Suction Experiment Research Articles

Experimental simulation of alternating aerodynamic loads induced by high-speed trains passing in tunnels

Tunnel passing at high speed produces aerodynamic load on railway trains, which may bring about fatigue failure on the car body, and damages passenger comfort due to interior penetration of the alternating wave. In this work, the air suction experiment approaches were developed. It performs excellently through internal and external loading utilizing valve controlling strategies. It is validated with an in-transit vehicle test when the train runs through 3 different tunnel lengths. The relative deviation between simulation and vehicle tests goes no more than 5.0%. Research outcome indicates that the proposed method provides an important experiment means for passenger comfort and car-body fatigue behavior research.

Numerical simulation research on suction process of concrete pumping system based on CFD method

In this paper, a numerical model of the suction process of the pumping system was established, and the accuracy of the numerical model was verified by the rheological experiment of fresh concrete and the suction experiment of the pumping system. By analyzing the numerical results, the distribution characteristics of the internal flow field of the hopper and the change law of the bubble shape in the fresh concrete during the suction process were explored. The results show that the established numerical model can effectively simulate the material suction process of the pumping system, and the flow velocity of the fresh concrete in the mixing area presents a periodic variation behavior. The simulation results show that there is a “flow dead zone” at the bottom of the hopper. Smaller flow speed of fresh concrete was found around the S valve, and the bubbles located inside the fresh concrete have a negative impact on the suction effect of the pumping system. The research results of this paper provide valuable references for designers to improve the hopper structure and optimize the operational parameter of the suction process of pumping system. Distribution characteristics of the internal flow field of the hopper in the suction process. • The model of suction process was established by the CFD method. • Flow velocity of concrete in hopper presents the law of periodic variation. • Flow velocity of concrete decreases when it flows through the S valve. • Air bubbles gather at the end face of the piston at the end of the suction.

A noncontact self-suction wheat shooting device for sustainable agriculture: A preliminary research

In this study, a noncontact self-suction wheat shooting device was developed through TRIZ theory to improve seed-filling performance and eliminate the contact between seed and device. A preliminary suction experiment was developed using FLUENT to simulate airflow velocity and evaluate the feasibility of self-suction performance of seeds. The DEM-CFD coupling simulation experiment was conducted to investigate the shooting performance. The simulation results showed the airflow velocity was over 6.5 m/s while rotational speed was more than 800 rpm, which could meet the seed-filling requirements. With the rotational speed increase, seed velocity and seed filling performance improves. On the contrary, a larger rotational speed and installation angle induced a higher CF (contact force). CF was significantly affected by rotational speed, window length and installation angle. The increasing window length resulted in the improvement of seed filling performance in a certain range. Meanwhile, the indicators of coefficient of variation for seeding uniformity (CVSU), coefficient of variation for seeding depth (CVSD) and seed damage rate (DR) were evaluated to investigate sowing performance of self-suction shooting device in validation experiment. Results from bench and field experiment showed the seed-filling and shooting performance of self-suction shooting device under optimized operation parameters could fully meet the sowing requirement of winter wheat in North China plain. The collision performance between seed and blades of optimized self-suction shooting device was superior to the mechanical one. In specific, CVSU, CVSD, ASD, ASS and seed germination rate of optimized self-suction shooting device were 11.3%, 8.7%, 31.0 m/s, 30.1 mm and 89.2%, respectively.

Study on Flow Characteristics of Working Medium in Microchannel Simulated by Porous Media Model

As a phase change evaporator, a microchannel array heat exchanger is of great significance in the field of microscale heat dissipation. The performance of which strongly depends on the flow resistance, capillary force, and other factors. In order to improve the heat dissipation efficiency, it is necessary to perform an in-depth study of the characteristics of microchannel flow using numerical simulation. However, the current simulation model requires high computational cost and long simulation time. To solve this problem, this paper simplifies the numerical simulation of the rectangular parallel array microchannels by building the basic flow model based on the concept of porous media. In addition, we explore the effect of aspect-ratio (AR), hydraulic diameter, inlet velocity, and other parameters of fluid flow behavior inside the microchannels. Meanwhile, a user-defined function (UDF) is formulated to add the capillary force into the model to introduce capillary force into the porous media model. Through the above research, the paper establishes the porous media model for single-phase and gas-liquid two-phase flow, which acts as a simplification of microchannel array simulation without grossly affecting the results obtained. In addition, we designed and manufactured experiments using silicon-based microchannel heat exchangers with different-ratios, and combined with the visualization method to measure the performance of the device and compared them with simulation results. The theoretical model is verified through the suction experiment of array microchannel evaporator capillary core. The simplified model of microchannel array significantly saves the computational cost and time, and provides guidance for the related experimental researches.

Investigation of Oil Adsorption Performance of Polypropylene Nanofiber Nonwoven Fabric

Nanofibers can be used in fields/applications such as medical care, environment protection, apparel, and agriculture. In addition, we believe that this field would continue to show substantial growth in the future. In this study, we focused on its application to oil adsorption. Oil adsorbing performances achieved polymeric nanofiber mass production by a melt-blowing method. We first tested the oil adsorption performance of fiber experimentally under different bulk densities and thicknesses. We also conducted the suction experiment with different bulk densities. Based on experimental result, we considered contact angle, capillarity, and surface tension to be the causes of oil adsorption. We also proposed a three-direction physical model for oil adsorption and used it to calculate the theoretical oil adsorption rate by different free volumes. As a result, we confirmed that the proposed three-direction model could accurately estimate the oil adsorption rate. Moreover, nanofiber has exceptional oil adsorption performance. Further, the fiber with average diameter of 1500 nm exceeds 60 times its self-weight. Therefore, we believe that the proposed nanofiber nonwoven fabric oil adsorption pad could adequately be used as oil adsorption material.

Fabrication of Stainless Steel Microneedle with Laser-Cut Sharp Tip and its Penetration and Blood Sampling Performance

The demand for minimally invasive injection needles or needle-shaped tools is growing from those who carry out medical practices such as blood or insulin injections. Applying the mosquito biomimetic, we have used a femtosecond laser to fabricate minimally invasive microneedles out of ultrafine hollow SUS304 pipes, 50μm in outer diameter and 20μm in inner diameter. When such a stainless steel needle tip is angled at 15°, it has the lowest penetration resistance, two and a half times lower than that of the finest hollow needle that is commercially available. A blood suction experiment with a newly developed microneedle has demonstrated that 2.8μellof blood can be drawn out in 20 seconds. Such stainless steel microneedles fabricated by femtosecond lasers have great potential as minimally invasive and mass-producible blood sampling needles to be used for diabetic inspections.

Moisture Migration in High Strength Concrete

Moisture transport in high strength concrete is investigated in this paper. The experiment that involves the water suction is carried out in a long-term. The moisture profiles are measured by non-destructive capacitance method, the last profile is determined gravimetrically. The suction experiment is carried out in isothermal condition at the temperature of 22±1 °C and 25-30% relative humidity.

Determining hydraulic properties of concrete and mortar by inverse modelling

ABSTRACTThis paper presents a methodology and results on estimating hydraulic properties of the concrete and mortar considered for the near surface disposal facility in Dessel, Belgium, currently in development by ONDRAF/NIRAS. In a first part, we estimated the van parameters for the water retention curve for concrete and mortar obtained by calibration (i.e. inverse modelling) of the van Genuchten model [1] to experimental water retention data [2]. Data consisted of the degree of saturation measured at different values of relative humidity. In the second part, water retention data and data from a capillary suction experiment on concrete and mortar cores was used jointly to successfully determine the van Genuchten retention parameters and the Mualem hydraulic conductivity parameters (including saturated hydraulic conductivity) by inverse modelling.

Development of Model Cell Based on the Myocardial Cell Experiments and Simulations

As one kind of the most important cells in human body, myocardial cell becomes the focus of attention, not only the biologist but also the researchers of mechanics. A new viscoelastic constitutive model of the living myocardial cell is developed based on the micropipette suction experiment in which the surface of the cell is aspirated into a small glass tube while tracking the leading edge of its surface. Some numerical simulations are presented by finite element to model the whole process of micropipette suction of the myocardial cell. Meanwhile, a model cell with both mechanical behavior and physiological function is being developed, to prove the viscoelastic constitutive model and to predict more results of myocardial cell under different physiology conditions.

Thermomechanics of Porous Media - I: Thermohydraulic Model for Compacted Bentonite

A general thermomechanical model is derived for a mixture. The model describes the behavior of the mixture via proper choices of free energy and dissipation function. A model for any combination of the mixture constituents can be reduced from the general model. The theory is applied to a thermohydraulic model for a mixture of compacted bentonite, liquid water, vapor, and air with the assumption of rigid skeleton and constant uniform porosity. The free energy of the system is chosen to take into account the individual nondissipative behaviors of the constituents and their mutual interactions, namely, adsorption and mixing of the gaseous constituents. The choices for the interaction terms are based on the equilibrium conditions for the water species in different combinations of the constituents. The resulting thermodynamically consistent macroscopic model is fitted to a suction experiment and applied to a simple one-dimensional thermohydraulic simulation of the bentonite buffer of the Febex in situ test. The results calculated with finite element method are successfully compared to measurements.

Preliminary evaluation of soil moisture probe for use with arcillite

There is a need for reliable methods of measuring the level and distribution of water in the solid substrates that are used for growing plants in space. In a microgravity environment, water distribution is governed generally by capillary forces. Arcillite is the solid substrate used in the ASTROCULTURE ™ system which was developed for growing plants in space. The goal of this study is to evaluate the applicability of heat pulse moisture sensors for measuring moisture levels in Arcillite. The ASTROCULTURE system uses suction as a means of controlling the moisture level in Arcillite, but the spatial distribution of the moisture is left unknown. Studies of the moisture content in a cell experiment were conducted to calibrate a heat pulse moisture sensor and then the sensor was used in a suction experiment to verify moisture content and distribution. Results of the studies demonstrate that head pulse moisture sensors can be used to monitor moisture content and distribution within the root module of the ASTROCULTURE system.

Deformation analyses in cell and developmental biology. Part II--Mechanical experiments on cells.

This study employs the finite element approach developed in Part I to analyze mechanical experiments on cells. It views cells as axisymmetric membrane structures containing a body of incompressible material, and models the mechanical contact between a cell and the loading apparatus by a contact algorithm. Since the method is valid for analyzing axisymmetric shell-like bodies with arbitrary shapes, it treates various mechanical experiments on cells in a unified manner. For demonstration purposes, three commonly used mechanical experiments on cells are considered; the compression experiment; the suction (micropipette aspiration) experiment; and the magnetic particle experiment. Based on an estimate of the mechanical property data for unfertilized sea urchin eggs, this analysis method predicts the responses for all three experiments using the same assumptions and approximations. This parallel treatment gives a broad basis for data correlation with experiments. The method also provides insights into mechanical experiments not offered by other approximate methods. For example, it gives the distributions of tensions and stretches on the cell cortex, and suggests the role of friction in the suction experiment.

Passive material behavior of granulocytes based on large deformation and recovery after deformation tests

In order to better understand the in vivo rheologic behavior of white cells, we have studied the time-dependent deformability, recovery, and mechanical activation of blood granulocytes. We have used micropipette aspiration methods to measure the large deformation response and recovery after deformation characteristics of neutrophils as functions of time, temperature, and collecting media. The cell response in the pipette experiment was characterized by three time domains: the first phase was the passive deformation response to the fixed suction pressure; the second phase was an obvious transition from the passive to active motile cellular state where the cell exhibited erratic length changes in the pipette; and the third phase was the steady recovery after the suction pressure had been zeroed. Tests on white cells were carried out with three different anticoagulants to evaluate the effect of calcium on deformation and recovery behavior; also, cells were separated by centrifugation in high molecular weight dextran to determine whether or not collection and separation procedures affected the cell properties. Our results have shown that the passive deformation of granulocytes into the pipette was a continuous flow process with no approach to a static deformation limit. In addition, there was an obvious threshold pressure below which the cell would not deform and enter the micropipette. For suction pressures significantly above the threshold, granulocytes were continuously deformed with a similar functional dependence on time. The coefficient of proportionality between aspiration length and time, as well as the exponent, depended on suction pressure, pipette dimension, and temperature. It was observed that the granulocytes always recovered to the spherical state after deformation, independent of the extent of deformation or location where the cell was aspirated. Based on the recovery behavior, plus the dependence of the pressure threshold on pipette size, we propose the concept that the granulocyte membrane and cortical shell behave like a “contractile surface carpet” under tension, where the cell interior responds passively like a highly viscous liquid. The membrane cortex appears to be subject to a persistent stress (tension) of about 10(-2) dyne/cm. Our observations of passive to active transition in the pipette suction experiment indicated that granulocytes may be stimulated by deformation at room temperature. This study represents the first detailed investigation of the large deformation behavior of granulocytes, and the results indicate a simple structural model to represent the passive rheologic behavior of the granulocyte.

Passive Material Behavior of Granulocytes Based on Large Deformation and Recovery After Deformation Tests

In order to better understand the in vivo rheologic behavior of white cells, we have studied the time-dependent deformability, recovery, and mechanical activation of blood granulocytes. We have used micropipette aspiration methods to measure the large deformation response and recovery after deformation characteristics of neutrophils as functions of time, temperature, and collecting media. The cell response in the pipette experiment was characterized by three time domains: the first phase was the passive deformation response to the fixed suction pressure; the second phase was an obvious transition from the passive to active motile cellular state where the cell exhibited erratic length changes in the pipette; and the third phase was the steady recovery after the suction pressure had been zeroed. Tests on white cells were carried out with three different anticoagulants to evaluate the effect of calcium on deformation and recovery behavior; also, cells were separated by centrifugation in high molecular weight dextran to determine whether or not collection and separation procedures affected the cell properties. Our results have shown that the passive deformation of granulocytes into the pipette was a continuous flow process with no approach to a static deformation limit. In addition, there was an obvious threshold pressure below which the cell would not deform and enter the micropipette. For suction pressures significantly above the threshold, granulocytes were continuously deformed with a similar functional dependence on time. The coefficient of proportionality between aspiration length and time, as well as the exponent, depended on suction pressure, pipette dimension, and temperature. It was observed that the granulocytes always recovered to the spherical state after deformation, independent of the extent of deformation or location where the cell was aspirated. Based on the recovery behavior, plus the dependence of the pressure threshold on pipette size, we propose the concept that the granulocyte membrane and cortical shell behave like a "contractile surface carpet" under tension, where the cell interior responds passively like a highly viscous liquid. The membrane cortex appears to be subject to a persistent stress (tension) of about 10(-2) dyne/cm. Our observations of passive to active transition in the pipette suction experiment indicated that granulocytes may be stimulated by deformation at room temperature. This study represents the first detailed investigation of the large deformation behavior of granulocytes, and the results indicate a simple structural model to represent the passive rheologic behavior of the granulocyte.