Frictional boundary layer effect on vortex condensation in rotating turbulent convection

The effects of Ekman pumping on quasi-geostrophic Rayleigh-Benard convection

Numerical simulations of 3D, rapidly rotating Rayleigh-Benard convection are performed using an asymptotic quasi-geostrophic model that incorporates the effects of no-slip boundaries through (i) parameterized Ekman pumping boundary conditions, and (ii) a thermal wind boundary layer that regularizes the enhanced thermal fluctuations induced by pumping. The fidelity of the model, obtained by an asymptotic reduction of the Navier-Stokes equations that implicitly enforces a pointwise geostrophic balance, is explored for the first time by comparisons of simulations against the findings of direct nu…

Heat transfer mechanisms in bubbly Rayleigh-Benard convection

The heat transfer mechanism in Rayleigh-Benard convection in a liquid with a mean temperature close to its boiling point is studied through numerical simulations with point-like vapor bubbles, which are allowed to grow or shrink through evaporation and condensation and which act back on the flow both thermally and mechanically. It is shown that the effect of the bubbles is strongly dependent on the ratio of the sensible heat to the latent heat as embodied in the Jacob number Ja. For very small Ja the bubbles stabilize the flow by absorbing heat in the warmer regions and releasing it in the col…

Theory and modeling of nonperturbative effects at high acoustic energy densities in thermoviscous acoustofluidics

A theoretical model of thermal boundary layers and acoustic heating in microscale acoustofluidic devices is presented. It includes effective boundary conditions allowing for simulations in three dimensions. The model is extended by an iterative scheme to incorporate nonlinear thermoviscous effects not captured by standard perturbation theory. The model predicts that the dominant nonperturbative effects in these devices are due to the dependency of thermoacoustic streaming on gradients in the steady temperature induced by a combination of internal frictional heating, external heating, and therm…

通过横向限制实现低普朗特数对流中的流动反转

Flow Reversal in Low-Prandtl-Number Convection via Lateral Confinement

研究低普朗特数流体中LSC流动反转问题，通过直接数值模拟液态金属对流，发现强横向限制能引发“羽流凝聚”转变，减少热损失，为角涡提供浮力驱动反转，绘制出“反转岛”，确立横向限制为控制参数。

Enhanced heat transport by turbulent two-phase Rayleigh-Bénard convection

We report measurements of turbulent heat-transport in samples of ethane (C$_2$H$_6$) heated from below while the applied temperature difference $ΔT$ straddled the liquid-vapor co-existance curve $T_ϕ(P)$. When the sample top temperature $T_t$ decreased below $T_ϕ$, droplet condensation occurred and the latent heat of vaporization $H$ provided an additional heat-transport mechanism.The effective conductivity $λ_{eff}$ increased linearly with decreasing $T_t$, and reached a maximum value $λ_{eff}^*$ that was an order of magnitude larger than the single-phase $λ_{eff}$. As $P$ approached the crit…

Spectrum of infrasound radiation from supercell storms

We consider the generation of acoustic waves by turbulent convection and perform spectral analysis of a monopole source of sound related to the heat production by condensation of moisture. A quantitative explanation of the correlation between intensity of infrasound generated by supercell storms and later tornado formation is given. It is shown that low lifting condensation level (LCL) and high values of convective available potential energy (CAPE), which are known to favor significant tornadoes, also lead to a strong enhancement of supercell's low frequency acoustic radiation.

三相Stefan问题的解析与数值解：同时发生熔化、固结、沸腾和冷凝现象

Analytical and numerical solutions to the three-phase Stefan problem with simultaneous occurrences of melting, solidification, boiling, and condensation phenomena

本文提出了一种解决同时发生熔化、固结、沸腾和冷凝现象的三相Stefan问题的解析与数值解方法。

Large Eddy Simulations of turbulent convective flow through a periodic groove channel

The use of extended surfaces find wide range of applications in heat transfer devices for achieving heat transfer augmentation like gas turbine blade cooling and nuclear reactor core since the last few decades. So, understanding the underlying flow physics physics and the transport phenomenon governing the heat transfer enhancement is the goal of the present study. In the present investigation, numerical computations of turbulent forced convection through a periodic groove channel are carried out using large eddy simulations. The lower wall of the grooved channel is provided with constant heat…

不同曲率周期性凹槽上湍流对流流动特性的数值研究

A numerical investigation on turbulent convective flow characteristics over periodic grooves of different curvatures

本文通过在周期性凹槽通道尖角处引入曲率，利用ANSYS Fluent 19.2中的k-epsilon(RNG)模型进行湍流强制对流数值模拟，发现曲率可使整体传热提升12%，传热强化幅度增加5%。