scholarly journals Wave and Current Generation in Wave Flumes Using Axial-Flow Pumps

2017 ◽  
Author(s):  
Aurélien Babarit ◽  
Simon Delvoye ◽  
Vincent Arnal ◽  
Laurent Davoust ◽  
Jeroen Wackers ◽  
...  
Keyword(s):  
Water Waves ◽  
Oscillatory Flow ◽  
Axial Flow ◽  
Proof Of Concept ◽  
Experimental Proof ◽  
Current Generation ◽  
Experimental Modelling ◽  
Flow Through ◽  
The Waves ◽  
A Current

We investigate a new concept for wave and current generation. It consists of axial-flow pumps driven such as to generate an oscillatory flow through an orifice located at one end of the flume. Oscillations of the flow lead to the generation of water waves at the free surface. If the average of the flow is different from zero, a current is generated that superposes on the waves. In this study, we explored the technical capabilities of this concept and the influence of geometric parameters on wave and current generation. We used numerical and experimental modelling. Most noticeably, the numerical results indicate that this concept is well suited for the generation of long and high waves. An experimental setup has been designed and built. We used it to make an experimental proof of concept for the wave and current generation, including waves propagating against the current.

scholarly journals WATER WAVES ON A BILINEAR SHEAR CURRENT

1974 ◽  
Vol 1 (14) ◽  
pp. 36 ◽  
Author(s):  
Robert A. Dalrymple
Keyword(s):  
Water Waves ◽  
Perturbation Technique ◽  
Wave Theory ◽  
Interfacial Velocity ◽  
Shear Current ◽  
Irregular Form ◽  
Vertical Velocity Profile ◽  
Mean Water Level ◽  
The Waves ◽  
A Current

A water wave theory is presented to describe waves propagating on a bilinear shear current flowing in the direction of the waves. The theory is derived assuming an ideal fluid in which a current exists, having a vertical velocity profile which varies linearly from a mean water level velocity of Ug, an interfacial velocity Uj at depth, d, and a bottom velocity Uj$. The theory is developed first for small amplitude waves and then extended to any arbitrary order by a numerical perturbation technique for symmetric waves. For measured waves, an irregular form of the theory is presented to provide a representation of these waves for analysis.

scholarly journals Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 221
Author(s):  
Manikantam G. Gaddam ◽  
Arvind Santhanakrishnan
Keyword(s):  
Respiratory Rate ◽  
Cross Sections ◽  
Particle Deposition ◽  
Oscillatory Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Stroke Length ◽  
Human Airway ◽  
Flow Through

Studies of flow through the human airway have shown that inhalation time (IT) and secondary flow structures can play important roles in particle deposition. However, the effects of varying IT in conjunction with the respiratory rate (RR) on airway flow remain unknown. Using three-dimensional numerical simulations of oscillatory flow through an idealized airway model (consisting of a mouth, glottis, trachea, and symmetric double bifurcation) at a trachea Reynolds number (Re) of 4200, we investigated how varying the ratio of IT to breathing time (BT) from 25% to 50% and RR from 10 breaths per minute (bpm) corresponding to a Womersley number (Wo) of 2.41 to 1000 bpm (Wo = 24.1) impacts airway flow characteristics. Irrespective of IT/BT, axial flow during inhalation at tracheal cross-sections was non-uniform for Wo = 2.41, as compared to centrally concentrated distribution for Wo = 24.1. For a given Wo and IT/BT, both axial and secondary (lateral) flow components unevenly split between left and right branches of a bifurcation. Irrespective of Wo, IT/BT and airway generation, lateral dispersion was a stronger transport mechanism than axial flow streaming. Discrepancy in the oscillatory flow relation Re/Wo2 = 2L/D (L = stroke length; D = trachea diameter) was observed for IT/BT ≠ 50%, as L changed with IT/BT. We developed a modified dimensionless stroke length term including IT/BT. While viscous forces and convective acceleration were dominant for lower Wo, unsteady acceleration was dominant for higher Wo.

Flow through axial-flow-turbomachinery blading

2018 ◽  
Author(s):  
Marcel Escudier
Keyword(s):  
Flow Velocity ◽  
Compressible Flow ◽  
Dimensional Analysis ◽  
Incompressible Flow ◽  
Compressible Fluid ◽  
Axial Flow ◽  
Linear Cascade ◽  
Dimensional Parameters ◽  
Flow Through

This chapter is concerned primarily with the flow of a compressible fluid through stationary and moving blading, for the most part using the analysis introduced in Chapter 11. The principles of dimensional analysis are applied to determine the appropriate non-dimensional parameters to characterise the performance of a turbomachine. The analysis of incompressible flow through a linear cascade of aerofoil-like blades is followed by the analysis of compressible flow. Velocity triangles for flow relative to blades, and Euler’s turbomachinery equation, are introduced to analyse flow through a rotor. The concepts introduced are applied to the analysis of an axial-turbomachine stage comprising a stator and a rotor, which applies to either a compressor or a turbine.

Riser Fatigue Due to Currents and Waves

2002 ◽  
Author(s):  
C. Le Cunff ◽  
E. Fontaine ◽  
F. Biolley
Keyword(s):  
Modal Analysis ◽  
Environmental Conditions ◽  
Navier Stokes ◽  
Vortex Induced Vibrations ◽  
Two Factors ◽  
Shedding Frequency ◽  
The Waves ◽  
Structural Mode ◽  
A Current

Fatigue due to environmental conditions is studied on a top-tensioned riser. The fatigue is due to two factors. First, the waves produce a displacement of the top of the riser, which excites the structure. Secondly, currents create vortices behind the structures. The phenomenon is then referred to as vortex-induced vibrations (VIV), whereby the vortices can lock onto a structural mode through the shedding frequency. In the present paper, we have two objectives. The first is to compare the fatigue estimates given either by a modal analysis or by Navier-Stokes calculations for a riser in a current. The second is to determine if studying the wave and current effects separately produces conservative results or if they must be studied together.

Effect of Feedback Control on the Power Consumption of Induced-Strain Actuators

2000 ◽  
Author(s):  
Sriram Chandrasekaran ◽  
Douglas K. Lindner ◽  
Don Leo
Keyword(s):  
Structural Control ◽  
Power Flow ◽  
Reactive Power ◽  
Flow Characteristics ◽  
Control Laws ◽  
The Real ◽  
Reactive Power Flow ◽  
Flow Through ◽  
Sinusoidal Disturbance ◽  
A Current

Abstract In this paper we study the closed loop power flow characteristics between a controlled piezoelectric actuator and a current controlled drive amplifier for two different structural control laws. We determine the real and reactive power flow through the structure and actuator into the amplifier when the structure is excited with a sinusoidal disturbance force under both control laws. The dependence of the real and reactive components of the power on the material properties of the actuator, structure and the configuration of the controller is presented. These real and reactive power estimates are useful for sizing the drive amplifier for the actuator.

scholarly journals MACH-REFLECTION AS A DIFFRACTION PROBLEM

1976 ◽  
Vol 1 (15) ◽  
pp. 45 ◽  
Author(s):  
Udo Berger ◽  
Soren Kohlhase
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Water Waves ◽  
Gas Dynamics ◽  
Mach Reflection ◽  
Diffraction Problem ◽  
Vertical Wall ◽  
Oblique Wave ◽  
Wave Heights ◽  
The Waves

As under oblique wave approach water waves are reflected by a vertical wall, a wave branching effect (stem) develops normal to the reflecting wall. The waves progressing along the wall will steep up. The wave heights increase up to more than twice the incident wave height. The £jtudy has pointed out that this effect, which is usually called MACH-REFLECTION, is not to be taken as an analogy to gas dynamics, but should be interpreted as a diffraction problem.

scholarly journals Orientation of Electrospun Magnetic Nanofibers Near Conductive Areas

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 47 ◽  
Author(s):  
Jan Lukas Storck ◽  
Timo Grothe ◽  
Al Mamun ◽  
Lilia Sabantina ◽  
Michaela Klöcker ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Flow ◽  
Strong Electric Field ◽  
Preferred Direction ◽  
Hand Grip ◽  
Conductive Substrates ◽  
Flow Through ◽  
Spinning Cylinder ◽  
Magnetic Nanofibers ◽  
A Current

Electrospinning can be used to create nanofibers from diverse polymers in which also other materials can be embedded. Inclusion of magnetic nanoparticles, for example, results in preparation of magnetic nanofibers which are usually isotropically distributed on the substrate. One method to create a preferred direction is using a spinning cylinder as the substrate, which is not always possible, especially in commercial electrospinning machines. Here, another simple technique to partly align magnetic nanofibers is investigated. Since electrospinning works in a strong electric field and the fibers thus carry charges when landing on the substrate, using partly conductive substrates leads to a current flow through the conductive parts of the substrate which, according to Ampère’s right-hand grip rule, creates a magnetic field around it. We observed that this magnetic field, on the other hand, can partly align magnetic nanofibers perpendicular to the borders of the current flow conductor. We report on the first observations of electrospinning magnetic nanofibers on partly conductive substrates with some of the conductive areas additionally being grounded, resulting in partly oriented magnetic nanofibers.

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