A New Cavitation-Induced-Momentum-Defect (CIMD) Correction Approach to Track Cavitation Events

2007 ◽  
Author(s):  
Vedanth Srinivasan ◽  
Abraham J. Salazar ◽  
Kozo Saito
Keyword(s):  
Liquid Phase ◽  
Transport Equation ◽  
Vapor Phase ◽  
Incompressible Flows ◽  
Vapor Transport ◽  
Source Terms ◽  
Local Pressure ◽  
Cloud Cavitation ◽  
Tracking Model ◽  
The Impact

A new unsteady cavitation event tracking model is developed for predicting vapor dynamics occurring in multi-dimensional incompressible flows. The procedure solves incompressible Navier-Stokes equations for the liquid phase with an additional vapor transport equation for the vapor phase. The model tracks regions of liquid vaporization and applies compressibility effects to compute the local variation in speed of sound using the Homogeneous Equilibrium Model (HEM) assumptions. The variation of local cell density as a function of local pressure is used to construct the source term in the vapor fraction transport equation. The novel Cavitation-Induced-Momentum-Defect (CIMD) correction methodology developed in this study serves to account for cavitation inception and collapse events as relevant momentum source terms in the liquid phase momentum equations. Effects of vapor phase accumulation and diffusion are incorporated by detailed relaxation models. A modified RNG K-ε model, including the effects of compressibility in the vapor regions, is employed for modeling turbulence effects. Turbulent kinetic energy and dissipation contributions from the vapor regions are integrated with the liquid phase turbulence using relevant source terms. Numerical simulations are carried out using a Finite Volume methodology available within the framework of commercial CFD software code Fluent v.6.2. Simulation results are in qualitative agreement with experiments for unsteady cloud cavitation behavior in planar nozzle flows. Multitude of mechanisms such as formation of vortex cavities, vapor cluster shedding and coalescence, cavity pinch off are sharply captured by the supplemented vapor transport equation. Our results concur with previously established theories concerning sheet and cloud cavitation such as the re-entrant jet motion, cavity closure and the impact of adverse pressure gradients on cavitation dynamics.

Oxide nanodot arrays templated from polymer nano-channels via a novel vapor-transport-assisted wet chemistry process

2008 ◽  
Vol 23 (8) ◽  
pp. 2061-2066 ◽  
Author(s):  
Yi-Feng Lin ◽  
Wen-Hsien Tseng ◽  
Hong-Zhi Luan ◽  
Liang-Yu Chen ◽  
Shih-Yuan Lu ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Vapor Phase ◽  
Low Temperatures ◽  
Vapor Transport ◽  
The Other ◽  
Wet Chemistry ◽  
Polymer Templates ◽  
Nanodot Arrays ◽  
Growth Problem ◽  
Soft Polymer

A novel vapor-transport-assisted wet chemistry process was developed to fabricate oxide nanodot arrays from soft polymer templates. The feasibility and wide applicability of the proposed process was demonstrated with creation of high-density oxide nanodot arrays of TiO2, ZnO, and Co3O4. The present process not only avoids the over-growth problem inevitable in wet chemistry processes but also enables formation of oxide nanodots at low temperatures. The process can be readily extended to other compound systems in which the products can be formed through reactions of two reactants, one in liquid phase and the other in vapor phase.

Chemical Transport Facilitated by Multiphase Flow Systems1

1985 ◽  
Vol 17 (9) ◽  
pp. 1-12 ◽  
Author(s):  
Carl G. Enfield
Keyword(s):  
Organic Carbon ◽  
Boundary Conditions ◽  
Transport Equation ◽  
Fluid Phase ◽  
Chemical Transport ◽  
Facilitated Transport ◽  
Organic Fraction ◽  
Dispersive Transport ◽  
Transformation Of Variables ◽  
The Impact

Relatively immobile chemicals have been observed moving significantly faster than anticipated from hydrophobic theory. A theory is developed considering transport in three mobile fluid phases which can be used to describe this facilitated transport. The convective dispersive transport equation is solved utilizing a transformation of variables which permits utilizing existing solutions covering a wide variety of boundary conditions. The impact of the facilitated transport is demonstrated for one case where the soils organic carbon is 10%. If 2% of the fluid phase is an organic fraction, the theory developed projects that hydrophobic theory may underestimate mobility by more than 100 times. At concentrations of dissolved organic carbon normally observed in nature (5 - 10 mg/l), a measurable increased mobility is anticipated for the very immobile compounds like dioxins.

scholarly journals A Mathematical Model for Swallowing of Concentrated Fluids in Oesophagus

2011 ◽  
Vol 8 (3-4) ◽  
pp. 309-321 ◽  
Author(s):  
S. K. Pandey ◽  
Dharmendra Tripathi
Keyword(s):  
Mathematical Model ◽  
Flow Rate ◽  
Plug Flow ◽  
Flow Region ◽  
Mechanical Efficiency ◽  
Casson Fluid ◽  
Local Pressure ◽  
Integral Number ◽  
Tomato Puree ◽  
The Impact

This model investigates particularly the impact of an integral and a non-integral number of waves on the swallowing of food stuff such as jelly, tomato puree, soup, concentrated fruits juices and honey transported peristaltically through the oesophagus. The fluid is considered as a Casson fluid. Emphasis is on the study of the dependence of local pressure distribution on space and time. Mechanical efficiency, reflux limit and trapping are also discussed. The effect of Casson fluid vis-à-vis Newtonian fluid is investigated analytically and numerically too. The result is physically interpreted as that the oesophagus makes more efforts to swallow fluids with higher concentration. It is observed that the pressure is uniformly distributed when an integral number of waves is there in the oesophagus; but it is non-uniform when a non-integral number of waves is present therein. It is further observed that as the plug flow region widens, the pressure difference increases, which indicates that the averaged flow rate will reduce for a Casson fluid. It is also concluded that Casson fluids are more prone to reflux.

The Influence of Environmental Temperature on the Response of the Skin to Local Pressure: The Impact of Aging and Diabetes

2009 ◽  
Vol 11 (12) ◽  
pp. 791-798 ◽  
Author(s):  
Katie McLellan ◽  
Jerrold S. Petrofsky ◽  
Grenith Zimmerman ◽  
Everett Lohman ◽  
Michelle Prowse ◽  
...  
Keyword(s):  
Environmental Temperature ◽  
Local Pressure ◽  
The Impact

scholarly journals Control of the Longitudinal Compression and Transverse Focus of Ultrafast Electron Beam for Detecting the Transient Evolution of Materials

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 571
Author(s):  
Xintian Cai ◽  
Zhen Wang ◽  
Chaoyue Ji ◽  
Xuan Wang ◽  
Zhiyin Gan ◽  
...  
Keyword(s):  
Electron Beam ◽  
Temporal Resolution ◽  
Fast Electron ◽  
Single Pulse ◽  
Coulomb Force ◽  
Single Shot ◽  
Longitudinal Compression ◽  
Rf Cavity ◽  
Tracking Model ◽  
The Impact

Ultrafast detection is an effective method to reveal the transient evolution mechanism of materials. Compared with ultra-fast X-ray diffraction (XRD), the ultra-fast electron beam is increasingly adopted because the larger scattering cross-section is less harmful to the sample. The keV single-shot ultra-fast electron imaging system has been widely used with its compact structure and easy integration. To achieve both the single pulse imaging and the ultra-high temporal resolution, magnetic lenses are typically used for transverse focus to increase signal strength, while radio frequency (RF) cavities are generally utilized for longitudinal compression to improve temporal resolution. However, the detection signal is relatively weak due to the Coulomb force between electrons. Moreover, the effect of RF compression on the transverse focus is usually ignored. We established a particle tracking model to simulate the electron pulse propagation based on the 1-D fluid equation and the 2-D mean-field equation. Under considering the relativity effect and Coulomb force, the impact of RF compression on the transverse focus was studied by solving the fifth-order Rung–Kutta equation. The results show that the RF cavity is not only a key component of longitudinal compression but also affects the transverse focusing. While the effect of transverse focus on longitudinal duration is negligible. By adjusting the position and compression strength of the RF cavity, the beam spot radius can be reduced from 100 μm to 30 μm under the simulation conditions in this paper. When the number of single pulse electrons remains constant, the electrons density incident on the sample could be increased from 3.18×1012 m−2 to 3.54×1013 m−2, which is 11 times the original. The larger the electron density incident on the sample, the greater the signal intensity, which is more conducive to detecting the transient evolution of the material.

scholarly journals Differential responsiveness of glabrous and non-glabrous skin to local transmural pressure elevations; the impact of 5 weeks of iterative local pressure loading

2021 ◽  
Author(s):  
Michail E. Keramidas ◽  
Roger Kölegård ◽  
Patrik Sundblad ◽  
Håkan Sköldefors ◽  
Ola Eiken
Keyword(s):  
Transmural Pressure ◽  
Glabrous Skin ◽  
Local Pressure ◽  
Wide Range ◽  
Forearm Skin ◽  
Differential Responsiveness ◽  
Pressure Resistance ◽  
The Impact ◽  
Pressure Perturbations

We examined the in vivo pressure-flow relationship in human cutaneous vessels during acute and repeated elevations of local transmural pressure. In 10 healthy men, red blood cell flux was monitored simultaneously on the non-glabrous skin of the forearm and the glabrous skin of a finger during a vascular pressure provocation, wherein the blood vessels of an arm were exposed to a wide range of stepwise increasing distending pressures. Forearm skin blood flux was relatively stable at slight and moderate elevations of distending pressure, whereas it increased ~3-4-fold at the highest levels (P = 0.004). Finger blood flux on the contrary, dropped promptly and consistently throughout the provocation (P < 0.001). Eight of the subjects repeated the provocation trial after a 5-week pressure-training regimen, during which the vasculature in one arm was exposed intermittently (40 min, 3 times･week-1) to increased transmural pressure (from +65 mmHg week-1 to +105 mmHg week-5). The training regimen diminished the pressure-induced increase in forearm blood flux by ~34% (P = 0.02), whereas it inhibited the reduction in finger blood flux (P < 0.001) in response to slight and moderate distending pressure elevations. The present findings demonstrate that, during local pressure perturbations, the cutaneous autoregulatory function is accentuated in glabrous compared to in the non-glabrous skin regions. Prolonged intermittent regional exposures to augmented intravascular pressure blunt the responsiveness of the glabrous skin, but enhance arteriolar pressure resistance in the non-glabrous skin.

scholarly journals Mechanical frustration of phase separation in the cell nucleus by chromatin

2020 ◽  
Author(s):  
Yaojun Zhang ◽  
Daniel S.W. Lee ◽  
Yigal Meir ◽  
Clifford P. Brangwynne ◽  
Ned S. Wingreen
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Cell Nucleus ◽  
Mechanical Environment ◽  
Coarsening Dynamics ◽  
The Impact ◽  
Droplet Phase ◽  
Liquid Liquid Phase Separation ◽  
Fundamental Mechanism

Liquid-liquid phase separation is a fundamental mechanism underlying subcellular organization. Motivated by the striking observation that optogenetically-generated droplets in the nucleus display suppressed coarsening dynamics, we study the impact of chromatin mechanics on droplet phase separation. We combine theory and simulation to show that crosslinked chromatin can mechanically suppress droplets’ coalescence and ripening, as well as quantitatively control their number, size, and placement. Our results highlight the role of the subcellular mechanical environment on condensate regulation.

scholarly journals Brief communication: Nowcasting of precipitation for leading-edge-erosion-safe mode

2020 ◽  
Vol 5 (3) ◽  
pp. 977-981 ◽  
Author(s):  
Anna-Maria Tilg ◽  
Charlotte Bay Hasager ◽  
Hans-Jürgen Kirtzel ◽  
Poul Hummelshøj
Keyword(s):  
Liquid Phase ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Leading Edge ◽  
Wind Turbine Blades ◽  
Spatio Temporal ◽  
The Impact ◽  
Theoretical Considerations ◽  
Mode A ◽  
Precipitation Events

Abstract. Leading-edge erosion (LEE) of wind turbine blades is caused by the impact of hydrometeors, which appear in a solid or liquid phase. A reduction in the wind turbine blades' tip speed during defined precipitation events can mitigate LEE. To apply such an erosion-safe mode, a precipitation nowcast is required. Theoretical considerations indicate that the time a raindrop needs to fall to the ground is sufficient to reduce the tip speed. Furthermore, it is described that a compact, vertically pointing radar that measures rain at different heights with a sufficiently high spatio-temporal resolution can nowcast rain for an erosion-safe mode.

scholarly journals Liquid-phase compositions from vapor-phase analyses

1989 ◽  
Author(s):  
W. Davis ◽  
H. Cochran ◽  
J. Leitnaker
Keyword(s):  
Liquid Phase ◽  
Vapor Phase
Sign in / Sign up

Export Citation Format

Share Document