scholarly journals Impulsive Motion in a Cylindrical Fluid-Filled Tube Terminated by a Converging Section

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Jean-Christophe Veilleux ◽  
Joseph E. Shepherd
Keyword(s):  
Free Surface ◽  
Internal Pressure ◽  
Model System ◽  
Complex Interaction ◽  
Normal Operation ◽  
Pressure Waves ◽  
Metal Tube ◽  
Impulsive Motion ◽  
Injection Mechanism ◽  
Auto Injector

The syringe in a subcutaneous auto-injector may be subjected to internal pressure transients due to the normal operation of the injection mechanism. These transients are similar to transients in fluid-filled pipelines observed during water hammer events. In this paper, the effect of an air gap in the syringe and a converging section is studied experimentally and numerically in a model system which consists of a fluid-filled metal tube that is impulsively loaded with a projectile to simulate the action of the auto-injector mechanism operation. The air between the buffer and the water results in a complex interaction between the projectile and the buffer. Also, there are tension waves inside the tube due to the presence of a free surface and the motion of the buffer, and this causes distributed cavitation which, in turn, gives rise to steepening of the pressure waves. The converging section can amplify the pressure waves if the wave front is sharp, and it can enhance the collapse of bubbles. Pressures as high as 50 MPa have been measured at the apex of the cone with impact velocities of 5.5 m/s.

Impulsively-Generated Pressure Transients and Strains in a Cylindrical Fluid-Filled Tube Terminated by a Converging Section

2017 ◽  
Author(s):  
Jean-Christophe Veilleux ◽  
Joseph E. Shepherd
Keyword(s):  
Free Surface ◽  
Internal Pressure ◽  
Wave Front ◽  
Model System ◽  
Complex Interaction ◽  
Normal Operation ◽  
Pressure Waves ◽  
Metal Tube ◽  
Pressure Transients ◽  
Injection Mechanism

The syringe in a subcutaneous autoinjector may be subjected to internal pressure transients due to the normal operation of the injection mechanism. These transients are similar to transients in fluid-filled pipelines observed during water hammer events. In this paper, the effect of an air gap in the syringe and a converging section are studied experimentally and numerically in a model system which consists of a fluid-filled metal tube that is impulsively loaded with a projectile to simulate the action of the autoinjector mechanism operation. The air between the buffer and the water results in a complex interaction between the projectile and the buffer. Also, there are tension waves inside the tube due to the presence of a free surface, and this causes distributed cavitation which, in turn, gives rise to steepening of the pressure waves. The converging section can amplify the pressure waves if the wave front is sharp. Pressures as high as 50 MPa have been measured at the apex of the cone with impact velocities of 5.5 m/s.

Stability Analysis of Hydropower Stations With Complex Flow Patterns in the Tailrace Tunnel

2013 ◽  
Author(s):  
Jianxu Zhou ◽  
Fulin Cai ◽  
Ming Hu
Keyword(s):  
Free Surface ◽  
Stability Analysis ◽  
Flow Patterns ◽  
Normal Operation ◽  
Complex Flow ◽  
Diversion Tunnel ◽  
Implicit Model ◽  
Special Cases ◽  
Tailrace Tunnel ◽  
Hydropower Stations

For some special tailrace tunnels in the hydropower stations, including the changing top-altitude tailrace tunnel and the tailrace tunnel with downstream reused flat-ceiling diversion tunnel, during normal operation and hydraulic transients, the flow patterns inside are relatively complex mainly including the free-surface pressurized flow and partial free flow if the tail water level is lower than the top elevation of tunnel’s outlet. These complex flow patterns have obvious effect on system’s stability, and can not be simulated accurately by the traditional models. Therefore, a characteristic implicit model is introduced to simulate these complex flow patterns for further stability analysis. In some special cases, the characteristic implicit model also fails to completely simulate the mixed free-surface pressurized flow in the flat-ceiling tailrace tunnel. A new method is presented based on both experimental research and numerical simulation, and then, system’s stability is analyzed by compared with traditional ordinary boundary condition. The results indicate that, with different simulation models for the complex water flow in the tailrace tunnel, system’s dynamic characteristic can be actually revealed with the consideration of the effect of complex flow patterns in the tailrace tunnel on system’s stability and regulation performance.

scholarly journals Internal Pressure Waves and Troposphere Dynamics

1966 ◽  
Vol 39 (6) ◽  
pp. 1261-1261
Author(s):  
Jessie M. Young ◽  
Howard S. Bowman
Keyword(s):  
Internal Pressure ◽  
Pressure Waves

Instability of thermocapillary–buoyancy convection in shallow layers. Part 2. Suppression of hydrothermal waves

1998 ◽  
Vol 359 ◽  
pp. 165-180 ◽  
Author(s):  
S. BENZ ◽  
P. HINTZ ◽  
R. J. RILEY ◽  
G. P. NEITZEL
Keyword(s):  
Free Surface ◽  
Crystal Growth ◽  
Growth Process ◽  
Thermocapillary Convection ◽  
Model System ◽  
Wave Instability ◽  
Float Zone ◽  
Crystal Growth Process ◽  
Hydrothermal Wave ◽  
Buoyancy Convection

Hydrothermal-wave instabilities in thermocapillary convection are known to produce undesirable effects when they occur during the float-zone crystal-growth process, and perhaps in other situations. Suppression of the hydrothermal-wave instability produced in the model system of Part 1 (Riley & Neitzel 1998) is demonstrated through the sensing of free-surface temperature perturbations and the periodic addition of heat at the free surface along lines parallel to the crests of the hydrothermal waves.

Free-surface flow due to impulsive motion of a submerged circular cylinder

1995 ◽  
Vol 286 ◽  
pp. 67-101 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Circular Cylinder ◽  
Hydrodynamic Force ◽  
Free Surface Flow ◽  
Small Time ◽  
Surface Flow ◽  
Constant Acceleration ◽  
Impulsive Motion ◽  
Gravitational Effects ◽  
Bipolar Coordinates

The impulsively starting motion of a circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The series expansion is taken as far as necessary to include the leading gravitational effects for two cases: constant velocity and constant acceleration, both commencing from rest. The hydrodynamic force on the cylinder and the surface elevation are calculated and expressed in terms of bipolar coordinates. Comparisons are also made with earlier theoretical and experimental work. The theory is valid for arbitrary value of submergence depth to cylinder radius.

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