Determining Pressure Recovery Time for Non-Steady-State Spherical Flow of Viscoplastic Oil in a Homogeneous Formation

2019 ◽  
pp. 58-70
Author(s):  
Dzh.N. Aslanov ◽  
S.D. Mustafaev ◽  
A.Kh.S.A. Akhmedov ◽  
Z.S. Нuseynli
Keyword(s):  
Steady State ◽  
Recovery Time ◽  
Transient Flow ◽  
Pressure Recovery ◽  
External Boundary ◽  
Distribution Laws ◽  
Function Of Two Variables ◽  
Two Stages ◽  
Homogeneous Formation ◽  
State Pressure

The paper solves a non-steady-state hydrodynamic problem concerning a spherical flow of viscoplastic oil in a homogeneous formation. Pressure recovery in the formation occurs in two stages after well operation stops instantaneously. At the first stage the perturbation region appears at the well, expands and eventually reaches the external boundary, and keeps expanding during the second stage until steady-state pressure is reached in every formation region. We solved the differential equations for specific initial and boundary conditions, assuming pressure distribution laws over the formation and respective integral relations, and derived equations to determine pressure recovery time. At each stage pressure in the formation is a function of two variables, that is, a spatial coordinate and time. We assume that the first variable equals zero. We derived an expression for recovering the bottomhole pressure in the wellbore. We used the transient flow method to study the wells, plotted the pressure recovery curve (PRC) and determined formation parameters.

scholarly journals Pressure Analysis in the Draft Tube of a Pump-Turbine under Steady and Transient Conditions

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4732
Author(s):  
Jing Yang ◽  
Yue Lv ◽  
Dianhai Liu ◽  
Zhengwei Wang
Keyword(s):  
Steady State ◽  
Pressure Pulsation ◽  
Transient Flow ◽  
Draft Tube ◽  
Simulation Method ◽  
Wall Pressure ◽  
Pump Turbine ◽  
Steady State Condition ◽  
Transient Conditions ◽  
Pumped Storage

Pumped-storage power stations play a regulatory role in the power grid through frequent transition processes. The pressure pulsation in the draft tube of the pump-turbine under transient processes is important for safe operation, which is more intense than that in the steady-state condition. However, there is no effective method to obtain the exact pressure in the draft tube in the transient flow field. In this paper, the pressure in the draft tube of a pump-turbine under steady-state and transient conditions are studied by means of CFD. The reliability of the simulation method is verified by comparing the real pressure pulsation data with the test results. Due to the distribution of the pressure pulsation in the draft tube being complex and uneven, the location of the pressure monitoring points directly affects the accurate judgement of cavitation. Eight monitoring surfaces were set in the straight cone of the draft tube and nine monitoring points were set on each monitoring surface to analyze the pressure differences on the wall and inside the center of the draft tube. The relationships between the pressure pulsation value inside the center of the draft tube and on the wall are studied. The “critical” wall pressure pulsation value when cavitation occurs is obtained. This study provides references for judging cavitation occurrences by using the wall pressure pulsation value in practical engineering.

Evaluation of Adrenergic Function

2016 ◽  
pp. 635-642
Author(s):  
Phillip A. Low
Keyword(s):  
Blood Pressure ◽  
Recovery Time ◽  
Baroreflex Sensitivity ◽  
Autonomic Function ◽  
Pressure Change ◽  
Pressure Recovery ◽  
Blood Pressure Change ◽  
Noninvasive Evaluation ◽  
Peripheral Neuropathies ◽  
Heart Period

Peripheral adrenergic function is important in the maintenance of postural normotension. It may be impaired in peripheral neuropathies, and this may be manifested as alterations in acral temperature, color, or sweating. Simple, accurate, and reproducible tests of peripheral adrenergic function are now routinely used in clinical autonomic laboratories. For noninvasive evaluation of autonomic function, tests of peripheral adrenergic function can be used to separately evaluate the vagal and adrenergic components of baroreflex sensitivity. The vagal component is derived from the heart period response to blood pressure change and the adrenergic component by the blood pressure recovery time in response to the preceding fall in blood pressure, induced by the Valsalva maneuver.This chapter describes methods used to determine peripheral adrenergic function and their value and shortcomings.

Enhancement of air entrainment in ejector-diffuser using plate guidance at slots to reduce infrared emission

2020 ◽  
pp. 095441002097193
Author(s):  
L Singh ◽  
SN Singh ◽  
SS Sinha
Keyword(s):  
Evaluation Criteria ◽  
Thermal Characteristics ◽  
Engine Performance ◽  
Air Entrainment ◽  
Infrared Emission ◽  
Pressure Recovery ◽  
Mass Entrainment ◽  
Infrared Emissions ◽  
Hybrid Plate ◽  
Two Stages

Ejector-diffuser reduces infrared emissions and are installed in combat aircraft to counter the threat of heat-seeking missile. The specific role of an ejector-diffuser is to reduce the heat emissions without substantially affecting the engine performance. The present study investigates a new design of ejector-diffuser wherein straight-plates and hybrid-straight-plates are installed at each slot for improving the ejector-diffuser performance. The evaluation criteria of an ejector-diffuser is specified in terms of air entrainment through the slots, thermal characteristics, and recovery of pressure. This work is carried out in two stages. In the first part, the orientation of the plate at the slot is investigated by varying the angle between the slot and diffuser axis over the range [Formula: see text]. The overall mass entrainment increases from 2.88 to 4.04 with the increase in plate angle. Further, the thermal characteristics also improves with increase in plate angle, but the pressure recovery decreases from 0.701 to 0.155. In the second part, the straight-plate at the slots are partially/fully replaced by hybrid-plate. Two configurations are proposed by first introducing a hybrid-plate at the first slot and straight-plate at the other slots, and subsequently by introducing hybrid-plate at all the slots. It is found that the pressure recovery in both the cases shows a significant improvement compared to the straight-plate case, the value being close to 0.75 for both the cases. However, the cumulative mass entrained by the first configuration of the hybrid-plate is better than the second configuration and is similar to the straight-plate guidance of 28°. Thus, the current study proposes an IRSS device having the hybrid-plate at the first slot and the straight-plate guidance at the remaining slots which reduces infrared emissions with minimum loading on the engine.

Unsteady natural convection in a cavity with internal heating and cooling

1984 ◽  
Vol 140 ◽  
pp. 135-151 ◽  
Author(s):  
John C. Patterson
Keyword(s):  
Steady State ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Transient Flow ◽  
Scaling Analysis ◽  
Steady State Flow ◽  
Internal Heating ◽  
Sources And Sinks ◽  
Heating And Cooling ◽  
Unsteady Natural Convection

The problem of transient natural convection in a cavity of aspect ratio A < 1 driven by internal buoyancy sources and sinks distributed linearly in the horizontal and uniformly in the vertical is considered. Scaling analysis is used to show that a number of possible transient flow regions are possible, collapsing ultimately onto one of conductive, transitional, or convective steady-state flow regimes. A number of numerical solutions are obtained, and their relationships to the scaling analysis are discussed.

Investigating the dynamics of gas hydrates in a gas dominant flow loop

2011 ◽  
Vol 51 (2) ◽  
pp. 734
Author(s):  
Yutaek Seo ◽  
Mauricio Di Lorenzo ◽  
Gerardo Sanchez-Soto
Keyword(s):  
Steady State ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Gas Flow ◽  
Transient Flow ◽  
Hydrate Formation ◽  
Hydrodynamic Condition ◽  
Gas Pipelines ◽  
Flow Loop ◽  
Offshore Pipelines

Offshore pipelines transporting hydrocarbon fluids have to be operated with great care to avoid problems related to flow assurance. Of these possible problems, gas hydrate is dreaded as it poses the greatest risk of plugging offshore pipelines and other production systems. As the search for oil and natural gas goes into deeper and colder offshore fields, the strategies for gas hydrate mitigation are evolving to the management of hydrate risks rather than costly complete prevention. CSIRO has been developing technologies that will facilitate the production of Australian deepwater gas reserves. One of its research programs is a recently commissioned investigation into the dynamic behaviour of gas hydrates in gas pipelines using a pilot-scale 1 inch and 40 m long flow loop. This work will provide experimental results conducted in the flow loop, designed to investigate the hydrate formation characteristics in steady state and transient flow. For a given hydrodynamic condition in steady state flow, the formation and subsequent agglomeration and deposition of hydrate particles appear to occur more severely as the subcooling condition is increasing. Transient flow during a shut-in and restart operation represents a more complex scenario for hydrate formation. Although hydrates develop as a thin layer on the surface of water during the shut-in period, most of the water is quickly converted to hydrate upon restart, forming hydrate laden slurry that is transported through the pipeline by the gas flow. These results could provide valuable insights into the present operation of offshore gas pipelines.

scholarly journals On the Measurement and Modeling of High-Pressure Flows in Poppet Valves Under Steady-State and Transient Conditions

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Stephan Mohr ◽  
Henry Clarke ◽  
Colin P. Garner ◽  
Neville Rebelo ◽  
Andrew M. Williams ◽  
...  
Keyword(s):  
Steady State ◽  
Transient Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Valve Lift ◽  
Transient Pressure ◽  
Dynamic Flow ◽  
Steady State Flow ◽  
State Flow ◽  
Piston Cylinder

Flow coefficients of intake valves and port combinations were determined experimentally for a compressed nitrogen engine under steady-state and dynamic flow conditions for inlet pressures up to 3.2 MPa. Variable valve timing was combined with an indexed parked piston cylinder unit for testing valve flows at different cylinder volumes while maintaining realistic in-cylinder transient pressure profiles by simply using a fixed area outlet orifice. A one-dimensional modeling approach describing three-dimensional valve flow characteristics has been developed by the use of variable flow coefficients that take into account the propagation of flow jets and their boundaries as a function of downstream/upstream pressure ratios. The results obtained for the dynamic flow cases were compared with steady-state results for the cylinder to inlet port pressure ratios ranges from 0.18 to 0.83. The deviation of flow coefficients for both cases is discussed using pulsatile flow theory. The key findings include the followings: (1) for a given valve lift, the steady-state flow coefficients fall by up to 21% with increasing cylinder/manifold pressure ratios within the measured range given above and (2) transient flow coefficients deviated from those measured for the steady-state flow as the valve lift increases beyond a critical value of approximately 0.5 mm. The deviation can be due to the insufficient time of the development of steady-state boundary layers, which can be quantified by the instantaneous Womersley number defined by using the transient hydraulic diameter. We show that it is possible to predict deviations of the transient valve flow from the steady-state measurements alone.

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