Fluid Flow Characteristics in Microchannels With Rib-Patterned Surface

2011 ◽  
Author(s):  
Toru Yamada ◽  
Chungpyo Hong ◽  
Otto J. Gregory ◽  
Mohammad Faghri
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Flow Characteristics ◽  
Single Crystal Silicon ◽  
Working Fluid ◽  
Patterned Surfaces ◽  
Crystal Silicon ◽  
Wide Range ◽  
Fluid Flow Characteristics ◽  
Good Agreement

The effects of rib-patterned surfaces and surface wettability on liquid flow in microchannels were experimentally investigated in this study. Microchannels were fabricated on single-crystal silicon wafers by photolithographic and wet-etching techniques. Rib structures were patterned in the silicon microchannel, and the surface was chemically treated by trichlorosilane to create the hydrophobic condition. Experiments with water as the working fluid were performed with these microchannels over a wide range of Reynolds number between 110 and 1914. The results for the rib-patterned microchannels showed that the friction factor with the hydraulic diameter based on the rib-to-upper-wall height was lower than that for the incompressible theory with the same height. The friction factor-Reynolds number products for the hydrophobic condition increased as Reynolds number increased in the laminar flow regime. The experimental results were also compared with the predictive expressions from the literature, and it was found that the experimental data for the small rib/cavity geometry was in good agreement with those in the literature.

Friction Reduction in Turbulent Journal Bearings by Highpolymers

1980 ◽  
Vol 102 (4) ◽  
pp. 439-444 ◽  
Author(s):  
H. Fukayama ◽  
M. Tanaka ◽  
Y. Hori
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Polymer Solution ◽  
Friction Factor ◽  
Polymer Concentration ◽  
Journal Bearings ◽  
Friction Reduction ◽  
Dilute Polymer Solutions ◽  
Wide Range ◽  
Good Agreement

The friction reduction by dilute polymer solutions is investigated experimentally in turbulent journal bearings. The effects of polymer substances, polymer concentration, bearing clearance, and journal eccentricity on friction reduction are examined over the wide range of Reynolds number in the superlaminar regime. In the experiments, the friction of polymer solution is less than 40 percent of that of Newtonian turbulent flow under the best conditions. The calculated friction factor for the Couette flow is in good agreement with the corresponding measured one. Degradation of highpolymer is also investigated experimentally, and is found to be affected by polymer concentration.

scholarly journals Possible causes of electrical resistivity distribution inhomogeneity in Czochralski grown single crystal silicon

2019 ◽  
Vol 5 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Svetlana P. Kobeleva ◽  
Ilya M. Anfimov ◽  
Vladimir S. Berdnikov ◽  
Tatyana V. Kritskaya
Keyword(s):  
Electrical Resistivity ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystallization Front ◽  
Single Crystal Silicon ◽  
Theoretical Interpretation ◽  
Azimuthal Direction ◽  
Crystal Silicon ◽  
Wide Range ◽  
Possible Cause

Electrical resistivity distribution maps have been constructed for single crystal silicon wafers cut out of different parts of Czochralski grown ingots. The general inhomogeneity of the wafers has proven to be relatively high, the resistivity scatter reaching 1–3 %. Two electrical resistivity distribution inhomogeneity types have been revealed: azimuthal and radial. Experiments have been carried out for crystal growth from transparent simulating fluids with hydrodynamic and thermophysical parameters close to those for Czochralski growth of silicon single crystals. We show that a possible cause of azimuthal electrical resistivity distribution inhomogeneity is the swirl-like structure of the melt under the crystallization front (CF), while a possible cause of radial electrical resistivity distribution inhomogeneity is the CF curvature. In a specific range of the Grashof, Marangoni and Reynolds numbers which depend on the ratio of melt height and growing crystal radius, a system of well-developed radially oriented swirls may emerge under the rotating CF. In the absence of such swirls the melt is displaced from under the crystallization front in a homogeneous manner to form thermal and concentration boundary layers which are homogeneous in azimuthal direction but have clear radial inhomogeneity. Once swirls emerge the melt is displaced from the center to the periphery, and simultaneous fluid motion in azimuthal direction occurs. The overall melt motion becomes helical as a result. The number of swirls (two to ten) agrees with the number of azimuthally directed electrical resistivity distribution inhomogeneities observed in the experiments. Comparison of numerical simulation results in a wide range of Prandtl numbers with the experimental data suggests that the phenomena observed in transparent fluids are universal and can be used for theoretical interpretation of imperfections in silicon single crystals.

Experimental analysis on thermal and friction factor characteristics of fluid flow in tube with novel double strip helical screw tape

2019 ◽  
Vol 234 (6) ◽  
pp. 874-886
Author(s):  
Shashank R Chaurasia ◽  
RM Sarviya
Keyword(s):  
Nusselt Number ◽  
Fluid Flow ◽  
Friction Factor ◽  
Experimental Analysis ◽  
Flow Characteristics ◽  
Performance Ratio ◽  
Working Fluid ◽  
Flow Rates ◽  
Twist Ratio ◽  
Single Strip

An experimental analysis has been carried out to investigate the thermal and friction factor characteristics of fluid flow in a tube with double strip helical screw tape (DS-HST) inserts with different values of twist ratio and compared with single strip helical screw tape inserts and plain tube. Water is used as a working fluid at different flow rates with constant heat flux conditions. CFD analysis is also carried out to visualize thermal and fluid flow characteristics of fluid flow in tube with inserts. Experimental results have showed that Nusselt number and friction factor have attained excellent enhancement with double strip helical screw tape inserts in the range of flow rates than single strip helical screw tape inserts at the value of twist ratio 1.5. Correlation is also developed for Nusselt number with a range of Reynolds number, twist ratio and number of strips. Moreover, the performance ratio has attained maximum value at twist ratio of 2.5 with high values of flow rate. It is concluded that DS-HST is able to attain enhancement in the efficiency of heat exchanger, causing a reduction in size for thermal applications.

Fluid Flow Characteristics of a Confined Slot Jet Without or With a Target Surface

2005 ◽  
Author(s):  
L. K. Liu ◽  
C. J. Fang ◽  
M. C. Wu ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Target Surface ◽  
Streamwise Velocity ◽  
Separation Distance ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the fluid flow characteristics of slot jet without or with a target surface have been successfully conducted. From all the fluid velocity data measured in the present study, the experimental conditions have been verified to be spanwise-symmetrically maintained and the results have been achieved in a spanwise-symmetric form. Three types of jet configuration without or with target surface are investigated: (A) Confined Slot Jet without Target Surfaces – the fluid flow parameters studied in the present investigation is the jet Reynolds number (ReD). Its ranges are ReD=506-1517. (B) Confined Slot Jet with Smooth Surfaces – the fluid flow parameters studied in the present investigation include the ratio of jet separation distance (H) to nozzle width (W) and the jet Reynolds number (ReD). The ranges of the relevant parameters are H/W=2–10 and ReD=504–1526. (C) Confined Slot Jet with Extended Surfaces – the fluid flow parameters studied include the ratio of jet separation distance (H) to nozzle width (W), the Reynolds number (ReD) and the ratio of extended surface height (Hes) to nozzle width (W). Their ranges are H/W=3–10, Hes/W=0.74-3.40 and ReD=501–1547. The flow characteristics such as the local mean streamwise velocity distribution, mean streamwise velocity decay along jet centerline, local jet turbulence intensity distribution, and turbulence intensities along jet centerline have been presented and discussed in the study.

scholarly journals Numerical investigation of flow characteristics over stepped spillways

2020 ◽  
Author(s):  
Aytaç Güven ◽  
Ahmed Hussein Mahmood
Keyword(s):  
Numerical Model ◽  
Turbulent Flow ◽  
Flow Characteristics ◽  
Air Entrainment ◽  
Stepped Spillway ◽  
Stepped Spillways ◽  
Entrainment Velocity ◽  
Fluid Flow Characteristics ◽  
3D Package ◽  
Good Agreement

Abstract Spillways are constructed to evacuate the flood discharge safely not to let the flood wave overtop the dam body. There are different types of spillways, ogee type being the conventional one. Stepped spillway is an example of nonconventional spillways. The turbulent flow over stepped spillway was studied numerically by using the Flow-3D package. Different fluid flow characteristics such as longitudinal flow velocity, temperature distribution, density and chemical concentration can be well simulated by Flow-3D. In this study, the influence of slope changes on flow characteristics such as air entrainment, velocity distribution and dynamic pressures distribution over the stepped spillway was modelled by Flow-3D. The results from the numerical model were compared with the experimental study done by others in the literature. Two models of the stepped spillway with different discharge for each model was simulated. The turbulent flow in the experimental model was simulated by the Renormalized Group (RNG) turbulence scheme in the numerical model. A good agreement was achieved between the numerical results and the observed ones, which were exhibited in terms of graphics and statistical tables.

An Electronic Stopping Power Model in Single-Crystal Silicon from a Few KeV to Several MeV

1996 ◽  
Vol 438 ◽  
Author(s):  
S. J. Morris ◽  
B. Obradovic ◽  
S.-H. Yang ◽  
A. F. Tasch ◽  
L. Rubin
Keyword(s):  
Single Crystal ◽  
Damage Accumulation ◽  
Single Crystal Silicon ◽  
Crystallographic Direction ◽  
Stopping Power ◽  
Power Model ◽  
Crystal Silicon ◽  
Wide Range ◽  
Physically Based ◽  
Electronic Stopping Power

AbstractAn electronic stopping power model for boron, arsenic, and phosphorus ion implantation into single-crystal Si is reported over the energy range from a few keV to several MeV, for both offand on-axis implant angles relative to the <100> crystallographic direction. Combined with previously developed models for damage accumulation, this model allows physically-based simulation of 3-D profiles over an extremely wide range of implant conditions. In particular, this allows modeling of MeV implants which are being used more and more frequently.

Numerical Simulation of Mt. Merapi Pyroclastic Flow in 2010

2019 ◽  
Vol 14 (1) ◽  
pp. 105-115 ◽  
Author(s):  
Makoto Shimomura ◽  
Raditya Putra ◽  
Niken Angga Rukmini ◽  
Sulistiyani ◽  
◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Friction Factor ◽  
Pyroclastic Flow ◽  
Influencing Factor ◽  
Flow Characteristics ◽  
Suitable Condition ◽  
Pyroclastic Material ◽  
Inundation Area ◽  
Wide Range ◽  
Granular Friction

A pyroclastic flow is one of the most dangerous hazardous phenomena. To escape a pyroclastic flow, the influenceable area must be evacuated before the flow occurs. Therefore, to predict the inundation area of a pyroclastic flow is important, and numerical simulation is a helpful tool in this prediction. This study simulated a pyroclastic flow by reproducing the pyroclastic flow of Mt. Merapi that occurred in 2010. However, necessary detailed information of the flow to conduct the simulation, such as total volume and the property of the pyroclastic flow material, flow rate, etc., were not available. Therefore, 20 simulations were conducted, varying the important conditions, such as the volume of pyroclastic material, inter-granular friction factor, and duration of the flow. The results showed that the volume of the pyroclastic material and inter-granular friction factor strongly control the flow characteristics. However, the friction factor does not result in a wide range of values; therefore, volume is the most influencing factor. The most suitable condition is a total volume of pyroclastic material of 30 × 106m3, a 5 min duration of flow, and a 0.6 friction factor.

Measurements of Thermal Performance of the Regenerator of a Cryocooler with a high Number of Transfer Units Value

1996 ◽  
Vol 210 (4) ◽  
pp. 341-352 ◽  
Author(s):  
P-H Chen ◽  
Z-C Chang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Thomson Effect ◽  
Empirical Correlations ◽  
External Tube ◽  
Improved Model

Hundreds of stacked wire screens are used in the regenerator matrix of a common cryocooler. The number of transfer units of such a matrix (denoted as NTUm) may well exceed 60. However, most of the earlier studies reported are limited to studies of regenerators with NTUm values less than 60, as the single-blow method was employed to measure the NTUm value of the regenerator matrix. Furthermore, in these earlier studies, the effect of heat transfer from the working fluid to the external tube and the Joule-Thomson effect were neglected. In the present study, three regenerators having high NTUm values have been constructed and a transient single-blow technique has been employed to measure the friction factor and the heat transfer performance of these regenerators. In addition, an improved model has been adopted to correct the shortcomings of the earlier studies. Empirical correlations have been provided for the relation between the friction factor and Reynolds number and between the Nusselt number and Reynolds number. The correlation with smaller NTUm values agreed well with those reported in earlier studies.

Effects of Al2O3–Cu/water hybrid nanofluid on heat transfer and flow characteristics in turbulent regime

2015 ◽  
Vol 26 (04) ◽  
pp. 1550047 ◽  
Author(s):  
Behrouz Takabi ◽  
Hossein Shokouhmand
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Pure Water ◽  
Flow Characteristics ◽  
Hydrodynamic Performance ◽  
Hybrid Nanofluid ◽  
Turbulent Regime ◽  
Average Increase ◽  
Finite Volume Discretization ◽  
Wide Range

In this paper, forced convection of a turbulent flow of pure water, Al 2 O 3/water nanofluid and Al 2 O 3– Cu /water hybrid nanofluid (a new advanced nanofluid composited of Cu and Al 2 O 3 nanoparticles) through a uniform heated circular tube is numerically analyzed. This paper examines the effects of these three fluids as the working fluids, a wide range of Reynolds number (10 000 ≤ Re ≤ 10 0000) and also the volume concentration (0% ≤ ϕ ≤ 2%) on heat transfer and hydrodynamic performance. The finite volume discretization method is employed to solve the set of the governing equations. The results indicate that employing hybrid nanofluid improves the heat transfer rate with respect to pure water and nanofluid, yet it reveals an adverse effect on friction factor and appears severely outweighed by pressure drop penalty. However, the average increase of the average Nusselt number (when compared to pure water) in Al 2 O 3– Cu /water hybrid nanofluid is 32.07% and the amount for the average increase of friction factor would be 13.76%.

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