Francis Turbine Operation at Excess Flow Rate Using Large Eddy Simulation: The Effect of Water Injection

2021 ◽  
Author(s):  
Muhannad Altimemy ◽  
Justin Caspar ◽  
Saif Watfeq ◽  
Alparslan Oztekin
Keyword(s):  
Large Eddy Simulation ◽  
Flow Rate ◽  
Water Injection ◽  
Francis Turbine ◽  
Effect Of Water ◽  
Eddy Simulation ◽  
Large Eddy

Simulations of rocket launch noise suppression with water injection from impingement pad

2020 ◽  
Vol 19 (3-5) ◽  
pp. 207-239
Author(s):  
Saman Salehian ◽  
Reda R Mankbadi
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Model ◽  
Water Injection ◽  
Broadband Noise ◽  
Computational Domain ◽  
Two Phase ◽  
Effect Of Water ◽  
Eddy Simulation ◽  
Impingement Plate ◽  
Large Eddy

The focus of this work is on understanding the effect of water injection from the launch pad on the noise generated during rocket’s lift-off. To simplify the problem, we consider a supersonic jet impinging on a flat plate with water injection from the impingement plate. The Volume of Fluid model is adopted in this work to simulate the two-phase flow. A Hybrid Large Eddy Simulation – Unsteady Reynolds Averaged Simulation approach is employed to model turbulence, wherein Unsteady Reynolds Averaged Simulation is used near the walls, and Large Eddy Simulation is used elsewhere in the computational domain. The numerical issues associated with simulating the noise of two-phase supersonic flow are addressed. The pressure fluctuations on the impingement plate obtained from numerical simulations agree well with the experimental data. Furthermore, the predicted effect of water injection on the far-field broadband noise is consistent with that of the experiment. The possible mechanisms for noise reduction by water injection are discussed.

scholarly journals Large Eddy Simulation of Periodic Transient Pressure Fluctuation in a Centrifugal Pump Impeller at Low Flow Rate

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 311
Author(s):  
Renfei Kuang ◽  
Xiaoping Chen ◽  
Zhiming Zhang ◽  
Zuchao Zhu ◽  
Yu Li
Keyword(s):  
Large Eddy Simulation ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Low Frequency ◽  
Pump Impeller ◽  
Eddy Simulation ◽  
Inlet Flow Rate ◽  
Large Eddy ◽  
Centrifugal Pump Impeller

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

Large eddy simulation of an axial pump with coupled flow rate calculation using the sharp interface immersed boundary method

2019 ◽  
Vol 29 (7) ◽  
pp. 2253-2276
Author(s):  
Mohammad Haji Mohammadi ◽  
Joshua R. Brinkerhoff
Keyword(s):  
Large Eddy Simulation ◽  
Flow Rate ◽  
Immersed Boundary Method ◽  
Sharp Interface ◽  
Immersed Boundary ◽  
Inlet Flow ◽  
Content Type ◽  
Eddy Simulation ◽  
Inlet Flow Rate ◽  
Large Eddy

Purpose Turbomachinery, including pumps, are mainly designed to extract/produce energy from/to the flow. A major challenge in the numerical simulation of turbomachinery is the inlet flow rate, which is routinely treated as a known boundary condition for simulation purposes but is properly a dependent output of the solution. As a consequence, the results from numerical simulations may be erroneous due to the incorrect specification of the discharge flow rate. Moreover, the transient behavior of the pumps in their initial states of startup and final states of shutoff phases has not been studied numerically. This paper aims to develop a coupled procedure for calculating the transient inlet flow rate as a part of the solution via application of the control volume method for linear momentum. Large eddy simulation of a four-blade axial hydraulic pump is carried out to calculate the forces at every time step. The sharp interface immersed boundary method is used to resolve the flow around the complex geometry of the propeller, stator and the pipe casing. The effect of the spurious pressure fluctuations, inherent in the sharp interface immersed boundary method, is damped by local time-averaging of the forces. The developed code is validated by comparing the steady-state volumetric flow rate with the experimental data provided by the pump manufacturer. The instantaneous and time-averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field. Design/methodology/approach The authors use control volume analysis for linear momentum to simulate the discharge rate as part of the solution in a large eddy simulation of an axial hydraulic pump. The linear momentum balance equation is used to update the inlet flow rate. The sharp interface immersed boundary method with dynamic Smagorinsky sub-grid stress model and a proper wall model is used. Findings The steady-state volumetric flow rate has been computed and validated by comparing to the flow rate specified by the manufacturer at the simulation conditions, which shows a promising result. The instantaneous and time averaged flow fields are also studied to reveal the flow pattern and turbulence characteristics in the pump flow field. Originality/value An approach is proposed for computing the volumetric flow rate as a coupled part of the flow solution, enabling the simulation of turbomachinery at all phases, including the startup/shutdown phase. To the best of the authors’ knowledge, this is the first large eddy simulation of a hydraulic pump to calculate the transient inlet flow rate as a part of the solution rather than specifying it as a fixed boundary condition. The method serves as a numerical framework for simulating problems incorporating complex shapes with moving/stationary parts at all regimes including the transient start-up and shut-down phases.

Large Eddy Simulation of Francis Turbine Flow Fields under Small Opening Condition

2013 ◽  
Vol 444-445 ◽  
pp. 281-285 ◽  
Author(s):  
Tao Guo ◽  
Jun Zhou ◽  
Xiao Nan Liu
Keyword(s):  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Turbulent Kinetic Energy ◽  
Guide Vane ◽  
Francis Turbine ◽  
Scale Model ◽  
Unstable Flow ◽  
Small Opening ◽  
Eddy Simulation ◽  
Large Eddy

The vibration intensity is strong in Francis turbine occurred under the small opening conditions, such as Lijia Gorges and Three Gorges project. In paper we use large eddy simulation (LES) method base on Vreman SubGrid-Scale model to study the generation and evolution process of turbulence flow, capturing the details of the flow structures and the dissipation of the turbulent kinetic energy. The SIMPIEC algorithm is applied to solve the coupled equation of velocity and pressure. The result shows that the small guide vane opening conditions deviate the optimal conditions most. So some unstable flow characters been induced. Such as the turbulent kinetic energy of fluid in guide vanes zone, the blade passage and the draft tube are very strong. The unstable flow phenomenon including the swirl, flow separation, interruption and vortex strip. It can be deduced that the vibration of unit is induced by these flow characteristic.

The Characteristics Research of Tube Vortex Based on Large Eddy Simulation

2011 ◽  
Vol 121-126 ◽  
pp. 3657-3661
Author(s):  
Dun Zhang ◽  
Yuan Zheng ◽  
Ying Zhao ◽  
Jian Jun Huang
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Complex Geometry ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Computational Method ◽  
Francis Turbine ◽  
Eddy Simulation ◽  
Large Eddy

Numerical simulation of three-dimensional transient turbulent flow in the whole flow passage of a Francis turbine were based upon the large eddy simulation(LES) technique on Smargorinsky model and sliding mesh technology. The steady flow data simulated with the standard k-εmodel was used as the initial conditions for the unsteady simulation. The results show that LES can do well transient turbulent flow simulation in a Francis turbine with complex geometry. The computational method provides some reference for exploring the mechanism of eddy formation in a complex turbulent of hydraulic machinery.

Large Eddy Simulation of Single-Sided Ventilated Room With Different Location of Windows

2014 ◽  
Author(s):  
A. Idris ◽  
B. P. Huynh
Keyword(s):  
Large Eddy Simulation ◽  
Flow Pattern ◽  
Flow Rate ◽  
Natural Ventilation ◽  
Air Flow ◽  
Navier Stokes ◽  
Eddy Motion ◽  
Eddy Simulation ◽  
Continuity Equations ◽  
Large Eddy

The natural ventilation contributes the improvement of internal thermal comfort and internal air quality when applied properly. An investigation of single-sided double opening was performed to a 3-dimensional rectangular-box room using a commercial Computational Fluid Dynamics (CFD) software package of ESI group. Sixteen models with different location of double-openings were investigated. The large eddy simulation (LES) turbulence model was used to predict the air’s flow rate and air flow pattern. The governing equations for large eddy motion was obtained by filtering the Navier-Stokes and continuity equations. From the overall results, the lowest and the highest air flow rates were obtained to be 1.14 × 10−3 m3/s and 2.12 × 100 m3/s respectively. The location & arrangement of opening influences the air flow rate and air flow pattern.

Large-Eddy Simulation of a Mixed-Flow Pump at Off-Design Conditions

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Antonio Posa ◽  
Antonio Lippolis ◽  
Elias Balaras
Keyword(s):  
Large Eddy Simulation ◽  
Flow Rate ◽  
Design Flow ◽  
Immersed Boundary ◽  
Mixed Flow ◽  
Eddy Simulation ◽  
Image Velocimetry ◽  
Large Eddy ◽  
The One ◽  
Flow Pump

The flow through turbopumps is characterized by highly unsteady phenomena at part load conditions, involving large separation and generation of vortical structures. This behavior is strongly dependent on the interaction between rotating and steady parts, which is significantly modified, compared to the one at the design flow rate. Therefore, at off-design conditions, eddy-resolving computations are more suitable to analyze the complex physics occurring inside turbomachinery channels. In this work the large eddy simulation (LES), coupled with an immersed-boundary (IB) method, is utilized to study a mixed-flow pump at a reduced flow rate, equivalent to 40% of the nominal one. The present approach has been already validated in a previous study, where a satisfactory agreement with two-dimensional (2D) particle image velocimetry (PIV) experiments has been shown at design conditions. In this paper a comparison with the LES results at the optimal flow rate is also proposed, in order to understand the important modifications of the flow occurring at part loads.

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