Aerodynamic window with a pressure separation ratio greater than 500

1991 ◽  
Vol 61 (6) ◽  
pp. 1492-1496 ◽  
Author(s):  
V. M. Khailov ◽  
V. V. Shelomovskii
Keyword(s):  
Separation Ratio

Numerical Analysis of Thermal-Solutal Convection in Heterogeneous Porous Media

2005 ◽  
Vol 73 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Charles-Guobing Jiang ◽  
M. Ziad Saghir ◽  
M. Kawaji
Keyword(s):  
Porous Media ◽  
Thermal Diffusion ◽  
Soret Effect ◽  
Heterogeneous Porous Media ◽  
Soret Coefficient ◽  
Solutal Convection ◽  
Coefficient Distribution ◽  
Separation Ratio ◽  
Diffusion In Porous Media ◽  
Vertical Cavity

Thermal diffusion, or Soret effect, in porous media is mathematically modeled with the Firoozabadi model based on non-equilibrium thermodynamics. The Soret effect in a binary mixture is investigated in a vertical cavity with heterogeneous permeability, where natural convection can occur. The thermo solutal convection with heterogeneous permeability was studied in terms of flow pattern, concentration distribution, component separation ratio, and Soret coefficient distribution. A consistent analysis was conducted and it is concluded that the Soret coefficient of thermal diffusion in porous media strongly depends on the heterogeneity of permeability.

scholarly journals Turbulent viscosity and magnetic Prandtl number from simulations of isotropically forced turbulence

2020 ◽  
Vol 636 ◽  
pp. A93 ◽  
Author(s):  
P. J. Käpylä ◽  
M. Rheinhardt ◽  
A. Brandenburg ◽  
M. J. Käpylä
Keyword(s):  
Magnetic Fields ◽  
Prandtl Number ◽  
Large Scale ◽  
Turbulent Viscosity ◽  
Scale Dependence ◽  
Scale Separation ◽  
Separation Ratio ◽  
Magnetic Prandtl Number ◽  
Magnetic Diffusivity ◽  
Forced Turbulence

Context. Turbulent diffusion of large-scale flows and magnetic fields plays a major role in many astrophysical systems, such as stellar convection zones and accretion discs. Aims. Our goal is to compute turbulent viscosity and magnetic diffusivity which are relevant for diffusing large-scale flows and magnetic fields, respectively. We also aim to compute their ratio, which is the turbulent magnetic Prandtl number, Pmt, for isotropically forced homogeneous turbulence. Methods. We used simulations of forced turbulence in fully periodic cubes composed of isothermal gas with an imposed large-scale sinusoidal shear flow. Turbulent viscosity was computed either from the resulting Reynolds stress or from the decay rate of the large-scale flow. Turbulent magnetic diffusivity was computed using the test-field method for a microphysical magnetic Prandtl number of unity. The scale dependence of the coefficients was studied by varying the wavenumber of the imposed sinusoidal shear and test fields. Results. We find that turbulent viscosity and magnetic diffusivity are in general of the same order of magnitude. Furthermore, the turbulent viscosity depends on the fluid Reynolds number (Re) and scale separation ratio of turbulence. The scale dependence of the turbulent viscosity is found to be well approximated by a Lorentzian. These results are similar to those obtained earlier for the turbulent magnetic diffusivity. The results for the turbulent transport coefficients appear to converge at sufficiently high values of Re and the scale separation ratio. However, a weak trend is found even at the largest values of Re, suggesting that the turbulence is not in the fully developed regime. The turbulent magnetic Prandtl number converges to a value that is slightly below unity for large Re. For small Re we find values between 0.5 and 0.6 but the data are insufficient to draw conclusions regarding asymptotics. We demonstrate that our results are independent of the correlation time of the forcing function. Conclusions. The turbulent magnetic diffusivity is, in general, consistently higher than the turbulent viscosity, which is in qualitative agreement with analytic theories. However, the actual value of Pmt found from the simulations (≈0.9−0.95) at large Re and large scale separation ratio is higher than any of the analytic predictions (0.4−0.8).

scholarly journals Tests Research on Grouting Materials of Waste-Concrete-Powder Cement for Goaf Ground Improvement

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhilin Dun ◽  
Mengqi Wang ◽  
Lianwei Ren ◽  
Zhiyuan Dun
Keyword(s):  
Ground Improvement ◽  
Setting Time ◽  
X Ray Diffraction ◽  
Microscopic Mechanism ◽  
Water Separation ◽  
Separation Ratio ◽  
Waste Concrete ◽  
Performance Indexes ◽  
Mixing Proportion ◽  
Grouting Materials

Waste concrete powder (WCP) is proposed to replace part of the cement to seek environmentally friendly grouting materials for ground improvement in mine goaf. The optimal mixing proportion was selected based on the performance indexes of the water-separation ratio, stone rate, viscosity, setting time, and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were also conducted to analyze mineralogical phases and investigate the microscopic mechanism. Test results show that the slurry prepared by the substitution rate of 70% and adding 0.05% water-reducing agent meets well the requirements of ground grouting in mine goaf. The WCP produced by grinding mainly exerts microaggregate effect in the slurry due to low activity. A lot of pores on the surface of WCP were shown by SEM which can absorb the water in the slurry and increase the stone rate. The WCP application for ground grouting in mine goaf can not only recycle WC but also provide new grouting materials for goaf ground.

scholarly journals Pengaruh Konsentrasi Liquor Kakao (Theobroma cacao L.) terhadap Karakteristik Krim Berbahan Aktif Ekstrak Kunyit dan Daun Asam

2021 ◽  
Vol 9 (2) ◽  
pp. 238
Author(s):  
Monica Rusiyantoro ◽  
Sri Mulyani ◽  
I Wayan Arnata
Keyword(s):  
Phenolic Compounds ◽  
Active Ingredient ◽  
Theobroma Cacao ◽  
Block Design ◽  
Total Phenol ◽  
Color Test ◽  
Color Preferences ◽  
Separation Ratio ◽  
Randomized Block Design ◽  
Theobroma Cacao L

The concentrations of cocoa liquor is an alternative to increase phenolic compounds and at the same time as a natural coloring agent in creams. This study aims to determine the effect of the concentration of the cocoa liquor on the characteristics of the cream with the active ingredient of turmeric and tamarind leaves and to determine the cocoa liquor concentration to produce the best characteristics of the cream with the active ingredient of turmeric and tamarind leaves. This study used a randomized block design with 6 levels of cocoa liquor concentration of 0%, 4%, 6%, 8%, 10%, and 12%. The variables observed were homogeneity, viscosity, pH, spreadability, separation ratio, adhesion, L*, a*, b* color test, and total phenol of the cream. The results showed that the treatment of cocoa liquor concentration had a very significant effect on pH, viscosity, adhesion, dispersion, L*, a*, b* color tes, total phenol test, and organoleptic color test. Meanwhile, the treatment of cocoa liquor concentration had a significant effect on the separation ratio of the cream with the active ingredient of turmeric and tamarind leaf. The results of this study indicate that the concentration of cocoa liquor as much as 4% produces a cream with the active ingredient of turmeric and tamarind leaves with the best characteristics that are homogeneous with pH 6.13, viscosity 15333cp and, adhesion 2.39sec, spreadability 7.18cm, separation ratio 0.95, color test values L * 15.39, the values of a * 11.55, the values of b * 13.92, with the organoleptic test for color preferences 5.1. Keywords: Liquor cacao, turmeric, tamarind leave, cream characteristics

scholarly journals FRONT STRUCTURES IN A REAL GINZBURG-LANDAU EQUATION COUPLED TO A MEAN FIELD

1994 ◽  
Vol 04 (05) ◽  
pp. 1343-1346 ◽  
Author(s):  
HENAR HERRERO ◽  
HERMANN RIECKE
Keyword(s):  
Analytical Study ◽  
Landau Equation ◽  
Mean Field ◽  
Travelling Wave ◽  
Opposite Orientation ◽  
Ginzburg Landau ◽  
Separation Ratio ◽  
Ginzburg Landau Equation ◽  
Front Solutions ◽  
Wave Trains

Localized travelling wave trains or pulses have been observed in various experiments in binary mixture convection. For strongly negative separation ratio, these pulse structures can be described as two interacting fronts of opposite orientation. An analytical study of the front solutions in a real Ginzburg-Landau equation coupled to a mean field is presented here as a first approach to the pulse solution. The additional mean field becomes important when the mass diffusion in the mixture is small as is the case in liquids.

Effect of the Separation Distance on the Aeroacoustic Source of Multiple Shallow Cavities

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Ayman A. Shaaban ◽  
Samir Ziada
Keyword(s):  
Standing Wave ◽  
Separation Distance ◽  
Destructive Interference ◽  
Acoustic Standing Wave ◽  
Separation Ratio ◽  
Sound Levels ◽  
Standing Wave Method ◽  
Image Velocimetry ◽  
Strong Source ◽  
Shallow Cavities

Flow over ducted shallow cavities can excite fluid resonant oscillations. A common industrial application is the flow in corrugated pipes that can be modeled as a series of consecutive shallow cavities. In the current study, the effect of the separation distance on the aeroacoustic source of multiple shallow cavities is investigated. The standing wave method (SWM) is used to measure the source, where multiple microphones reconstruct the acoustic standing wave upstream and downstream of the cavities. The effect of the ratio between the separation distance to cavity length is investigated for a practical range from 0.5 to 1.375 for two- and three-cavity configurations. At low and intermediate sound levels, constructive hydrodynamic interference, resulting in a strong source, is observed for the extremum spacing ratios of 0.5 and 1.375. However, at high excitation levels, 10% and higher, the source, slightly but consistently, decreases upon increasing the separation ratio. These trends persist for both the double- and triple-cavity configurations. On the other hand, the separation distance of destructive interference is found to depend on the number of cavities of the tested configuration. Particle image velocimetry (PIV) measurements of the constructive interference cases show strong synchronized vorticity shedding in all cavities. Each cavity contribution to the total aeroacoustic source is then examined by means of Howe's analogy, and the percentage contribution of each cavity is found to depend on the excitation level.

Resistance Predictions for Asymmetrical Configurations of High-Speed Catamaran Hull Forms

2015 ◽  
Author(s):  
Srikanth Asapana ◽  
Prasanta K. Sahoo ◽  
Vaibhav Aribenchi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Comparative Analysis ◽  
High Speed ◽  
Public Domain ◽  
Literature Survey ◽  
Historical Background ◽  
Resistance Analysis ◽  
Separation Ratio ◽  
Hull Forms

This paper attempts to undertake a comparative analysis of resistance characteristics between newly developed asymmetrical catamaran hull forms which were derived from existing conventional NPL series of round bilge catamaran hull forms by Molland, Wellicome and Couser (1994). A set of asymmetrical catamaran hull forms with waterline length of 1.6 m with a separation ratio (s/L) of 0.4 were generated by using standard modelling software. The resistance analysis had been carried out by using STAR CCM+, a computational fluid dynamics package for Froude numbers of 0.25, 0.30, 0.60, 0.80 and 1.0. Literature survey indicates that there is scant historical background in public domain to perform resistance analysis on asymmetrical catamaran hull forms. As this is not feasible due to lack of data in areas that were considered crucial, separate resistance analysis is carried out for each hull configuration. Finally, the compared resistance results will attempt to conclude whether asymmetrical catamaran hull forms are more efficient than the conventional catamaran hull forms.

scholarly journals Pengaruh Nilai Hydrophile-Liphophile Balance (HLB) dan Jenis Ekstrak terhadap Karakteristik Krim Kunyit-Lidah Buaya (Curcuma domestica val.-Aloe Vera)

2019 ◽  
Vol 4 (2) ◽  
pp. 54
Author(s):  
I Gusti Ayu Sri Krsna Devi ◽  
Sri Mulyani ◽  
Lutfi Suhendra
Keyword(s):  
Block Design ◽  
Aloe Vera ◽  
Total Phenol ◽  
Separation Ratio ◽  
Turmeric Extract ◽  
Randomized Block Design ◽  
The Right

ABSTRACT This study aimed to determine the effect of  value Hydrophile-Liphophile Balance (HLB) and type of extract on the characteristics of turmeric-aloe vera cream (Curcuma domestica Val. – Aloe Vera) also determine the HLB and the right type of extract to produce the best characteristics of turmeric-aloe vera cream (Curcuma domestica Val. – Aloe Vera). This study used a factorial randomized block design with two factor. The first factor was the HLB which consist of three levels, namely HLB 9, 10 and 11. The second factor was an extract consisting of two levels, namely the addition of turmeric and aloe vera extract. The result of the study showed that HLB has an effect on the spread power. The extract has an effect on the degree of acidity and total phenol. The treatment of HLB and the addition of the extract did not affect homogeneity, separation ratio, viscocity and adhesion time. All creams fulfill the characteristics of SNI. Aloe vera and turmeric extract cream with HLB 10 were the best formulated cream at the 6th week storage of the following characteristics: homogeneus, separation ratio =1, spread power 4.8-5.2 cm, viscocity 15733–16667 cp, adhesion time 14.43–17.31 second, pH 4.87-5.00 and total phenol 1.08–1.36 mg GAE/g. ABSTRAK Penelitian ini bertujuan untuk mengetahui pengaruh nilai Hydrophile-Liphophile Balance (HLB) dan jenis ekstrak terhadap karakteristik krim kunyit – lidah buaya (Curcuma domestica Val. – Aloe Vera) yang dihasilkan serta menentukan perbandingan HLB dan jenis ekstrak yang tepat untuk menghasilkan karakteristik terbaik krim kunyit – lidah buaya (Curcuma domestica Val – Aloe Vera). Penelitian ini menggunakan Rancangan Acak Kelompok Faktorial dengan dua faktor. Faktor pertama yaitu HLB yang terdiri dari 3 taraf yaitu HLB 9, 10 dan 11. Faktor kedua yaitu penambahan ekstrak terdiri dari 2 taraf yaitu penambahan ekstrak kunyit dan lidah buaya. Hasil penelitian menunjukkan perlakuan HLB berpengaruh terhadap daya sebar. Perlakuan penambahan ekstrak berpengaruh terhadap derajat keasaman dan total senyawa fenolik. Perlakuan HLB dan penambahan ekstrak tidak berpengaruh terhadap homogenitas, rasio pemisah, viskositas dan waktu lekat. Semua krim memenuhi karakteristik SNI. Krim ekstrak lidah buaya dan kunyit dengan HLB 10 merupakan krim dengan formulasi terbaik pada minggu ke-6 dengan karakteristik sebagai berikut : homogen, rasio pemisahan =1, daya sebar 4.8-5.2 cm, viskositas 15733–16667 cp, waktu lekat 14.43–17.31 detik, pH 4.87-5.00 dan total fenol 1.08–1.36 mg GAE/g.

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