Papers by Keyword: Flow Control

Abstract: Molecular dynamics simulation is used to study the water flow in a charged nanotube. The simulation results show that the charge patterns on the nanotube have an important role in determining the flow behavior. In a nanotube charged with one pattern, the water flow rate decreases with increasing charge value, when the charge value increases from 0 to 0.8 e, the water flow rate decreases to 7%. While in the other one with a different charge pattern, the water flow rate is independent of charge value. By analyzing the morphology of water molecules, it is determined that this unexpected phenomenon is caused by the structure of water molecules near the nanotube wall. For the first charge pattern, the network of hydrogen bonds formed by water molecules near the wall had a hexagonal structure, similar to single layer ice, which changes the interactions between the wall and the water molecules. By contrast, the second pattern did not exhibit such an effect. This study provides a means to control the rate of water flow in nanotubes using an electric field. These results may provide new insights and lead to new methods for flow control in complex micro- or nanofluidic systems.

Abstract: This study presents the possibility of control of nanofluidics in the bio-inspired nanosized ion channel using a field effect transistor (FET) structure. We analyzed effects from main dominant factors to control the ion flow in nanosized channel such as electro-osmosis, diffusion effect, Coulomb force between ions and pressure force. Additionally, we suggest a strategy to control the ion flow accurately at the specific position in the nanochannel by handling the viscosity, ion molecular density, pressure, gate and trans-cis voltages of FET structure.

Abstract: This work is devoted to control problem for unsteady flow of heat and electrically conducting fluid at small magnetic Reynolds numbers. This problem is connected with vortex reduction using temperature control on some parts of the boundary. Numerical algorithm based on finite-dimensional minimization is proposed and numerical results are discussed.

Abstract: The authors present by means of this paper a transfer function model for the flow of a cytostatic solution and the design of a flow classical controller for a Hyperthermic Intraperitoneal Chemotherapy device, that they intend to develop. An analytical approach is used in order to obtain the model of the solution’s flow and a classical controller is designed for the flow control structure, in order to minimize the cost and obtain an affordable device.

Abstract: In fluid power systems, flow control may be done either with variable displacement pump or using variable orifice. In this paper is considered the second method for flow control. In a hydraulic system, working pressure is frequently variable and therefore the use of the method does not provide constant flow rates in all operating conditions. In order to keep a constant flow, if this is important in a certain case, the flow control must be accomplished using a pressure compensated flow control valve. In this paper are analyzed possible structural diagrams, mathematical model, block diagram and functional diagram for this kind of equipment. The influence of the spring compression is analyzed also. The diagrams proposed in the paper will be used for the study of a hydraulic system designated for applications with strict flow control. It will represent an important research instrument for such cases.

Abstract: Wind energy has been attracting more and more attentions due to its clean and renewable source. The aerodynamic characteristic of wind turbine airfoil directly affects the turbine efficiency. In order to improve the airfoil aerodynamic characteristic, a new concept airfoil configuration for wind turbine is presented. A cave on the upper surface near the trailing edge is designed to generate a trapped vortex in the cave. The trapped vortex is used to stabilize the separated flow when the airfoil at high angle of attack. Combining with the Gurney flap, the airfoil with the cave behaves very good aerodynamic characteristics at wide range of incidences, especially at high angles of attack. The method is used on the well-known FFA-W3-301 turbine airfoil. By using numerical simulation, it is shown that the new airfoil has a higher lift than the original airfoil at the same angle of attack, the stall angle of attack increases from 12 degree to 17 degree, and the maximum lift coefficient increases approximately 64 percents. In addition, the effects of the chord-wise location of starting point of the designed cave are discussed. Therefore, it is believed that the new-designed concept can be investigated and explored further for wind turbine.

Abstract: 2nd order implicit format is implemented in the Navier-Stokes code to deal with instantaneous item unsteady flows. Three simulations are made to testify the method on flow control. First, the external flow fields of synthetic jets are simulated, the mean velocity on the center line, the jet width and velocity distribution are compared well with experimental results. Secondly, the flow fields of synthetic jet in a crossflow are simulated, orifice slot, the mean velocity on the center line and velocity distribution are compared well with experimental results. Finally, the flow control experiments on separation of airfoil are simulated, control methods include steady suction and synthetic jets. Both methods show their ability to favorably effect the flow separation, shortening the length of separation bubble and improving the pressure levels in separation areas in different degrees.

Abstract: The present investigations focus attention on PIV measurements and three-dimensional numerical investigation on flow past a modified square prism with a sinusoidal surface. The detailed near wake vortex structures and velocity fields of such modified square prism are captured and compared with a straight square prism in the same flow conditions. The three-dimensional free shear layers behind the modified square prism extend further downstream and become more stable than those of the straight one. For a modified square prism, significant mean drag coefficient reduction and fluctuating lift suppression are obtained at the Reynolds numbers of 600 and 5900. It indicates that such modified square prism is capable of minimization of flow induced vibration and force reduction.

Abstract: The magnetohydrodynamic (MHD) flow control techniques for inlet based on “AJAX” vehicle concept have attracted many researchers’ attention for its potential wide applications in the supersonic flights or the hypersonic ones. In this paper, a preliminary discussion for basic problems that are ionization and magnetic field in the MHD applications is presented. And three major MHD techniques for enhancing inlet aerodynamic performance and operability, which are large scale flow control for enlarging flight scope in Mach/angle-of-attack, near surface flow control for shock wave/boundary layer interaction and leading edge heating-transfer control for enormous thermal load on leading edge of the compression ramp, are briefly explained and reviewed.

Abstract: Based on the shortcomings of traditional multi actuator composite action on its coordination and load adaptability, this paper has put forward a hydraulic system model where separate meter-in separate meter-out controls the multi actuator, according to different action working conditions of actuator, it has provided a composite control strategy based on pressure flow, and through AMEsim and MATLAB, it has established the composite action hydraulic transmission model of double-actuator system and simulation model of control system, and then conducted co-simulation to verify the designed controller’s good coordination and load adaptability to the separate meter-in and separate meter-out control system under different composite action working conditions.