Waves incident on a circular harbour

1985 ◽  
Vol 401 (1821) ◽  
pp. 349-371 ◽  
Keyword(s):  
Resonant Frequency ◽  
Wave Amplitude ◽  
Single Frequency ◽  
Mathematical Treatment ◽  
Total Flow ◽  
Internal Resonances ◽  
Through Flow ◽  
Significant Difference ◽  
Flow Through ◽  
Incident Waves

The wave amplitude inside a harbour that is subject to incident waves is greatly affected by the frequency of the incident waves. If the harbour entrance is small it is expected that the internal resonances of the harbour will be excited at the appropriate incident frequencies. Published arguments concerning the magnitude of the resonances are, however, not conclusive. In this paper a circular harbour with a small entrance is studied with the use of a rigorous mathematical treatment. It is found that as the harbour entrance decreases in size the magnitude of resonance owing to a single frequency increases slowly (logarithmically). However, this increase is too slow to make a significant difference. The magnitude of resonance in relation to a continuous spectrum input increases, but for the Helmholtz mode only. Again the increase is slow (logarithmic). These results are found to be in agreement with the work of J. Miles ( J. Fluid Mech. 46, 241-265 (1971)). In many approximate calculations it is assumed that the total flow through the gap will effectively determine the flow near a resonant frequency. This is correct near the Helmholtz resonance, but incorrect near the higher resonances where the through-flow is small.

scholarly journals Effect of Resonant Frequency Vibration on Delayed Onset Muscle Soreness and Resulting Stiffness as Measured by Shear-Wave Elastography

2021 ◽  
Vol 18 (15) ◽  
pp. 7853
Author(s):  
Garrett C. Jones ◽  
Jonathan D. Blotter ◽  
Cameron D. Smallwood ◽  
Dennis L. Eggett ◽  
Darryl J. Cochrane ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Shear Wave ◽  
Time Course ◽  
Biceps Brachii ◽  
Shear Wave Elastography ◽  
Upper Body ◽  
Maximum Voluntary Isometric Contraction ◽  
Post Exercise ◽  
Significant Difference ◽  
Pain Ratings

This study utilized resonant frequency vibration to the upper body to determine changes in pain, stiffness and isometric strength of the biceps brachii after eccentric damage. Thirty-one participants without recent resistance training were randomized into three groups: a Control (C) group and two eccentric exercise groups (No vibration (NV) and Vibration (V)). After muscle damage, participants in the V group received upper body vibration (UBV) therapy for 5 min on days 1–4. All participants completed a visual analog scale (VAS), maximum voluntary isometric contraction (MVIC), and shear wave elastography (SWE) of the bicep at baseline (pre-exercise), 24 h, 48 h, and 1-week post exercise. There was a significant difference between V and NV at 24 h for VAS (p = 0.0051), at 24 h and 1-week for MVIC (p = 0.0017 and p = 0.0016, respectively). There was a significant decrease in SWE for the V group from 24–48 h (p = 0.0003), while there was no significant change in the NV group (p = 0.9341). The use of UBV resonant vibration decreased MVIC decrement and reduced VAS pain ratings at 24 h post eccentric damage. SWE was strongly negatively correlated with MVIC and may function as a predictor of intrinsic muscle state in the time course of recovery of the biceps brachii.

Forces on Unstaggered Airfoil Cascades in Unsteady In-Phase Motion

1976 ◽  
Vol 98 (3) ◽  
pp. 521-530 ◽  
Author(s):  
N. H. Kemp ◽  
H. Ohashi
Keyword(s):  
Flow Velocity ◽  
Incompressible Flow ◽  
Kutta Condition ◽  
Harmonic Motion ◽  
Thin Airfoil ◽  
Through Flow ◽  
Flow Through ◽  
Unsteady Effects ◽  
Analytical Expressions ◽  
Phase Motion

Incompressible flow through an unstaggered cascade in general, unsteady, in-phase motion is considered. By methods of thin-airfoil theory, using the assumptions of wakes trailing back at the through-flow velocity, and the Kutta condition, exact analytical expressions are derived for loading, lift and moment. As application, harmonic motion is considered for plunging, pitching, and sinusoidal gusts. Numerical values of lift and moment for these three cases are given graphically (tables are available from the authors). The results show strong analogies with isolated unsteady thin-airfoil theory. They should prove useful as simple examples of unsteady effects in cascades, and as check cases for other approximate or purely numerical analyses.

Towards flow-through/flow injection electronic tongue for the analysis of pharmaceuticals

2015 ◽  
Vol 207 ◽  
pp. 1087-1094 ◽  
Author(s):  
Patrycja Ciosek ◽  
Małgorzata Wesoły ◽  
Marcin Zabadaj ◽  
Joanna Lisiecka ◽  
Krzysztof Sołłohub ◽  
...  
Keyword(s):  
Flow Injection ◽  
Electronic Tongue ◽  
Through Flow ◽  
Flow Through

Entraining the natural frequencies of running and breathing in guinea fowl (Numida meleagris)

2001 ◽  
Vol 204 (9) ◽  
pp. 1641-1651 ◽  
Author(s):  
P.N. Nassar ◽  
A.C. Jackson ◽  
D.R. Carrier
Keyword(s):  
Resonant Frequency ◽  
Respiratory System ◽  
Natural Frequencies ◽  
Lung Ventilation ◽  
Guinea Fowl ◽  
Forced Oscillation Technique ◽  
Step Frequency ◽  
Numida Meleagris ◽  
Significant Difference ◽  
Treadmill Locomotion

Lung ventilation of tetrapods that synchronize their locomotory and ventilatory cycles during exercise could be economized if the resonant frequency of the respiratory system matched the animal's preferred step frequency. To test whether animals utilize this strategy, the input impedance of the respiratory system of five anesthetized, supine guinea fowl (Numida meleagris) was measured using a forced oscillation technique. The resonant frequency of the respiratory system was 7.12+/−0.27 Hz (N=5, mean +/− S.E.M.). No statistically significant difference was found between the resonant frequency of the respiratory system and the panting frequency used by guinea fowl at rest (6.67+/−0.16 Hz, N=11) or during treadmill locomotion (6.71+/−0.12 Hz, N=8) or to their preferred step frequency (6.73+/−0.09 Hz, N=7) (means +/− S.E.M.). These observations suggest (i) that, at rest and during exercise, panting guinea fowl maximize flow while expending minimal mechanical effort, and (ii) that natural selection has tuned the natural frequencies of the respiratory and locomotor systems to similar frequencies.

scholarly journals A Mild-Slope System for Bragg Scattering of Water Waves by Sinusoidal Bathymetry in the Presence of Vertically Sheared Currents

2019 ◽  
Vol 7 (1) ◽  
pp. 9 ◽  
Author(s):  
Kostas Belibassakis ◽  
Julien Touboul ◽  
Elodie Laffitte ◽  
Vincent Rey
Keyword(s):  
Resonant Frequency ◽  
Water Waves ◽  
Bottom Topography ◽  
Wave System ◽  
Bragg Scattering ◽  
Wave Flume ◽  
Seabed Topography ◽  
Incident Waves ◽  
Slope System ◽  
A Current

Extended mild-slope models (MMSs) are examined for predicting the characteristics of normally incident waves propagating over sinusoidal bottom topography in the presence of opposing shearing currents. It is shown that MMSs are able to provide quite good predictions in the case of Bragg scattering of waves over rippled bathymetry without a current, but fail to provide good predictions concerning the resonant frequency in the additional presence of a current. In order to resolve the above mismatch, a two-equation mild-slope system (CMS2) is derived from a variational principle based on the representation of the wave potential expressed as a superposition of the forward and backward components. The latter system is compared against experimentally measured data collected in a wave flume and is shown to provide more accurate predictions concerning both the resonant frequency and the amplitude of the reflection coefficient. Future work will be devoted to the examination of the derived model for a more general wave system over realistic seabed topography.

Control of Dielectric Fluid Flow Distribution in Micro-Tubes With EHD Conduction Pumping: Numerical Study

2011 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Fluid Flow ◽  
Electric Field ◽  
Conduction Mechanism ◽  
Numerical Study ◽  
Fluid Motion ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Dielectric Fluid ◽  
Total Flow ◽  
Flow Through

The control of fluid flow distribution in micro-scale tubes is numerically investigated. The flow distribution control is achieved via electric conduction mechanism. In electrohydrodynamic (EHD) conduction pumping, when an electric field is applied to a fluid, dissociation and recombination of electrolytic species produces heterocharge layers in the vicinity of electrodes. Attraction between electrodes and heterocharge layers induces a fluid motion and a net flow is generated if the electrodes are asymmetric. The numerical domain comprises a 2-D manifold attached to two bifurcated tubes with one of the tubes equipped with a bank of uniquely designed EHD-conduction electrodes. In the absence of electric field, the total flow supplied at the manifold’s inlet is equally distributed among the tubes. The EHD-conduction, however, operates as a mechanism to manipulate the flow distribution to allow the flow through one branch surpasses the counterpart of the other branch. Its performance is evaluated under various operating conditions.

scholarly journals On compressible and piezo-viscous flow in thin porous media

2018 ◽  
Vol 474 (2209) ◽  
pp. 20170601 ◽  
Author(s):  
F. Pérez-Ràfols ◽  
P. Wall ◽  
A. Almqvist
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Viscous Fluid ◽  
Linear Equation ◽  
Nonlinear Function ◽  
Viscous Fluids ◽  
Total Flow ◽  
Thin Porous Media ◽  
Flow Through ◽  
The One

In this paper, we study flow through thin porous media as in, e.g. seals or fractures. It is often useful to know the permeability of such systems. In the context of incompressible and iso-viscous fluids, the permeability is the constant of proportionality relating the total flow through the media to the pressure drop. In this work, we show that it is also relevant to define a constant permeability when compressible and/or piezo-viscous fluids are considered. More precisely, we show that the corresponding nonlinear equation describing the flow of any compressible and piezo-viscous fluid can be transformed into a single linear equation. Indeed, this linear equation is the same as the one describing the flow of an incompressible and iso-viscous fluid. By this transformation, the total flow can be expressed as the product of the permeability and a nonlinear function of pressure, which represents a generalized pressure drop.

Pneumatically Controlled Pallet Conveying and Accumulation System

Manufacturing ◽  
2002 ◽  
Author(s):  
Mel Beikmann ◽  
Jim Kuecker
Keyword(s):  
Material Handling ◽  
Storage Systems ◽  
Storage System ◽  
High Density ◽  
Weight Changes ◽  
Private Industry ◽  
Accumulation System ◽  
Significant Difference ◽  
Type Size ◽  
Flow Through

First In / First Out (FIFO) accumulating storage systems combine high-density storage with automatic material handling. A traditional FIFO storage system is a flow-through rack which uses gravity to move the pallet from the load end to the unload end. High-density storage installations require a significant difference in height between the load end and the unload end which results in a loss of available storage space. Rack configuration in terms of slope, brake configuration, and roller density is inflexible and are a function of pallet type, size, and weight. Changes in pallet characteristics cannot be easily accommodated by traditional gravity flow storage rack systems. Alternate FIFO storage systems are available that do not use gravity but rather use rollers on a horizontal reciprocating frame with directional flippers to ensure that the load indexes from the load end to the unload end. The limitations of these existing systems have prompted the development of alternative FIFO storage system. This paper details an innovative FIFO storage/handling system and the collaborative effort between a university and private industry to develop this product.

scholarly journals Investigation of the Modulation of the Tidal Stream Resource by Ocean Currents through a Complex Tidal Channel

2019 ◽  
Vol 7 (10) ◽  
pp. 341 ◽  
Author(s):  
Alice J. Goward Brown ◽  
Matt Lewis ◽  
Benjamin I. Barton ◽  
Gus Jeans ◽  
Steven A. Spall
Keyword(s):  
Tidal Energy ◽  
Resource Assessment ◽  
Tidal Currents ◽  
The West ◽  
Ocean Modelling ◽  
Through Flow ◽  
The World ◽  
Tidal Stream ◽  
Flow Through ◽  
Resource Uncertainty

Tidal energy has the opportunity to bring reliable electricity to remote regions in the world. A resource assessment, including the response of the tidal stream resource to fluctuations in the Indonesian Through Flow (ITF) is performed using the Regional Ocean Modelling System (ROMS) to simulate four different scenarios for flow through the Lombok Strait in Indonesia. Tidal currents simulated with a variable ITF are compared against a tide-only (TO) simulation to identify how the ITF spatially changes the resource across the Lombok Strait. We find that the uncertainty in the tidal currents from the TO simulation is 50% greater than the variable ITF simulation. To identify change to resource, surface velocities from Strong ITF and Weak ITF scenarios are considered. As a result of the fluctuations in the ITF, certain characteristics, such as the asymmetry and magnitude, of the tidal current vary greatly. However, the magnitude of change is variable, with regions to the west of the strait experiencing greater modulation than in the east, suggesting that resource uncertainty can be minimised with selective site positioning.

Numerical simulation and experiment for study on internal flow pattern of vortex pump

2019 ◽  
Vol 36 (5) ◽  
pp. 1579-1596
Author(s):  
Hui Quan ◽  
Yi Chai ◽  
Rennian Li ◽  
Jianhui Guo
Keyword(s):  
Flow Pattern ◽  
Theoretical Foundation ◽  
Internal Flow ◽  
Content Type ◽  
Vortex Pump ◽  
Hydraulic Design ◽  
Through Flow ◽  
Simulation And Experiment ◽  
Flow Through ◽  
Working Out

Purpose The special structure of the vortex pump contributes to its complex internal flow pattern. A type of horizontal 150WX-200-20 vortex pump is taken as a research subject to deeply study the progression and distribution of flow pattern in its channel. To explain the mechanism of flow in this pump, numerical analysis of the whole flow and experiment have been conducted. Design/methodology/approach The authors studied and analyzed the distribution and evolution of flow pattern under different flow, such as circulating-flow, through-flow and other forms. Finally, a model of flow pattern in the vortex pump has been built, which has more perfectly fit the reality. Findings They are through-flow affected by circulating-flow, main and subsidiary circulating-flow, vortices between vanes and other vortices (or liquid impingement) in volute. Entering the pump, part of the flow stays in vanes and turn into vortices while the other goes into the front chamber. The flow that runs into the front chamber will be divided into two parts. One part will be collected by viscosity into a vortex rope when it passing through the interface between the impeller and the vaneless chamber, which closely relates to the circulating-flow, and the rest directly goes out of the field through the diffuser. Besides, a fraction of circulating-flow joins the through-flow when it goes through the section V and leaves the pump. Originality/value The research results build a theoretical foundation for working out the flow mechanism of the vortex pump, improving its efficiency and optimizing its hydraulic design.

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