Visualization of Fluid Mixing in a Microchamber on a Rotating Disk

2008 ◽  
Author(s):  
H.-C. Chiu ◽  
J.-Y. Chen ◽  
Jerry M. Chen
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Rotating Disk ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Channel Depth ◽  
Clockwise Rotation ◽  
Two Fluids ◽  
Speed Range ◽  
Lower Speed Range

This paper reports flow visualization experiments of fluid mixing in a microchamber on a rotating disk. The two centrifuge-driven sample fluids were brought in contact at the Y-junction microchannel and then flowed to a circular mixing chamber where the main course of mixing took place. The flow images were acquired using a micro-image-capturing unit in synchronization with the rotational motion to allow only one shot of the targeted object on the rotating disk per revolution. Both the visualization and quantification of flow images show that the mixing efficiency of the two fluids depends not only on the rotational speed but also on the depth of the channels. It is found that the mixing efficiency generally decrease with increasing rotational speed in the lower speed range (≤ 420 rpm). Beyond this lower speed range, the mixer with a larger channel depth h = 300 μm shows an increase of mixing efficiency with increasing rotational speed to reach as much as 83% at 1200 rpm. For the mixer with a smaller channel depth h = 200 μm, however, the mixing efficiency continues deceasing or becomes flat with increasing rotational speed. It is also found that the counter-clockwise rotation produces a better mixing efficiency than the clockwise rotation in the high speed range.

Numerical Study of Fluid Mixing in a Microchannel with a Circular Chamber on a Rotating Disk

2012 ◽  
Vol 542-543 ◽  
pp. 1113-1119 ◽  
Author(s):  
Huan Chao Chiu ◽  
Jerry M Chen
Keyword(s):  
Rotational Speed ◽  
Numerical Study ◽  
Rotating Disk ◽  
Transverse Flow ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Straight Channel ◽  
Lower Range ◽  
Speed Range ◽  
Flat Distribution

This paper reports numerical simulations of fluid mixing in a rotating microchannel with a microchamber fabricated on a CD-like substrate. The sample fluids are driven by the centrifugal force and brought in contact at a Y-shaped junction, and then the mixing flow moves through a straight channel with a circular chamber where the main course of mixing takes place. The CD-like micromixer is rotated clockwise at speeds ranging from 300 to1200 rpm. With increasing rotational speed, the mixing efficiency is found dropping in the lower range (≤ 540 rpm), where the diffusion still dominates the mixing, and then grows progressively to reach as much as 90%. The progressively growth in the higher speed range significantly improves the slightly descending and flat distribution for a straight mixing channel without a circular chamber. This significant enhancement of mixing is due mainly to the vortices generated in the circular chamber and the strong transverse flow induced by the Coriolis force.

New Centrifugal Pump in Very Low Specific Speed Range

2011 ◽  
Author(s):  
Shusaku Kagawa ◽  
Junichi Kurokawa
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Rotating Disk ◽  
Capacity Curve ◽  
Speed Range ◽  
Low Specific Speed ◽  
Specific Speed

In the range of very low specific speed, such as ns < 80 [min.−1, m3/min., m], or Ns < 533 [min.−1, USGPM, ft.], stable head-capacity curve is one of the most important issues. The head-capacity curve of a conventional closed impeller tends to be unstable with a positive slope characteristic in such a very low ns range. To solve this problem, a new type of centrifugal pump “J-groove pump” is proposed and tested in this study. The J-groove pump is composed of a rotating disk mounted with many shallow radial grooves and a circular casing. The experimental results reveal that the proposed J-groove pump is quite effective in the very low specific speed range. The pump head is about 1.2 times higher than that of a conventional centrifugal pump and the head-capacity curve is almost stable, though the efficiency becomes a little lower because of a large friction power of the stationary wall. The cavitation performance is also measured and is shown to be almost same as that of a conventional centrifugal pump. This pump is applicable to high speed pump, as it has no small clearance, high strength due to simple impeller configuration, and easy to assemble. In order to determine the internal flow characteristics of the J-groove pump, CFD simulation is carried out. It is revealed that the high head of the J-groove pump is caused by a strong vortex flow existing in both clearances near the impeller tip over the whole flow range.

Analysis on dynamical properties of the foil bearing rotor system with the unbalanced magnetic pull

2020 ◽  
Vol 64 (1-4) ◽  
pp. 181-189
Author(s):  
Hao Li ◽  
Haipeng Geng ◽  
Hao Lin ◽  
Sheng Feng
Keyword(s):  
High Speed ◽  
Paper Analysis ◽  
Rotor System ◽  
Synchronous Motors ◽  
Unbalanced Magnetic Pull ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Speed Range ◽  
Working Principle ◽  
Lower Speed Range

Gas foil bearings (GFBs) are widely used in synchronous motors for their splendid performance in high speed. However, its working principle can produce unbalanced magnetic pull (UMP) between stator and rotor inevitably. Based on the rotor transverse vibration, this paper analysis the influence of UMP on the dynamic behavior of the rotor system supported by GFBs. The results show that the UMP accounts for a higher proportion of the exciting force acting on the rotor system at lower speed range. And the UMP declines with the decrease of nominal clearance. It is found that UMP will advance the critical speed of rotor system. According to the simulation results, the rated speed of synchronous motor is set at 90 000 rpm, and the nominal clearance of GFBs is 8 μm. The experimental results show that the rotor system designed in this paper works stably and achieves the predetermined design goal.

Fluid Mixing Using Induced Charge Electro-Osmotic Transverse Flow Actuated by Asymmetrical Driving Electrode Sequence

2019 ◽  
Author(s):  
Xiaoming Chen ◽  
Yukun Ren ◽  
Likai Hou ◽  
Tianyi Jiang ◽  
Hongyuan Jiang
Keyword(s):  
Nanoparticle Synthesis ◽  
Transverse Flow ◽  
Fluid Mixing ◽  
Mixing Efficiency ◽  
Device Structure ◽  
Two Fluids ◽  
Electro Osmosis ◽  
Potential Alternative ◽  
Induced Charge ◽  
Electrolyte Characteristics

Abstract Microfluid mixing is an essential process in chemical analysis, drug test, and nanoparticle synthesis. Induced charge electro-osmosis (ICEO) has good capability in microfluid mixing for its reconfigurable vortex profile. We found experimentally ICEO transverse flow induced by the asymmetrical driving electrode has a good performance in disturbing the interface of two fluids. Encouraged by these aspects, we proposed a micromixer using ICEO transverse flows actuated by the asymmetrical driving electrode sequence to mix microfluids. We established a simulation model to investigate the evolution of the interface and demonstrate the work principle of this method. Moreover, we numerically explored the effects of device structure, and electrolyte characteristics on the capability of micromixer. Finally, we validated this method experimentally, and studied the effects of voltage intensity, frequency and flow rate on the mixing capability, obtaining mixing efficiency exceeding 94%. This method is a potential alternative in various microfluidic and lab-on-a-chip applications.

scholarly journals Enhancement of Fluid Mixing with U-Shaped Channels on a Rotating Disc

Micromachines ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1110
Author(s):  
Chi-Wei Hsu ◽  
Po-Tin Shih ◽  
Jerry M. Chen
Keyword(s):  
Secondary Flow ◽  
Rotational Speed ◽  
Fluid Mixing ◽  
Maximum Efficiency ◽  
Mixing Efficiency ◽  
Rotating Disc ◽  
Mixing Performance ◽  
Simple Geometry ◽  
Visualization Experiments ◽  
Good Agreement

In this study, centrifugal microfluidics with a simple geometry of U-shaped structure was designed, fabricated and analyzed to attain rapid and efficient fluid mixing. Visualization experiments together with numerical simulations were carried out to investigate the mixing behavior for the microfluidics with single, double and triple U-shaped structures, where each of the U-structures consisted of four consecutive 90° bends. It is found that the U-shaped structure markedly enhances mixing by transverse secondary flow that is originated from the Coriolis-induced vortices and further intensified by the Dean force generated as the stream turns along the 90° bends. The secondary flow becomes stronger with increasing rotational speed and with more U-shaped structures, hence higher mixing performance. The mixing efficiency measured for the three types of mixers shows a sharp increase with increasing rotational speed in the lower range. As the rotational speed further increases, nearly complete mixing can be achieved at 600 rpm for the triple-U mixer and at 720 rpm for the double-U mixer, while a maximum efficiency level of 83–86% is reached for the single-U mixer. The simulation results that reveal detailed characteristics of the flow and concentration fields are in good agreement with the experiments.

scholarly journals High-enthalpy hypersonic flows

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Joseph J. S. Shang ◽  
Hong Yan
Keyword(s):  
Hypersonic Flow ◽  
High Speed ◽  
Quantum Physics ◽  
Nonequilibrium Thermodynamic ◽  
Strong Shock ◽  
Hypersonic Flows ◽  
Electrically Conducting ◽  
High Enthalpy ◽  
Speed Range ◽  
Flow Theories

Abstract Nearly all illuminating classic hypersonic flow theories address aerodynamic phenomena as a perfect gas in the high-speed range and at the upper limit of continuum gas domain. The hypersonic flow is quantitatively defined by the Mach number independent principle, which is derived from the asymptotes of the Rankine-Hugoniot relationship. However, most hypersonic flows encounter strong shock-wave compressions resulting in a high enthalpy gas environment that always associates with nonequilibrium thermodynamic and quantum chemical-physics phenomena. Under this circumstance, the theoretic linkage between the microscopic particle dynamics and macroscopic thermodynamics properties of gas is lost. When the air mixture is ionized to become an electrically conducting medium, the governing physics now ventures into the regimes of quantum physics and electromagnetics. Therefore, the hypersonic flows are no longer a pure aerodynamics subject but a multidisciplinary science. In order to better understand the realistic hypersonic flows, all pertaining disciplines such as the nonequilibrium chemical kinetics, quantum physics, radiative heat transfer, and electromagnetics need to bring forth.

scholarly journals Color Response Modification of Encapsulated Liquid Crystals Used in Rotating Disk Heat Transfer Studies

1995 ◽  
Author(s):  
Cengiz Camci ◽  
Boris Glezer
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Rotational Speed ◽  
Rotating Disk ◽  
Point Of View ◽  
Centrifugal Acceleration ◽  
Relative Shift ◽  
Color Response ◽  
Stationary Conditions

The liquid crystal thermography can be successfully used in both transient and steady-state heat transfer experiments with excellent spatial resolution and good accuracy. Although most of the past liquid crystal based heat transfer studies are reported in the stationary frame, measurements from the rotating frame of turbomachinery systems exist The main objective of the present investigation is to determine the influence of rotation on the color calibration of encapsulated liquid crystals sprayed on the flat surface of a rotating aluminum disk. The investigation is performed for a rotational speed range from 0 rpm to 7500 rpm using three different liquid crystal coatings displaying red at 30, 35 and 45° C, under stationary conditions. An immediate observation from the present study is that the color response of liquid crystals is strongly modified by the centrifugal acceleration of the rotating environment. It is consistently and repeatedly observed that the hue versus temperature curve is continuously shifted toward lower temperatures by increasing rotational speed. The relative shift of the display temperature of the green can be as high as 7°C at 7500 rpm when compared to the temperature of the green observed under stationary conditions. The present study shows that relative shift of the liquid crystal color has a well-defined functional dependency to rotational speed. The shift is linearly proportional to the centrifugal acceleration. It is interesting to note that the individual shift curves of the green for all three liquid crystal coatings collapse into a single curve when they are normalized with respect to their own stationary green values. When the color attribute is selected as “intensity” instead of “hue”, very similar shifts of the temperature corresponding to the intensity maximum value appearing around green is observed. An interpretation of the observed color shift is made from a thermodynamics energy balance point of view.

scholarly journals Operating temperatures of oil-lubricated medium-speed gears: Numerical models and experimental results

2003 ◽  
Vol 217 (2) ◽  
pp. 87-106 ◽  
Author(s):  
H Long ◽  
A A Lord ◽  
D T Gethin ◽  
B J Roylance
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Rotational Speed ◽  
High Speed ◽  
Applied Load ◽  
Frictional Heat ◽  
Transfer Coefficients ◽  
Gear Teeth ◽  
Heat Transfer Coefficients

This paper investigates the effects of gear geometry, rotational speed and applied load, as well as lubrication conditions on surface temperature of high-speed gear teeth. The analytical approach and procedure for estimating frictional heat flux and heat transfer coefficients of gear teeth in high-speed operational conditions was developed and accounts for the effect of oil mist as a cooling medium. Numerical simulations of tooth temperature based on finite element analysis were established to investigate temperature distributions and variations over a range of applied load and rotational speed, which compared well with experimental measurements. A sensitivity analysis of surface temperature to gear configuration, frictional heat flux, heat transfer coefficients, and oil and ambient temperatures was conducted and the major parameters influencing surface temperature were evaluated.

Analysis of the Lubrication Regimes at the Small End and Big End of a Connecting Rod of a High Performance Motorbike Engine

2012 ◽  
Author(s):  
Luca Bertocchi ◽  
Matteo Giacopini ◽  
Daniele Dini
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
High Performance ◽  
Hydrodynamic Lubrication ◽  
Vertical Axis ◽  
Connecting Rod ◽  
Lubrication Regimes ◽  
High Speed Rotation ◽  
Speed Rotation ◽  
Squeeze Effect

In the present paper, the algorithm proposed by Giacopini et. al. [1], based on a mass-conserving formulation of the Reynolds equation using the concept of complementarity is suitably extended to include the effects of compressibility, piezoviscosity and shear-thinning on the lubricant properties. This improved algorithm is employed to analyse the performance of the lubricated small end and big end bearings of a connecting rod of a high performance motorbike engine. The application of the algorithm proposed to both the small end and the big end of a con-rod is challenging because of the different causes that sustain the hydrodynamic lubrication in the two cases. In the con-rod big end, the fluid film is mainly generated by the relative high speed rotation between the rod and the crankshaft. The relative speed between the two races forms a wedge of fluid that assures appropriate lubrication and avoids undesired direct contacts. On the contrary, at the con-rod small end the relative rotational speed is low and a complete rotation between the mating surfaces does not occurs since the con-rod only oscillates around its vertical axis. Thus, at every revolution of the crankshaft, there are two different moments in which the relative rotational speed between the con-rod and the piston pin is null. Therefore, the dominant effect in the lubrication is the squeeze caused by the high loads transmitted through the piston pin. In particular both combustion forces and inertial forces contribute to the squeeze effect. This work shows how the formulation developed by the authors is capable of predicting the performance of journal bearings in the unsteady regime, where cavitation and reformation occur several times. Moreover, the effects of the pressure and the shear rate on the density and on the viscosity of the lubricant are taken into account.

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