Effect Of Different Velocities Research Articles

Integration of 3-D 4-directional braided composites into dynamic modeling of plates with large overall motions

In this study, a dynamic model of a 3-D 4-directional braided composite plate with large overall motions is proposed. Based on the Kirchhoff’s plate hypothesis, the deformation of the orthotropic plate is described. The assumed mode method is employed to discretize the displacement variables, and the rigid-flexible coupled dynamic model of the plate is derived from the Lagrange equation. The equivalent stiffness matrices of 3-D 4-directional braided composites with different braided angles are obtained using the homogenization method. The effects of different velocities and braided angles on the dynamic characteristics of the plate with translational motion and fixed-axis rotation, respectively, are investigated. The present study lays the theoretical foundation for analyzing the dynamic properties of orthotropic plates in engineering components. For example, the dynamic model established in this study can be used to estimate the dynamic responses of braided composite parts in aeronautical structures.

Virial Velocities for Stellar Flybys with Planetary Disks in Star Formation Regions

In this work, we show the effect of different velocities of stellar encounters with planetary disks to support the use of virial or constant velocities in simulations of typical star-forming clusters; the variety of observed member velocity values in such objects can cause concern when selecting velocities for simulations. In this work, we employ different velocities from 1.5 to 10 km s−1 with constant flyby masses, approach distances, and impact angles for encounters with a disk. We found that these velocities produce similar results, which suggests that such simulations can use virial or constant velocities without loss of accuracy.

Analysis of Core Annular Flow Behavior of Water-Lubricated Heavy Crude Oil Transport

A possible method for fluid transportation of heavy oil through horizontal pipes is core annular flow (CAF), which is water-lubricated. In this study, a large eddy simulation (LES) and a sub-grid-scale (SGS) model are used to examine CAF. The behavior of heavy oil flow through turbulent CAF in horizontal pipes is numerically investigated. The Smagorinsky model is utilized to capture small-scale unstable turbulent flows. The transient flow of oil and water is first separated under the behavior of the core fluid. Two different conditions of the horizontal pipes, one with sudden expansion and the other with sudden contraction, are considered in the geometry to investigate the effects of different velocities of oil and water on the velocity distribution, pressure drop, and volume fraction. The model was created to predict the losses that occur due to fouling and wall friction. According to the model, increasing water flow can reduce fouling. Additionally, the water phase had an impact on the CAF’s behavior and pressure drop. Also, the increased stability in the CAF reduces the pressure drop to a level that is comparable to water flow. This study demonstrated that a very viscous fluid may be conveyed efficiently utilizing the CAF method.

Numerical study on the impact-induced failure mechanism of cylindrical glass projectile using the FEM-SPH conversion method

Brittle materials have been used for projectiles in recent years. To investigate the failure mechanism of glass cylinder during the impact, a light gas gun was adopted to conduct dynamic experiments on aluminum targets with polyurea coating. The residual glass projectiles collected perform a discrepancy after impacting different sides of the targets. By comparing different numerical method to simulate the experiments, the FEM-SPH adaptively conversion method was validated with significant advantage and reliability, and it was then used to reveal the brittle material failure mechanism. In addition, the effect of different velocities and impact surfaces on glass failure was numerically and theoretically analyzed characterized by the residual mass of elements and corresponding failure mass of particles converted from failure elements. An initial-contact-stress-based equivalent model was proposed to provide analytic and satisfied assessment of the projectile failure extents when impacting different targets. Our findings provide a reliable reference for further revealing the fracture mechanism of brittle materials during impact.

Normalized evaluation index of jet length and resistance for square diffuser shape optimization

In public buildings, the energy consumption of HVAC system fans due to the resistance of the HVAC ducts accounts for approximately 20–40% of the total energy consumption of the building. This study focuses on the structural design of square diffusers in HVAC systems. By introducing the concept of a conversion coefficient for the diffuser jet length, a comprehensive evaluation index that is suitable for describing the performance of square diffusers is developed and improved upon. This study employs a combination of kriging surrogate modeling and multi-island genetic algorithm (MIGA) optimization to obtain the optimal structural parameters of the square diffuser. This study also analyzes the effects of different velocities on the square diffuser's resistance and jet length characteristics and conducts full-scale experimental verification of the square diffuser manufactured using 3D printing technology. The results show that the traditional square diffusers in ventilation and air-conditioning systems are optimized by using the Kriging model and multi-island genetic algorithm, resulting in a new type of square diffuser with the best parameters and a final reduction of 2.98 in the Square Diffuser Effective Index (SDEI). Through a comparative analysis of experimental data and numerical simulation results, the effectiveness and practicality of the proposed optimization method are demonstrated.

On-Ramp Merging Strategy with Two-Stage Optimization Based on Fully Proactive and Cooperative Merging of Vehicles

The on-ramp area has been a hot spot for research as a bottleneck area. In this paper, an on-ramp cooperative merging control strategy is proposed to make full use of active cooperative vehicles, and alleviate the negative influence of merging on the main road. First, a two-stage framework is proposed to illustrate the merging strategy. At the vehicle level, the cooperative merging controllers of vehicles are designed based on an optimization algorithm that considers the penalty function. At the traffic level, the cooperative distance of the upstream and downstream vehicles at the main road target merging position are optimized to improve merging efficiency. Meanwhile, to ensure the implementation of the proposed strategy in mixed traffic, we propose a method to determine the lead vehicles based on the proximity principle. Numerical experiments were performed to verify the fully proactive and cooperative merging (FPCM) strategy, the effectiveness of the vehicle cooperative controllers, the necessity of optimizing the cooperative distance, the effect of different velocities on the main road and ramp, and the effectiveness of determining the lead vehicles. In the case of multivehicle merging, the proposed strategy can improve merging efficiency by 44.42% and save fuel consumption by 39.11%. In the case of a single merging vehicle, the optimized proposed strategy can improve merging efficiency by 48.4% and save fuel consumption by 31.4%. Finally, the simulation experiments for the different maximum speeds of vehicles show that a sufficient speed adjustment range can improve the advantages of the strategy.

Viscoelasticity and friction of solid foods measurement by simulating meal-assisting robot

ABSTRACT The operation object of the meal-assisting robot is a non-rigid food individual with complex and differentiated physical characteristics, and the contact force between the spoon and the food is very complicated, which brings difficulties to the fetching of the food and has a large impact on the fetching rate and force of the foods. In this paper, the finite element simulation of the display algorithm is used to reproduce the scenario of the meal-assisting robot fetching food and verify the measurement method of viscoelasticity and friction coefficient of solid foods. A standard linear solid model in Maxwell form is characterized using moment relaxation and the model parameters are estimated. The tangential and normal forces obtained by the induced slippage method are used to estimate the friction coefficient of the contact surface of the food and the spoon. Simulation results show that the viscoelastic properties of solid foods can be characterized by moment relaxation, the parameters of the model can be estimated, and the friction coefficient can be measured by the induced slippage method. Finally, the effects of food traits and predetermined angular displacement on food fetching rates were verified by fetching a mixture of block and diced foods, and comparing the effects of different velocities on the moments and forces of action.

Performance analysis and structure optimization of shale gas desander

ABSTRACT The shale gas desander often has erosion failure, and its effect of removing sand is not ideal, especially for small-size sand particles, which leads to a large number of sand particles entering the pipeline and increases the risk of failure of the pipeline, posing a great threat to shale gas production. To solve this problem, a novel desander was designed based on the existing desander of the Changning area and FLUENT software. Moreover, the structure of the desander was optimized (inlet aspect ratio, cylinder diameter ratio, and cone diameter ratio), and the effects of different velocities and sand particle diameters on the amount of erosion wear and separation efficiency were studied. The results show that the optimal inlet aspect ratio, cylinder diameter ratio, and cone diameter ratio are 2.5, 1.5, and 2, respectively, and the maximum erosion rate is only 3.54 × 10−9 kg/(s·m2). When the inlet velocity is lower than 10 m/s, the annual erosion thickness is less than 20.6 μm, and when the particle diameter is larger than 20 μm, the separation efficiency is above 88.1%. This greatly improves the separation efficiency of the desander and reduces erosion wear, ensuring the safe operation of shale gas production.

Impact of velocities and geometry on flow components and heat transfer in plate heat exchangers

• Influence of velocity on flow is investigated experimentally and numerically. • The flow is mainly determined by substreams velocity and angle β . • Higher velocities promote furrow component and at fixed Re entail lower f and Nu. • Redefined Re , Nu and f shall reflect substreams flow path and velocity. • Numerical results are best validated in terms of heat flux and pressure drop. This study aims at better understanding of the complex flow phenomena in plate heat exchangers. This is identified in the literature to be crucial for improvement of numerical models and generalized heat transfer and pressure drop correlations with respect to their applicability in heat exchanger optimization. 3D numerical simulations of the flow in corrugated channels of plate heat exchangers with different corrugation angles ( β 28° and 65°) were performed in order to investigate in detail complex flow patterns and their influence on the heat transfer and pressure drop at laminar, transient and turbulent flow conditions. The study is supported by the visualization and thermal–hydraulic tests ( Re = 0.1–6037) carried out on the channels with corresponding chevron angles, using fluids of different viscosity to explore effects of different velocities at fixed Re numbers. Consequent alternation of flow patterns is believed to cause recorded differences in heat transfer and pressure drop data. Results from the simulations are analysed in different sections of the channels in light of the flow substreams, velocity distribution, wall shear stress and wall heat flux distribution. They confirm assumptions from the present visualization tests on the longitudinal and furrow substreams interactions and characteristics, as well as on the thermally and hydrodynamically developing flow conditions within a basic cell. A suitability of comparing simulations and experimental data in terms of Fanning friction factor and Nusselt number is discussed relative to the definitions of characteristic length, hydraulic diameter and mean velocity at different flow patterns. The computed heat transfer and pressure drop is in a relatively good agreement with the performed tests and literature data. The presented numerical-experimental analysis outlines importance of the substreams velocity on their interactions and flow components size, which in turn determines PHE channel heat transfer and pressure drop characteristics. The present findings may serve for improvement of CFD modelling, generalized correlations and definition of Re , Nu and f to allow for comparison of heat transfer and pressure drop data at different geometries and flow conditions.

Analysis of coiled tube waste heat storage tank under water injection

Abstract In this paper, attempts are made to increase the heat transfer in the hot water storage tank via water injection into the storage water. With new water injection system, increasing mixing effect especially around the coiled tube was aimed. The experimental study was conducted to obtain the effect of different velocity (0.03 ≤ V ≤ 1.3), different flow pressures and different outlet hole diameters on dimensionless temperature distribution, Nusselt number and second law efficiency. The results showed, depending on the velocity, water injection into the tank provided an increase in the range of 15–60% for the Nusselt number. The highest enhancement in average Nusselt number occurred when the V = 1.3 m/s. The highest decrease in the second law efficiency was observed around 5% for the 1 mm hole diameter. In addition, the water injection method compared with air bubble injection method in the literature. The comparison indicated, average Nusselt number of the air bubble method 0.6% higher than the water injection method but second law efficiency and average dimensionless temperature 1.7% and 25.7% respectively less than the water injection method.

Finite element model for predicting the initiation of subsurface damage in railway crossings—A parametric study

In this study, the initiation of subsurface damage due to the impact of new and worn wheels on differently deformed crossing nose geometries is calculated using the Dang-Van criterion. Three crossings with different materials (manganese steel, chromium-bainitic steel, and tool steel) were cyclically loaded in an FE crossing model reported in a previous study to evaluate the run-in state of plastic deformation. The impacts of the wheels on the deformed crossings were then calculated by considering the behaviour of an elastic material. This parametric study showed the effects of different velocities, axle loads, and wheel types on the vertical contact forces, contact pressures, and Dang-Van damage parameters. Additionally, the ability of manganese steel crossings to withstand unfavorable load situations was observed by including plastic material behavior and considering material history, such as residual stresses and hardening.

Finite Element Modelation of Temperature and Residual Stress Caused by Welding

The temperature field and the residual stress were obtained using the finite element method (FEM), for a plane plate with a single-pass welding. The length and width of the plates were 250 and 300 [mm] respectively, and three different thicknesses of 6.25, 12.7 and 25.4 [mm] (¼ [in], ½[in] and 1[in]) were considered. The model used was a two dimensional simplification of the three-dimensional actual problem, and the temperature field was calculated using an uncoupled scheme, this means, the temperature was calculated first and then the stress. The effects of different velocities of the arc between 6 and 8 [mm/s], initial temperature (preheat) between 20 and 200 [°C] (72 and 392 [°F]), and thicknesses of the plate were studied regarding mainly about the final distribution and maximum values for the residual stress.

The Influence of Velocity Variation on the Adhesive Contact Behavior and the Deformation of Substrate Based on Molecular Dynamics Method

The contact behavior between indenter and single crystal copper substrate is performed to investigate based on EAM and Morse potentials and Verlet algorithm. Effects of different velocities on the contact behavior and substrate deformation are compared and analyzed. The results show that the single crystal copper material’s resist deformation level is limited by low velocity, and more dislocated atoms were accumulated under the direction of indenter moving in higher indenting velocity. During sliding process, lager chip volume is produced in front of the indenter as the sliding speed or sliding distance increases. The dislocated band in basis lies at the angle of 45 degrees with the direction of indenter moving in indenting and sliding process. Furthermore, the contact force, friction force and normal force increase with the rising of speed. On the contrary, the friction coefficient decrease gradually with higher sliding speed.

Acute effects of movement velocity on blood lactate and growth hormone responses after eccentric bench press exercise in resistance-trained men.

This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL−1) relative to the FEV group (0.1 ± 0.0 ng · mL−1). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response.

A Study on the Effect of Different Velocities on the Handover Delay in WiMAX Systems

Mobile WiMAX is a wireless networking system based on the IEEE 802.16e standard. Currently, mobile WiMAX has a long handover delay that contributes to the overall end-to-end communication delay. Since the data transmission should be paused during the hard handover process, it causes handover delay in mobile communication. The handover delay makes severe degradation in system performance when implemented in real-time applications such as IPTV and VoIP. However, serving a large number of Mobile Stations (MS) in practice requires an efficient handover scheme which guarantees lower level of the handover delay, particularly within the mobility in the coverage area. Many factors are affecting the performance of the handover delay. In this paper, the study has been done on location management area based multimedia and multicast/broadcast handover and the modifying different velocity levels of Mobile WiMAX, by comparing the number of Cells and the size in the location area have shown how all these parameters within the simulation logarithm can affect the handover delay.

Pattern formation in a reaction-diffusion-advection system with wave instability

In this paper, we show by means of numerical simulations how new patterns can emerge in a system with wave instability when a unidirectional advective flow (plug flow) is added to the system. First, we introduce a three variable model with one activator and two inhibitors with similar kinetics to those of the Oregonator model of the Belousov-Zhabotinsky reaction. For this model, we explore the type of patterns that can be obtained without advection, and then explore the effect of different velocities of the advective flow for different patterns. We observe standing waves, and with flow there is a transition from out of phase oscillations between neighboring units to in-phase oscillations with a doubling in frequency. Also mixed and clustered states are generated at higher velocities of the advective flow. There is also a regime of "waving Turing patterns" (quasi-stationary structures that come close and separate periodically), where low advective flow is able to stabilize the stationary Turing pattern. At higher velocities, superposition and interaction of patterns are observed. For both types of patterns, at high velocities of the advective field, the known flow distributed oscillations are observed.

Multiflood and Multilayer Method for Scour Rate Prediction at Bridge Piers

The SRICOS method was proposed in 1999 to predict the scour depth versus time curve at a cylindrical bridge pier for a constant velocity flow, a uniform soil, and a deep-water condition. In this article, the method is extended to include a random velocity-time history and a multilayer soil stratigraphy; it is called the Extended-SRICOS or E-SRICOS. The algorithms to accumulate the effects of different velocities and to sequence through a series of soil layers are described. The procedure followed by the computer program to step into time is outlined. A simplified version of E-SRICOS called S-SRICOS is also presented; calculations for the S-SRICOS method can easily be done by hand. Eight bridges in Texas are used as case histories to compare predictions by the two new methods (E-SRICOS and S-SRICOS) with measurements at the bridge sites.

Effect of a Crossflow at the Entrance to a Film-Cooling Hole

Understanding the complex flow of jets issuing into a crossflow from an inclined hole that has a short length-to-diameter ration is relevant for film-cooling applications on gas turbine blades. In particular, this experimental study focused on the effect of different velocities in a coflowing channel at the cooling hole entrance. Flows on both sides of the cooling hole (entrance and exit) were parallel and in the same direction. With the blowing ratio and the mainstream velocity at the hole exit remaining fixed, only the flow velocity in the channel at the hole entrance was varied. The Mach number at the hole entrance was varied between 0 &lt; Mac &lt; 0.5, while the Mach number at the hole exit remained constant at Ma∞ = 0.25. The velocity ratio and density ratio of the jet were unity giving a blowing ratio and momentum flux ratio also of unity. The single, scaled-up film-cooling hole was inclined at 30 deg with respect to the mainstream and had a hole length-to-diameter ratio of L/D = 6. Flowfield measurements were made inside the hole, at the hole inlet and exit, and in the near-hole region where the jet interacted with the crossflow at the hole exit. The results show that for entrance crossflow Mach numbers of Mac = 0 and 0.5, a separation region occurs on the leeward and windward side of the cooling hole entrances, respectively. As a result of this separation region, the cooling jet exits in a skewed manner with very high turbulence levels.

Temperature and Emission-Line Structure at the Edges of H II Regions

view Abstract Citations (24) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Temperature and Emission-Line Structure at the Edges of H II Regions Mallik, Dipankar C. V. Abstract Models of ionization fronts located at the edges of expanding H ii regions are presented. These fronts are of the weak D-type and are preceded by shocks in the H I clouds. Since the energy input time is smaller than the cooling time, the gas is found to heat up to a high temperature immediately following ionization. At the trailing edge of the front, the temperature decreases and the ionized gas merges with the main bulk of the nebula where the physical processes are in equilibrium. The emission in [0 ii] and [N ii] lines is greatly enhanced because of the high temperature at the front. The emission in these and other important lines is calculated and compared with H . Effects of different velocities of flow, of different exciting stars, and of different gas densities on the structure of the fronts are also investigated. Observations of bright rims of H ii regions where enhanced emission of [N ii] lines has been reported are discussed on the basis of these models. Subject heading: nebulae Publication: The Astrophysical Journal Pub Date: April 1975 DOI: 10.1086/153521 Bibcode: 1975ApJ...197..355M full text sources ADS | Related Materials (1) Erratum: 1975ApJ...200..803M