Horizontal Surface Research Articles

Turbulent Thermal Convection At A Rough Surface

We present measurements of the near-wall velocity field in highly turbulent Rayleigh-Bénard(RB) convection with rough horizontal surfaces. The measurements have been undertaken in a large-scale RB experiment which is called "Barrel of Ilmenau". We used the technique of stereoscopic Particle Image Velocimetry to measure the three components of the velocity field in horizontal planes parallel to the heated bottom plate. The measurements reported here comprise two Rayleigh numbers Ra=8.6×10^{10} and Ra=6.3×10^{11}. The Prandtl number of the working fluid was Pr=0.7. We used a chess board-like pattern of cuboids with a base area of 30 mm by 30 mm and a height of h=12 mm. Our measurements confirm the observation from previous experiments that the relation Nu=f(Ra) remains unchanged with respect to RB convection with smooth surfaces as long as the thickness of the thermal boundary layer \delta_{th}=H/(2Nu) exceeds the height of the roughness elements h. If \delta_{th} falls below h, Nu becomes larger and grows faster with increasing Ra then it does in RB convection with smooth plates. We also could identify the valleys in between the cuboids as the main contribution for the increase of Nu

Estimating incident infrared radiation intensity on a horizontal surface

The study aims to characterize external IR heating sources, operating in free convection atmosphere, qualitatively and quantitatively for various applications. It employs non-invasive IR thermography to measure steady-state irradiations from a ceramic IR heater at variable voltages (60–150 V) using the surface energy budget (SEB) method which relies on only two measured parameters (surface and ambient temperature). The free convection heat transfer from the plate is demarcated between the thermal boundary layer (TBL) and buoyant plume-dominated region by temperature histogram tool. Nearly 78 ± 5 % of the plate area is occupied by the hot plume(s) in the studied voltage range. Estimated irradiation agrees fairly well with one another (within ± 10 %). Additionally, the time response of the plate was measured to be ∼ 120 s. This fast response can be made even faster, by reducing the thermal mass, eventually leading to low-cost IR sensors.

The effect of adding layers of date stones on the profitability of brackish water solar desalination process

Lately, there has been a pronounced and alarming up tick in the global demand for fresh water, resulting in a limited availability of this precious resource. Solar desalination emerges as a promising solution, particularly for supplying the sparsely populated desert regions in the southern regions of Algeria, where plentiful solar energy and subterranean brackish water resources are present.The current paper seeks to optimize the performance of traditional solar stills and elevate the quality of distilled water by incorporating layers of blackened date stones as an additional heat storage medium. Date stones, typically discarded post-date consumption, undergo a process of washing and blackening before being introduced in two forms (stone and powder). They are then uniformly distributed across the horizontal surface of solar still’s absorber.Three solar stills of identical design featuring glass sides were designed, manufactured, and subjected to testing to compare their productivity with that of a control unit. Experimental trials conducted at Ouargla University reveal significant enhancements the inclusion of a single layer of date stones (approximately 2.210 kg/ (m2 of absorber area)) leads to a remarkable 45.66 % increase in yield. Conversely, an equivalent amount (≈ 504 g) of date stones in powder form results in a 29.42 % improvement in yield. Notably, the distillate quality is substantially enhanced in both cases contrasted with the conventional setup.

Text-to-building: experiments with AI-generated 3D geometry for building design and structure generation

The paper seeks to investigate novel potentials for building design and structure generation that arise at the intersection of computational design and AI-generated 3D geometries. Although the use of AI technologies is exponentially increasing inside the architectural discipline, the design of spatial building configurations using AI-generated 3D geometries is still limited in its applications and represents an ongoing field of investigation in advanced architectural research. In this regard, several questions still need to be answered: how can we design new building typologies from AI-generated 3D geometries? And how can we use these typologies to shape both the real and the virtual world?The paper proposes a new approach to architectural design where artificial intelligence is used as the starting point for design exploration, while computational design procedures are employed to convert AI-generated 3D geometries into building elements – such as columns, beams, horizontal and vertical surfaces. The paper starts with a general overview of the current use of artificial intelligence inside the architectural discipline, and then it moves towards the explanation of specific AI generative models for 3D geometry reconstruction and representation. Subsequently, the proposed working pipeline is analysed in more detail – from the creation of 3D geometries using generative AI models to the conversion of such geometries into building elements that can be further designed and optimised using computational design tools and methods. The results shown in the paper are achieved using Shap-E as the main AI model, though the proposed pipeline can be implemented with multiple AI models. The paper ends by showing some of the generated results, finally adding some considerations to the relationship between human and artificial creativity inside the architectural discipline.The work presented in the paper suggests that the use of computational design tools and methods combined with the tectonics of the latent space opens new opportunities for topological and typological explorations. In a time where traditional architectural typologies are moving towards stagnation due to their inability to satisfy new human needs and ways of living, exploring AI-based working pipelines related to architectural design allows the definition of new design solutions for the generation of new architectural spaces. In doing so, the serendipitous aspect of AI biases is used as an auxiliary force to inform design decisions, promoting the discovery of a new inbuilt dynamism between human and artificial creativity. In a time where AI is everywhere, understanding the measure of such dynamism represents a key aspect for the future of the architectural discipline.

Solar global irradiance from actinometric degree data for Filaret Observatory (Bucharest), 1892–1903

Long-term series of solar irradiation measured at ground level are not available in the old times. However, long-term series of actinometric degree data obtained by using the Arago-Davy instrument have been recorded in the second half of the 19th century in several locations of the world. We have developed recently a method to estimate global solar irradiance on horizontal surface from actinometric degree data (doi.org/10.1007/s00704-023-04485-2). This opens a way of finding proxy information about the incident solar irradiance on various areas of the globe before the 20th century. Hourly actinometric degree data for the years 1892–1903 are available at the Filaret Observatory (Bucharest, Romania, South-Eastern Europe). The observed series have a systematic decreasing tendency, which has been removed by using a correction procedure. The proposed method is used here to evaluate solar global irradiance at Filaret Observatory. Solar irradiance data provided by the Twentieth Century Reanalysis Project version 3 (20CRv3) are used as a reference. The expected hourly and daily average solar irradiance values show reasonable qualitative consistency with the 20CRv3 data. This consistency is notably stronger during the warmer months from April to September. Much better agreement is found for the monthly averaged solar global irradiance values. At this level, the proposed method and the procedure of the 20CRv3 project seem to validate each other.

Prediction of Global Solar Radiation across the Region of Northern Sudan

Available data for solar resources indicates that northern Sudan has solar potentials among the highest in world. However, in this vast area (about 471×103 km2) only two stations, at Hudeiba and Dongola, have records for global solar radiation. Four other stations (at Atbara, Karima, Abu-Hamed and Wadi-Halfa) in this region have records for sunshine duration. In this study, recorded data at Hudeiba and Dongola stations have been used to develop 15 models for estimation of monthly average daily global solar radiation on a horizontal surface in northern Sudan. The developed models have been extensively evaluated by using 14 statistical indicators. All developed models revealed good performance (percentage errors within ±4.5%). Then, the most accurate regional model (Model M3) has been used to predict the global solar radiation at Atbara, Karima, Abu-Hamed and Wadi-Halfa stations. Results showed that the whole region receives abundant solar energy throughout the year. The yearly average of daily global solar radiation over the entire region is 23.16 MJ/m2. Furthermore, the developed models can be used to predict global radiation at adjacent places that lack such data.

A 2D equivalent linear inversion model of bedrock motions in a layered transversely isotropic half-space

Inversion is the process that evaluates input motion on the bedrock from surface motions, primarily for use as input excitation for site seismic response or soil-structure interaction analyses. The paper presents a two-dimensional (2D) equivalent linear inversion model for bedrock motion in a multi-layered transversely isotropic (TI) half-space. Based on the exact dynamic stiffness matrices of TI soil layer and bedrock half-space, an inversion objective function is established from both horizontal and vertical surface acceleration records, and the optimization method is adopted to update the control parameters for the inversion process. Moreover, an equivalent linear method is used to account for the TI soil nonlinearity, thus realizing the nonlinear inversion for bedrock motion and incident angle. The inversion procedure is verified by using a single-layered TI soil profile model with three different materials. The numerical results demonstrate that the bedrock motion and the incident angle in the TI medium can be accurately inversed according to the surface motions and the TI site characteristics, indicating that the inversion method can be used for reliable engineering applications in the TI medium.

Numerical investigation of printed circuit board response during solder float test: Influence of thermal boundary conditions

During qualification, a Printed Circuit Board (PCB) must pass several electrical and thermomechanical tests. Among the tests required by the European Cooperation for Space Standardization (ECSS), the solder float test consists in resting a sample on a 288 °C solder bath. In order to simulate and better understand the latter, the heat transfer coefficient (HTC) of the PCB/solder bath interface has to be characterized.In this work, an experimental setup has been developed to measure the HTC of the interface between SnPb and a horizontal surface. In addition, a finite element model of the solder float test has been developed in order to study the temperature and stress fields inside the PCB. The temperature field is highly heterogeneous at the beginning of the heating. A direct consequence of this early temperature heterogeneity is the development of stress fields that can be correlated to the observed failure modes. A parametric study revealed the sensitivity of the stress and strain development to changes in the HTC value. The difference observed in finite element simulations between isothermal assumptions and transient regime holds true for any maximum temperature in the range of 100 °C to 288 °C. The present work highlights the importance of considering exact thermal boundary conditions when studying the reliability of PCBs under thermal loading (especially with fast changes).

Saturated nucleate pool boiling of cryogenic fluids: Review of databases, assessment of existing models and correlations, and development of new universal correlation

The absence of a comprehensive and reliable nucleate pool boiling database for heat transfer coefficient (HTC) of cryogenic fluids is the driving force behind this study. Such a database is essential to evaluating the predictive accuracy of existing tools, including both models and correlations, and to pioneering the development of a new, more accurate predictive method. To address this need, a new Consolidated Cryogenic Nucleate Pool Boiling Database (comprised of 2908 data points) was compiled, with emphasis on HTC from flat horizontal and vertical surfaces, drawing from the broad literature resources available from across the globe. The database enabled a comprehensive assessment of prior models and correlations, and careful examination showed most of these tools yield unacceptably large errors in predicting the HTC data, especially for elevated pressures and large heat fluxes. Consequently, a new correlation is proposed for all cryogenic fluids combined, which is fine-tuned to outperform prior predictive tools, particularly for elevated pressures and large heat fluxes. The new correlation has a Mean Absolute Error (MAE) of 25.36 %, with 64.5 % of the predictions falling within ±30 % of the data and 87.2 % within ±50 %. This exceptional predictive capability positions the new correlation as a robust tool for both thermal design and performance assessment of a broad variety of devices and systems.

Heat transfer evaluation of (CaTe+SiC) hybrid nanofluid flow based RT42 HC (Rubitherm) phase change material: Cooling photovoltaic panels application

This paper inspects the combined effects of heat and mass transfers in a hybridized Williamson viscous nanofluid composed of cadmium telluride (CdTe) and silicon carbide (SiC) nanoparticles in RT42 (Rubitherm) as base fluid in the existence of heat source and thermal radiative aspects. Knowing that the base fluid RT42 is a phase change material (PCM), it is also considered that the surface on which the nanofluid flows is an expandable surface with varying thickness. The influence of chemical reactions process and viscous dissipation on the flow and temperature of the hybridized nanofluid is examined. The parameters’ influences on the problem are evaluated after setting appropriate similarity transformations to transform the collection of major partial differential equations (PDEs) into nondimensional ordinary differential equations (ODEs). The study concludes that the presence of hybridized nanoparticles of CdTe and SiC reduces the horizontal and vertical surface frictional forces of the hybrid nanofluid. The integration of nanoparticles in RT42 enhances heat transfer rates and reduces mass transfer. The thermal radiative variable declines the heat transfer of hybridized nanofluid. The results indicate that altering the variable parameter of surface thickness reduces frictional forces in both directions.

Expanding manufacturability of sheet-based triply periodic minimal surfaces by electron beam powder bed fusion in Wafer theme

Porous biomaterials based on triply periodic minimal surfaces (TPMS) are intensely studied and discussed in the literature. Manufacturing of these structures with a complex geometry became possible using additive manufacturing methods, having their own specifics and challenges. Previously, we demonstrated that sheet-based gyroids, one of TPMS structures, manufactured by electron beam powder bed fusion in Melt and Wafer themes could possess identical mechanical properties (quasi-elastic gradient). In the current research sheet-based gyroids were produced using Wafer Theme with five different settings, including electron beam current and scan speed variation with MultiBeam turned on and off, in attempt to obtain thin walls without losing mechanical performance. Mechanical tests revealed that the specimens manufactured with higher beam line energy on average show better mechanical properties. The specimens produced with MultiBeam showed slightly lower mechanical properties, and do not demonstrate significant improvement in the TPMS surface roughness. According to SEM studies, the average wall thickness was about 0.4 mm for specimens with high line energy, and 0.3 mm for low line energy. Through-hole defects on the horizontal surfaces, noticed and discussed by us previously, have larger average area of the hole and more irregular shape for increased beam line energy. TPMS surface morphology of the specimens produced with higher beam energy and no MultiBeam was on average more even. According to EBSD, α/α` martensite with laths oriented in a Widmanstätten basket-weave pattern was observed with no β phase in the resulting material. No significant differences in microstructure between specimens produced with different beam energy was detected. FEA modeling revealed the impact of the wall thickness, through holes size and orientation on quasi-elastic gradient of a gyroid. It was demonstrated that, through holes with small size located on the horizontal surfaces (layer plane) have only a minor impact on the mechanical properties of the samples if they are not extremely abundant.

Critical transitions on a route to chaos of natural convection on a heated horizontal circular surface

The transition route and bifurcations of the buoyant flows developing on a heated horizontal circular surface are elaborated using direct numerical simulations and direct stability analysis. A series of bifurcations, as a function of Rayleigh numbers ( $Ra$ ) ranging from $10^6$ to $6.0\times 10^7$ , are found on the route to chaos of the flows at $Pr=7$ . When $Ra<1.0\times 10^3$ , the buoyant flows above the heated horizontal surface are dominated by conduction, because of which the distinct thermal boundary layer and plume are not present. At $Ra=1.1\times 10^6$ , a Hopf bifurcation occurs, resulting in the flow transition from a steady state to a periodic puffing state. As $Ra$ increases further, the flow enters a periodic rotating state at $Ra=1.9\times 10^6$ , which is a unique state that was rarely discussed in the literature. These critical transitions, leaving from a steady state and subsequently entering a series of periodic states (puffing, rotating, flapping and period-doubling) and finally leading to chaos, are diagnosed using two-dimensional Fourier transforms. Moreover, direct stability analysis is conducted by introducing random numerical perturbations into the boundary condition of the surface heating. We find that when the state of a flow is in the vicinity of critical values (e.g. $Ra=2.0\times 10^6$ ), the flow is conditionally unstable to perturbations, and it can bifurcate from the rotating state to the flapping state in advance. However, for relatively stable flow states, such as at $Ra=1.5\times 10^6$ , the flow remains in its periodic puffing state even though it is being perturbed.

A method for predicting deformation field of deep foundation pit considering spatial effect

Urban underground spaces have experienced significant development and utilization due to the rapid progress of urban construction and continuous advancements in construction technology. The number of foundation-pit projects immediately adjacent to buildings, structures, and pipelines has been increasing. Ensuring the safety of construction and surrounding facilities, it is essential to predict deformation caused by foundation pit excavations. In this study, a simple calculation method was proposed for predicting deformation of an envelope structure and surface settlement caused by deep foundation excavation with spatial effects. Firstly, the principle of minimum potential energy was applied and the lateral displacement equation of the envelope structure was derived, considering spatial deformation effects. Secondly, based on linear elasticity theory, a surface settlement expression was formulated utilizing the plane strain boundary. Finally, the stratigraphic loss method was used to establish a connection between horizontal envelope deformation and surface settlement, allowing for calculations of surface settlement at any position behind the envelope structure. The effectiveness and practicability of the proposed method were demonstrated by comparison of two existing foundation-pit engineering examples.

A High-Resolution Measurement Method for Inner and Outer 3D Surface Profiles of Laser Fusion Targets Using a Laser Differential Confocal–Atomic Force Probe Technique

The high-resolution and nondestructive co-reference measurement of the inner and outer three-dimensional (3D) surface profiles of laser fusion targets is difficult to achieve. In this study, we propose a laser differential confocal (LDC)–atomic force probe (AFP) method to measure the inner and outer 3D surface profiles of laser fusion targets at a high resolution. This method utilizes the LDC method to detect the deflection of the AFP and exploits the high spatial resolution of the AFP to enhance the spatial resolution of the outer profile measurement. Nondestructive and co-reference measurements of the inner profile of a target were achieved using the tomographic characteristics of the LDC method. Furthermore, by combining multiple repositionings of the target using a horizontal slewing shaft, the inner and outer 3D surface profiles of the target were obtained, along with a power spectrum assessment of the entire surface. The experimental results revealed that the respective axial and lateral resolutions of the outer profile measurement were 0.5 and 1.3 nm, while the respective axial and lateral resolutions of the inner profile measurement were 2.0 nm and approximately 400.0 nm. The repeatabilities of the root-mean-square deviation measurements for the outer and inner profiles of the target were 2.6 and 2.4 nm, respectively. We believe our study provides a promising method for the high-resolution and nondestructive co-reference measurement of the inner and outer 3D profiles of laser fusion targets.

Numerical investigation of the hydrodynamic properties of oscillating water column air chambers

Abstract The oceans occupy nearly 71% of the Earth’s surface area. The ocean is rich in energy, and wave energy is one of its important components. Therefore, the study of wave energy generation devices is an important issue. In this paper, we analyze the effect of the size of the air chamber structure on the OWC (oscillating water column) wave energy conversion device under the action of unidirectional regular waves. To analyze the performance of the OWC device under real sea conditions, the wave climate at Sanmenxia is used as the experimental parameter. The performance and characteristic response with the variation of incident wave height, air chamber width and front wall thickness, are analyzed. The results show that the incident wave height, air chamber width, and front wall draft have significant effects on the performance of OWC. With the increase of incident wave height, the wave nonlinear effect increases. As the air chamber width decreases, the horizontal surface inside the air chamber undulates smoothly and the standing wave phenomenon disappears.

Design & Fabrication of Vertical Surface Cleaner

Abstract: The Wall Climbing Robot designed in this study to combines the innovative propulsion system of propellers with the traditional locomotion method of wheels to achieve versatile and efficient mobility on both vertical and horizontal surfaces. By integrating propellers and wheels, the robot can seamlessly transition between climbing walls and moving along flat surfaces. The hybrid design not only enhances the robot's mobility but also optimizes its energy efficiency, making it suitable for prolonged missions in various environments. This research explores the synergistic integration of propellers and wheels, showcasing the robot's adaptability in real- world applications such as surveillance, inspection, and maintenance tasks in both indoor and outdoor scenarios. The developed Wall Climbing Robot presents a significant advancement in robotic mobility, offering a promising solution for complex tasks in diverse settings

Regressive and Spatio-Temporal Accessibility of Variability in Solar Energy on a Short Scale Measurement in the Southern and Mid Region of Mozambique

Solar energy reaching a horizontal surface can possess fluctuations that impact electricity generation at a solar plant. Despite this, energy access remains inadequate, particularly in rural areas, with an estimated 82% deficiency. This drives us to assess the regressive and spatial-temporal accessibility of solar energy in the southern and mid regions of Mozambique. This evaluation aims to determine the actual availability of energy for electrification purposes. Data on global horizontal irradiation from approximately 8 stations across all provinces in the specified regions, collected between 2012 and 2014 at intervals of 1 and 10 min, were analyzed using regression and correlation methods along with a specialized algorithm for classifying days based on clear sky index terms. The statistical analysis identified days with significant potential for energy accessibility, exceeding 50% of the average. The findings suggest a correlation coefficient of approximately 0.30 for energy and non-linear regression with clear sky index coefficients around 0.80. The method employed demonstrated accuracy when compared to theoretical simulations of the clear sky index in the region, indicating its potential applicability in other regions of interest.

Modeling, simulation, and experiments of a flexible track robot over rigid horizontal and inclined surfaces

This paper studies the locomotion of a robot fitted with flexible rubber tracks while driving and climbing over rigid horizontal and inclined surfaces. We developed a model that accounts for sliding during rotation and the distribution of the normal forces along the track. On horizontal surfaces, we found that the size of the robot (width and length) and the normal force distribution along the track had a substantial influence on its turning speed and radius, whereas the coefficient of friction (COF), the robot's mass and inertia had a much lesser influence. The model shows that on inclined surfaces, even on relatively small slopes, the robot substantially slides downwards as it tries to rotate. The results of the model and the simulations were validated using a tracked vehicle that was built and tested on a solar panel. The experimental results of the turning radius and rotational speed were within 2% of the model (see video).

Envirotype-based delineation of environmental effects and genotype × environment interactions in Indian soybean (Glycine max, L.)

Soybean is a rainfed crop grown across a wide range of environments in India. Its grain yield is a complex trait governed by many minor genes and influenced by environmental effects and genotype × environment interactions. In the current investigation, grain yield data of different sets of 41, 30 and 48 soybean genotypes evaluated during 2019, 2020 and 2021, respectively across 19 locations and twenty years’ data on 19 different climatic parameters at these locations was used to study the environmental effects on grain yield, to understand the genotype × environment interactions and to identify the mega-environments. Through analysis of variance (ANOVA), it was found that predominant portion of the variation was explained by environmental effects (E) (53.89, 54.86 and 60.56% during 2019, 2020 and 2021, respectively), followed by genotype × environment interactions (GEI) (31.29, 33.72 and 28.82% during 2019, 2020 and 2021, respectively). Principal Component Analysis (PCA) revealed that grain yield was positively associated with RH (Relative humidity at 2 m height), FRUE (Effect of temperature on radiation use efficiency), WSM (Wind speed at 2 m height) and RTA (Global solar radiation based on latitude and Julian day) and negatively associated with VPD (Deficit of vapour pressure), Trange (Daily temperature range), ETP (Evapotranspiration), SW (Insolation incident on a horizontal surface), n (Actual duration of sunshine) and N (Daylight hours). Identification of mega-environments is critical in enhancing the selection gain, productivity and varietal recommendation. Through envirotyping and genotype main effect plus genotype by environment interaction (GGE) biplot methods, nineteen locations across India were grouped into four mega-environments (MEs). ME1 included five locations viz., Bengaluru, Pune, Dharwad, Kasbe Digraj and Umiam. Eight locations—Anand, Amreli, Lokbharti, Bidar, Parbhani, Ranchi, Bhawanipatna and Raipur were included in ME2. Kota and Morena constitutes ME3, while Palampur, Imphal, Mojhera and Almora were included in ME4. Locations Imphal, Bidar and Raipur were found to be both discriminative and representative; these test locations can be utilized in developing wider adaptable soybean cultivars. Pune and Amreli were found to be high-yielding locations and can be used in large scale breeder seed production.

Scraping of a thin layer of viscoplastic fluid

We analyze the scraping of a thin layer of viscoplastic fluid residing on a horizontal surface by a translating rigid scraper. This motion generates a mound of fluid upstream of the scraper and a residual layer behind it, both of which are modelled using a shallow layer theory for a Bingham or Herschel-Bulkley fluid. The flows ahead of and behind the scraper are coupled by the motion in the gap under the scraper, which is driven both by the translation of the scraper and by the induced pressure gradient due to the difference in flow thickness upstream and downstream. When the gap between the scraper and the underlying surface is sufficiently small, we find that a steady state emerges after a relatively long transient and that en route to this state, the unsteady dynamics exhibit a variety of regimes that are self-similar to leading order. We construct these solutions explicitly and derive key scalings for the temporal development of the flowing viscoplastic layer, as well as identifying the timescales at which there are transitions between the regimes. These predictions are confirmed by comparison with results from the numerical integration of the full system. Finally, we report results from preliminary laboratory experiments, which are compared with predictions from the shallow-layer theory, obtaining reasonable agreement once a slip boundary condition is included in the model, as motivated by experimental observations. Published by the American Physical Society 2024