scholarly journals SCOUR AROUND A CIRCULAR CYLINDER DUE TO WAVE MOTION

1970 ◽  
Vol 1 (12) ◽  
pp. 79
Author(s):  
Donald R. Wells ◽  
Robert M. Sorenson
Keyword(s):  
Circular Cylinder ◽  
Wave Motion ◽  
Oscillatory Flow ◽  
Fine Sand ◽  
Time Interval ◽  
Relative Depth ◽  
Incipient Motion ◽  
Critical Flow Velocity ◽  
Time Required ◽  
Influential Parameters

A vertical circular cylinder to simulate a pile was installed in the Texas A&M Hydrodynamics Lab two dimensional wave tank along with a built up section containing a horizontal bed of fine sand This was subjected to monochromatic waves of differing characteristics and conditions for mcipi ent motion were observed for each of three sands Also, the magnitude and pattern of ultimate scour and the time interval required to reach this state were measured for six different conditions of wave steepness and relative depth These results were related to influential parameters, including wave, pile and sediment character istics, and developed by dimensional analysis with consideration of the literature pertaining to past work on the movement of sediment by oscillatory flow Conclusions regarding the critical flow velocity for incipient motion, the effect of the above parameters on incipient motion and ultimate scour depth, the time required tor maximum scour, the significance of eddies generated by the pile, and the catalytic action of the pile in causing the initiation of scour are presented The above conclusions are also generally discussed in light of the difficulties involved in extend ing the results to prototype conditions.

Oscillatory flow past a circular cylinder in a rotating frame

1997 ◽  
Vol 345 ◽  
pp. 101-131
Author(s):  
M. D. KUNKA ◽  
M. R. FOSTER
Keyword(s):  
Circular Cylinder ◽  
Steady Flow ◽  
Stagnation Point ◽  
Oscillatory Flow ◽  
Numerical Solutions ◽  
Initial Conditions ◽  
Temporal Integration ◽  
Oncoming Flow ◽  
Flow Past ◽  
Rear Stagnation Point

Because of the importance of oscillatory components in the oncoming flow at certain oceanic topographic features, we investigate the oscillatory flow past a circular cylinder in an homogeneous rotating fluid. When the oncoming flow is non-reversing, and for relatively low-frequency oscillations, the modifications to the equivalent steady flow arise principally in the ‘quarter layer’ on the surface of the cylinder. An incipient-separation criterion is found as a limitation on the magnitude of the Rossby number, as in the steady-flow case. We present exact solutions for a number of asymptotic cases, at both large frequency and small nonlinearity. We also report numerical solutions of the nonlinear quarter-layer equation for a range of parameters, obtained by a temporal integration. Near the rear stagnation point of the cylinder, we find a generalized velocity ‘plateau’ similar to that of the steady-flow problem, in which all harmonics of the free-stream oscillation may be present. Further, we determine that, for certain initial conditions, the boundary-layer flow develops a finite-time singularity in the neighbourhood of the rear stagnation point.

scholarly journals Delay in presentation of acute ischemic stroke in Lahore General Hospital, Lahore

2016 ◽  
Vol 11 (3) ◽  
Author(s):  
Rafiq A Basharat ◽  
Kamran Rashid Mirza ◽  
Muhammad Yousuf Qamar
Keyword(s):  
Emergency Department ◽  
Ischemic Stroke ◽  
Ct Scan ◽  
Acute Ischemic Stroke ◽  
General Hospital ◽  
Clinical History ◽  
Clinical Findings ◽  
Study Data ◽  
Time Interval ◽  
Time Required

Objectives: To find out the time interval from onset of the symptoms to admission in the hospital of patients suffering from acute ischemic stroke, in order to assess the feasibility of thrombolytic therapy in Lahore General Hospital. Design: Hospital-based, prospective and observational study Setting: Lahore General Hospital Lahore. Duration: Six months from January - June 2004. Patients: Seventy two patients with acute ischemic stroke diagnosed on basis of clinical findings and CT scan. Methods: Patients o f a cute ischemic stroke including cerebral infarct, T IA, venous infarct and lacunar infarct were diagnosed on basis of clinical history, examination and CT scan and enrolled in the study. Data was collected on a Performa. Time taken by patients to reach hospital after onset of symptoms, distance of patients` residences from hospital, education level of patients and time required to do a CT scan after arrival of patient in hospital were studied. Results: 54.2% were male and mean age of patients was 60 years. 58 patients had cerebral infarction, TIA`s and venous infarction were 8 and 6 respectively. Delay in presentation was divided in three groups. Within three hours (hrs) 15 (21%) patients arrived. 54 and 18 patients arrived in 3-- 24 hrs group and >24 firs group. Mean distance was roughly 44 km. Mean distance for 0-3hrs, 3-24hrs and >24hrs group was 14, 35, and 85 Km respectively. Average time required to do CT scan was nine hours after arrival of patient in emergency department. Sixty-five percent of patients coming were illiterate. Conclusion: Majority of the patients with ischemic stroke present late to. emergency department. Many factors including distance from hospital, illiteracy, non-availability of ambulance services responsible for it. Evaluation-of patients and provision of urgent CT scan is required. in hospitals.

Continuous recording of arteriolar dimensions with a television microscope

1963 ◽  
Vol 18 (5) ◽  
pp. 1041-1042 ◽  
Author(s):  
Curt A. Wiederhielm
Keyword(s):  
Experimental Study ◽  
Electron Beam ◽  
Viscoelastic Properties ◽  
Continuous Recording ◽  
Time Interval ◽  
Short Term ◽  
Small Arteries ◽  
Glass Capillaries ◽  
Time Required ◽  
Analog Voltage

A system which permits continuous recording of dimensions of microscopic blood vessels is described. The system utilizes information contained in the video signal of a television microscope to develop an analog voltage proportional to the time required for the electron beam to sweep across the image of the blood vessel. This time interval is also proportional to the dimension of the vessel. Calibration of the system yielded a standard error of estimate of ±3.7 μ on a series of glass capillaries, ranging in size from 15 to 150 μ. The rise time of the system was in the order of 40 msec. Long- and short-term drift was less than 3 μ/hr. The system is used in an experimental study of viscoelastic properties of small arteries and arterioles. microcirculation; viscoelastic properties; frog mesentery Submitted on April 17, 1963

Kinetic Parameters of Continuous Flow Analysis

1967 ◽  
Vol 13 (6) ◽  
pp. 451-467 ◽  
Author(s):  
R E Thiers ◽  
R R Cole ◽  
W J Kirsch
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Continuous Flow ◽  
Flow Analysis ◽  
Transient State ◽  
Steady States ◽  
Lag Phase ◽  
Time Interval ◽  
Base Line ◽  
Time Required

Abstract Unlike systems of batch analysis, continuous flow systems possess kinetic parameters. Associated with the steady state are such measurements as noise level and drift. This study reports on kinetic parameters associated with the transient state between the steady states including time required to change from base-line steady state to sample steady state and vice versa, characteristics of this change, time interval between samples, proportionality of sampling and washing time, fraction of steady state reached in any given sampling time, and interaction between samples. The transition between steady states has been found to obey first order kinetics to a good first approximation. This observation enables correlation of all of the above listed properties in quantitative fashion using new characteristic constants for continuous flow-the half-wash time (W1/2) and the lag phase time (L). These parameters, well known in other contexts such as radioactivity, can be employed as "figures of merit" for any continuous flow system or component, can be utilized to calculate performance characteristics, and are useful in evaluating and optimizing over-all performance.

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