scholarly journals Upstream rheotaxis of catalytic Janus spheres

2021 ◽  
Author(s):  
Priyanka Sharan ◽  
Zuyao Xiao ◽  
Viviana Mancuso ◽  
William E. Uspal ◽  
Juliane Simmchen
Keyword(s):  
Fluid Flow ◽  
Type System ◽  
Shear Plane ◽  
High Flow ◽  
Physical Factors ◽  
Theoretical Studies ◽  
Directional Response ◽  
Swimming Pattern ◽  
Flow Speeds ◽  
Stream Migration

Fluid flow is ubiquitous in many environments that form habitats for microorganisms. The tendency of organisms to navigate towards or away from flow is termed rheotaxis. Therefore, it is not surprising that both biological and artificial microswimmers show responses to flows that are determined by the interplay of chemical and physical factors. In particular, to deepen understanding of how different systems respond to flows, it is crucial to comprehend the influence played by swimming pattern. In recent studies, pusher-type Janus particles exhibited cross-stream migration in externally applied flows. Earlier, theoretical studies predicted a positive rheotactic response for puller-type spherical Janus micromotors. To compare to a different swimmer, we introduce Cu@SiO2 micromotors that swim towards their catalytic cap. Based on experimental observations, and supported by flow field calculations using a model for self-electrophoresis, we hypothesize that they behave effectively as a puller-type system. We investigate the effect of externally imposed flow on these spherically symmetrical Cu@SiO2 active Janus colloids, and we indeedobserve a steady upstream directional response. Through a simple squirmer model for a puller, we recover the major experimental observations. Additionally, the model predicts a unique “jumping” behaviour for puller-type micro- motors at high flow speeds. Performing additional experiments at high flow speeds, we capture this phenomenon, in which the particles “roll” with their swimming axes aligned to the shear plane, in addition to being dragged down- stream by the fluid flow.

scholarly journals Large amplitude, short wave peristalsis and its implications for transport

2015 ◽  
Author(s):  
Lindsay D Waldrop ◽  
Laura A. Miller
Keyword(s):  
Fluid Flow ◽  
Large Amplitude ◽  
Compression Wave ◽  
Wave Speed ◽  
Flow Direction ◽  
Short Wave ◽  
Flow Speed ◽  
Biological Pumps ◽  
Flow Speeds ◽  
Flow Compression

Valveless, tubular pumps are widespread in the animal kingdom, but the mechanism by which these pumps generate fluid flow are often in dispute. Where the pumping mechanism of many organs was once described as peristalsis, other mechanisms, such as dynamic suction pumping, have been suggested as possible alternative mechanisms. Peristalsis is often evaluated using criteria established in a technical definition for mechanical pumps, but this definition is based on a small-amplitude, long-wave approximation which biological pumps often violate. In this study, we use a direct numerical simulation of large-amplitude, short-wave peristalsis to investigate the relationships between fluid flow, compression frequency, compression wave speed, and tube occlusion. We also explore how the flows produced differ from the criteria outlined in the technical definition of peristalsis. We find that many of the technical criteria are violated by our model: fluid flow speeds produced by peristalsis are greater than the speeds of the compression wave; fluid flow is pulsatile; and flow speed have a non-linear relationship with compression frequency when compression wave speed is held constant. We suggest that the technical definition is inappropriate for evaluating peristalsis as a pumping mechanism for biological pumps because they too frequently violate the assumptions inherent in these criteria. Instead, we recommend that a simpler, more inclusive definition be used for assessing peristalsis as a pumping mechanism based on the presence of non-stationary compression sites that propagate uni-directionally along a tube without the need for a structurally fixed flow direction.

Modeling high flow speeds in the inner corona

1996 ◽  
Author(s):  
Ruth Esser ◽  
Shadia Rifai Habbal
Keyword(s):  
High Flow ◽  
Flow Speeds

Performance of Undershot Waterwheel Curved Blade of the Laboratory Scale

2019 ◽  
Vol 967 ◽  
pp. 250-255
Author(s):  
Irwan Lie Keng Wong ◽  
Atus Buku ◽  
Josefine Ernestine Latupeirissa ◽  
Herby Calvin Pascal Tiwouy
Keyword(s):  
Rural Areas ◽  
High Speed ◽  
Large Diameter ◽  
Small Diameter ◽  
Water Source ◽  
High Flow ◽  
The People ◽  
Flow Speeds ◽  
Curved Blade ◽  
High Torque

Undershot waterwheels have been used by the people in rural areas to lift and distribute the water to the bottom which is higher than the water source. Waterwheels has a relatively simple design, large diameter, high speed and high torque. But applying it as a microhydro with high speed and small diameter still has to be explored. Waterwheels can operate efficiently in locations with high flow speeds. The Waterwheel functions from a waterwheel blade as a place to ride water so that the wheel can spin. From the results of the study, it can be concluded that the higher the flow of water with a large number of buckets, the speed of rotation of the wheel will be slower. Conversely, the lower the flow of water with the number of buckets a little then the spinning wheel is faster.

Experimental Techniques for Studying Poroelasticity in Brain Phantom Gels Under High Flow Microinfusion

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
O. Ivanchenko ◽  
N. Sindhwani ◽  
A. Linninger
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Computational Model ◽  
Alternative Pathway ◽  
Volumetric Strain ◽  
High Flow ◽  
Optical Methods ◽  
Solid Matrix ◽  
Convection Enhanced Delivery ◽  
Catheter Tip

Convection enhanced delivery is an attractive option for the treatment of several neurodegenerative diseases such as Parkinson, Alzheimer, and brain tumors. However, the occurrence of a backflow is a major problem impeding the widespread use of this technique. In this paper, we analyze experimentally the force impact of high flow microinfusion on the deformable gel matrix. To investigate these fluid structure interactions, two optical methods are reported. First, gel stresses during microinfusion were visualized through a linear polariscope. Second, the displacement field was tracked using 400 nm nanobeads as space markers. The corresponding strain and porosity fields were calculated from the experimental observations. Finally, experimental data were used to validate a computational model for fluid flow and deformation in soft porous media. Our studies demonstrate experimentally, the distribution and magnitude of stress and displacement fields near the catheter tip. The effect of fluid traction on porosity and hydraulic conductivity is analyzed. The increase in fluid content in the catheter vicinity enhances the gel hydraulic conductivity. Our computational model takes into account the changes in porosity and hydraulic conductivity. The simulations agree with experimental findings. The experiments quantified solid matrix deformation, due to fluid infusion. Maximum deformations occur in areas of relatively large fluid velocities leading to volumetric strain of the matrix, causing changes in hydraulic conductivity and porosity close to the catheter tip. The gradual expansion of this region with increased porosity leads to decreased hydraulic resistance that may also create an alternative pathway for fluid flow.

Use of an Optical Property of Glycerine-Water Solutions to Study Viscous Fluid-Flow Problems

1950 ◽  
Vol 17 (1) ◽  
pp. 54-58
Author(s):  
W. W. Hagerty
Keyword(s):  
Fluid Flow ◽  
Optical Property ◽  
Shear Plane ◽  
University Of Michigan ◽  
Water Solutions ◽  
Flow Problems ◽  
Glycerine Water ◽  
Ordinary Light ◽  
Scope Of Application ◽  
The University

Abstract It is a property of certain concentrations of glycerine-water solutions, when in a state of steady flow, that the planes of equal shear in the liquid become visible in ordinary light, if viewed along a path tangent to the shear plane. This phenomenon has been used successfully to study a fluid-flow problem at the University of Michigan. The nature and scope of application of this optical property is currently being studied further. This report gives details of what may prove to be a useful tool in certain phases of experimental fluid-flow problems.

scholarly journals Strain Rate of Metal Deformation in the Machining Process from a Fluid Flow Perspective

2020 ◽  
Vol 10 (9) ◽  
pp. 3057
Author(s):  
Keguo Zhang ◽  
Keyi Wang ◽  
Zhanqiang Liu ◽  
Xiaodong Xu
Keyword(s):  
Fluid Flow ◽  
Strain Rate ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Shear Plane ◽  
Cutting Process ◽  
Machining Process ◽  
Rake Face ◽  
Metal Deformation

Metal cutting speeds are getting faster with the development of high-speed cutting technology, and with the increase in cutting speed, the strain rate will become larger, which makes the study of the metal cutting process more inconvenient. At the same time, with the increase in strain rate, the dislocation movement controlling the plastic deformation mechanism of metal will change from thermal activation to a damping mechanism, which makes the metal deformation behave more like a fluid. Therefore, it is necessary to explore new ways of studying machining from the perspective of fluid flow. Based on this, a fluid model of the metal cutting process is established, and a method for calculating the strain rate is proposed from the point of view of flow. The results of the simulation and measurements are compared and analyzed. The results show that the strain rate on the rake face will be affected by the friction between the chip and tool; the nearer the distance between the chip layer and tool rake face, the bigger the strain rate will be. The strain rate in the central shear plane is much larger than in other areas along the shear plane direction, and in which two ends are the biggest. It can achieve rougher, quantitative research. This shows it is feasible to study machining from the viewpoint of fluid flow, though it still needs a lot of theoretical support and experimental confirmation.

Computer-controlled fluid-flow chemical analysis (CC-FCA) and its application to environmental analytical chemistry

2012 ◽  
Vol 84 (10) ◽  
pp. 1999-2013 ◽  
Author(s):  
Shoji Motomizu
Keyword(s):  
Fluid Flow ◽  
Chemical Analysis ◽  
Water Samples ◽  
Type System ◽  
Environmental Water ◽  
Sequential Injection ◽  
System A ◽  
Injection Type ◽  
Computer Controlled

Computer-controlled fluid-flow chemical analysis (CC-FCA) was investigated for the determination of trace amounts of toxic pollutants in the environment. For CC-FCA, automated chemical analysis systems were developed by using computer-controllable pumping and valve modules, and polytetrafluorethylene (PTFE) tubing and connectors. The systems demonstrated in this work were a flow injection-type system, a sequential injection-type system, a mini-column pretreatment system (Auto-Pret system), and an Auto-Pret hyphenated with flow injection analysis (FIA) system. Such systems were fully controlled by a computer program; the lab-made programs were written in Visual Basic. The systems can be hyphenated with some detectors, such as a spectrophotometric detector, an electrochemical detector, electrothermal-atomic absorption spectrometry (ET-AAS), a liquid electrode plasma-atomic emission spectrometry (LEP-AES) and inductively coupled plasma (ICP)-AES. Such systems were successfully applied to the determination of trace amounts of toxic pollutants in environmental water samples: they were heavy metal ions (Pb, Cd, Cr, etc.). In this paper, the author aims mainly at investigating the CC-FCA method for the determination of trace amounts of Cr(VI) in environmental water samples by spectrophotometry. The techniques used in this work were FIA, sequential injection analysis (SIA), and Auto-Pret/FIA, which were all computer-controllable. Limits of detection of Cr(VI) by FIA, SIA, and Auto-Pret/FIA were 8 × 10–9 mol/L (0.4 μg/L), 1.1 × 10–8 mol/L (0.6 μg/L), and 1.4 × 10–9 (0.07 μg/L), respectively. The methods were applied to the determination of Cr(VI) in river and drinking waters.

scholarly journals Exploring hydrologically similar catchments in terms of the physical characteristics of upstream regions

2017 ◽  
Vol 49 (5) ◽  
pp. 1467-1483 ◽  
Author(s):  
Yi Jin ◽  
Jintao Liu ◽  
Lu Lin ◽  
Aihua Wang ◽  
Xi Chen
Keyword(s):  
Hydrologic Model ◽  
Physical Characteristics ◽  
High Flow ◽  
Low Flow ◽  
Model Parameters ◽  
Physical Factors ◽  
Ungauged Catchments ◽  
Response Factors ◽  
Average Annual Runoff ◽  
Huai River

Abstract Catchment classification strategies based on easily available physical characteristics are important for extrapolating hydrologic model parameters and improving hydrologic predictions in ungauged catchments. In this study, we conduct an experiment of catchment classification and explore the feasibility of characterizing hydrologically similar catchments using certain physical characteristics in upstream regions of the Huai River Basin. The similarity metrics of hydrologic response factors (high flow, low flow and average annual runoff) and physical factors (topography, shape, soil and vegetation) are fed into the K-means algorithm for catchment classification. All the catchments are classified into two classes regardless of the types of metrics used. By comparing the overlap coefficient (η) and Rand index (RI) between any two classification results, we found that the topography classification displays the highest concordance with the high flow classification (η = 79.2% and RI = 0.66) among all metrics. Including more metrics would not produce consistently better classification results. The optimal combination of metrics, with η = 87.5%, is the high flow metrics (Q10%, SFH and MAX90) with the topography metrics (AS and HI). The results indicate that the physical metrics adopted for hydrologic classification should be determined carefully in terms of specific hydrologic characteristics.

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