Interfacial dynamics of stationary gas bubbles in flows in inclined tubes

1999 ◽  
Vol 398 ◽  
pp. 225-244 ◽  
Author(s):  
DANIEL P. CAVANAGH ◽  
DAVID M. ECKMANN
Keyword(s):  
Pressure Gradient ◽  
Bubble Size ◽  
Contact Angle Hysteresis ◽  
Gas Bubbles ◽  
Solid Material ◽  
Contact Forces ◽  
Tube Material ◽  
Experimental Conditions ◽  
Axial Pressure Gradient ◽  
Inclination Angles

We have experimentally examined the effects of bubble size (0.4 [les ] λ [les ] 2.0), inclination angle (0° [les ] α [les ] 90°), and tube material on suspended gas bubbles in flows in tubes for a range of Weber (0 [les ] We [les ] 3.6), Reynolds (0 [les ] Re [les ] 1200), and Froude (0 [les ] Frα [les ] 1) numbers. Flow rates and associated pressure differences which allow the suspension of bubbles in glass and acrylic tubes are measured. Due to contact angle hysteresis, bubbles which dry the tube wall (i.e. form a gas–solid interface) may remain suspended over a range of flows while non-drying bubbles remain stationary for a single flow rate depending on experimental conditions. Stationary bubbles increase the axial pressure gradient with larger bubbles and steeper inclination angles leading to the greatest increase in the pressure gradient. Both the suspension flow range and pressure difference modifications are strongly dependent upon gas/liquid/solid material interactions. Stronger contact forces, i.e. smaller spreading coefficients, cause dried bubbles in acrylic tubes to remain stationary over a wider range of suspension flows than bubbles in glass tubes. Bubble deformation is governed by the interaction of interfacial, contact, and flow-derived forces. This investigation reveals the importance of bubble size, tube inclination, and tube material on gas bubble suspension.

Influence of bubble size and blood perfusion on absorption of gas bubbles in tissues

1969 ◽  
Vol 7 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Hugh D. Van Liew ◽  
Michael P. Hlastala
Keyword(s):  
Bubble Size ◽  
Gas Bubbles ◽  
Blood Perfusion

Study on the High Shear Degassing Process with Water Simulation

2015 ◽  
Vol 1120-1121 ◽  
pp. 1214-1219
Author(s):  
Yi Yao Kang ◽  
Yue Lin ◽  
Xu Dong Liu ◽  
Chao Sun ◽  
Sen Sen Yuan ◽  
...  
Keyword(s):  
Bubble Size ◽  
Aluminium Alloys ◽  
High Efficiency ◽  
Rotation Speed ◽  
Gas Bubbles ◽  
Inert Gas ◽  
High Shear ◽  
Gas Porosity ◽  
Water Simulation ◽  
Proper Rotation

Hydrogen as the main cause of the gas porosity in aluminium alloys should be removed before casting. The degassing process with intensive melt shearing shows a high efficiency. In the present work, the water simulation was used to study the high shear degassing process and the effect of rotation speed on the size and distribution of inert gas bubbles. The results show that with the increase of rotation speed, the bubble size decreases and the affected region becomes larger. The proper rotation speed of the rotor for the rotor-stator high shear degassing process is 5000-6000 RPM.

Multidigit Control of Contact Forces During Transport of Handheld Objects

2007 ◽  
Vol 98 (2) ◽  
pp. 851-860 ◽  
Author(s):  
Sara A. Winges ◽  
John F. Soechting ◽  
Martha Flanders
Keyword(s):  
Contact Force ◽  
Muscle Activity ◽  
Center Of Mass ◽  
Contact Forces ◽  
Load Force ◽  
Emg Activity ◽  
Experimental Conditions ◽  
Contact Plane ◽  
Grasping Forces ◽  
Grasp Stability

When an object is lifted vertically, the normal force increases and decreases in tandem with tangential (load) force to safely avoid slips. For horizontal object transport, horizontal forces at the contact surfaces can be decomposed into manipulation forces (producing acceleration/deceleration) and grasping forces. Although the grasping forces must satisfy equilibrium constraints, it is not clear what determines their modulation across time, nor the extent to which they result from active muscle contraction or mechanical interactions of the digits with the moving object. Grasping force was found to increase in an experimental condition where the center of mass was below the contact plane, compared with when it was in the contact plane. This increase may be aimed at stabilizing object orientation during translation. In another experimental condition, more complex moments were introduced by allowing the low center of mass to swing around a pivot point. Electromyographic (EMG) activity recorded from several intrinsic and extrinsic hand muscles failed to reveal active feedback regulation of contact force in this situation. Instead, in all experimental conditions, EMG data revealed a strategy of feedforward stiffness modulation. Multiple regression analysis revealed that muscle activity at remote digits (e.g., the index and ring fingers) was highly correlated with the contact force measured at another digit (e.g., the thumb). The data suggest that to maintain grasp stability during horizontal translation, predictable as well as somewhat unpredictable inertial forces are compensated for by controlling the stiffness of the hand through cocontraction and modulation of hand muscle activity.

First-order approximation for the pressure-flow relationship of spontaneously contracting lymphangions

2008 ◽  
Vol 294 (5) ◽  
pp. H2144-H2149 ◽  
Author(s):  
Christopher M. Quick ◽  
Arun M. Venugopal ◽  
Ranjeet M. Dongaonkar ◽  
Glen A. Laine ◽  
Randolph H. Stewart
Keyword(s):  
Pressure Gradient ◽  
Order Approximation ◽  
Empirical Relationship ◽  
Lymph Flow ◽  
Pressure Flow ◽  
First Order ◽  
Axial Pressure Gradient ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
First Order Approximation

To return lymph to the great veins of the neck, it must be actively pumped against a pressure gradient. Mean lymph flow in a portion of a lymphatic network has been characterized by an empirical relationship (Pin − Pout = −Pp + RLQL), where Pin − Pout is the axial pressure gradient and QL is mean lymph flow. RL and Pp are empirical parameters characterizing the effective lymphatic resistance and pump pressure, respectively. The relation of these global empirical parameters to the properties of lymphangions, the segments of a lymphatic vessel bounded by valves, has been problematic. Lymphangions have a structure like blood vessels but cyclically contract like cardiac ventricles; they are characterized by a contraction frequency ( f) and the slopes of the end-diastolic pressure-volume relationship [minimum value of resulting elastance ( Emin)] and end-systolic pressure-volume relationship [maximum value of resulting elastance ( Emax)]. Poiseuille's law provides a first-order approximation relating the pressure-flow relationship to the fundamental properties of a blood vessel. No analogous formula exists for a pumping lymphangion. We therefore derived an algebraic formula predicting lymphangion flow from fundamental physical principles and known lymphangion properties. Quantitative analysis revealed that lymph inertia and resistance to lymph flow are negligible and that lymphangions act like a series of interconnected ventricles. For a single lymphangion, Pp = Pin ( Emax − Emin)/ Emin and RL = Emax/ f. The formula was tested against a validated, realistic mathematical model of a lymphangion and found to be accurate. Predicted flows were within the range of flows measured in vitro. The present work therefore provides a general solution that makes it possible to relate fundamental lymphangion properties to lymphatic system function.

Slip Flow with Axial Pressure Gradient

1962 ◽  
Vol 29 (11) ◽  
pp. 1393-1394 ◽  
Author(s):  
A. Pozzi ◽  
P. Renno
Keyword(s):  
Pressure Gradient ◽  
Slip Flow ◽  
Axial Pressure ◽  
Axial Pressure Gradient

An Experimental Study of Three-Dimensional Turbulent Boundary Layer and Turbulence Characteristics Inside a Turbomachinery Rotor Passage

1978 ◽  
Vol 100 (4) ◽  
pp. 676-687 ◽  
Author(s):  
A. K. Anand ◽  
B. Lakshminarayana
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Stream Line ◽  
Shear Stresses ◽  
Axial Pressure ◽  
Mean Velocity ◽  
Large Defect ◽  
Axial Pressure Gradient

Three-dimensional boundary layer and turbulence measurements of flow inside a rotating helical channel of a turbomachinery rotor are described. The rotor is a four-bladed axial flow inducer operated at large axial pressure gradient. The mean velocity profiles, turbulence intensities and shear stresses, and limiting stream-line angles are measured at various radial and chordwise locations, using rotating triaxial hot-wire and conventional probes. The radial flows in the rotor channel are found to be higher compared to those at zero or small axial pressure gradient. The radial component of turbulence intensity is found to be higher than the streamwise component due to the effect of rotation. Flow near the annulus wall is found to be highly complex due to the interaction of the blade boundary layers and the annulus wall resulting in an appreciable radial inward flow, and a large defect in the mainstream velocity. Increased level of turbulence intensity and shear stresses near the midpassage are also observed near this radial location.

Sign in / Sign up

Export Citation Format

Share Document