-Stokes equations is performed for an accurate description of near-field flow dynamics and far-field sound. As the core temperature increasing, the positions of vortex roll-up and pairing move...