Energy Head Dissipation and Flow Pressures in Vortex Drop Shafts

Vortex drop shafts are special manholes designed to link sewer channels at different elevations. Significant energy head dissipation occurs across these structures, mainly due to vertical shaft wall friction and turbulence in the dissipation chamber at the toe of the shaft. In the present study two aspects, sometimes neglected in the standard hydraulic design, are considered, namely the energy head dissipation efficiency and the maximum pressure force in the dissipation chamber. Different physical model results derived from the pertinent literature are analyzed. It is demonstrated that the energy head dissipation efficiency is mostly related to the flow impact and turbulence occurring in the chamber. Similarly to the drop manholes, a relation derived from a simple theoretical model is proposed for the estimation of the energy head loss coefficient. The analysis of the pressures measured on the chamber bottom allows to provide a useful equation to estimate the pressure peak in the chamber as a function of the approach flow energy head.

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Charts for water hammer in pipelines resulting from valve closure from full opening only

Canadian Journal of Civil Engineering ◽

10.1139/l85-027 ◽

1985 ◽

Vol 12 (2) ◽

pp. 241-264 ◽

Cited By ~ 10

Author(s):

Bryan W. Karney ◽

Eugen Ruus

Keyword(s):

Good Accuracy ◽

Pipe Wall ◽

Pressure Head ◽

Wall Friction ◽

Maximum Pressure ◽

Valve Closure ◽

Closure Time ◽

Basic Parameters ◽

Valve Opening ◽

Open Position

Maximum pressure head rises, which result from total closure of the valve from an initially fully open position, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Uniform, equal-percentage, optimum, and parabolic closure arrangements are analysed. Basic parameters such as pipeline constant, relative closure time, and pipe wall friction are considered with closures from full valve opening only. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe with good accuracy for the closure arrangements considered. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the parabolic closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Uniform closure produces pressure head rise that usually lies between those produced by the parabolic and the equal-percentage closure arrangements, except for the range of low pressure head rise combined with low or zero friction, where the rise due to uniform closure approaches that produced by optimum closure.

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Investigation of the flow energy dissipation law in a centrifugal impeller in pump mode

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/09576509211034976 ◽

2021 ◽

pp. 095765092110349

Author(s):

Ran Tao ◽

Puxi Li ◽

Zhifeng Yao ◽

Ruofu Xiao

Keyword(s):

Energy Dissipation ◽

Flow Rate ◽

Performance Estimation ◽

Vortical Flow ◽

Wall Friction ◽

Negative Slope ◽

Centrifugal Impeller ◽

Pump Mode ◽

Flow Energy ◽

Flow Interaction

Centrifugal impeller is usually designed for water pumping. Fluid get energy from impeller but also lose energy when passing through it. To improve the efficiency and have a better operation stability, it is necessary to understand the flow energy dissipation in centrifugal impeller in pump mode. In this case, a thermodynamic analysis is conducted on a model centrifugal pump unit based on computational fluid dynamics (CFD) simulation. Typical performance curve is found with a positive-slope efficiency curve and a negative-slope head curve. With the decreasing of flow rate, both the impeller head and the flow energy dissipation (FED) will rise up. The FED is found related to the flow regime. The complex undesirable flow pattern induces high FED under off-design conditions especially at very small partial-load. Based on the visualization, FED is found with two main sources including the wall friction and the flow interaction. At over-load and design-load, the wall friction induced FED is dominant. With the decreasing of flow rate, flow interaction induced FED becomes dominant. The typical strong FED sites are found related to the striking, separation, merging and interaction of both smooth flow and vortical flow. The FED analysis will correlate the pump performance estimation and guide the design.

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Frequency-dependent variation in the two-dimensional beam pattern of an echolocating dolphin

Biology Letters ◽

10.1098/rsbl.2011.0396 ◽

2011 ◽

Vol 7 (6) ◽

pp. 836-839 ◽

Cited By ~ 19

Author(s):

Josefin Starkhammar ◽

Patrick W. Moore ◽

Lois Talmadge ◽

Dorian S. Houser

Keyword(s):

Sound Propagation ◽

Sound Field ◽

Spatial Separation ◽

Acoustic Properties ◽

Maximum Pressure ◽

Frequency Bandwidth ◽

Sound Sources ◽

Pressure Peak ◽

Prey Localization ◽

Dominant Peak

Recent recordings of dolphin echolocation using a dense array of hydrophones suggest that the echolocation beam is dynamic and can at times consist of a single dominant peak, while at other times it consists of forward projected primary and secondary peaks with similar energy, partially overlapping in space and frequency bandwidth. The spatial separation of the peaks provides an area in front of the dolphin, where the spectral magnitude slopes drop off quickly for certain frequency bands. This region is potentially used to optimize prey localization by directing the maximum pressure slope of the echolocation beam at the target, rather than the maximum pressure peak. The dolphin was able to steer the beam horizontally to a greater extent than previously described. The complex and dynamic sound field generated by the echolocating dolphin may be due to the use of two sets of phonic lips as sound sources, or an unknown complexity in the sound propagation paths or acoustic properties of the forehead tissues of the dolphin.

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Experimental investigation of the aerodynamics of a freight train passing through a tunnel using a moving model

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409718811736 ◽

2018 ◽

Vol 233 (8) ◽

pp. 857-868 ◽

Cited By ~ 1

Author(s):

P Iliadis ◽

D Soper ◽

C Baker ◽

H Hemida

Keyword(s):

Visual Information ◽

Compression Wave ◽

Separation Bubble ◽

Technical Specification ◽

Maximum Pressure ◽

Tunnel Wall ◽

Piston Effect ◽

Freight Train ◽

Pressure Peak ◽

Tunnel Entrance

The objective of this study was to investigate the aerodynamic effects of a freight train passing through a tunnel. The nose entry generates a complex pattern of reflective pressure waves (piston effect) which can lead to intense aerodynamic forces. Previous research on the topic has focused on passenger trains because of higher speeds. The experiments of this study use a 1/25th scaled moving model at the TRAIN Rig at a speed of 33.5 m/s with a blockage ratio of 0.202. The monitored pressure along the tunnel wall can increase up to almost 1000 Pa because of the initial compression wave, while it drops when an expansion wave or the tail passes by. The maximum pressure is observed at the train nose due to air stagnation (1500 Pa) where the flow is steady, while the roof and sides experience negative pressures due to unsteady flow separation. The effect of loading configuration is significant as partially loaded trains can create a second pressure peak on the tunnel walls (after the initial compression wave) and affect the flow at the tunnel entrance wall. Under the current testing conditions, the results indicated compliance with the requirements of the Technical Specification for Interoperability and a constant pressure gradient of the initial compression wave which is in contrast with the passenger train's two-part gradient. Further work on the topic could provide visual information about the exiting jet towards the portal and the separation bubble around the train.

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Charts for water hammer in pipelines resulting from valve closure

Canadian Journal of Civil Engineering ◽

10.1139/l80-032 ◽

1980 ◽

Vol 7 (2) ◽

pp. 243-255 ◽

Cited By ~ 2

Author(s):

Eugen Ruus ◽

Farouk A. El-Fitiany

Keyword(s):

Pipe Wall ◽

Pressure Head ◽

Water Hammer ◽

Wall Friction ◽

Maximum Pressure ◽

Valve Closure ◽

Closure Time ◽

Basic Parameters

Maximum pressure head rises, which result from valve closure according to (a) uniform, (b) equal-percentage, and (c) optimum valve closure arrangements, are calculated and plotted for the valve end and for the midpoint of a simple pipeline. Basic parameters such as the pipeline constant, relative closure time, and pipe wall friction are considered for closures both from partial as well as from full valve openings. The results of this paper can be used to draw the maximum hydraulic grade line along the pipe for these closure arrangements. It is found that the equal-percentage closure arrangement yields consistently less pressure head rise than does the uniform closure arrangement. Further, the optimum closure arrangement yields consistently less head rise than the equal-percentage one. Closures from partial valve openings increase the pressure head rise considerably and must always be considered.

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On Origin of a Maximum Pressure Peak Outside of the Stagnation Point at Normal Impact of a Blunted Body on Water

AIAA/CIRA 13th International Space Planes and Hypersonics Systems and Technologies Conference ◽

10.2514/6.2005-3203 ◽

2005 ◽

Author(s):

Alexander Gonor ◽

Mikhail Gilinsky

Keyword(s):

Stagnation Point ◽

Maximum Pressure ◽

Normal Impact ◽

Pressure Peak ◽

Blunted Body

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Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

Journal of Tribology ◽

10.1115/1.2833498 ◽

1997 ◽

Vol 119 (3) ◽

pp. 375-384 ◽

Cited By ~ 77

Author(s):

Dong Zhu ◽

Xiaolan Ai

Keyword(s):

Rough Surface ◽

Rough Surfaces ◽

Three Dimensional ◽

Point Contact ◽

Elastohydrodynamic Lubrication ◽

Peak Height ◽

Machining Process ◽

Maximum Pressure ◽

Pressure Peak ◽

Surface Profiles

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

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3D HUMAN LIFTING MOTION PREDICTION WITH DIFFERENT PERFORMANCE MEASURES

International Journal of Humanoid Robotics ◽

10.1142/s0219843612500120 ◽

2012 ◽

Vol 09 (02) ◽

pp. 1250012 ◽

Cited By ~ 13

Author(s):

YUJIANG XIANG ◽

JASBIR S. ARORA ◽

KARIM ABDEL-MALEK

Keyword(s):

Performance Measures ◽

Shear Force ◽

Degrees Of Freedom ◽

Human Performance ◽

Three Dimensional ◽

Optimal Solution ◽

Performance Measure ◽

Maximum Pressure ◽

Pressure Force ◽

Digital Human

This paper presents an optimization-based method for predicting a human dynamic lifting task. The three-dimensional digital human skeletal model has 55 degrees of freedom. Lifting motion is generated by minimizing an objective function (human performance measure) subjected to basic physical and kinematical constraints. Four objective functions are investigated in the formulation: the dynamic effort, the balance criterion, the maximum shear force at spine joint and the maximum pressure force at spine joint. The simulation results show that various human performance measures predict different lifting strategies: the balance and shear force performance measures predict back-lifting motion and the dynamic effort and pressure force performance measures generate squat-lifting motion. In addition, the effects of box locations on the lifting strategies are also studied. All kinematics and kinetic data are successfully predicted for the lifting motion by using the predictive dynamics algorithm and the optimal solution was obtained in about one minute.

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