Water Velocity Profiles Research Articles

Drag reducing surfactants for district heating

An application of specific surfactants in district heating and cooling systems can give notable economical benefits due to a reduction in friction and heat transfer attributed to a formation of an additional viscous sublayer along the pipe walls, buffering the turbulence. A mathematical three-layer model of water velocity profile is composed for the calculation of drag reduction and flow-capacity increase. At a properly chosen surfactant and concentration, the local drag can be reduced up to 80%. A computer simulation and optimization for a selected district heating network model with additive shows 4% saving in total costs because smaller pipes and weaker pumps are required.

Extended Fourth-Order Depth-Integrated Model for Water Waves and Currents Generated by Submarine Landslides

In this paper, a preexisting higher-order depth-integrated wave propagation model is extended to include a moving seabed. As a result, the extended model can be applied to both wave propagation and the dynamic process of wave generation by a seabed disturbance such as a submarine landslide. The model has the linear dispersion relation in a form of (4,4) Padè approximant, and approximates the water velocity profiles along the water depth with a fourth-order polynomial of the vertical coordinates. The fourth-order model is aimed at extending the validity of the lower-order depth-integrated models from long waves to both long and shorter waves, as well as improving the approximation of the velocity field from the second order to the fourth order. Laboratory experiments are carried out in a wave flume to study wave generation by a submerged landslide model. Both water waves and water velocities are measured by using resistance-type wave gauges and a particle image velocimetry. The experimental data are then compared with the predicted wave height and water current based on the new model and two existing lower-order Boussinesq-type models. The results clearly show that the new model predicts the fluid velocity more accurately and is also able to predict the shorter trailing waves very well where the traditional Boussinesq model may be inadequate, thus validating the improvement provided by the fourth-order model.

Experimental investigation of the IFMIF target mock-up

The international fusion materials irradiation facility (IFMIF) lithium neutron target mock-ups have been constructed and tested at water and lithium test facilities in the IPPE of Russia. Jet velocity in both mock-ups was up to 20 m/s. Calculations and experiments showed lithium flow instability at conjunction point of straight and concave sections of the mock-up back wall. Water velocity profile across the mock-up width, jet thickness, and wave height were measured. The significant increase of thickness of both water and lithium jets near the mock-up sidewalls was observed. The influence of shape of the nozzle outlet part on jet stability was investigated. Lithium evaporation from the jet free surface was investigated as well as lithium deposition on vacuum pipe walls of the target mock-up. It was shown that these phenomena are not very critical for the target efficiency. The possibility of lithium denitration down to 2 ppm (at 10 ppm requested) by means of aluminium getter was shown. Two types of cold traps and plug indicators of impurities were tested. The results are presented in the paper.

Vertical velocity distributions through and above submerged, flexible vegetation

A one-dimensional steady-state model was constructed and used to study vertical profiles of longitudinalvelocities in open channel flows through, and above, submerged vegetation. The eddy viscosity was evaluated by using the analogue of the mixing length theory. The model of water velocity profiles takes into account the surface roughness of the channel bottom and the drag exerted by submerged flexible stems. The verification of the calculated velocity profiles was carried out based on data obtained in laboratory experiments. The proportionality coefficients for the analogue of the mixing length formulae in both layers—within homogenous flexible stems and above them—were determined.

Velocity Profiles of Water Flowing Past Solid Glass Surfaces Using Fluorescent Nanoparticles and Molecules as Velocity Probes

Measurements of the velocity profile of water flowing on a glass surface using fluorescent nanoparticles and single fluorescent molecules as velocity probes show that the no slip boundary condition holds down to at least 10 nm from the surface. For water flowing on a hydrophobic solid surface, silanized glass, the no slip boundary condition fails, and a slip length of 45 nm is measured. These velocity measurements are complemented with atomic force microscopy measurements of dissipation on a small sphere oscillating near the surface with results in agreement with the velocity profiles.

Flow Measurements in a Near Wall Flow Using Evanescent Wave Illumination (Effect of Polymer Additive on Flow in a Microchannel)

The flow characteristics of a dilute polymer solution and distilled water near the wall surface were clarified experimentally using evanescent wave illumination. Based on the integrated value of the particle tracking velocimetry data in the illumination, the velocity profile near the wall surface was obtained. Fluorescent particles with a diameter of 100 nm were used as tracer particles. The test polymer is polyethylene-oxide (Peo 15) solution at 5 ppm. The results obtained for the velocity profile of distilled water was found to agree well with the two-dimensional Poiseuille velocity profile at 100nm<z<250nm. On the other hand, the velocity profile of the dilute polymer solution decreased significantly compared with that of distilled water within 250nm of the wall surface. In addition, the particle diffusion of polymer solution decreased in flow conditions comparing that of distilled water, thought there were few differences for quiescent condition.

Effects of Concentration of Surfactant Solutions on Drag-Reducing Turbulent Boundary Layer

In this study, the influence of a drag-reducing surfactant on the turbulent boundary layer was extensively investigated under different solution concentrations using a two-component laser-Doppler velocimetry system. The surfactant solution used here was a mixture of cetyltrimethyl ammonium chloride (CTAC) with sodium salicylate as counterion, which was dissolved in tap water. The concentrations tested were 100 and 150 ppm, and the previous data on surfactant solution of 65 ppm were also used.The temperature of surfactant solution was T=20°C.It is found that the drag reduction ratio DR becomes larger downstream, and decreases with the increase of concentration from C=65 to 150 ppm. Regardless of solution concentrations, the value of the mean velocity scaled by the friction velocity increases with increasing the amount of drag reduction, while the mean velocity scaled by the free-stream velocity, which are collapsed for the different Reynolds number and drag reduction ratio, are about in the middle between the mean velocity profile of water and the Blasius laminar profile. For the present experimental conditions tested, the maximum of streamwise turbulence intensity near the wall is not related to the amount of DR directly and seems to be affected by the low Reynolds number effect strongly, while the location of the maximum becomes more distant from the wall with the increase of DR. The additional maximum of streamwise turbulence intensity near the center of the boundary layer, which is observed for all the concentration tested, and the wall-normal location of additional maximum are almost constant and are independent of the amount of drag reduction.

ADCP Measurements of Gravity Currents in the Chicago River, Illinois

A unique set of observations of stratified flow phenomena in the Chicago River was made using an upward-looking acoustic Doppler current profiler (ADCP) during the period November 20, 2003 to February 1, 2004. Water density differences between the Chicago River and its North Branch (NB) seem to be responsible for the development of gravity currents. With the objective of characterizing the occurrence, frequency, and evolution of such currents, the ADCP was configured to continuously collect high-resolution water velocity and echo intensity profiles in the Chicago River at Columbus Drive. During the observation period, 28 gravity current events were identified, lasting a total of 77% of the time. Sixteen of these events were generated by underflows from the NB and 12 of these events were generated by overflows from the NB. On average, the duration of the underflow and overflow events was 52.3 and 42.1 h , respectively. A detailed analysis of one underflow event, which started on January 7, 2004, and lasted...

Application of dam-break flow to green water prediction

The present study investigates, through analysis of laboratory measurements, the practice of applying Ritter’s dam-break flow solution to the prediction of overtopping green water on an offshore structure. The flow field of green water has been very difficult to obtain from either numerical computation or laboratory measurement. The dam-break flow model has been used in design to approximate the effect of green water due to the possible resemblance of the two flows, the simplicity of the dam-break flow, and the availability of analytical solutions of dam-break flow. In this study, the velocity of green water on a two-dimensional simplified model structure was measured using a newly developed technique called bubble image velocimetry (BIV). The profiles of horizontal green water velocity along the model deck are presented herein. Ritter’s analytical solution for the dam-break flow problem is examined and compared with the measurements. Two alternative approaches for quantifying the initial water depth, a parameter required in the analytical dam-break flow model, are investigated. The solution with the initial water depth estimated using the front velocity of green water is found to be in good agreement with the green water measurements. In addition, the influence of the deck length on green water velocity is examined.

1420 エバネッセント光によるマイクロチャネル内希薄高分子水溶液の流動特性の評価(S30-4 複雑流体の流動現象(4),S30 複雑流体の流動現象)

The velocity profile of a dilute polymer solution and a distilled water near the wall surface in a microchannel was clarified using a particle tracking velocimetry technique combined with evanescent wave illumination. Fluorescent particles with a diameter of 100nm were used as tracer particles. The test polymer is polyethylene-oxide (Peo15) solution at 5ppm. The results obtained for the velocity profile of distilled water was found to agree well with the two-dimensional Poiseuille velocity profile at 100nm<z<250nm. On the other hand, the velocity profile of the dilute polymer solution decreases significantly compared with that of a distilled water within 250nm of the wall surface.

난류 중 부유사의 속도 지체 측정

부유사의 거동을 나타내는 데는 이송-확산 방정식이나 이 방정식을 간략화한 식들이 이용된다 이 방정식은 여러 가지 가정하에서 유도되었으나, 이러한 가정에 대해서는 심도있는 검토가 되지 못한 상태에 있다 그 이유는 난류의 측정 자체가 매우 힘들며, 유사가 혼합된 흐름의 경우 물과 유사의 속도를 구별해서 측정하기 매우 힘들기 때문이다. 본 연구는 입자 영상 유속계(PIV, Particle Image Velocimeoy)의 일종인 입자 추적 유속계(PTV, Particle Tracking Velocimetry)를 이용하여 개수로 난류에서 물과 유사의 속도를 측정하는 실험적 연구이다. 측정 결과, 하상에서 어느 정도 떨어진 영역에서는 유사의 속도가 물보다 느린 경향을 보였다. 이 속도 지체의 양은 본 연구의 경우 평균 유속 의 약 <TEX>$5\%$</TEX> 정도였으며, 속도 지체가 최대에 이르는 지점은 <TEX>$g/h\approx0.05\;(g^{+}=30\~50)$</TEX>정도인 것으로 나타났다. 유사 입자가 물보다 느리게 이동하는 것은 전적으로 유사의 비중이 물보다 크기 때문으로 보인다. 반면, 하상에 근접한 점성 저층에서는 오히려 유사 입자의 속도가 물보다 빠르게 나타났으며, 이것은 물은 고체 경계면에서 점착 조건에 종속되는 데 반하여, 유사 입자는 점성의 영향을 받지 않기 때문으로 보인다. To describe the behavior of suspended-sediment particles in turbulent open-channel flows, the advection-diffusion equation or its simplified form has been used. Though this equation was derived upon several assumptions, only a few studies tried to evaluate the limit of the assumptions. The reason is that it is very difficult to measure turbulence in open-channel flows and to discriminate the velocities of water and sediment particles. The present study aims to measure the velocity profiles of water and sediment particles in open-channel flows by using PTV (Particle Tracking Velocimetry), a kind of PIV (Particle Image Velocimetry). The measured results showed that sediment particles moved slower than water tracers did in the outer region. In the present study, the amount of velocity-lag reached about <TEX>$5\%$</TEX> of the mom flow velocity and the position of the maximum velocity-lag was <TEX>$g/h\approx0.05\;(g^{+}=30\~50)$</TEX> The main cause of the velocity-lag of sediment particles seems that the sediment particles have larger density than water has. On the other hand, in the viscous sublayer, sediment particle has a larger velocity than water tracers. The reason of the inversion of velocity-lag may be due to the no-sleep condition of water at the solid boundaries.

Flow Characteristics of Dilute Polymer Solutions in a Micro Tube

Pressure drop and velocity profile for a micro tube were investigated on laminar flow of distilled water and dilute polymer solutions. It is the range of 50.2-251.8μmin diameter, and the value of l/d is about 340. By a pressure drop measurement it is shown that the experimental data agree with Hagen-Poiseuille equation in the case of Newtonian fluids. And the flow rate of the dilute polymer solutions increased comparing with that of distilled water at the low Reynolds number range. The increase ratio of the flow rate is about 15% in maximum in the case of d=251.8μm. For the result of micro PIV measurement, there are few differences between the velocity profile of distilled water and Peo 5 ppm solution.

Mapping the Operation of the DMT Continuous Flow CCN Counter

This work thoroughly analyzes a new commercial instrument for measuring Cloud Condensation Nuclei (CCN), the Droplet Measurement Technologies Cylindrical Continuous-Flow Streamwise Thermal Gradient CCN Chamber (CFSTGC). This instrument can measure CCN concentrations at supersaturations from 0.06% to 3% (potentially up to 6%), at a 1 Hz sampling rate that is sufficient for airborne operation. Our analysis employs a fully coupled numerical flow model to simulate the water vapor supersaturation, temperature, velocity profiles and CCN growth in the CFSTGC for its entire range of operation (aerosol sample flow rates 0.25–2.0 L min − 1 , temperature differences 2–15 K and ambient pressures 100–1000 mb). The model was evaluated by comparing simulated instrument responses for calibration aerosol against actual measurements from an existing CCN instrument. The model was used to evaluate the CCN detection efficiency for a wide range of ambient pressures, flow rates, temperature gradients, and droplet growth kinetic...

Direct measurement of the apparent slip length

We measure velocity profiles in water flowing through thin microchannels, using particle image velocimetry combined with a nanopositioning system. From the velocity profiles, we determine the slip lengths in two cases: Smooth hydrophilic glass surfaces, and smooth hydrophobic glass surfaces, grafted with a monolayer of silane. The slip length is determined within (+/-100 nm) , i.e., five times more accurately than previous work. In all cases, we find that the slip length is below 100 nm.

Moored Fish Cage Dynamics in Waves and Currents

Recent work in the area of open ocean aquaculture system dynamics has focused separately upon either the response of fish cages in waves or the steady drag response due to ocean currents. In reality, however, forcing on these open ocean structures is a nonlinear, multidirectional combination of both wave and current profiles. At the University of New Hampshire-operated Open Ocean Aquaculture site, data were collected from a wave measurement buoy and a downward-looking Acoustic Doppler Current Profiler to characterize the surface elevation and water velocity profiles during an extreme northeast storm event. In addition to waves and currents, fish cage motion response in heave, surge, and pitch was inferred from accelerometer measurements during the same storm. The environmental data sets obtained during the peak of the storm were processed, analyzed, and used as input to a dynamic finite-element model. Simulations were performed using three load case scenarios: 1) in both waves and currents; 2) in waves only; and 3) in currents only. Model motion response results in both the time and frequency domain were compared with data obtained in situ . In addition to the motion response tests, the wave and current forcing influencing the mooring line tension response was also investigated. Analysis shows that in this case, the currents do not severely influence the oscillatory motion response, but do cause the cage to tilt, layback, and sink. The wave and current interaction effect did, however, influence the anchor line loads with a portion being attributed to nonlinear effects.

B211 Velocity Measurements of Physiological Flows in Microchannels using a Confocal micro-PIV System

The in vitro experimental investigations provide an excellent approach to understand complex blood flow phenomena involved at a microscopic level. This paper emphasizes an emerging experimental technique capable to quantify the flow patterns inside microchannels with high spatial and temporal resolution. This technique, known as confocal micro-PIV, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser. Velocity profiles of both pure water and physiological fluid were measured within a square microchannel. The good agreement obtained between measured and estimated results suggests that this system is a very promising technique to obtain detail information about micro-scale effects in microchannels by using both homogeneous and nonhomogeneous fluids such as physiological fluids

Wind-induced exchange at the entrance to Concepción Bay, an equatorward facing embayment in central Chile

Abstract Hydrographic and underway water velocity profiles were measured at the entrance to Concepcion Bay, an equatorward facing embayment in central Chile, in order to illustrate the wind-induced exchange flow. Observations took place over a 25-h period (5–6 January 2002) during the austral summer, which is characterized by upwelling winds in the region. One portion of the observational transect was directly influenced by the wind and the other was protected from such influence by an island. The portion of the transect influenced by wind showed a surface layer, delimited by a pycnocline, moving downwind owing to the direct action of wind stress. This surface transport should have caused an onshore decrease of surface elevation that would drive upwind flow below the surface layer. The portion of the transect protected by the island was influenced by its wake and perhaps forced by a semidiurnal tide. This study is one of the few observational examples of wind-induced flow that documents the wind-induced exchange pattern under weak internal friction (low Ekman number). This pattern consists of downwind flow in an upper layer delimited by the pycnocline and upwind flow below.

Solids flushing, mixing, and water velocity profiles within large (10 and 150 m3) circular ‘Cornell-type’ dual-drain tanks

The objectives of this research were to evaluate how bottom drain flow rate and water inlet structure affect solids flushing, water mixing, and water velocity profiles within large (i.e., 10 and 150m3) circular ‘Cornell-type’ dual-drain culture tanks. Results show relatively uniform water mixing was achieved in both ‘Cornell-type’ dual-drain culture tanks when tested at high fish densities (90–98kg/m3) and at hydraulic exchange rates of one tank volume every 20–32min. The results of the dissolved oxygen profiles showed that the minimum and maximum dissolved oxygen concentrations ranged from 10.0 to 10.6mg/L across the cross-section of the 10m3 tank and from 9.0 to 11.2mg/L across the cross-section of the 150m3 tank when inlet dissolved oxygen levels were 16–18mg/L. Mixing was not influenced by bottom-drain flow over the range tested, but was influenced by the orientation of the water injection nozzles projecting through the side-wall of the culture tanks.Adjustment of the orientation of the water inlet structure and of the water flow discharged through the bottom-center drain was shown to influence the water rotational velocities throughout the circular tank. Water rotational velocity profiles taken in a vertical plane bisecting the tank indicated that velocities were consistently higher at the tank’s perimeter and that these velocities increased nearly linearly with radial distance from the tank center. Results also show that higher rotational velocities were produced at larger bottom flow rates, i.e., a 12% bottom flow created higher rotational velocities than 6 or 0% bottom flows. Reorienting the direction of the water inlet nozzles also provided a simple method for adjusting rotational water velocities within the culture tank. For example, simply reversing the direction of one of the six 45° flow injection nozzles decreased the rotational velocity about the perimeter of the 10m3 tank from 17.8 to 13.4cm/s.Additional studies with arctic char or rainbow trout present at commercial culture densities showed that the rate that settleable solids are flushed from 10 and 150m3 circular ‘Cornell-type’ dual-drain culture tanks depended strongly on the water flow exiting the bottom-center drain and on the rotational period of the water within the tank. A rotational period of 1.3–1.7min produced optimal water velocities for flushing solids from the ‘Cornell-type’ dual-drain tank. Also, a water flow through the tank’s bottom-center drain of at least 5–6L/min for every 1m2 of tank plan area was found to flush settleable solids within 1–2min and 3–6min from 10 and 150m3 ‘Cornell-type’ dual-drain tanks, respectively.

Non-aqueous phase liquid drop formation within a water saturated fracture

This work focuses on the mechanisms of non-aqueous phase liquid (NAPL) drop formation within a single fracture fed from a NAPL reservoir by way of a circular orifice, such as a pore. The fracture is assumed to be fully saturated, the relative wettability of the system is assumed water-wet, and the water velocity profile within the fracture is described by a Poiseuille flow. The size of the NAPL drops is investigated for various water flow velocities and NAPL entrance diameters. A force balancing method was used to determine the radii of detached drops. The drop sizes calculated from the model developed here are shown to be in agreement with available experimental drop size data. It is shown that at low Reynolds numbers the buoyancy force is the dominant force acting on the drop during the formation process and at high Reynolds numbers the viscous forces dominate. A simplified expression relating the geometry of the fractured system to the drop radii is developed from the model equations, and it is shown to predict drop radii that match well with both the model simulations and the available experimental data.

Micro-PIV를 이용한 마이크로 튜브/채널 내에서의 혈장유동측정

In this paper, flow characteristics of plasma flow in a micro-tube were investigated experimentally using micro particle image velocimetry(micro-PIV). For comparison, the experiments were repeated for deionized(DI) wale. instead of plasma. Both velocity profiles of plasma and do-ionized water are well agreed with the theoretical velocity distribution of newtonian fluid. We also carried out generating plasma-in-oil droplet formation at a Y-junction microchannel. In order to clarify the hydrodynamic aspects involved in plasma droplet formation, Rhodamine-B were mixed with plasma only for visualization of plasma droplet. With oil as the continuous phase and plasma as the dispersed phase, plasma droplet can be generated in a continuous phase flow at a Y-junction. For given experimental parameters, regular-sized droplets are reproducibly formed at a uniform flow conditions.