Numerical Predication Research Articles

Around the World They Go: Circumnavigating Balloon Satellites!

Abstract Students from the University of Alabama in Huntsville successfully deployed three micro superpressure balloon satellites in winter 2021. Students planned and implemented all phases of the project: obtaining funding, determining project timelines, preparing equipment, launching balloons, designing and implementing a website, writing daily blogs on the balloon progress, and analyzing the data. The objective of the flights was to use the balloons as a meteorological tool to study conditions in the lower stratosphere (12–14 km), as a tracer for evaluating modeled air parcel trajectories, and as an outreach and educational tool. The three balloons successfully traveled hundreds of thousands of kilometers, making an accumulated total of 16 global circumnavigations. Throughout the project, students made connections with hundreds of researchers, ham radio operators, STEM groups, and other students around the globe. The balloons provided velocity telemetry within many different weather regimes, including vigorous jets over the Himalayas, slow-moving equatorial air masses over the middle of the Pacific Ocean, and dense polar air masses over the Arctic Circle. This study has found that the accuracy of HYSPLIT-calculated trajectories using numerical weather predication (NWP) meteorological data can be quantified using parcel velocity, duration of trajectory forecast, and spatial resolution of the NWP model.

Numerical Simulation and Experimental Study on Energy Absorption of Foam-Filled Local Nanocrystallized Thin-Walled Tubes under Axial Crushing.

A crashworthiness design of foam-filled local nanocrystallized thin-walled tubes (FLNTs) is proposed by using foam-filled structures and ultrasonic impact surface treatment. The crashworthiness and deformation modes of FLNTs are studied using an experiment and numerical analysis. A finite element numerical model of FLNTs is established, and the processing and test platform of FLNTs is set up to verify the numerical predication and analytical design. The results show that local nanocrystallization is an effective method to enhance crashworthiness for hexagonal FLNTs. The FLNTs with four circumferential continuous stripes of surface nanocrystallization exhibit a level of 47.12% higher specific energy absorption than the untreated tubes in numerical simulations for tubes with a 50% ratio of nanocrystallized area. Inspired by the strength mechanism, a novel nested foam-filled local surface nanocrystallization tube is further designed and studied in detail.

Spatial–Temporal Relationship Study between NWP PWV and Precipitation: A Case Study of ‘July 20’ Heavy Rainstorm in Zhengzhou

In order to study and forecast extreme weather, a comprehensive and systematic analysis of the spatial and temporal relationship between Precipitable Water Vapor (PWV), predicted by Numerical Weather Predication (NWP) data, and precipitation, is necessary. The goal of this paper was to study the temporal and spatial relationship between PWV and precipitation during the so-called ‘July 20’ (18–21 July 2021) heavy rainstorm in Zhengzhou. Firstly, the PWV data provided by 120 radiosonde stations uniformly distributed throughout the world, and two IGS stations in China, in 2020, was used to evaluate the accuracy of PWV estimation by ERA5 and MERRA-2 data, and the factors affecting the accuracy of NWP PWV were explored. Secondly, ERA5 PWV and the precipitation data of six meteorological stations were used to qualitatively analyze the relationship between PWV and precipitation during the ‘July 20’ heavy rainstorm in Zhengzhou. Finally, a quantitative study was conducted by an eigenvalue matching method. The main experimental results were as follows. Compared with MERRA-2 PWV, the accuracy of ERA5 PWV was slightly higher. Latitude, altitude and season were the influencing factors of the NWP PWV estimation accuracy. The change trend of ERA5 PWV was consistent with both 24 h cumulative precipitation and surface precipitation during the ‘July 20’ heavy rainstorm in Zhengzhou. The average optimal matching degree and optimal matching time between NWP PWV and surface precipitation during the ‘July 20’ heavy rainstorm in Zhengzhou was 56.6% and 3.68 h, respectively. The maximum optimal matching degree was 80.3%. The spatial–temporal relationship between NWP PWV and surface precipitation was strong.

A smoothly tunable shape memory metamaterial with adaptive bandgaps for ultra-wide frequency spectrum vibration control

This article presents a smoothly tunable shape memory elastic metamaterial with adaptive bandgaps enabling the broadband frequency vibration control. The underlying bandgap-tuning mechanism arises from the reversible large deformation induced by shape memory alloy (SMA) element under electro-thermal loads, through which, various microstructural shape morphing could be achieved. Via delicately designing the unit cell, the numerically obtained band structures and effective medium properties display a successful attainment of the vibration stop-passing band formation and smoothly controllable two-way tuning phenomenon for a series of transitional and intermediate status. The overall controllable frequency scope could be shifted over an ultra-wide band. Subsequently, a systematic parametric study is carried out to unfold the bandgap-adjusting patterns by altering the apparent structural stiffness and the SMA elastic modulus, individually. The finite element harmonic analysis of a metamaterial unit-cell-chain model is further investigated to verify the effectiveness of vibration suppression and the variability of the stopband region from the frequency spectra and the equivalent stresses images. Finally, the experimental demonstration is performed to validate the numerical predication from a practical perspective. The proposed design may possess enabling application potentials for future active vibration control and noise isolation in engineering facilities.

Does Frege Have Aristotle's Number?

AbstractFrege argues that number is so unlike the things we accept as properties of external objects that it cannot be such a property. In particular, (1) number is arbitrary in a way that qualities are not, and (2) number is not predicated of its subjects in the way that qualities are. Most Aristotle scholars suppose either that Frege has refuted Aristotle's number theory or that Aristotle avoids Frege's objections by not making numbers properties of external objects. This has led some to conclude that Aristotle's accounts of arithmetical and geometrical objects differ substantially. I close this supposed gap by showing that Aristotle's arithmetical objects, like geometrical objects, are just certain sensible things qua certain properties they in fact possess. Specifically, numbers are pluralities qua quantitative or relational properties like ten units or ten. I show that this view is resistant to the Fregean concerns about arbitrariness and numerical predication.

Variation of Internal Tides on the Continental Slope of the Southeastern East China Sea

The semidiurnal internal tides (ITs) on the continental slope of the southeastern East China Sea (ECS) exhibited abrupt enhancement in November of 2017. This enhancement resulted from the intensification of the coherent semidiurnal ITs. Coherent and incoherent semidiurnal ITs had a comparative energy contribution in October; however, coherent semidiurnal ITs dominated with a variance contribution of 90% in November. The variance contribution of vertical modes of the semidiurnal ITs varied between October and November, and the mode with most variance contribution changed from the second mode to the first mode. Altimeter data and the observed background currents indicated that the Kuroshio mainstream meandered and abruptly intruded into the ECS in November. The upper layer background currents were significantly related to the kinetic energy of the semidiurnal ITs, and the correlation coefficient between them reached 0.81. The frequent occurrences of the Kuroshio intrusion have suggested that the ITs in the ECS are susceptible to the modulation of the Kuroshio current. Numerical modeling and predication of ITs should consider the meander of the Kuroshio mainstream.

Transverse Vibration of Viscoelastic Sandwich Structures: Finite Element Modeling and Experimental Study.

In the present work, the nonlinear vibration behavior of elastic-viscoelastic-elastic sandwich (EVES) beams is studied. A finite element (FE) equation taking intoaccount the transverse compression deformation of the viscoelastic core for the EVES beams is derived. In order toaccurately characterize the frequency-dependent feature of the viscoelastic materials layer, athird-order seven-parameter Biot model isused. A 2-node 8-DOF element is established to discretize the EVES beams. The experimental testing onEVES beams validates the numerical predication of the FE model. Numerical and analytical investigations are carried on a series of EVES beams with different thicknesses. The results indicate that the presented FE model has better accuracy in predicting the natural frequency of the sandwich beams, and in predicting damping, the accuracy is related to the thickness of each layer. The results of this paper have important reference values for the design and optimization of the viscoelastic sandwich structure.

Numerical Predication of Solidification Phenomena of Phase Change Material in Concentric Annulus Pipe

Two-dimensional numerical simulation is performed aiming to understand the role of buoyancy force convection during restricted solidification of phase change materials (PCMs) inside a shell and tube heat exchanger according to annulus cross section. Where the transient history of PCM solidification evolution was studied. The governing equations of mass, momentum and energy are solved to study the solidification behavior inside the annulus geometry. The fluid flow in the mushy zone was accounted for using the Darcy drag source term in momentum, and the liquid percentage in each cell was updated using the enthalpy-porosity method. Thermal conditions of the outer cylinder insulated (adiabatic) and the inner cylinder at constant temperature (isothermal). The results are presents as a temperature contour and liquid fraction distribution in the domain. The predicted result shows the capturing phenomenon: primary heat conduction in all regions, then heat convection and conduction become dominant in the top and bottom regions, respectively. The max. and min. temperature changes near the outer pipe surface during 16 hrs. are 56.25% and 42.5%, respectively.

Numerical and Experimental Predication of the Structural Cracking Within Reinforced Concrete Structure due to Conventional State of Loading

It has been well understanding that the occurrence of various crack patterns in the building during its construction life (from first time of construction up to finishing) then subjected to super imposed load or during the service life. Cracks developed due to exceeding of stresses more than the allowable strength, wherever happened on building component. This research works used the finite element method as a powerful tool to simulate the behavior of full constructed building with both concrete system and brick bearing wall. Where the adopted numerical procedure allows to the users to predict the response of building elements due to conventional state of loading. one of the most important response features was the cracking phenomenon, where the numerical model shown that its capability to predict the cracking sequence from the first time of initiating. The prediction of full response and behavior of each element and their connection, shown that the precise of factor of safety used by the designer, where the analysis prove that the design load was about 67% from the cracking load, and the ultimate load was about 260% from the design load. That will allow more sustainability and stability for long time deformation. Beside the numerical solution, there was an experimental part of study, where site investigation, it shown that all data recorded was constant values and the building was stable. Actually, with no increasing of loading, the building reach its stable state, and defect will not develop. That basically because of good design within conventional state of loading.

Did the Climate Forecast System Anticipate the 2015 Caribbean Drought?

AbstractIn groundwater-limited settings, such as Puerto Rico and other Caribbean islands, societal, ecological, and agricultural water needs depend on regular rainfall. Though long-range numerical weather predication models explicitly predict precipitation, such quantitative precipitation forecasts (QPF) critically failed to detect the historic 2015 Caribbean drought. Consequently, this work examines the feasibility of developing a drought early warning tool using the Gálvez–Davison index (GDI), a tropical convective potential index, derived from the Climate Forecast System, version 2 (CFSv2). Drought forecasts are focused on Puerto Rico’s early rainfall season (ERS; April–July), which is susceptible to intrusions of strongly stable Saharan air and represents the largest source of hydroclimatic variability for the island. A fully coupled atmosphere–ocean–land model, the CFSv2 can plausibly detect the transatlantic advection of low-GDI Saharan air with multimonth lead times. The mean ERS GDI is calculated from semidaily CFSv2 forecasts beginning 1 January of each year between 2012 and 2018 and monitored as the initialization approaches 1 April. The CFSv2 demonstrates a broad region of statistically significant correlations with observed GDI across the eastern Caribbean up to 30 days prior to the ERS. During 2015, the CFSv2 forecast a low-GDI tongue extending across the Atlantic toward the Caribbean with 60–90 days lead time and placed Puerto Rico’s 2015 ERS beneath the 15th percentile of all 1982–2018 ERS forecasts with up to 30 days lead time. A preliminary GDI-based QPF tool tested herein is a statistically significant improvement over climatology for the driest years.

A numerical and experimental study on the divergence instability of an inverted cantilevered plate in wall effect

We present a numerical and experimental study on the static-divergence instability of an inverted cantilevered plate in an uniform axial subsonic airflow. The flow is assumed ideal and is confined by a rigid channel wall. The inverted cantilevered plate, unlike a conventional one, is with a clamped trailing edge and a free leading edge. The equation of the plate motion is solved by the finite-difference method, and the linearized boundary element method is applied for the fluid equations. A new trigonometric form vortex panel model is developed for the solution of fluid force. An equivalent test method is developed for the divergence instability and is applied for the experimental study. The effect of the rigid wall is evaluated for various distances between the plate and the rigid channel wall, and the critical airflow velocity increases with the increase in the distance. The numerical calculations and predication show good agreement with the experimental results. When the distance is large enough, the numerical results are in accordance with the existing theory for an unconfined airflow. Finally, an approximated solution of the critical airflow velocity in terms of the distance is suggested.

A Finite Element Model for the Vibration Analysis of Sandwich Beam with Frequency-Dependent Viscoelastic Material Core.

In this work, a finite element model was developed for vibration analysis of sandwich beam with a viscoelastic material core sandwiched between two elastic layers. The frequency-dependent viscoelastic dynamics of the sandwich beam were investigated by using finite element analysis and experimental validation. The stiffness and damping of the viscoelastic material core is frequency-dependent, which results in complex vibration modes of the sandwich beam system. A third order seven parameter Biot model was used to describe the frequency-dependent viscoelastic behavior, which was then incorporated with the finite elements of the sandwich beam. Considering the parameters identification, a strategy to determine the parameters of the Biot model has been outlined, and the curve fitting results closely follow the experiment. With identified model parameters, numerical simulations were carried out to predict the vibration and damping behavior in the first three vibration modes, and the results showed that the finite model presented here had good accuracy and efficiency in the specific frequency range of interest. The experimental testing on the viscoelastic sandwich beam validated the numerical predication. The experimental results also showed that the finite element modeling method of sandwich beams that was proposed was correct, simple and effective.

Evaluation of season long rainfall simulated by WRF over the NWH region: KF vs. MSKF

Abstract This study is aimed to assess the performance of Numerical Weather Predication (NWP) model Weather Research and Forecasting (WRF) in simulating the season long rainfall pattern over the North-West Himalayan (NWH) region. For this purpose, two experiments are designed with identical initial conditions but varying cumulus physics options viz.; Kain-Fritsch (KF) and Multi-scale Kain-Fritsch (MSKF). WRF simulations have been carried out for multiple nested domains (45, 15 and 5 km) configuration for monsoon season of 2017. Model derived rainfall corresponding to two experiments has been evaluated against the gridded rainfall data prepared by India Meteorological Department (IMD) and satellite based GPM-IMERGE and INSAT-3D HE-rain. Present results unveiled that the KF scheme overestimates the amount of rainfall over the entire study domain; whereas, MSKF scheme is capable to simulate the magnitude of rainfall comparable to the observations. Model simulated rainfall corresponding to both the experiments yields stronger correlation with satellite based GPM-IMERG as compared to the IMD data. It is noted based on statistically robust Chow test that the WRF simulation with KF scheme estimates break point in the rainfall pattern at 1200 m whereas WRF simulation with MSKF scheme resolves break point at 2000 m which is in close agreement with the previous studies. Categorical statistics metrics and qualitative analysis of WRF simulations suggest that the scale aware cumulus scheme MSKF performs better in resolving monsoon season rainfall pattern over the rugged topography of the NWH region. Present study has implications for improved understanding of spatial pattern of monsoon rainfall over the NWH region.

Diagnosis for Nonmagnetic Topological Semimetals in the Absence of Spin-Orbital Coupling

Topological semimetals are under intensive theoretical and experimental studies. The first step of these studies is always the theoretical (numerical) predication of one of several candidate materials, starting from first principles. In these calculations, it is crucial that all topological band crossings, including their types and positions in the Brillouin zone, are found. While band crossings along high-symmetry lines, which are routinely scanned in numerics, are simple to locate, the ones at generic momenta are notoriously time-consuming to find, and may be easily missed. In this paper, we establish a theoretical scheme of diagnosis for topological semimetals where all band crossings are at generic momenta in systems with time-reversal symmetry and negligible spin-orbital coupling. The scheme only uses the symmetry (inversion and rotation) eigenvalues of the valence bands at high-symmetry points in the BZ as input, and provides the types, numbers and configurations of all topological band crossings, if any, at generic momenta. The nature of new diagnosis scheme allows for full automation and parallelizations, and paves way to high throughput numerical predictions of topological materials.

Impact of Bias-Correction Methods on Effectiveness of Assimilating SMAP Soil Moisture Data into NCEP Global Forecast System Using the Ensemble Kalman Filter

Improving numerical weather prediction was one of the main justifications for National Aeronautics and Space Administration's Soil Moisture Active/Passive (SMAP) Mission. The ensemble Kalman filter (EnKF) has been extensively applied to assimilate the SM observations into numerical weather predication models. Implementation of EnKF requires the observations and model simulations to be Gaussian distributed and not biased from each other. In this letter, we tested the impacts of three bias-correction methods on effectiveness of assimilating SMAP retrievals into the National Oceanic and Atmospheric Administration-National Centers for Environmental Prediction Global Forecast System (GFS). They are: 1) global cumulative distribution function (CDF) matching with only one CDF for all grids and time series; 2) monthly CDF matching with one CDF for each grid; 3) the linear transformation technique that matches monthly mean and standard deviation of the SMAP retrievals and model simulations for each grid; and 4) assimilating SMAP SM data into GFS without any bias-correction procedure. With respect to the global land data assimilation (DA) system precipitation product, the results demonstrate that the effectiveness of assimilating SMAP retrievals into GFS is significantly impacted by the bias-correction methods. Relative to other DA cases, the monthly CDF matching produces the best precipitation forecast performance. Improvements of the three-hourly GFS precipitation prediction with SMAP assimilation using the monthly CDF matching can reach to 8% and 10% in sparsely and densely vegetated areas, respectively, and marginally positive in medium vegetation areas. Based on these results, assimilating SMAP retrievals into the GFS with the EnKF algorithm using the monthly CDF matching method is suggested for enhancing accuracy of the precipitation forecasts.

Application and Evaluation of an Explicit Prognostic Cloud‐Cover Scheme in GRAPES Global Forecast System

AbstractAn explicit prognostic cloud‐cover scheme (PROGCS) is implemented into the Global/Regional Assimilation and Prediction System (GRAPES) for global middle‐range numerical weather predication system (GRAPES_GFS) to improve the model performance in simulating cloud cover and radiation. Unlike the previous diagnostic cloud‐cover scheme (DIAGCS), PROGCS considers the formation and dissipation of cloud cover by physically connecting it to the cumulus convection and large‐scale stratiform condensation processes. Our simulation results show that clouds in mid‐high latitudes arise mainly from large‐scale stratiform condensation processes, while cumulus convection and large‐scale condensation processes jointly determine cloud cover in low latitudes. Compared with DIAGCS, PROGCS captures more consistent vertical distributions of cloud cover with the observations from Atmospheric Radiation Measurements (ARM) program at the Southern Great Plains (SGP) site and simulates more realistic diurnal cycle of marine stratocumulus with the ERA‐Interim reanalysis data. The low, high, and total cloud covers that are determined via PROGCS appear to be more realistic than those simulated via DIAGCS when both are compared with satellite retrievals though the former maintains slight negative biases. In addition, the simulations of outgoing longwave radiation (OLR) at the top of the atmosphere (TOA) from PROGCS runs have been considerably improved as well, resulting in less biases in radiative heating rates at heights below 850 hPa and above 400 hPa of GRAPES_GFS. Our results indicate that a prognostic method of cloud‐cover calculation has significant advantage over the conventional diagnostic one, and it should be adopted in both weather and climate simulation and forecast.

Bike sharing demand prediction using artificial immune system and artificial neural network

From the viewpoint of bike sharing service, the rental number is a critical performance indicator for managers and controllers to assess the demand. Bike demand prediction in bike sharing systems is hence a key indicator in economic systems. In this study, a novel prediction framework integrating AIS and the artificial neural network forecasting technique is developed for numerical predication; it is named AIS-ANN. In this proposed AIS-ANN prediction framework, there are three major mechanisms applied to build the predication system which includes cell creation by ANN, antibody generation by clonal selection, and antibody’s center adaption by similarity measuring. The experimental results show that our proposed AIS-ANN has better performance when compared with other 6 forecasting models.

AN INTEGRATED NUMERICAL AND EXPERIMENTAL INVESTIGATION ON IMPROVING ACOUSTIC AND COOLING PERFORMANCES OF A HIGH POWER MOTOR

This research focuses on noise reduction of a 175-Hp motor under the same cooling need. First, the electromagnetic field is calculated numerically to provide the total losses to be 5.7 KW. Later, based on the numerical predication, the appropriate design, which consists of an inline fan rotor with a 2-cm diameter reduction and a streamlined housing, successfully reduce the noise by 3–5 dBA over various locations under the 3,000 rpm. Furthermore, the motor mockup is manufactured for testing, and result indicates that a similar noise reduction (4–7 dBA) is obtained while an acceptable deviation range between CFD and test results is observed. Consequently, this design and analysis tool offers a rigorous and systematic scheme for the thermal management on the high-power motor.

Adaptation Needs and Countermeasures of China’s Agricultural Sector in Response to Climate Change

China’s agricultural production will be greatly impacted by the climate change, and in order to accurately evaluate the impact degree of the climate change on China’s corn yield, this paper proposes an analytical method of impact of climate change on China’s corn yield based on numerical predication of fuzzy inference. Firstly, this paper provides research region and data description and the condition of data sources of this experiment and provides its regressive formal model at the same time; secondly, proposes a kind of numerical predication method of fuzzy inference and realizes the valid predication of climate change with the use of improved TS fuzzy model for improving the accuracy of climate change predication; finally, evaluates the impact on China’s corn yield and makes targeted analysis through the experiment.

Numerical Study on Effect of Volume Fraction of Nanoparticles on Rayleigh-Bernard Convection in Different Enclosures

Numerical investigations of Rayleigh-Bernard convection in enclosures of different modified bottom and top surfaces filled with Au-Water Nanofluid with different volume fractions are presented. This paper describes a numerical predication of heat transfer and fluid flow characteristics inside enclosures bounded by modified bottom and top surfaces and two periodic straight vertical walls. Simulations are carried out for a Rayleigh number of 6×104 and two aspect ratios (0.25 & 0.5) with working fluid as Au-Water Nanofluid and The same analyses are performed with the Nanofluid having Au nanoparticles of same size and different volume fraction of φ = 5%, 10%, 15% and 20 % in order to see the effect of Nanofluid volume fraction on heat transfer. The Boussinesq approximation is used in order to take density change effect in the governing equations. The study investigates the effect of the nanoparticles volume fraction, and the aspect ratio on the heat transfer. The results are presented in terms of isotherms, streamlines local and average surface Nusselt numbers. Results show that the flow and isotherms are affected by the geometry shape and by the presence of nanoparticles with different volume fractions. It is also shown that for a fixed value of aspect ratio, the convective heat transfer is decreased for the increase in volume fraction of Nanofluid.