Effective Reflection Coefficients for the Mean Acoustic Field Between Two Rough Interfaces

1994 ◽  
Author(s):  
David H. Berman
Keyword(s):  
Acoustic Field ◽  
Reflection Coefficients ◽  
The Mean ◽  
Rough Interfaces

Protein osmotic pressure gradients and microvascular reflection coefficients

1997 ◽  
Vol 273 (2) ◽  
pp. H997-H1002 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
R. A. Teague ◽  
J. C. Gabel
Keyword(s):  
Reflection Coefficient ◽  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Reflection Coefficients ◽  
Pressure Gradients ◽  
Fluid Filtration ◽  
The Mean ◽  
Osmotic Reflection Coefficient ◽  
New Equation ◽  
Osmotic Pressure Gradient

Microvascular membranes are heteroporous, so the mean osmotic reflection coefficient for a microvascular membrane (sigma d) is a function of the reflection coefficient for each pore. Investigators have derived equations for sigma d based on the assumption that the protein osmotic pressure gradient across the membrane (delta II) does not vary from pore to pore. However, for most microvascular membranes, delta II probably does vary from pore to pore. In this study, we derived a new equation for sigma d. According to our equation, pore-to-pore differences in delta II increase the effect of small pores and decrease the effect of large pores on the overall membrane osmotic reflection coefficient. Thus sigma d for a heteroporous membrane may be much higher than previously derived equations indicate. Furthermore, pore-to-pore delta II differences increase the effect of plasma protein osmotic pressure to oppose microvascular fluid filtration.

scholarly journals A note on acoustic turbulence

2019 ◽  
Vol 874 ◽  
Author(s):  
Erik Lindborg
Keyword(s):  
Structure Function ◽  
Entropy Production ◽  
Acoustic Field ◽  
Three Dimensional ◽  
Weak Shock ◽  
Separation Distance ◽  
Ideal Gas ◽  
Order Structure ◽  
Specific Heats ◽  
The Mean

We consider a three-dimensional acoustic field of an ideal gas in which all entropy production is confined to weak shocks and show that similar scaling relations hold for such a field as for forced Burgers turbulence, where the shock amplitude scales as $(\unicode[STIX]{x1D716}d)^{1/3}$ and the $p$th-order structure function scales as $(\unicode[STIX]{x1D716}d)^{p/3}r/d$, $\unicode[STIX]{x1D716}$ being the mean energy dissipation per unit mass, $d$ the mean distance between the shocks and $r$ the separation distance. However, for the acoustic field, $\unicode[STIX]{x1D716}$ should be replaced by $\unicode[STIX]{x1D716}+\unicode[STIX]{x1D712}$, where $\unicode[STIX]{x1D712}$ is associated with entropy production due to heat conduction. In particular, the third-order longitudinal structure function scales as $\langle \unicode[STIX]{x1D6FF}u_{r}^{3}\rangle =-C(\unicode[STIX]{x1D716}+\unicode[STIX]{x1D712})r$, where $C$ takes the value $12/5(\unicode[STIX]{x1D6FE}+1)$ in the weak shock limit, $\unicode[STIX]{x1D6FE}=c_{p}/c_{v}$ being the ratio between the specific heats at constant pressure and constant volume.

scholarly journals Klein’s paradox in the presence of a scalar potential

2019 ◽  
Vol 35 (04) ◽  
pp. 2050004
Author(s):  
B. Ainouz ◽  
S. Haouat
Keyword(s):  
Scalar Potential ◽  
Particle Creation ◽  
Critical Value ◽  
Reflection Coefficients ◽  
Potential Barriers ◽  
Transmission And Reflection Coefficients ◽  
Related Pair ◽  
The Mean ◽  
Forbidden Region ◽  
Transmission And Reflection

In this paper, we have studied the Klein’s paradox in the presence of both scalar and vector potential barriers. From the corresponding Dirac equation, we have calculated the transmission and reflection coefficients. It is shown that the presence of a scalar barrier the scalar potential widens the gap between positive and negative energies and so the forbidden region. Accordingly, the Klein’s paradox disappears when the scalar barrier exceeds a critical value. Considering the problem within the framework of quantum field theory, we have calculated the related pair creation probability, the mean number of created particles and the probability of a vacuum to remain a vacuum. Then it is shown that the scalar potential cuts down the Klein range and minimizes the creation of particles; the particle creation decreases as the scalar potential increases and ceases definitely when the scalar potential reaches the critical value.

Noise generation by high-frequency gusts interacting with an airfoil in transonic flow

2000 ◽  
Vol 411 ◽  
pp. 91-130 ◽  
Author(s):  
I. EVERS ◽  
N. PEAKE
Keyword(s):  
Steady Flow ◽  
Acoustic Field ◽  
Transonic Flow ◽  
High Frequency ◽  
Power Series Expansion ◽  
Outer Region ◽  
Leading Edge ◽  
Mean Flow ◽  
Flow Distortion ◽  
The Mean

The method of matched asymptotic expansions is used to describe the sound generated by the interaction between a short-wavelength gust (reduced frequency k, with k [Gt ] 1) and an airfoil with small but non-zero thickness, camber and angle of attack (which are all assumed to be of typical size O(δ), with δ [Lt ] 1) in transonic flow. The mean-flow Mach number is taken to differ from unity by O(δ2/3), so that the steady flow past the airfoil is determined using the transonic small-disturbance equation. The unsteady analysis is based on a linearization of the Euler equations about the mean flow. High-frequency incident vortical and entropic disturbances are considered, and analogous to the subsonic counterpart of this problem, asymptotic regions around the airfoil highlight the mechanisms that produce sound. Notably, the inner region round the leading edge is of size O(k−1), and describes the interaction between the mean-flow gradients and the incident gust and the resulting acoustic waves. We consider the preferred limit in which kδ2/3 = O(1), and calculate the first two terms in the phase of the far-field radiation, while for the directivity we determine the first term (δ = 0), together with all higher-order terms which are at most O(δ2/3) smaller – in fact, this involves no fewer than ten terms, due to the slowly-decaying form of the power series expansion of the steady flow about the leading edge. Particular to transonic flow is the locally subsonic or supersonic region that accounts for the transition between the acoustic field downstream of a source and the possible acoustic field upstream of the source. In the outer region the sound propagation has a geometric-acoustics form and the primary influence of the mean-flow distortion appears in our preferred limit as an O(1) phase term, which is particularly significant in view of the complicated interference between leading- and trailing-edge fields. It is argued that weak mean- flow shocks have an influence on the sound generation that is small relative to the effects of the leading-edge singularity.

scholarly journals UPDATE OF THE EUROTOP NEURAL NETWORK TOOL: IMPROVED PREDICTION OF WAVE OVERTOPPING

2017 ◽  
pp. 2
Author(s):  
Barbara Zanuttigh ◽  
Sara Mizar Formentin ◽  
Jentsje Wouter Van der Meer
Keyword(s):  
Wave Reflection ◽  
Extreme Values ◽  
Wave Structure ◽  
The Internet ◽  
Reflection Coefficients ◽  
Wave Overtopping ◽  
Structure Interaction ◽  
Interaction Processes ◽  
The Mean ◽  
Wave Structure Interaction

The goal of this work is to present a synthesis of the improvements and updates developed to deliver the final version of the ANN tool adopted by the second edition of the wave overtopping manual, EurOtop, released on the internet in 2016. This tool consists of three identical but independent ANNs able to predict the main parameters representative of the wave-structure interaction processes, i.e. the mean wave overtopping discharge, the wave transmission and the wave reflection coefficients. The contribution focuses on the modifications of the ANN architecture carried out since the last ICCE conference to achieve an optimized representation of the wave overtopping, especially in case of low and extreme values of the overtopping discharge. The consistency of the ANN predictions is assessed through an artificial dataset including geometrical and climate input parameters that are varied with continuity, while the robustness of the tool is checked by applying the ANN to selected geometries excluded from the training database.

Simulation and Analysis of the Radiated Acoustic Field Measurement of the Underwater Vehicle Based on NAH

2012 ◽  
Vol 503-504 ◽  
pp. 1575-1579
Author(s):  
Shao Chun Ding ◽  
Lin Na Zhou ◽  
Jing Jun Lou ◽  
Shi Jian Zhu
Keyword(s):  
Acoustic Field ◽  
Sound Pressure ◽  
Power Level ◽  
Sound Intensity ◽  
Sound Power ◽  
Pressure Method ◽  
Sound Power Level ◽  
Measuring Surface ◽  
Source Level ◽  
The Mean

we use the NAH method for the simulation and analysis of sound power level and source level with the plan measuring surface under the same distance and size. The sound intensity integral method, the mean square sound pressure method and the NAH reversal method have been adopted in this paper. We also compare the sound power level between the plan measuring surface and the cylinder measuring surface, thus helps verifying the accuracy of the measurement of the radiated acoustic field based on the method of NAH. The conclusion we have drawn here can also provides dependable experimental basis for the choosing of measuring surfaces

scholarly journals An effective methodology to design scale model of non-metallic structural entity

2018 ◽  
Vol 242 ◽  
pp. 01008
Author(s):  
Liming Yuan ◽  
Zhijie Xie ◽  
Fei Dai ◽  
Yonggang Xu ◽  
Yuan Zhang
Keyword(s):  
Cross Section ◽  
High Frequency ◽  
High Accuracy ◽  
Practical Significance ◽  
Scale Model ◽  
Mean Deviation ◽  
Reflection Coefficients ◽  
The Mean ◽  
Structural Entity ◽  
Frequency Approximation

In order to solve the problem on designing scale model of non-metallic structural entity, a method is first proposed according to the high-frequency approximation algorithm, in which reflection coefficients of designed scale model are optimized to be as identical as possible with those of theoretical scale model. An example is given to verify the effectiveness of the method, where a non-metallic cone is constructed and FEKO is employed to simulate the monostatic radar Cross Section (RCS) of the designed scale cone and the theoretical scale cone. Result reveals that the monostatic RCS of the designed scale cone agrees very well with that of the theoretical scale cone. The mean deviation of the monostatic RCS is just 1.31 dB in simulated elevation angles of 0°~90°. Thus, the method proposed in this paper is of important theoretical and practical significance in constructing scale model of high accuracy.

Sign in / Sign up

Export Citation Format

Share Document