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.

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.

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 Transient Excitation of an Elastic Half Space by a Point Load Traveling on the Surface

1969 ◽  
Vol 36 (3) ◽  
pp. 505-515 ◽  
Author(s):  
D. C. Gakenheimer ◽  
J. Miklowitz
Keyword(s):  
Exact Solution ◽  
Free Surface ◽  
Steady State ◽  
Wave Front ◽  
Half Space ◽  
Displacement Field ◽  
Elastic Half Space ◽  
Point Load ◽  
Limit Case ◽  
Transient Waves

The propagation of transient waves in a homogeneous, isotropic, linearly elastic half space excited by a traveling normal point load is investigated. The load is suddenly applied and then it moves rectilinearly at a constant speed along the free surface. The displacements are derived for the interior of the half space and for all load speeds. Wave-front expansions are obtained from the exact solution, in addition to results pertaining to the steady-state displacement field. The limit case of zero load speed is considered, yielding new results for Lamb’s point load problem.

scholarly journals Experimental Assessment on Air Clearance of Multiple Valve Unit Considering Switching Impulse and DC Superimposed Switching Impulse

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2958
Author(s):  
Jae-Hong Koo ◽  
Jae-Kyu Seong ◽  
Ryul Hwang ◽  
Bang-Wook Lee
Keyword(s):  
Wave Front ◽  
High Voltage ◽  
Normal Operation ◽  
Reliable Operation ◽  
Peak Voltage ◽  
Experimental Assessment ◽  
Dielectric Characteristics ◽  
Valve Unit ◽  
Hvdc Transmission ◽  
Flashover Voltage

Multiple valve unit (MVU), which converts AC to DC and DC to AC, is one of the key elements of high voltage DC (HVDC) transmission. Therefore, the insulation design of MVU against overvoltage should be considered for the stable and reliable operation of HVDC transmission system. Especially, the air clearance of MVU should be calculated based the switching impulse, since it is fatal to MVU in terms of electrical insulation. However, the previous studies were limited to wave front, and the air clearance of the switching impulse is specified only for an ultra-high voltage (UHV) above 750 kV. As a result, it is difficult to calculate the air clearance of MVU which must endure for a switching impulse under 750 kV. In addition, when the switching impulse introduced while the MVU is in normal operation, it is superimposed to DC and creates the most severe situation, but the studies on such subjects are also insufficient. Therefore, as a fundamental step to calculate the air clearance of MVU, the dielectric characteristics of switching impulse and DC superimposed switching impulse in air have been investigated. The experiments on switching impulse showed that the critical flashover voltage was varied according to the curvature of electrode in the gap distance, up to eight times of the electrode radius. However, beyond that gap distance, the critical flashover voltage became similar, regardless of the radius of electrodes. In case of the superimposed experiment, it was performed according to DC pre-stress level and the polarities of switching impulse. The results were most severe when the positive switching impulse was superimposed on the positive DC, and the peak voltage at which flashover occurs was independent of DC pre-stress.

A Herschel–Bulkley model for mud flow down a slope

1998 ◽  
Vol 374 ◽  
pp. 305-333 ◽  
Author(s):  
XIN HUANG ◽  
MARCELO H. GARCÍA
Keyword(s):  
Free Surface ◽  
Wave Front ◽  
Nonlinear Partial Differential Equations ◽  
Outer Region ◽  
Surface Profile ◽  
Shear Thinning ◽  
Experimental Results ◽  
Runout Distance ◽  
The Impact ◽  
Mud Flow

The spreading and sediment deposit of a two-dimensional, unsteady, laminar mud flow from a constant-volume source on a relatively steep slope is studied theoretically and experimentally. The mud under consideration has the rheological properties of a Herschel–Bulkley fluid. The flow is of low-Reynolds-number type and has a well-formed wave front moving a substantial distance downslope. Due to the nonlinear rheological characteristics, a set of nonlinear partial differential equations is needed for this transient problem. Depth-integrated continuity and momentum equations are derived by applying von Kármán's momentum integral method. A matched-asymptotic perturbation method is implemented analytically to get asymptotic solutions for both the outer region away from, and the inner region near, the wave front. The outer solution gives accurate results for spreading characteristics, while the inner solution, which is shown to agree well with experimental results of Liu & Mei (1989) for a Bingham fluid, predicts fairly well the free-surface profile near the wave front. A composite solution uniformly valid over the whole spreading length is then achieved through a matching of the inner and outer solutions in an overlapping region. The range of accuracy of the solution and the size of the inner and overlapping regions are quantified by physical scaling analyses. Rheological and dynamic measurements are obtained through laboratory experiments. Theoretical predictions are compared with experimental results, showing reasonable agreement. The impact of shear thinning on the runout characteristics, free-surface profiles and final deposit of the mud flow is examined. A mud flow with shear thinning spreads beyond the runout distance estimated by a Bingham model, and has a long and thin deposit.

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.

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