scholarly journals Time Dependent Root‐Mean‐Square Response to Nonstationary Random Excitations

1973 ◽  
Vol 53 (1) ◽  
pp. 308-308
Author(s):  
Gary C. Hart
Keyword(s):  
Root Mean Square ◽  
Time Dependent ◽  
Mean Square ◽  
Mean Square Response

Non-invasive turbulent mixing across a density interface in a turbulent Taylor–Couette flow

2010 ◽  
Vol 663 ◽  
pp. 347-357 ◽  
Author(s):  
ANDREW W. WOODS ◽  
C. P. CAULFIELD ◽  
J. R. LANDEL ◽  
A. KUESTERS
Keyword(s):  
Root Mean Square ◽  
Richardson Number ◽  
Outer Cylinder ◽  
Salt Transport ◽  
Time Dependent ◽  
Mean Square ◽  
Mean Flow ◽  
Flow Measurements ◽  
Cylindrical Annulus ◽  
The Mean

In this paper, we present new experimental measurements of the turbulent transport of salt across an interface between two layers of fluid of equal depth but different salinities. The fluid is confined to a cylindrical annulus with a vertical axis. The outer cylinder is stationary and the inner cylinder rotates to produce a turbulent flow field consisting of an approximately irrotational mean azimuthal flow, with narrow boundary layers on the inner and outer cylinders. We focus on the limit of high-Richardson-number flow, defined as Ri = gΔρH/(ρ0u2rms), where ρ0 is a reference density, Δρ is the time-dependent difference of the layers' mean densities, urms is the root mean square of the turbulent velocity fluctuations and H is the layer depth. The mean flow has Reynolds number of the order of 104−105, and the turbulent fluctuations in the azimuthal and radial directions have root-mean-square speed of order 10% of the mean azimuthal flow. Measurements based on our experimental system show that when the Richardson number is in the range 7 < Ri < 200, the interface between the two layers remains sharp, each layer remains well mixed, and the vertical flux of salt between the layers, Fs ~(1.15 ± 0.15)Ri−1𝒜(H/ΔR)urmsΔS, where ΔS is the spatially-averaged time-dependent salinity difference between the layers and in general 𝒜(H/ΔR) is a dimensionless function of the tank aspect ratio, here taken to be unity, with ΔR being the gap width of the annulus. The salt transport appears to be caused by turbulent eddies scouring and sharpening the interface and implies a constant rate of conversion of the turbulent kinetic energy to potential energy, independent of the density contrast between the layers. For smaller values of Ri, the flow regime changes qualitatively, with eddies penetrating the interface, causing fluid in the two layers to co-mingle and rapidly homogenize.

scholarly journals Deterministic and Probabilistic Foundation Forces Resulting From an Unbalanced Turbine

1976 ◽  
Author(s):  
L. Boyce ◽  
T. J. Kozik
Keyword(s):  
Root Mean Square ◽  
Center Of Mass ◽  
Random Variable ◽  
Degree Of Freedom ◽  
Mean Square ◽  
Single Degree Of Freedom ◽  
Principal Mode ◽  
Single Degree ◽  
Rotating Machine ◽  
Mean Square Response

This paper considers the problem of the unbalanced rotating turbine as a single degree of freedom system, wherein the principal mode of vibration is a translation in the direction of the machine supports. The distance from the center of mass of the rotating mass to the geometric axis, also known as the effective eccentricity, is modeled as a random variable. The expression for the root mean square response of the rotating machine is derived and related to the statistical analog for the deterministic expression for the foundation force. These results are numerically compared to their equivalent deterministic values.

Diaphragm electromyogram root mean square response to hypercapnia and its intersubject and day-to-day variation

2005 ◽  
Vol 98 (1) ◽  
pp. 274-281 ◽  
Author(s):  
Bhajan Singh ◽  
Janine A. Panizza ◽  
Kevin E. Finucane
Keyword(s):  
Root Mean Square ◽  
Functional Residual Capacity ◽  
Minute Ventilation ◽  
Random Order ◽  
Mean Square ◽  
Quiet Breathing ◽  
Diaphragm Position ◽  
Mean Square Response ◽  
Residual Capacity ◽  
End Tidal

Diaphragm activation can be quantified by measuring the root mean square of crural EMG (RMSdi) (Beck J, Sinderby C, Lindstrom L, and Grassino A, J Appl Physiol 85: 1123–1134, 1998). To examine intersubject and day-to-day variation in the RMSdi-Pco2 relationship, end-tidal Pco2, minute ventilation (V̇e), respiratory frequency (fB), and RMSdi were measured in seven healthy subjects on two occasions during steady-state ventilation at seven levels of inspired O2 fraction (FiCO2) from 0 to 0.08 in random order. RMSdi was measured with a multielectrode esophageal catheter and controlled for signal contamination and diaphragm position. RMSdi was normalized for values obtained during quiet breathing at functional residual capacity, at FiCO2 of 0.04, and during an inspiratory capacity maneuver (RMSdi%max) as well as ECG R-wave amplitude at functional residual capacity (RMSdi/ECGR), fB, and thickness of the costal diaphragm measured by ultrasound. RMSdi increased linearly with Pco2 (mean r2 = 0.83 ± 0.10); at the highest FiCO2, RMSdi%max was 40.2 ± 11.6%. Relative to the intersubject variation in the V̇e-Pco2 relationship, intersubject variations in the slopes and intercepts of the RMSdi-Pco2 relationships were 1.7 and 1.8 times, respectively, and RMSdi%max-Pco2 relationships 0.9 and 1.3 times, respectively, and were unrelated to fB and diaphragm thickness. Relative to the day-to-day variation in the V̇e-Pco2 relationship, day-to-day variation in the slopes and intercepts of the RMSdi-Pco2 relationships were 2.8 and 4.4 times, respectively, and RMSdi/ECGR-Pco2 relationships 1.3 and 2.2 times, respectively. It was concluded that the RMSdi-Pco2 relationship measures chemosensitivity and is best compared between subjects via RMSdi%max and on separate occasions in the same subject via RMSdi/ECGR.

scholarly journals Analytical Predictions of the Air Gap Response of Floating Structures

2001 ◽  
Vol 123 (3) ◽  
pp. 112-117 ◽  
Author(s):  
Lance Manuel ◽  
Bert Sweetman ◽  
Steven R. Winterstein
Keyword(s):  
Root Mean Square ◽  
Air Gap ◽  
Second Order ◽  
Mean Square ◽  
Floating Structures ◽  
Field Point ◽  
Extreme Response ◽  
Wave Effects ◽  
Mean Square Response ◽  
Single Field

Two separate studies are presented here that deal with analytical predictions of the air gap for floating structures. 1) To obtain an understanding of the importance of first and second-order incident and diffracted wave effects as well as to determine the influence of the structure’s motions on the instantaneous air gap, statistics of the air gap response are studied under various modeling assumptions. For these detailed studies, a single field point is studied here—one at the geometric center (in plan) of the Troll semi-submersible. 2) A comparison of the air gap at different locations is studied by examining response statistics at different field points for the semi-submersible. These include locations close to columns of the four-columned semi-submersible. Analytical predictions, including first and second-order diffracted wave effects, are compared with wave tank measurements at several locations. In particular, the gross root-mean-square response and the 3-h extreme response are compared.

The Relationship of Root Mean Square Value of Electromyography and Isometric Torque of Quadriceps in Normal Subjects

2016 ◽  
Vol 26 (1) ◽  
pp. 58
Author(s):  
Qiurong XIE ◽  
Zheng JIANG ◽  
Qinglu LUO ◽  
Jie LIANG ◽  
Xiaoling WANG ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Normal Subjects ◽  
Mean Square ◽  
Isometric Torque ◽  
Relationship Of ◽  
The Relationship
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