Unsaturated flow characteristics in dual-scale fibre fabrics at one-dimensional constant flow rate

2016 ◽  
Vol 23 (6) ◽  
pp. 617-624
Author(s):  
Yan Shilin ◽  
Yan Fei ◽  
Li Dequan ◽  
Li Yongjing
Keyword(s):  
Flow Rate ◽  
Unsaturated Flow ◽  
Flow Characteristics ◽  
Constant Flow ◽  
One Dimensional ◽  
Constant Flow Rate ◽  
Liquid Composite Moulding ◽  
Mould Filling ◽  
Set Up ◽  
Dual Scale

AbstractFibre fabrics in liquid composite moulding can be considered as dual-scale porous media. In different gap scales, an unsaturated flow is produced during the mould filling process. This particular flow behaviour deviates from the traditional Darcy’s law, which is used to calculate the filling pressure and will cause errors. To prove the mechanism of this unsaturated flow, an experimental device was set up with a one-dimensional constant flow rate. The influencing factors, such as injected media, flow velocity and fibre fabric, were investigated in this study. Based on the experimental data, several useful conclusions were drawn, providing good references for optimising the process parameters and controlling the product quality.

scholarly journals Characterisation of Permeability around a 90° Corner

2000 ◽  
Vol 9 (1) ◽  
pp. 096369350000900 ◽  
Author(s):  
Nicolas Laval ◽  
E. Murat Sozer ◽  
Suresh G. Advani
Keyword(s):  
Flow Direction ◽  
Time Derivative ◽  
Constant Flow ◽  
Bend Section ◽  
One Dimensional ◽  
Constant Flow Rate ◽  
Mould Filling ◽  
Order Of Magnitude ◽  
Resistive Model ◽  
Complicated Geometries

One-dimensional mould filling experiments were done in L- and T-shaped moulds with constant flow rate injection, and the pressure history was measured. Transient relationship between the preform permeability along the flow direction and the time derivative of pressure was used to measure the permeability. It was found that the resistance to flow around the bend increased by an order of magnitude within the boundary layer of the 90° bend. A simple resistive model with three different permeabilities could be used to describe the decrease in the permeability around the bend using a corner model and hence one could predict the permeability in the bend region. While considering numerical simulations of complicated geometries with bends, one should account for the variation in the bend section to capture the physics of flow in such structures.

Experimental Study on Planar Unidirectional Permeability of Glass Fiber Preforms at Constant Flow Rate

2010 ◽  
Vol 154-155 ◽  
pp. 494-497
Author(s):  
Shi Lin Yan ◽  
Fei Yan ◽  
Zhong Qi Qiu
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Resin Flow ◽  
Constant Flow ◽  
Flow Rates ◽  
One Dimensional ◽  
Constant Flow Rate ◽  
Transfer Molding ◽  
The One ◽  
Fiber Preforms

During the resin flow of Resin Transfer Molding, the permeability of fiber performs is an important parameter, which reflects the interaction between the resin and fiber. In this paper the Darcy’s law was used as the fundamentals to determine the permeability of fiber performs, an experiment installation was designed, and do some experimental study on the one-dimensional permeability of resin in the multilayer fibrous plaids at a constant flow rate. The installation was designed base on condition of different flow rates and different fiber volumes (or porosity), and compared the results of the permeability of different flow rates. Then analyzed the results, and some content conclusions were obtained.

The Simulation of the Un-Saturated Flow in the Dual-Scale Porous Media under Constant Flow Rate

2013 ◽  
Vol 753-755 ◽  
pp. 2747-2751
Author(s):  
Xin Ye ◽  
Shi Lin Yan
Keyword(s):  
Porous Media ◽  
Flow Rate ◽  
Constant Flow ◽  
Filling Process ◽  
Saturated Flow ◽  
Constant Flow Rate ◽  
Single Scale ◽  
Pore Flow ◽  
Dual Scale

Considering the un-saturated in the experiment, the purpose of this paper is achieving a simple 1d molds unsaturated simulation of the filling process through the compiled software pore-flow and compare the single-scale result with the dual-scale result.

scholarly journals A Gas Ion Source for Radiocarbon Measurements at 200 kV

Radiocarbon ◽  
2007 ◽  
Vol 49 (2) ◽  
pp. 307-314 ◽  
Author(s):  
M Ruff ◽  
L Wacker ◽  
H W Gäggeler ◽  
M Suter ◽  
H-A Synal ◽  
...  
Keyword(s):  
Flow Rate ◽  
Radiocarbon Dating ◽  
Ion Source ◽  
Negative Ion ◽  
The Novel ◽  
Feeding System ◽  
Constant Flow ◽  
Constant Flow Rate ◽  
Set Up ◽  
Better Than

The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable currents of up to 6 μA C− out of gaseous samples with an efficiency of 3–6%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 3–30 μg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was <1 pMC.

Pumpless Fuel Supply Using Pressurized Fuel Regulated by Autonomous Flow-Rate Regulation Valves

2012 ◽  
Vol 9 (3) ◽  
Author(s):  
Il Doh ◽  
Young-Ho Cho
Keyword(s):  
Fuel Cells ◽  
Flow Rate ◽  
Electrical Power ◽  
Initial Pressure ◽  
Flow Regulation ◽  
Present System ◽  
Constant Flow ◽  
Constant Flow Rate ◽  
Fuel Supply ◽  
Fuel Flow

A pumpless fuel supply using pressurized fuel with autonomous flow regulation valves is presented. Since micropumps and their control circuitry consume a portion of the electrical power generated in fuel cells, fuel supply without micropumps makes it possible to provide more efficient and inexpensive fuel cells than conventional ones. The flow regulation valves in the present system maintain the constant fuel flow rate from the pressurized fuel chamber even though the fuel pressure decreases. They autonomously adjust fluidic resistance of the channel according to fuel pressure so as to maintain constant flow rate. Compared to previous pumpless fuel supply methods, the present method offers more uniform fuel flow without any fluctuation using a simple structure. The prototypes were fabricated by a polymer micromolding process. In the experimental study using the pressurized deionized water, prototypes with pressure regulation valves showed constant flow rate of 5.38 ± 0.52 μl/s over 80 min and 5.89 ± 0.62 μl/s over 134 min, for the initial pressure in the fuel chamber of 50 and 100 kPa, respectively, while the other prototypes having the same fluidic geometry without flow regulation valves showed higher and gradually decreasing flow rate. The present pumpless fuel supply method providing constant flow rate with autonomous valve operation will be beneficial for the development of next-generation fuel cells.

scholarly journals Axisymmetric three-dimensional gravity currents generated by lock exchange

2018 ◽  
Vol 851 ◽  
pp. 507-544 ◽  
Author(s):  
Roberto Inghilesi ◽  
Claudia Adduce ◽  
Valentina Lombardi ◽  
Federico Roman ◽  
Vincenzo Armenio
Keyword(s):  
Froude Number ◽  
Flow Rate ◽  
Rapid Development ◽  
Three Dimensional ◽  
Gravity Currents ◽  
Constant Flow ◽  
Axially Symmetric ◽  
Grashof Number ◽  
Constant Flow Rate ◽  
Dimensional Gravity

Unconfined three-dimensional gravity currents generated by lock exchange using a small dividing gate in a sufficiently large tank are investigated by means of large eddy simulations under the Boussinesq approximation, with Grashof numbers varying over five orders of magnitudes. The study shows that, after an initial transient, the flow can be separated into an axisymmetric expansion and a globally translating motion. In particular, the circular frontline spreads like a constant-flow-rate, axially symmetric gravity current about a virtual source translating along the symmetry axis. The flow is characterised by the presence of lobe and cleft instabilities and hydrodynamic shocks. Depending on the Grashof number, the shocks can either be isolated or produced continuously. In the latter case a typical ring structure is visible in the density and velocity fields. The analysis of the frontal spreading of the axisymmetric part of the current indicates the presence of three regimes, namely, a slumping phase, an inertial–buoyancy equilibrium regime and a viscous–buoyancy equilibrium regime. The viscous–buoyancy phase is in good agreement with the model of Huppert (J. Fluid Mech., vol. 121, 1982, pp. 43–58), while the inertial phase is consistent with the experiments of Britter (Atmos. Environ., vol. 13, 1979, pp. 1241–1247), conducted for purely axially symmetric, constant inflow, gravity currents. The adoption of the slumping model of Huppert & Simpson (J. Fluid Mech., vol. 99 (04), 1980, pp. 785–799), which is here extended to the case of constant-flow-rate cylindrical currents, allows reconciling of the different theories about the initial radial spreading in the context of different asymptotic regimes. As expected, the slumping phase is governed by the Froude number at the lock’s gate, whereas the transition to the viscous phase depends on both the Froude number at the gate and the Grashof number. The identification of the inertial–buoyancy regime in the presence of hydrodynamic shocks for this class of flows is important, due to the lack of analytical solutions for the similarity problem in the framework of shallow water theory. This fact has considerably slowed the research on variable-flow-rate axisymmetric gravity currents, as opposed to the rapid development of the knowledge about cylindrical constant-volume and planar gravity currents, despite their own environmental relevance.

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