Dynamic Pressure at Flip Buckets of Chute Spillways: A Numerical Study

2021 ◽  
Author(s):  
Yasamin Aghaei ◽  
Fouad Kilanehei ◽  
Shervin Faghihirad ◽  
Mohammad Nazari-Sharabian
Keyword(s):  
Numerical Study ◽  
Dynamic Pressure

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

Numerical Investigation of an Improved Gas and Steam Turbine Seal

1996 ◽  
Vol 210 (6) ◽  
pp. 477-479 ◽  
Author(s):  
M H Gordon ◽  
U M Kelkar ◽  
M C Johnson
Keyword(s):  
High Temperature ◽  
Numerical Investigation ◽  
High Speed ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Labyrinth Seal ◽  
Optimal Shape ◽  
Steam Turbines ◽  
Brush Seal ◽  
Sealing Mechanism

A numerical study has been conducted to assess the viability of a new sealing mechanism for gas and steam turbines. This new static-to-rotating sealing mechanism is mounted on flexible legs which permit radial movement and is designed to take advantage of the hydro-dynamic pressure forces, which result from fluid leaking around the seal, to maintain an ideally small and constant clearance. Relatively simple seal geometries have been numerically tested to find an optimal shape. These results indicate that a substantial sealing improvement (between two and four times less leakage) relative to a labyrinth seal is possible. Although these results show that a brush seal is more effective than the present seal, the present seal is designed to operate in high-speed and high-temperature environments in which the brush seal would degrade.

scholarly journals A numerical study on the dynamic pressure method for CO2 storage projects

2020 ◽  
Vol 205 ◽  
pp. 13016
Author(s):  
Vincenzo Sergio Vespo ◽  
Alessandro Messori ◽  
Giorgio Volonté ◽  
Guido Musso
Keyword(s):  
Numerical Study ◽  
Dynamic Pressure ◽  
Co2 Storage ◽  
Pressure Method

Application of Shunted Piezoelectric Materials in Aeroelasticity

2016 ◽  
Vol 1135 ◽  
pp. 88-103 ◽  
Author(s):  
L.S. Leao ◽  
Maurício Vicente Donadon ◽  
A.M.G. de Lima ◽  
A.G.C. Filho
Keyword(s):  
Composite Structures ◽  
Passive Control ◽  
Numerical Study ◽  
Nonlinear Eigenvalue Problem ◽  
Piezoelectric Materials ◽  
Dynamic Pressure ◽  
Iterative Solution ◽  
Passive Element ◽  
In Series ◽  
Shunt Circuit

This paper presents a numerical study on the influence of multimodal shunt circuit parameters in the flutter velocity of a typical section under an unsteady airflow. Flutter on typical sections is a kind of self-excited oscillation which can occur due to the interaction with the airflow. In the flutter point, when the critical dynamic pressure is reached, the vibrations of the typical section become unstable and increase fast and significantly in time. As a result, it can lead the structure to failure. Thus, it becomes important to investigate the possibility of reducing the effects of flutter in order to increase the reliability of composite structures during service. In this work, the aero-electromechanical dynamic model formulation is based on the Hamilton principle. The unsteady aerodynamic forces are calculated based on the linearized thin-airfoil theory, proposed by Theodorsen. The passive element responsible for the energy dissipation is a multimodal resonant shunt circuit in series topology, attached to a piezoelectric patch. An iterative solution algorithm is proposed to solve the resultant nonlinear eigenvalue problem. The optimum shunt tuning is firstly performed using Hagood and Flotow’s propositions; then, it is used an heuristic optimization algorithm, based on Differential Evolution. The preliminary results indicate that the flutter speed can be affected by the passive control, both in its mechanical aspect as electrical.

Numerical Study Optimal Timing of the Axial Piston Pump

2011 ◽  
Author(s):  
Shusen Zhang ◽  
Noah D. Manring ◽  
Viral S. Mehta
Keyword(s):  
Numerical Study ◽  
Dynamic Pressure ◽  
Piston Pump ◽  
Optimal Timing ◽  
Axial Piston Pump ◽  
Pump Design ◽  
Inlet Port ◽  
Actual Design ◽  
Pressure Ripple ◽  
Axial Piston

In this paper, the theoretical optimal timing of the axial piston pump is first derived to confirm the analysis published by Professor Kevin Edge [1]. It is discovered that the optimal discharge port delay is different from the optimal inlet port delay. The dimensional analysis also shows that higher shaft angular velocity indicates less delay required in both discharge port and inlet port. Numerical studies show that optimal timing can reduce the dynamic pressure ripple greatly, but since it does not affect the kinematic component, it will not eliminate the entire pressure ripple. The optimal timing could also induce an increase in efficiency where the baseline pump design has cross-porting. However, there is certain tradeoff between pressure ripple reduction and efficiency consideration. Actual design consideration to affect independent timing of the portplate is not studied in this work.

Experimental and Numerical Study of Flow and Dynamics on LSB at 34 MW Steam Turbine

2020 ◽  
Author(s):  
Michal Hoznedl ◽  
Kamil Sedlák ◽  
Lukáš Mrózek ◽  
Tereza Dadáková ◽  
Zdeněk Kubín ◽  
...  
Keyword(s):  
Experimental Data ◽  
Steam Turbine ◽  
Static Pressure ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Vibration Monitoring ◽  
Exhaust Hood ◽  
Ventilation Modes ◽  
Blade Tip ◽  
Last Stage

Abstract The paper deals with experimental research of the flow and dynamics of the blades in the last stage of a steam turbine with nominal output of 34 MW and a connected axial exhaust hood. The experiments were carried out on a turbine with relatively low inlet steam parameters “- 64 bars and 445 °C. It was possible to change the operating modes of the turbine during the course of measurement so that significant ventilation would be achieved in the last stage up to the point when aerodynamic throttling occurred in the last stage. In other words the turbine output varied from about 2 to 35 MW. The output of 2 MW was for the case of the island mode turbine operation. The experiments were carried out using static pressure taps and measurements of temperatures at the root and tip limiting wall. In addition to static pressure taps and temperature measurement, it was also possible to carry out probing by pneumatic probe with a diameter of 30 mm. Blade vibration monitoring sensors, so called last stage blade tip-timing, were also installed. The blade tip-timing acquisition hardware was used to monitor rotor blades tip amplitude. Due to the obtained experimental data, it was possible to verify the behaviour of the last stage and the connected exhaust hood for four measured variants. The courses of pressures and steam angles along the length of the LSB were determined. Furthermore, basic parameters of the last stage were determined, i.e. reactions of the stage, Mach and Reynolds numbers and values of pressure recovery coefficients. Based on experimental data the boundary conditions for CFD calculations were determined. Comparison of CFD calculations done for ventilation modes and for a nominal mode was also included. Another phenomenon which occurred during the probing of the flow parameters, particularly in ventilation modes, was the inability to determine parameters of steam due to low values of measured dynamic pressure in the vortex area at the root of the blade. The probe was able to detect dynamic pressure at the level of 50 Pa and more. In other words the transition point between backward and forward flows was identified. This limit point was used for further analysis of ventilation character of the steam flow depending on the ventilation coefficient c2x/u. where c2x is the average axial velocity at the LSB outlet, calculated from volumetric mass flow and u is LSB circumferential velocity calculated at LSB middle diameter. Due to the fact that it was also possible to measure vibration amplitudes of blades using the tip-timing method for a variety of modes, the relationships between pressure ratio over the tip and root of the last moving blade and vibration amplitude were also determined. This verified that the highest amplitude of blade tips occurred just when the compression of the medium on the blade tip was maximum, i.e. c2x/u = 0.05.

Numerical Study of Thermo-Acoustic Waves Generation by a Swirling Flame Using a New Approach Based on Large Eddy Simulation

2005 ◽  
Author(s):  
Christophe Duwig ◽  
Bogdan Gherman ◽  
Mihai Mihaescu ◽  
Mirko Salewski ◽  
Laszlo Fuchs
Keyword(s):  
Acoustic Waves ◽  
New Technologies ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Reacting Flow ◽  
Computationally Efficient ◽  
Demand Growth ◽  
Eddy Simulation ◽  
Instability Modes

The new challenge of the Gas Turbine industry is to develop new technologies for meeting electricity demand growth and reducing harmful emissions. Thus, a better understanding of the combustion phenomenon and an improvement in simulation capabilities are needed. In this paper, we present a new technique that is computationally efficient, for capturing the thermo-acoustic waves in low Mach number combustors. The idea is to utilize the fact that the acoustic related pressure fluctuations are small as compared to the dynamic pressure. Semi-compressible LES of reacting flow is performed and while the pressure perturbations related to the acoustic-wave propagation are handled separately. The equations are solved individually while allowing interaction between the two systems. The technique has been applied to the study of the generation and propagation of thermo-acoustic waves in a combustion chamber. A sensitivity analysis is presented and most important instability modes are identified.

scholarly journals Influence of guide vanes on the flow fields and performance of axial pump under unsteady flow conditions: Numerical study

2020 ◽  
Vol 14 (2) ◽  
pp. 6570-6593 ◽  
Author(s):  
Ahmed Ramadhan Al-Obaidi
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Axial Flow ◽  
Internal Flow ◽  
Design Flow ◽  
Guide Vanes ◽  
Axial Pump

Influence of different guide vanes on structural of flow field and axial pump performance under unsteady flow is carried out using numerical method. A three-dimensional axial flow pump model is numerically simulated using computational fluid dynamics (CFD) method with four number of impeller blades and 3, 4, 5 and 6 guide vanes depend on the SIMPLE code, standard turbulence k-ε model as well as sliding mesh method (SMM). The static, dynamic, total pressures, shear stress, velocity magnitude and turbulent kinetic energy are the important features which affecting instability operation in the pump. By monitoring above parameters and setting different measurement pressure points, the average pressures in the pump are discussed and the effect of guide vanes on the average pressure is analyzed. The results demonstrate that the numerical calculations can provide good accurately prediction for the characteristics of internal flow in the pump. The numerical results are closed to experimental results the minimum errors of pressure differences can reach 2.5% and the maximum errors 6.5%. The guide vanes have more effect on the flow field and pressure variations especially at outlet region in the axial pump. As compared with the using various guide vanes, the pressure increases as number of vanes increase that can lead the performance of pump also increases. Pressure differences in the pump at variety mass flow for vane 6 is higher than other vanes 3, 4 and 5 by 14.13, 11.35 and 3.85% for flow of 5 L/min. Further, the dynamic pressure differences for design flow between different vanes 6, 5, 4 and 3 are about by 2.87, 7.26 and 8.51% respectively.

scholarly journals Modeling of the Large Deformation and Rupture of a Metallic Plate Subjected to Explosive Loading

2008 ◽  
Author(s):  
Benjamin Daudonnet ◽  
Fre´de´ric Mercier ◽  
Krzysztof Woznica
Keyword(s):  
Large Deformations ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Pressure Vessels ◽  
Dynamic Responses ◽  
Pressure Loading ◽  
Static Loads ◽  
Metal Plates ◽  
Metal Pressure ◽  
Fragment Production

Thin walled metal pressure vessels or pipes commonly used in industry can burst under certain circumstances: as a result, the pressure envelope may undergo large deformations, which may eventually lead to a rupture. The response of these vessels to static and quasi-static loads is relatively well-understood but their response to highly dynamic pressure loading conditions is not. This paper describes a numerical study of the response of circular metal plates to the dynamic loads produced by hydrogen-oxygen explosions. In this study, a range of dynamic responses and rupture criteria models are considered and compared with the results of experiments. The ability of MSC MARC software to model the rupture phase and, in some cases, the post-rupture phase (i.e., fragment production) is also discussed.

scholarly journals Numerical Study on the Route of Flame-Induced Thermoacoustic Instability in a Rijke Burner

2021 ◽  
Vol 11 (4) ◽  
pp. 1590
Author(s):  
Nannan Dang ◽  
Jiazhong Zhang ◽  
Yoshihiro Deguchi
Keyword(s):  
Turbulent Flow ◽  
Limit Cycle ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Oscillation Mode ◽  
Model Verification ◽  
Limit Cycle Oscillation ◽  
Reacting Flow ◽  
Reaction Heat ◽  
Thermoacoustic Instability

The self-excited thermoacoustic instability in a two-dimensional Rijke-type burner with a center-stabilized premixed methane–air flame is numerically studied. The simulation considers the reacting flow, flame dynamics, and radiation model to investigate the important physical processes. A finite volume-based approach is used to simulate reacting flows under both laminar and turbulent flow conditions. Chemical reaction modeling is conducted via the finite-rate/eddy dissipation model with one-step reaction mechanisms, and the radiation heat flux and turbulent flow characteristics are determined by using the P-1 model and the standard k-ε model, respectively. The steady-state reacting flow is first simulated for model verification. Then, the dynamic pressure, velocity, and reaction heat evolutions are determined to show the onset and growth rate of self-excited instability in the burner. Using the fast Fourier transform (FFT) method, the frequency of the limit cycle oscillation is obtained, which agrees well with the theoretical prediction. The dynamic pressure and velocity along the tube axis provide the acoustic oscillation mode and amplitude, also agreeing well with the prediction. Finally, the unsteady flow field at different times in a limit cycle shows that flame-induced vortices occur inside the combustor, and the temperature distribution indicates that the back-and-forth velocity changes in the tube vary the distance between the flame and honeycomb in turn, forming a forward feedback loop in the tube. The results reveal the route of flame-induced thermoacoustic instability in the Rijke-type burner and indicate periodical vortex formation and breakdown in the Rijke burner, which should be considered turbulent flow under thermoacoustic instability.

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