A Comparative Study of Laminar-Turbulent Displacement in Eccentric Annulus Under Imposed Flow Rate Conditions

2021 ◽  
Author(s):  
Yasaman Foolad ◽  
Majid Bizhani ◽  
Ian A. Frigaard
Keyword(s):  
Comparative Study ◽  
Flow Rate ◽  
Eccentric Annulus

How Does a Stationary Sand Bed Affect the Flow Dynamics in an Eccentric Annulus?

2019 ◽  
Author(s):  
Majid Bizhani ◽  
Ergun Kuru
Keyword(s):  
Shear Stress ◽  
Velocity Field ◽  
Turbulent Flow ◽  
Flow Rate ◽  
The Other ◽  
Flow Loop ◽  
Hole Cleaning ◽  
Eccentric Annulus ◽  
Bed Height ◽  
Bed Erosion

Abstract In the drilling operations, it is common to have a stationary bed of the drilled cuttings in the high angle sections of the wellbore. The bed must be removed in the later stages before running the casing, or when it starts to cause high torque and drag on the drill string. The mere act of circulating drilling fluid, however, may not clean the well (i.e., critical flow rate and shear stress for bed erosion must be reached). In an effort to better understand the underlying mechanisms of bed removal process during hole cleaning, in this paper, we look at how the presence of a stationary sand bed affects the flow field in an eccentric annulus. Experiments simulating turbulent flow of water in an eccentric annulus with/without the presence of stationary sand bed have been conducted by using a 9m long horizontal flow loop (with an annular configuration of 95 mm ID outer pipe and 38 mm OD inner pipe). The flow loop was equipped with particle image velocimetry (PIV) system, which was used to collect velocity field data. The PIV data were then used to study the characteristics of the turbulent flow of water in the eccentric annulus. The velocity field and Reynolds stress profiles were analyzed in two planes, one perpendicular to the bed interface and off-center of the annulus, and the other along the center-line of the annulus. Experiments were carried out with the presence of two different height stationary sand beds and also without a sand bed as the control case. The extent to which the presence of the sand bed affects the flow appears to be a strong function of the bed height in the annulus. For a small bed height, deviation of the velocity field from the no bed case was slight. In this case, Reynolds normal and shear stress values were lower near the bed interface comparing to the annulus centerline. On the other hand, for a flow over a thicker bed, this behavior changed, and the flow became more uniform in the annulus (in terms of turbulence and mean flow properties). The results help in understanding the mechanism of bed erosion under constant pump flow rate. From the practical point of view, data presented here suggest that hole cleaning in an eccentric annulus progressively becomes more difficult as the bed becomes smaller. The results also explain why in long horizontal and extended reach wells often wiper trips are required for proper cleaning of the hole.

Clot Formation in Angiographic Catheters — An in Vitro Comparative Study

1993 ◽  
Vol 34 (1) ◽  
pp. 78-82 ◽  
Author(s):  
R. Raininko ◽  
H. Söder
Keyword(s):  
Comparative Study ◽  
Flow Rate ◽  
Clot Formation ◽  
Low Flow ◽  
Significant Difference ◽  
Physiologic Saline ◽  
Polyurethane Catheters

Clot formation was compared in 6 brands of angiographic catheters, each of which was tested in 3 states: untreated, heparinized, and albumin-coated. Forty-six samples of each brand in each state (in total 828) were filled with blood from 23 donors and incubated at +37 °C for 5 or 15 min. Physiologic saline was then injected through the catheters at a flow rate of 5 and 50 ml/s, respectively, and any expelled clots identified on a filter. Heparinization reduced the number of clotted catheters at 5 min, but not at 15 min. The only significant difference related to catheter brands was found between the heparinized nylon and polyurethane catheters at 5-min incubation with fewer clotted polyurethane catheters. This difference was not found between the same materials made by two other manufacturers. Albumin coating had no effect on clot formation, but clots were more easily expelled by low-flow injections in albumin-coated and, to a lesser degree, in heparinized than in untreated catheters.

Comparative Study of Hemodialysis in Arteriovenous Fistulas in Low Versus High Blood Flow Rate

2021 ◽  
Vol 24 (1) ◽  
pp. 66-71
Author(s):  
Sultan Abdulwadou ◽  
Ali Twyla Almutairi ◽  
Fahad H. Alhazmi ◽  
Abdulaziz A. Qurashi ◽  
Abdulrahman Saleh Alha ◽  
...  
Keyword(s):  
Blood Flow ◽  
Comparative Study ◽  
Flow Rate ◽  
Blood Flow Rate ◽  
Arteriovenous Fistulas

Long-term effect of tobacco on resting whole mouth salivary flow rate and pH: An institutional based comparative study

2013 ◽  
Vol 2 (3) ◽  
pp. 296 ◽  
Author(s):  
Kunal Sah ◽  
Neeraj Grover ◽  
Sunira Chandra ◽  
RanaRandeep Singh ◽  
Alpana Kanwar
Keyword(s):  
Comparative Study ◽  
Flow Rate ◽  
Salivary Flow ◽  
Term Effect ◽  
Salivary Flow Rate ◽  
Long Term Effect
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