Effect Of Grid Spacing Research Articles

Flexural behavior of FA-GGBS geopolymer concrete beams reinforced with carbon textile rods

Geopolymer concrete reinforced with carbon textile rods is a comparatively new technology that needs more research for a better understanding and application in the construction industry. Since, corrosion in steel is a serious issue that demands the repair and maintenance of structural concrete elements, use of non-corrosive carbon fibers as carbon textile rods is an alternative to replace steel reinforcement in concrete. High tensile strength, excellent durability, and light weight of carbon fibers make it more prevalent. Geopolymer concrete was used in this study since it has lower carbon dioxide emissions and adds sustainability by using waste materials. Industrial waste materials, such as fly ash (FA) and ground granulated blast-furnace slag (GGBS), were used to make geopolymer concrete (GC).The present work attempts to provide a deep understanding of ambient temperature-cured GC and the behavior of carbon textile rods as flexural reinforcement in GC. In addition, the effect of grid spacing of textile rods on improving the load-bearing behavior of GC beams was evaluated by a four-point bending test. From the experimental observations, it was observed that adding GGBS into FA helps to develop a GC having setting time and compressive strength comparable to that of cement concrete. The optimum proportion of GC has a binder content of 400 kg/m3 (70% FA and 30% GGBS), AL of 200 kg/m3, 10 M SH solution and SS/SH ratio 2, coarse aggregate of 985.58 kg/m3, fine aggregate of 779.86 kg/m3, EW/B ratio of 14% and SP of 2%. With ambient temperature curing, the aforementioned optimum mix attained a compressive strength of 50 MPa. Carbon textile rods improved the flexural strength of the beams and confirmed the reinforcing benefits as seen from ultimate load-carrying capacity, post-peak behavior, and failure mode. Beams reinforced with carbon textile rods with grid spacing-15 mm carried more load and showed ductile behavior due to the higher number of warp rods to take the flexural loading.

Investigation on the flow around a submarine under the rudder deflection condition by using URANS and DDES methods

Considering the complex flow features of a submarine under the maneuvering condition and their close relationship with the maneuverability, a numerical study is performed for the flow around the submarine under the rudder deflection condition. Taking the submarine model DARPA SUBOFF as the study object, the rudder force test with a wide range of rudder angles is simulated based on the open source CFD platform OpenFOAM. Two numerical methods of Unsteady Reynolds-Averaged Navier-Stokes (URANS) method and Delayed Detached Eddy Simulation (DDES) method are employed. A systematic convergence study is performed to clarify the effect of grid spacing and time step on the numerical solution. The computed hydrodynamic forces are compared with the available experimental data, and the effectiveness of the adopted numerical methods is validated. Besides, the obtained rudder forces and rudder parameters are compared and discussed. Based on the obtained flow field details of vortex structures, velocity fields, streamline distribution, turbulence levels, and pressure distribution, the flow mechanisms of the deflected rudders are analyzed. Compared with URANS method, DDES method presents a better capability of capturing the flow field details around the submarine under the tight maneuvering condition, where remarkable flow separation is involved.

Effects of grid spacing on high-frequency precipitation variance in coupled high-resolution global ocean–atmosphere models

High-frequency precipitation variance is calculated in 12 different free-running (non-data-assimilative) coupled high resolution atmosphere–ocean model simulations, an assimilative coupled atmosphere–ocean weather forecast model, and an assimilative reanalysis. The results are compared with results from satellite estimates of precipitation and rain gauge observations. An analysis of irregular sub-daily fluctuations, which was applied by Covey et al. (Geophys Res Lett 45:12514–12522, 2018. https://doi.org/10.1029/2018GL078926) to satellite products and low-resolution climate models, is applied here to rain gauges and higher-resolution models. In contrast to lower-resolution climate simulations, which Covey et al. (2018) found to be lacking with respect to variance in irregular sub-daily fluctuations, the highest-resolution simulations examined here display an irregular sub-daily fluctuation variance that lies closer to that found in satellite products. Most of the simulations used here cannot be analyzed via the Covey et al. (2018) technique, because they do not output precipitation at sub-daily intervals. Thus the remainder of the paper focuses on frequency power spectral density of precipitation and on cumulative distribution functions over time scales (2–100 days) that are still relatively “high-frequency” in the context of climate modeling. Refined atmospheric or oceanic model grid spacing is generally found to increase high-frequency precipitation variance in simulations, approaching the values derived from observations. Mesoscale-eddy-rich ocean simulations significantly increase precipitation variance only when the atmosphere grid spacing is sufficiently fine (< 0.5°). Despite the improvements noted above, all of the simulations examined here suffer from the “drizzle effect”, in which precipitation is not temporally intermittent to the extent found in observations.

Micromorphology of metallic surfaces for hydrophobicity by waterjet-guided laser processing

Waterjet-guided laser processing is a novel machining technique for metallic materials. To investigate and analyse the effects of processing parameters on surface topography change, micro-texturing evolution, and hydrophobicity, micromorphology machining experiments were conducted on stainless steel using self-developed waterjet-guided laser processing equipment. Nd:DPSS laser system with repetition frequency of 20–120 kHz and maximum power of 50W is used in the equipment. A scanning electron microscope (SEM) is used to measure surface topography. Energy-dispersive spectrometer (EDS) is used to evaluate the material composition of processing zone and no processing zone. The effects of grid spacing and laser power coupled into the jet are examined and processing conditions for hydrophobicity are provided. There was oxidation and no crack on the kerf edge. The surface contact angle dramatically increases from 92.94 to 138.41° with the decreasing of the grid size. It has been shown that waterjet-guided laser processing yields textures with a hydrophobic surface and is suit for micro-texture micro-machining.

PIV measurement and CFD analysis of the turbulent flow in a 3 × 3 rod bundle

The turbulent flow in a fuel bundle affects the heat transfer from the fuel rods to the coolant, which is a concerned issue in the design of fuel assemblies. In this paper, an experiment was performed using particle image velocimetry to measure the velocity distribution of water in a 3 × 3 rod bundle at various Reynolds numbers. The technique of matching index of refraction was utilized to fully visualize the flow field. Emphases were put on the flow inside a bare bundle that is free from the effects of grid spacer. It was found that the axial mean velocity in the subchannel is 30% higher than that in the gap center due to the cross-sectional nonuniform flow area. However, the axial root-mean-square velocity showed an inverse trend. The Reynolds shear stress exhibited a wavy variation in the lateral direction. A quasi-periodic large-scale flow pulsation was observed across the gap, and its wave length increases with Reynolds number. It was also found that the turbulent mixing coefficient was higher than that predicted by classical correlations. A numerical simulation was conducted signifying the acceptable performance of the EB-RSM model in predicting the flow behavior of water in the 3 × 3 rod bundle. Transient simulation with this turbulence model is able to capture the main flow phenomenon in the rod bundle.

Texturing of metallic surfaces for superhydrophobicity by water jet guided laser micro-machining

This experimental work demonstrates a new cost-effective way of achieving superhydrophobicity on metallic surfaces by micro-texturing with a novel water jet guided laser process. Compared to conventional pure laser texturing by nanosecond, picosecond and femtosecond lasers, water jet guided laser processing yields textures with an almost zero heat affected zone while the debris on the textured surface is simultaneously cleaned by the jet during the process. The effects of grid spacing, laser power coupled into the jet and water jet diameter are examined and processing conditions for achieving superhydrophobicity are provided. Changes in the wetting of the surface over time under ambient conditions from hydrophilic to superhydrophobic, due to changes in surface chemistry, were explored. It has been shown that the surface contact angle dramatically increases within the first couple of days after texturing when exposed to air. After around 20 days, the contact angle stabilized at 150°, 130° and 129° on textured 304 stainless steel, titanium and 6061 aluminum surfaces, respectively.

Toward Large‐Eddy Simulations of Dust Devils of Observed Intensity: Effects of Grid Spacing, Background Wind, and Surface Heterogeneities

AbstractDust devils are convective vortices with a vertical axis of rotation made visible by lifted soil particles. Currently, there is great uncertainty about the extent to which dust devils contribute to the atmospheric aerosol input and thereby influence Earth's radiation budget. Past efforts to quantify the aerosol transport and study their formation, maintenance, and statistics using large‐eddy simulation (LES) have been of limited success. Therefore, some important features of dust devil‐like vortices simulated with LES still do not compare well with those of observed ones. One major difference is the simulated value of the core pressure drop, which is almost 1 order of magnitude smaller compared to the observed range of 250 to 450 Pa. However, most of the existing numerical simulations are based on highly idealized setups and coarse grid spacings. In this study, we investigate the effects of various factors on the simulated vortex strength with high‐resolution LES. For the fist time, we are able to reproduce observed core pressures by using a high spatial resolution of 2 m, a model setup with moderate background wind and a spatially heterogeneous surface heat flux. It is found that vortices mainly appear at the lines of horizontal flow convergence above the centers of the strongly heated patches, which is in contrast to some older observations in which vortices seemed to be created along the patch edges.

Effects of grid spacer with vanes on liquid film for gas-liquid two-phase annular flow in 3×3 rod bundle channel

Effects of grid spacer with vanes on liquid film for gas-liquid two-phase annular flow in 3×3 rod bundle channel

Effects of Grid Spacing on Topology Optimization of Flow around an Object

Effects of Grid Spacing on Topology Optimization of Flow around an Object

3D model discretization in assessing urban solar potential: the effect of grid spacing on predicted solar irradiation

The increasing interest in solar energy production in urban areas requires an accurate simulation of solar irradiation on building surfaces, including vertical surfaces. However, solar potential analyses are usually conducted on 2.5D models, which are limited to roof surfaces. Methods based on 3D models, instead, allow the simulation of solar radiation on all building surfaces also accounting for inter-reflections. 3D models are thus discretized by grids of sensor points on which the solar potential is calculated.This paper investigates the discretization error in the assessment of solar potential based on 3D models. To this end, we tested the sensitivity of simulated solar irradiation to the resolution of the sensor grid. We analyzed the impact of the grid resolution using typical discretization approaches affecting the spatial arrangement of the sensor points.The study was conducted in a dense area of the city of Geneva represented at level of detail (LOD) 2. The simulated solar irradiation on 109 buildings was analyzed at different spatial, i.e. per surface and per building, and temporal granularities, i.e. hourly and yearly.The results show that the error increases linearly for grids spaced at up to 4 m with maximum relative root mean square error lower than 7%. The impact of the grid resolution was found greater for structured grids than unstructured grids. The results also highlight that finer grid resolutions (i.e. smaller spacing) are necessary if the analysis is conducted at high spatial or temporal granularity, notably when analyzing roof surfaces with shading artifacts.

WRF Model Study of the Great Plains Low-Level Jet: Effects of Grid Spacing and Boundary Layer Parameterization

AbstractPrevious studies have shown that the Weather Research and Forecasting (WRF) Model often underpredicts the strength of the Great Plains nocturnal low-level jet (NLLJ), which has implications for weather, climate, aviation, air quality, and wind energy in the region. During the Lower Atmospheric Boundary Layer Experiment (LABLE) conducted in 2012, NLLJs were frequently observed at high temporal resolution, allowing for detailed documentation of their development and evolution throughout the night. Ten LABLE cases with observed NLLJs were chosen to systematically evaluate the WRF Model’s ability to reproduce the observed NLLJs. Model runs were performed with 4-, 2-, and 1-km horizontal spacing and with the default stretched vertical grid and a nonstretched 40-m vertically spaced grid to investigate which grid configurations are optimal for NLLJ modeling. These tests were conducted using three common boundary layer parameterization schemes: Mellor–Yamada Nakanishi Niino, Yonsei University, and Quasi-Normal Scale Elimination. It was found that refining horizontal spacing does not necessarily improve the modeled NLLJ wind. Increasing the number of vertical levels on a non-stretched grid provides more information about the structure of the NLLJ with some schemes, but the benefit is limited by computational expense and model stability. Simulations of the NLLJ were found to be less sensitive to boundary layer parameterization than to grid configuration. The Quasi-Normal Scale Elimination scheme was chosen for future NLLJ simulation studies.

Effects of grid spacer with mixing vane on liquid film thickness for gas-liquid annular flow in a vertical pipe

Effects of grid spacer with mixing vane on liquid film thickness for gas-liquid annular flow in a vertical pipe

Grid-spacing and the quality of abundance maps for species that show spatial autocorrelation and zero-inflation

The effect of grid-spacing on the quality of species abundance maps is explored for species that show zero-inflation and spatial autocorrelation. Using a zero-inflated Poisson mixture model multiple fields of the prevalence parameter π and the intensity parameter μ were simulated. A selected field was sampled by grid-sampling with 200, 400, 800, 1600, and 3200 m grid-spacing and used to predict at a fixed set of validation locations by simple kriging with an external drift. The external drift variables were silt, silt squared and altitude. The estimated sampling distribution of MSE against grid-spacing shows that beyond a spacing of 1600 m the mean of MSE increases at a much faster rate. Based on these findings the 1600 m grid which consists of 446 locations for our study area of 2400 km2 gives a compromise between sampling costs and prediction accuracy.

Effects of Mixing-vane Attached to Grid Spacer on Pressure Drop and Deposition Rate in BWR Simulated Channel

This paper describes the experimental study on the effects of grid spacer with mixing-vane (MV) on gas-liquid two-phase annular flow in a vertical circular pipe of 16 mm i.d. In order to know the effects, grid spacers with and without MV were inserted in turn into the test channel. Furthermore, in order to know the effects of inclination angle of the mixing-vane to main flow, two inclination angles, i.e., 30° (MV30) and 20° (MV20) were tested. Pressure drop of flow through the spacer and liquid droplets deposition rate in the section downstream from the spacer were measured with a pressure transducer and double liquid film extraction method, respectively. Experimental data revealed that deposition mass transfer coefficient and the pressure drop were higher for the spacer with MV than that without MV. Regarding the effects of the inclination angle of MV, the vane of MV30 gave higher deposition mass transfer coefficient than MV20 although it increased the pressure drop.

E-13 垂直円管流路内の混合翼付グリッドスペーサが気液環状二相流に及ぼす影響

E-13 垂直円管流路内の混合翼付グリッドスペーサが気液環状二相流に及ぼす影響

Effects of grid spacer with mixing vane on entrainments and depositions in two-phase annular flows

The effects of mixing vanes (MVs) attached to a grid spacer on the characteristics of air ewater annular flows were experimentally investigated. To know the effects, a grid spacer with or without MV was inserted in a vertical circular pipe of 16-mm internal diameter. For three cases (i.e., no spacer, spacer without MV, and spacer with MV), the liquid film thickness, liquid entrainment fraction, and deposition rate were measured by the constant current method, single liquid film extraction method, and double liquid film extraction method, respectively. The MVs significantly promote the re-deposition of liquid droplets in the gas core flow into the liquid film on the channel walls. The deposition mass transfer coefficient is three times higher for the spacer with MV than for the spacer without MV, even for cases 0.3-m downstream from the spacer. The liquid film thickness becomes thicker upstream and downstream for the spacer with MV, compared with the thickness for the spacer without MV and for the case with no spacer.

403 Effects of grid spacer with mixing vane on gas-liquid two-phase annular flow

403 Effects of grid spacer with mixing vane on gas-liquid two-phase annular flow

107 単純化されたBWR流路と中央サブチャンネルの流れに及ぼすグリッドスペーサ混合翼の影響(OS.3 環境とエネルギー1)

107 単純化されたBWR流路と中央サブチャンネルの流れに及ぼすグリッドスペーサ混合翼の影響(OS.3 環境とエネルギー1)

The effect of grid spacing on size selectivity of shrimps in a pink shrimp trawl with a dual-grid size-sorting system

A Nordmøre-style grid is required in many pink shrimp (Pandalus borealis) trawl fisheries in Europe and North America. However, the Nordmøre Grid does not reduce the catch of small shrimps. To reduce catch of small shrimps, a size-sorting grid with 11mm grid spacing was developed and has been used by some trawlers. However, we do not know if the 11mm spacing is the optimal spacing for the fishery. We thus compared two sizes of grid spacing: 9 and 11mm. A trouser trawl system was developed and used to compare a codend with a 9mm spacing size-sorting grid and another identical codend with an 11mm spacing size-sorting grid. No significant differences were observed in the catch rate of shrimp, or major bycatch species between the two grids (p=0.35). The 11mm grid caught slightly less shrimps between 18 and 22mm carapace lengths that correspond to carapace widths of 8.5–10.5mm. This indicates that shrimps with 8.5–10.5mm carapace width might have escaped through the 11mm grid, but not the 9mm grid. These findings provide a scientific base and practical guidance for choosing grid spacing based on the size of shrimp to be released.

The Effect of Grid Spacing and Domain Size on the Quality of Ensemble Regional Climate Downscaling over South Asia during the Northeasterly Monsoon

Abstract The performance of an ensemble-based dynamical regional climate downscaling system is evaluated over southern Asia in a northeasterly monsoon season for different choices in grid spacing and domain size. A seven-member ensemble of the ECHAM4.5 global climate model at a resolution of about 300-km grid size was used to drive the RegCM3 regional climate model with grid sizes of 100, 50, 25, and 20 km, respectively. The performance is reported in detail over Sri Lanka. Two sets of regional model runs were undertaken to assess the effect of grid spacing and model domain size on the downscaling performance. The RegCM3 simulation with 100-km grid size significantly underestimates the height of the central mountain range in Sri Lanka, in a manner that is too coarse to capture orographic influences on the rainfall. However, the RegCM3 simulations with grid sizes from 20 to 50 km capture mesoscale features that arise from uplift condensation on the windward side of the monsoon winds due to the topography. These simulations also capture the orographic influences on the month-to-month rainfall over Sri Lanka that were absent in the ECHAM4.5. While the “small domain” runs [where only the forcings for the region immediately around Sri Lanka (4°–11°N, 76°–85°E) are used] are computationally more efficient, the results are overly controlled by the lateral boundary driving of the ECHAM4.5 so they inherit large uncertainty from the seven ECHAM4.5 realizations used for the RegCM3 ensemble runs. The “large domain” simulation used a domain comprising both land and ocean (approximately 4°S–22°N, 65°–96°E). The large-domain group of simulations produced reasonable spatial distribution of precipitation over the region. Moreover, the ensemble spread was considerably reduced in the large-domain high-resolution runs. Therefore, fine enough grid resolution (25 km or less) and sufficiently large domain size are both needed to simulate the essential features of precipitation in this tropical and monsoonal region.