In situ measurements of Arctic clouds frequently show that ice
crystal number concentrations (ICNCs) are much higher than the number of
available ice-nucleating particles (INPs), suggesting that ...secondary ice production (SIP) may be active. Here we use a Lagrangian parcel model (LPM) and a
large-eddy simulation (LES) to investigate the impact of three SIP mechanisms
(rime splintering, break-up from ice–ice collisions and drop shattering) on
a summer Arctic stratocumulus case observed during the Aerosol-Cloud Coupling And
Climate Interactions in the Arctic (ACCACIA) campaign. Primary ice alone
cannot explain the observed ICNCs, and drop shattering is ineffective in the
examined conditions. Only the combination of both rime splintering (RS) and
collisional break-up (BR) can explain the observed ICNCs, since both of these
mechanisms are weak when activated alone. In contrast to RS, BR is currently
not represented in large-scale models; however our results indicate that
this may also be a critical ice-multiplication mechanism. In general, low
sensitivity of the ICNCs to the assumed INP, to the cloud condensation nuclei
(CCN) conditions and also to the choice of BR parameterization is found.
Finally, we show that a simplified treatment of SIP, using a LPM constrained
by a LES and/or observations, provides a realistic yet computationally
efficient way to study SIP effects on clouds. This method can eventually
serve as a way to parameterize SIP processes in large-scale models.
The vertical distribution of PM2.5 and meteorological parameters from ground to upper levels were observed simultaneously using meteorological tower, tethered balloons and aerosol laser radar in Dec ...of 2016 in the urban area of Tianjin and its southern district, Jinghai. The influence of the vertical structure of boundary layer on a typical haze-fog episode was analyzed. There existed long distance transport of PM in the high layers before the haze formed in Tianjin and the downward airflows brought the PM from the high layer to the ground. In the early stages of this episode, periodic temperature inversions occurred, leading to conspicuous diurnal variations in the vertical profile of the PM2.5. In the middle and late stages of this episode, strong inversion and thick humidity layer were sustained below 400 m, and there were no big daily changes in the vertical profiles of the PM2.5. During the rapid formation period of the fog, the inversion layer was damaged and turbulence was strengthened. During the stationary phase of the fog process, wind and turbulence in the boundary layer became weak again. Rime was the main weather-related, wet cleaning mechanism that lowered pollutants concentration during this fog episode. High concentrations of water soluble ions in the rime samples and the concentrations of those ions in ambient PM2.5 appeared significant decrease during the rime period, which illustrated the scavenging effect of rime.
•Field experiment was conducted during a haze-fog episode in 2016 in Tianjin.•Vertical profiles of PM2.5 and meteorological parameters were analyzed.•Inversion layer and turbulence were different for haze and fog period.•Wet cleaning mechanism by rime was analyzed.
•According to the calculation of local collision coefficients at different positions on the surface of the insulator, the mechanism of the uneven ice coating on the surface of the insulator is ...revealed.•The icing morphology of the shed edge and the rod in the radial direction are similar. Conversely, in the axial direction, there is a big difference due to the shielding effect of the shed.•According to the modeling method from low-dimensional to high-dimensional, a 3-D visualization dynamic rime icing growth prediction model on the surface of the insulator is established, and its prediction performance is verified by field tests.
Icing on transmission lines is a challenging problem in the world. Rime icing on silicone rubber insulator was taken as research object in this paper. The position coordinates of supercooled water droplets collided with the surface of the insulator were extracted, the local collision coefficient (E) of the droplet was calculated by a triangular area ratio method. The “point-line-face-solid” ice shape reconstruction algorithm was proposed to realize three-dimensional numerical simulation of rime ice accretion on the insulator. The results shown that the effect of median volume diameter (MVD) of the droplet on the E is greater than that of wind speed (v). The most serious icing occurs on the rod and the edge of the shed. Due to the shielding effect of the shed, the icing on the rod presents the shape of the nose. The length, thickness and amount of rime icing on the insulator calculated by the model increases with time, whose average errors with that obtained by the tests are 7.68%, 7.96%, 10.34%, and 9.45%, respectively. Moreover, the simulated icing distribution is well consistent with the experimental results. Therefore, the effectiveness of the numerical simulation method was proved in the present research.
This study aims to develop a three-dimensional icing simulation code named WISE (Wind turbine Icing Simulation code with performance Evaluation) integrated into OpenFOAM®. The freely available source ...code can contribute to icing simulations that require parallel computations. The rotational motion is explained by a Moving Reference Frame (MRF) in both aerodynamic and droplet fields. The thin water film theory is applied in the thermodynamic module. To verify WISE, ice accretion shapes on NREL Phase VI under rime and glaze icing conditions were considered. The ice accretion shapes obtained by WISE were compared against FENSAP-ICE and another numerical simulation without the MRF method for the droplet field. For the rime condition, the icing limits, maximum thickness, and its location are well predicted by WISE compared with FENSAP-ICE while the simulation without the MRF method overestimates the icing limits and maximum thickness. For the glaze condition, only WISE and FENSAP-ICE results are compared where the icing limits are slightly different. On the suction side, WISE accurately predicts the maximum thickness, ice growth direction, and icing limits. However, the thickness of ice on the pressure side is underestimated. It might be necessary to have a turbulence model that can predict the flow transition.
•Full there-dimensional wind turbine icing code named WISE (Wind turbine Icing Simulation code with performance Evaluation).•Open-source CFD, OpenFOAM® based icing simulation tool.•Moving reference frame method for both aerodynamic and droplet field modules.•Rime and glaze ice shapes on NREL Phase VI wind turbine.
The innovation of green and flexible sources of electricity is identified as one of the key enablers to a more electric-dependent world aiming at meeting the technology needs and promised ...sustainability goals. The thermoelectric generator device is one of these innovative sources as it directly converts the wasted heat to electric power with a cheap, silent, and no-emissions process. Yet, the power output of the thermoelectric generator is primarily based on the temperature distribution on its sides. Towards efficiently saving the wasted heat and maximizing the output power of the thermoelectric generator, optimizing the configuration for the thermoelectric generator array is paramount. In this regard, this paper proposes an optimal dynamic reconfiguration for several design options of the thermoelectric generator array, including series–parallel, total-cross-tied, bridge-linked, and honey-comp, to better enhance the thermoelectric generator array output power under nonuniform temperature distribution. The proposed dynamic reconfiguration approach is mathematically formulated as a maximization optimization problem for the thermoelectric generator array output power. The physics-based optimization of RIME is tailored to provide the optimal array reconfiguration layout that realizes the maximum power, upon which the overall power loss is potentially decreased, and the energy conversion efficiency is significantly improved. The efficacy and superiority of the proposed configuration types and optimal dynamic reconfiguration technique are assessed for two sizes of the thermoelectric generator array: a symmetric 9x9 array and an asymmetric 10x15 array. A detailed analysis is conducted to compare the thermoelectric generator output power of the studied configurations without and with the proposed dynamic reconfiguration technique. The results affirm that optimized dynamic reconfiguration significantly enhances the thermoelectric generator array-generated power. One of the key observations from the results is that employing a dynamic reconfiguration for the bridge-linked type yields up to a 10% increase in the output power of the thermoelectric generator array compared to the design options without reconfiguration. Also, the results show that the dynamically reconfigured bridge-linked type could yield about a 5% increase in the produced output power compared to other dynamically reconfigured design options.
•Proposing multiple design options for thermoelectric generator array.•Determining the optimal reconfiguration to enhance the array harvested power.•Symmetric and asymmetric thermoelectric generator arrays are studied.•Implementing efficient optimizer-based-RIME to reconfigure the array dynamically.•The reconfigured bridge-linked shows a significant improvement in the output power.
Ice formation and accumulation on blades is a serious threat to the reliable performance of wind turbines. This work investigates the microscopic icing characteristics around an entrapped air film ...during droplet impacts, which is closely related to the formation of rime ice and glaze ice. By coupling the Phase Field Method (PFM), a Dynamic Contact Angle (DCA) model and an enthalpy-porosity Phase Change Model (PCM), the heat transfer and icing characteristics around entrapped air films during droplets impact onto a cold surface was investigated. The initial morphology of the air film was firstly studied and compared with different theories. It was found that for ambient impact, the initial centerline height of the air film h0 showed a linear relationship with the square root of the Stokes number. Heat transfer analysis then revealed the dominant role of conductive heat transfer over convection contribution between the water and cold surface nearby entrapped air film region, while the flow field showed the vortex flow stirred by the retraction of the air film locally strengthened the heat transfer between water and the cold surface. As a consequence, the impact of droplets showed three possible regimes depending on the competition between icing damping effect and air film dynamics, including i) air film retraction and detachment similar to the isothermal impact for the case of no icing, due to small cooling effect; ii) restricted air film dynamics due to the forming of ice on top of the upper film surface, but the air film can still fully contract into a bubble; and iii) confined air film as the ice spreading on film surfaces that leads to the confinement of the air film, i.e., formation of porosity, inside a freezing droplet. Such microscopic insight into the entrapped air film thermal/hydro dynamics is of high implication to many droplet related applications, such as the presence of higher air volume in rime ice with reduced ice adhesion on wind turbine blades.
Different ice type dependent on the substrate and droplet temperature.
Description: The blue/red color of wind turbine blades indicates the temperature zone to be T < -20 °C or − 20 °C < T < 0 °C respectively; while the blue/red color of the droplets indicates whether the droplets are supercooled (to be more specific, T < 3 °C) or not. The rime ice is denoted in the white and opaque appearance (as shown in the innermost part), while the glaze ice is denoted in the transparent and runback flow fashion. The rime ice only occurs when the initial state of the droplets is close to supercooled and at the same time the temperature of the substrate is relatively lower. Display omitted
•Theoretical Contribution: In terms of the initial size of the air film, our simulation results show more support to Klaseboer's prediction than the Mandre's model.•Phenomenon Discovery: Based on detailed analysis of the heat transfer and flow field around the entrapped air film, three regimes are identified in terms of the freezing behavior nearby the air film depending on the competition between the ice damping effect and air film retraction hydrodynamics, which could be demarcated by the initial temperatures of the droplet and the solid surface. Further, the influence of icing on the attachment/detachment to the surface of the final air bubble is discussed, and compared to our previous finding in non-icing situations.•Application Prospect: This work may provide a plausible explanation for the relatively high air volume and low surface adhesion of rime ice compared with glaze ice, both of which are the main types of ice accretion on wind turbine blades and aircraft surface etc.
•Icing model considering rime ice property variability and runback water effect is developed.•Rime ice physical properties vary with airflow parameters and ice thickness.•Influences of rime ice ...properties and runback water on ice accretion are investigated.•Results generated by various icing models are compared.
An improved one-dimensional model has been developed to describe the aircraft icing process, which can be divided into the dry and wet mode icing stages. Rime ice forms on aircraft skin at the dry mode icing stage while glaze ice grows on the rime ice and water film develops on the glaze ice at the wet mode icing stage. The model differs from the traditional icing models in its assumption that the rime ice is a kind of porous medium and its physical properties are initially affected by airflow parameters and then vary linearly with the rime ice thickness. Further, it differs from our previous icing model in its inclusion of runback water effect. Calculations are performed to analyze the ice accretion characteristics, and the results are presented and discussed in comparison with those given by the traditional model and our previous model. The results show that the rime ice property variability and runback water influence the heat conductions in the ice layer and water film and consequently the ice accretion characteristics. The model proposed in this research provides an alternative approach for modeling the ice accretion process.
Understanding the dynamics of endogenous protein-protein interactions in complex networks is pivotal in deciphering disease mechanisms. To enable the in-depth analysis of protein interactions in ...chromatin-associated protein complexes, we have previously developed a method termed RIME (Rapid Immunoprecipitation Mass spectrometry of Endogenous proteins). Here, we present a quantitative multiplexed method (qPLEX-RIME), which integrates RIME with isobaric labelling and tribrid mass spectrometry for the study of protein interactome dynamics in a quantitative fashion with increased sensitivity. Using the qPLEX-RIME method, we delineate the temporal changes of the Estrogen Receptor alpha (ERα) interactome in breast cancer cells treated with 4-hydroxytamoxifen. Furthermore, we identify endogenous ERα-associated proteins in human Patient-Derived Xenograft tumours and in primary human breast cancer clinical tissue. Our results demonstrate that the combination of RIME with isobaric labelling offers a powerful tool for the in-depth and quantitative characterisation of protein interactome dynamics, which is applicable to clinical samples.
PDF
